IMMUNOREACTIVE POLYPEPTIDES

Abstract

Methods and compositions for diagnosis and vaccination against Ehrlichia chaffeensis are provided.

Description

IMMUNOREACTIVE POLYPEPTIDES Background of the invention This application claims the benefit of United States Provisional Patent Application No. 62 / 667,925, filed on May 7, 2018, the entirety of which is incorporated herein by reference. 1. Field of the invention The present invention relates generally to the fields of molecular biology and medicine. More specifically, it relates to diagnostic methods and the composition of vaccines for E. coli. 2. Description of the related state of the art Human monocytotropic ehrlichiosis (HME) is a Group 1 emerging disease listed by the NIAID, and its causative agent, E. chaffeensis, is classified as a Category C priority pathogen. HME is a life-threatening, undifferentiated febrile illness; clinical diagnosis is challenging, and definitive diagnosis is often retrospective (Walker and Dumler, 1997; Walker et al., 2004; Dumler et al., 2007). Although more than 8,000 cases have been reported to the Centers for Disease Control and Prevention as of 2012, this number likely underestimates the true number of cases by a factor of 100 (Glano et al., 2003). The disease is often not diagnosed due to the nonspecific symptoms associated with the onset, but results in hospitalization of the patient in 43-62% of cases (Fishbein et al., 1994).The progression of the disease can result in a fatal outcome and often involves multisystem organ failure, with acute respiratory distress syndrome (ARDS) and meningoencephalitis being common in many fatal cases (Fishbein et al., 1994; Paparone et al., 1995). The threat to public health is increasing with newly emerging ehrlichiosis agents; however, vaccines for human ehrlichiosis are not available, and therapeutic options are limited. New predictive information and bioinformatics tools have recently been developed that make the broad identification of genome-wide candidates for protective immunodiagnostics / vaccines feasible (He et al., 2010; Magnan et al., 2010). The prospects for developing effective subunit vaccines and immunodiagnostics for Ehrlichia have been limited due to many factors, most notably the small repertoire of immunoreactive / protective proteins that have been molecularly defined (McBride and Walker, 2010). The gaps in knowledge needed to address this problem of Ehrlichia chaffeensis have been reduced thanks to recent advances in understanding protective / pathological immunological mechanisms (Feng and Walker 2004; Nandi et al., 2007; Winslow et al., 2000), the immunomolecular characterization of some vaccine / diagnostic antigens (Kuriakose et al., 2012; Li et al., 2002), the genome, transcriptome and proteome profiles (Kuriakose et al., 2011; Lin et al., 2011), new animal models (Winslow et al., 1998; Sotomay et al., 2001), and other technological advances. Studies that MA / E / ZUZl / un I z using low-productivity approaches to define the antigenic components of E. chaffeensis have yielded a small group of protective antigens, including an outer membrane major protein (OMP) and a family of tandem repeat protein (TRP) effectors secreted with major protective linear antibody epitopes (Kuriakose et al., 2012; L¡ et al., 2001). However, these antigens likely represent a significant, but incomplete, repertoire of immunoreactive / protective proteins. Furthermore, it is well established that antibody-mediated immunity is necessary for protection against E. chaffeensis infection (Winslow et al., 2000; L1 et al., 2002; Kuriakose et al., 2012; L1 et al., 2001; Racine et al., 2011; Yager et al., 2005), and antibodies are the basis of the most effective vaccines for humans. The removal of E.Chaffeensis occurs, at least in part, during the extracellular stage of infection (L and Winslow 2003); however, intracellular immune mechanisms may also be important, and that can define the characteristics of antigens / antibodies that are protective in both environments is critical for the effective development of a vaccine. While some immunoreactive proteins from E. chaffeensis have been identified, it is currently unclear which of the many unevaluated E. chaffeensis proteins produced by the E. chaffeensis genome, if any, might exhibit immunoreactivity or be important for immune responses against E. chaffeensis. Approximately 45% of the open frequency receptors (ORFs) in the E. chaffeensis genome encode proteins <20 kDa (Kuriakose et al., 2011; Dunning Hotopp et al., 2006), and many small-molecular-weight proteins remain unstudied. Clearly, there is a need for new and improved methods for diagnosing and vaccinating against E. chaffeensis. Brief description of the invention The present invention, in some respects, overcomes the limitations of the prior art by providing new and improved methods for diagnosing and vaccinating against Ehrlichia chaffeensis or Ehrlichia canis. As shown in the examples below, highly immunoreactive E. chaffeensis proteins were identified, and the in vivo significance of these immunoreactive proteins was verified using ELISA tests on human monocytotropic ehrlichiosis (HME)-positive sera obtained from patients. ELISA tests with HME-positive sera from patients revealed that the following proteins induced significant responses, indicating that these proteins could be used, for example, in diagnostic methods to detect E. chaffeensis infection or to induce an immune response in a subject against E. chaffeensis: Table 1: Immune-Reactive Proteins A4 (Ech_0261; SEQ ID NO:1), A5 (Ech_0255; SEQ ID NO:2), A9 (Ech_0722; SEQ ID NO:3), A14 (Ech_0535; SEQ ID NO:4), A15 (Ech_0251; SEQ ID NO:5), ivia / t / zuz i / un yy iz A19(Ech_0745 A21 (Ech_0825 A23(Ech_0166 A34(Ech_0252 A38(Ech_0763 A42(Ech_0240 A47(Ech_0345 A50(Ech_0700 A51 (Ech_0607 A54(Ech_0614 A55(Ech_1103 A56(Ech_0846 A62(Ech_0578 A63(Ech_0716 SEQ ID NO:6), SEQ ID NO:7), SEQ ID NO:8), SEQ ID NO:9), SEQ ID NO:10), SEQ ID NO:11), SEQ ID NO:12), SEQ ID NO: 28) SEQ ID NO:13), SEQ ID NO:14), SEQ ID NO:15), SEQ ID NO:16), SEQ ID NO:1 / 18), SEQ ID NO:1 / 18). i / un yy iz A64 IN (Ech_0778; SEQ ID NO:19), A66 (Ech_0398; SEQ ID NO:20), A75 (Ech_0388; SEQ ID NO:21), A77 (Ech_1053; SEQ ID NO:22). As shown in the examples below, all polypeptides listed in Table 1 demonstrated reactivity with the sera used for analysis. As shown in the following results, the proteins listed in Table 1 exhibited an optical density (OD) of at least 0.3 or greater. In some cases, the protein is a protein from Table 2. Table 2: Proteins of medium immunoreactivity A14(Ech_0535 A19(Ech_0745 A38(Ech_0763 A42(Ech_0240 A47(Ech_0345 A55(Ech_1103 A62(Ech_0578 SEQ ID NO:5), SEQ ID NO:6), SEQ ID NO:10) SEQ ID NO:11) SEQ ID NO:12) SEQ ID NO:15) SEQ ID NO:17) As shown in the following examples, the proteins in Table 2 showed 100% reactivity in all the sera tested and showed ELISA OD values ​​between 0.2 and 0.5. Even more preferable, the immunoreactive protein is a protein like the one shown in Table 3: Table 3: Highly immunoreactive proteins A4 (Ech_0261; SEQ ID NO:1), A5 (Ech_0255; SEQ ID NO:2), A51 (Ech_0607; SEQ ID NO:13), A56 (Ech_0846; SEQ ID NO:16), Α63 (Ech_0716; SEQ ID NO:18), A77 (Ech_1053; SEQ ID NO:22). As shown in the following examples, the proteins in Table 3 showed 100% reactivity to all sera tested and had an optical density >0.5 with at least 4 sera. In some modalities, it is anticipated that a protein having at least 90%, more preferably at least 95%, 97.5%, or at least 99% sequence identity with a protein in Table 1 or Table 2, or more preferably Table 3, while retaining at least some of its immunoreactivity, may be used in various modalities as described herein (e.g., in a diagnostic test, or to induce an immune response against Ehrlichia in a subject, for inclusion in a vaccine formulation).In some modalities, the protein can be used to generate an antibody that selectively binds to the protein, and the antibody can be used, for example, in a diagnostic assay; for example, in some modalities, the antibody is labeled or bound to a solid substrate (for example, in a lateral flow assay). In some modalities, the protein is A77 (SEQ ID NO:22), A62 (SEQ ID NO:17), A56 (SEQ ID NO:16), A19 (SEQ ID NO:6), A50 (Ech_0700; SEQ ID NO: 28), A51 (SEQ ID NO:13), A14 (SEQ ID NO:4), A63 (SEQ ID NO:18), A34 (SEQ ID NO:9), A9 (SEQ ID NO:3), or A42 (Ech_0240; SEQ ID NO:11). One aspect of the present invention relates to a method for detecting antibodies that bind specifically to an Ehrlichia organism in a test sample, comprising: (a) contacting an isolated polypeptide from Table 1, Table 2, or Table 3, or a polypeptide having at least 95% sequence identity with it, with the test sample under conditions that permit the formation of peptide-antibody complexes; (b) detecting the peptide-antibody complexes; wherein the detection of the peptide-antibody complexes is an indication that antibodies specific to an Ehrlichia organism are present in the test sample, and wherein the absence of the peptide-antibody complexes is an indication that antibodies specific to an Ehrlichia organism are not present in the test sample. In some embodiments, the isolated polypeptide may comprise or consist of an isolated peptide from Table 1, Table 2, or Table 3.In some embodiments, the polypeptide is selected from the group consisting of a polypeptide in Table 2 or Table 3. In some embodiments, the isolated polypeptide comprises, consists of, or is A77 (SEQ ID NO:22), A62 (SEQ ID NO:17), A56 (SEQ ID NO:16), A19 (SEQ ID NO:6), A50 (Ech_0700; SEQ ID NO: 28), A51 (SEQ ID NO:13), A14 (SEQ ID NO:4), A63 (SEQ ID NO:18), A34 (SEQ ID NO:9), A9 (SEQ ID NO:3), or A42 (Ech_0240; SEQ ID NO:11). In some embodiments, the Ehrlichia organism is Ehrlichia chaffeensis. The detection step may include performing an enzyme-linked immunoassay, a radioimmunoassay, an immunoprecipitation, a fluorescence immunoassay, a chemiluminescence assay, an immunoblotting assay, a lateral flow assay, a flow cytometry assay, a multiplex immunoassay (e.g., a Bio-Plex® suspension multiplexing array assay), a mass spectrometry assay, or a particle-based assay.In some modalities, the detection step comprises a lateral flow assay or an enzyme-linked immunoassay, where the enzyme-linked immunoassay is an ELISA. ML / E / ZuZ / UI yy I z Another aspect of the present invention relates to a method for identifying an Ehrlichia infection in a mammalian subject comprising: (a) contacting a biological sample from the subject with a polypeptide isolated from Table 1, Table 2, or Table 3 under conditions that permit the formation of peptide-antibody complexes; and (b) detecting the peptide-antibody complexes; wherein the detection of the peptide-antibody complexes is an indication that the subject has an Ehrlichia infection. In some embodiments, the polypeptide is selected from Table 2 or Table 3. In some embodiments, the isolated polypeptide may comprise or consist of a peptide isolated from Table 1, Table 2, or Table 3.In some forms, the isolated polypeptide is A77 (SEQ ID NO:22), A62 (SEO ID NO:17), A56 (SEQ ID NO:16), A19 (SEQ ID NO:6), A50 (Ech_0700; SEQ ID NO: 28), A51 (SEQ ID NO:13), A14 (SEQ ID NO:4), A63 (SEQ ID NO:18), A34 (SEQ ID NO:9), A9 (SEQ ID NO:3) or A42 (Ech_0240; SEQ ID NO:11). The detection step may include performing an enzyme-linked immunoassay, a radioimmunoassay, an immunoprecipitation assay, a fluorescence immunoassay, a chemiluminescence assay, an immunoblotting assay, a lateral flow assay, a flow cytometry assay, a multiplex immunoassay (e.g., a Bio-Plex® suspension multiplexing array assay), a test strip test, or a particle-based assay. In some modalities, the subject is a human. In some modalities, the subject is a dog. Yet another aspect of the present invention relates to an isolated polypeptide comprising a sequence of Table 1, Table 2 or Table 3, wherein the isolated peptide is immobilized on a surface of a support substrate. In certain embodiments, the polypeptide is selected from the group consisting of Table 2. In certain embodiments, the polypeptide is selected from the group consisting of Table 3. In some embodiments, the isolated polypeptide may comprise or consist of an isolated peptide from Table 1, Table 2, or Table 3. In some embodiments, the isolated polypeptide is A77 (SEQ ID NO:22), A62 (SEQ ID NO:17), A56 (SEQ ID NO:16), A19 (SEQ ID NO:6), A50 (Ech_0700; SEQ ID NO: 28), A51 (SEQ ID NO:13), A14 (SEQ ID NO:4), A63 (SEQ ID NO:18), A34 (SEQ ID NO:9), A9 (SEQ ID NO:3), or A42 (Ech_0240; SEQ ID NO:11). In some forms, the support substrate comprises latex, polystyrene, nylon, nitrocellulose, cellulose, silica, agarose, or magnetic resin.In some embodiments, the support substrate is a reaction chamber, well, membrane, filter, paper, emulsion, bead, microbead, reagent strip, card, glass slide, lateral flow apparatus, microchip, comb, silica particle, magnetic particle, nanoparticle, or self-assembling monolayer. The peptide may be contained in a kit. In some embodiments, the peptide is produced by peptide synthesis or in vitro transcription and translation (IVTT). In some embodiments, the peptide is produced recombinantly. Another aspect of the present invention relates to an isolated polypeptide comprising a sequence from Table 1, Table 2, or Table 3, wherein the isolated peptide is covalently linked to a detectable tag. In certain embodiments, the polypeptide is selected from the group consisting of Table 2. In certain embodiments, the polypeptide is selected from the group consisting of Table 3. In some embodiments, the isolated polypeptide may comprise or consist of an isolated peptide from Table 1, Table 2, or Table 3. In some embodiments, the polypeptide comprises or consists of A77 (SEQ ID ML / ιζ / ζυζΊ / un yy iz NO:22), A62 (SEQ ID NO:17), A56 (SEQ ID NO:16), A19 (SEQ ID NO:6), A50 (Ech_0700; SEQ ID NO: 28), A51 (SEQ ID NO:13), A14 (SEQ ID NO:4), A63 (SEQ ID NO:18), A34 (SEQ ID NO:9), A9 (SEQ ID NO:3), or A42 (Ech_0240; SEQ ID NO:11). In some embodiments, the detectable tag is a fluorescent tag, a radioactive tag, an enzyme tag, or a luminescent nanoparticle. In some embodiments, the luminescent nanoparticle is a rare-earth luminescent nanoparticle, a luminescent nanoparticle, or a strontium alumina nanoparticle. The polypeptide may be contained in a kit. In some modalities, the polypeptide is produced by peptide synthesis or in vitro transcription and translation (IVTT). In some modalities, the polypeptide is produced recombinantly. Another aspect of the present invention relates to a kit comprising: (a) the polypeptide isolated from the present embodiments or as described above, (b) an anti-dog or anti-human secondary antibody linked to a reporter molecule, and (c) a reagent suitable for detecting the reporter molecule. In some embodiments, the peptide is immobilized on a membrane or a microtiter plate. In some embodiments, the reporter molecule is selected from the group consisting of luciferase, horseradish peroxidase, a luminescent nanoparticle, P-galactosidase, and a fluorescent tag. In some embodiments, the luminescent nanoparticle is a strontium aluminate nanoparticle. The kit may further comprise a dilution buffer solution for dog or human serum. The kit may comprise a lateral flow immunoassay or a lateral flow immunochromatographic assay.In some versions, the kit includes an enzyme-linked immunosorbent assay (ELISA). Another aspect of the present invention relates to a method for inducing an immune response in a mammalian subject comprising administering to the subject an effective amount of a pharmaceutical preparation comprising a polypeptide from Table 1, Table 2, or Table 3. In some embodiments, the polypeptide is selected from the group consisting of Table 2 and Table 3. In some embodiments, the isolated polypeptide may comprise or consist of an isolated peptide from Table 1, Table 2, or Table 3. In some embodiments, the polypeptide comprises or consists of A77 (SEQ ID NO:22), A62 (SEQ ID NO:17), A56 (SEQ ID NO:16), A19 (SEQ ID NO:6), A50 (Ech_0700; SEQ ID NO: 28), A51 (SEQ ID NO:13), A14 (SEQ ID NO:4), A63 (SEQ ID NO:18), A34 (SEQ ID NO:9), A9 (SEQ ID NO:3) or A42 (Ech_0240; SEQ ID NO:11). The subject can be a human.In some forms, the pharmaceutical preparation is administered subcutaneously, intramuscularly, nasally, by inhalation or administration as aerosols, or intradermally. Yet another aspect of the present invention relates to a method for treating an Ehrlichia chaffeensis infection in a subject, comprising: (a) contacting a biological sample from the subject with a polypeptide isolated from Table 1, Table 2, or Table 3 under conditions permitting the formation of peptide-antibody complexes; (b) detecting the peptide-antibody complexes, wherein the detection of the peptide-antibody complexes is an indication that the subject has an Ehrlichia chaffeensis infection; and (c) administering a therapeutic compound to treat the Ehrlichia infection in the subject. In certain embodiments, the polypeptide is selected from the group consisting of Table 2. In certain embodiments, the polypeptide is selected from the group consisting of Table 3. In some embodiments, the isolated polypeptide may comprise or consist of a peptide isolated from Table 1, Table 2, or Table 3.In some embodiments, the polypeptide is A77 (SEQ ID NO:22), A62 (SEQ ID NO:17), A56 (SEQ ID NO:16), A19 (SEQ ID NO:6), A50 (Ech_0700; SEQ ID NO: 28), A51 (SEQ ID NO:13), A14 (SEQ ID NO:4), A63 (SEQ ID NO:18), A34 (SEQ ID NO:9), A9 (SEQ ID NO:3) or A42 (Ech_0240; SEQ ID NO:11). The detection step may involve performing an enzyme-linked immunoassay, a radioimmunoassay, an immunoprecipitation assay, a fluorescence immunoassay, a chemiluminescence assay, an immunoblotting assay, a lateral flow assay, a flow cytometry assay, a multiplex immunoassay (e.g., a Bio-Plex® suspension multiplexing array assay), a test strip test, or a particle-based assay. In certain modalities, the subject is a dog or a human. The therapeutic compound may be an antibiotic, such as doxycycline. Another aspect of the present invention relates to a method for detecting antibodies that bind specifically to an Ehrlichia organism in a test sample, comprising: (a) contacting a polypeptide isolated from: Ecaj_0919, Ecaj_0073, Ecaj_0104, Ecaj_0663, or Ecaj_0881, more preferably Ecaj_0919, Ecaj_0073, Ecaj_0104, or Ecaj_0663, even more preferably Ecaj_0919, Ecaj_0073, Ecaj_0104, even more preferably Ecaj_0919 or Ecaj_0073; or a polypeptide having at least 95% sequence identity with the same, with the test sample, under conditions allowing the formation of peptide-antibody complexes; (b) detecting the peptide-antibody complexes;where the detection of peptide-antibody complexes is an indication that antibodies specific to an Ehrlichia organism are present in the test sample, and where the absence of peptide-antibody complexes is an indication that antibodies specific to an Ehrlichia organism are not present in the test sample. The detection step may comprise performing an enzyme-linked immunoassay, a radioimmunoassay, an immunoprecipitation assay, a fluorescence immunoassay, a chemiluminescence assay, an immunoblotting assay, a lateral flow assay, a flow cytometry assay, a multiplex immunoassay, a mass spectrometry assay, or a particle-based assay. In some embodiments, the detection step comprises a lateral flow assay or an enzyme-linked immunoassay, where the enzyme-linked immunoassay is an ELISA. Yet another aspect of the present invention relates to a method for identifying an Ehrlichia infection in a mammalian subject comprising: (a) contacting a biological sample from a subject with a polypeptide isolated from Ecaj_0919, Ecaj_0073, Ecaj_0104, Ecaj_0663, or Ecaj_0881, more preferably Ecaj_0919, Ecaj_0073, Ecaj_0104, or Ecaj_0663, even more preferably Ecaj_0919, Ecaj_0073, Ecaj_0104, even more preferably Ecaj_0919 or Ecaj_0073, under conditions allowing the formation of peptide-antibody complexes; and (b) detecting the peptide-antibody complexes; wherein the detection of the peptide-antibody complexes is an indication that the subject has an Ehrlichia infection. The detection step may include performing an enzyme-linked immunoassay, a radioimmunoassay, an immunoprecipitation assay, a fluorescence immunoassay, a chemiluminescence assay, an immunoblotting assay, a lateral flow assay, or a flow cytometry assay. ML / E / ζυζΊ / un yy iz de flujo, un immunoensayo múltiple, una prueba con tirados o un ensayo base de matemático. In some modalities, the subject is a dog. Another aspect of the present invention relates to an isolated polypeptide comprising a sequence of Ecaj_0919, Ecaj_0073, Ecaj_0104, Ecaj_0663 or Ecaj_0881, more preferably Ecaj_0919, Ecaj_0073, Ecaj_0104 or Ecaj_0663, even more preferably Ecaj_0919, Ecaj_0073, Ecaj_0104, even more preferably Ecaj_0919 or Ecaj_0073, wherein the isolated peptide is immobilized on a surface of a support substrate. The support substrate may comprise or consist of latex, polystyrene, nylon, nitrocellulose, cellulose, silica, agarose, or magnetic resin. In some embodiments, the support substrate is a reaction chamber, well, membrane, filter, paper, emulsion, bead, microbead, reagent strip, card, glass slide, lateral flow apparatus, microchip, comb, silica particle, magnetic particle, nanoparticle, or self-assembling monolayer. In some embodiments, the peptide is contained in a kit.The peptide can be produced by peptide synthesis or in vitro transcription and translation (IVTT). In some cases, the peptide is produced recombinantly. Yet another aspect of the present invention relates to an isolated polypeptide comprising a sequence of or consisting of Ecaj_0919, Ecaj_0073, Ecaj_0104, Ecaj_0663, or Ecaj_0881, more preferably Ecaj_0919, Ecaj_0073, Ecaj_0104, or Ecaj_0663, even more preferably Ecaj_0919, Ecaj_0073, Ecaj_0104, even more preferably Ecaj_0919 or Ecaj_0073, wherein the isolated peptide is covalently linked to a detectable tag. The detectable tag may be a fluorescent tag, a radioactive tag, an enzyme tag, or a luminescent nanoparticle. The luminescent nanoparticle may be a rare-earth luminescent nanoparticle, a luminescent nanoparticle, or a strontium aluminate nanoparticle. The polypeptide may be contained in a kit. In some embodiments, the polypeptide is produced by peptide synthesis or in vitro transcription and translation (IVTT). In some embodiments, the polypeptide is produced via recombinant DNA technology. Another aspect of the present invention relates to a kit comprising: (a) an isolated polypeptide disclosed herein or listed above, (b) a secondary anti-dog or anti-human antibody linked to a reporter molecule, and (v) a reagent suitable for detecting the reporter molecule. The peptide may be immobilized on a membrane or on a microtiter plate. In some embodiments, the reporter molecule is selected from the group consisting of luciferase, horseradish peroxidase, a luminescent nanoparticle, P-galactosidase, and a fluorescent tag. The luminescent nanoparticle may be a strontium aluminate nanoparticle. The kit may further include a dilution buffer solution for dog or human serum. The kit may comprise a lateral flow immunoassay or a lateral flow immunochromatographic assay. In some embodiments, the kit comprises an enzyme-linked immunosorbent assay (ELISA). Yet another aspect of the present invention relates to a method for inducing an immune response in a mammalian subject comprising administering to the subject an effective amount of a pharmaceutical preparation comprising a polypeptide of Ecaj_0919, Ecaj_0073, Ecaj_0104, Ecaj_0663, or Ecaj_088l, more preferably Ecaj_0919, Ecaj_0073, Ecaj_0104, or Ecaj_0663, even more preferably μλ / ε / zuzi / un yy iz Ecaj_0919, Ecaj_0073, Ecaj_0104, or even more preferably Ecaj_0919 or Ecaj_0073. In some modalities, the subject is a human. In some modalities, the pharmaceutical preparation is administered subcutaneously, intramuscularly, nasally, by inhalation or administration as aerosols, or intradermally. Another aspect of the present invention relates to a method of treating an Ehrlichia infection in a mammalian subject comprising: (a) contacting a biological sample from the subject with a polypeptide isolated from Ecaj_0919, Ecaj_0073, Ecaj_0104, Ecaj_0663 or Ecaj_0881, more preferably Ecaj_0919, Ecaj_0073, Ecaj_0104 or Ecaj_0663, even more preferably Ecaj_0919, Ecaj_0073, Ecaj_0104, even more preferably Ecaj_0919 or Ecaj_0073, under conditions allowing the formation of peptide-antibody complexes; (b) detecting the peptide-antibody complexes; wherein the detection of the peptide-antibody complexes is an indication that the subject has an Ehrlichia canis infection; and (c) administer a therapeutic compound to treat Ehrlichia infection in the subject.In some modalities, the detection step involves performing an enzyme-linked immunoassay, a radioimmunoassay, an immunoprecipitation assay, a fluorescence immunoassay, a chemiluminescent assay, an immunoblotting assay, a lateral flow assay, a flow cytometry assay, a multiplex immunoassay, a reagent strip test, or a particle-based assay. The subject may be a dog. In some modalities, the therapeutic compound is an antibiotic (e.g., doxycycline). As used herein, the term “polypeptide” encompasses amino acid chains comprising at least 50 amino acid residues and more preferably at least 100 amino acid residues, wherein the amino acid residues are linked by covalent peptide bonds. As used herein, an “antigenic polypeptide” or an “immunoreactive polypeptide” is a polypeptide which, when introduced into a vertebrate, can stimulate the production of antibodies in the vertebrate, i.e., is antigenic, and wherein the antibody can selectively recognize and / or bind to the antigenic polypeptide. An antigenic polypeptide may comprise or consist of an immunoreactive sequence derived from an immunoreactive Ehrlichia protein as described herein (e.g., as shown in Table 1, Table 2, Table 3, Ecaj_0919, Ecaj_0073, Ecaj_0104, and / or Ecaj_0663), and the polypeptide may comprise one or more additional sequences.In some formulations, the additional sequences can be derived from a naturally occurring Ehrlichia antigen and can be heterologous; such sequences may (but do not necessarily) be immunogenic. In some formulations, the antigenic or immunoreactive polypeptide can be covalently bound to a solid substrate, for example, in an immunoassay such as a lateral flow assay, etc. The immunoreactive polypeptides of Ehrlichia, as described herein, may be a recombinant polypeptide, a synthetic polypeptide, a purified polypeptide, an immobilized polypeptide, a detectably labeled polypeptide, an encapsulated polypeptide, or a vector-expressed polypeptide. In several forms, the immunoreactive polypeptides of Ehrlichia provided herein may be truncated or may comprise a deletion mutation, without eliminating the immunoreactivity of the resulting peptide or polypeptide. An immunoreactive peptide or polypeptide MA / IZ / 2U2T / UI yy I 2 disclosed herein may be included in a pharmaceutical composition such as, for example, a vaccine composition formulated for administration to a human or canine subject. As used herein in the specification, “a” may mean one or more. As used in the claims, when used in conjunction with the word “comprising”, the words “a” may mean one or more. The use of the term “or” in the claims is intended to mean “and / or” unless explicitly stated to refer only to alternatives or to mutually exclusive alternatives, although the disclosure supports a definition that refers only to alternatives and “and / or”. As used herein, “other” may mean at least one other or more. Throughout this application, the term “approximately” is used to indicate that a value includes the inherent error variation for the device, the method that is used to determine the value, or the variation that exists among the study subjects. Other objects, features, and advantages of the present invention will become apparent from the following detailed specification. It should be understood, however, that the detailed specification and specific examples, while indicating preferred embodiments of the invention, are provided for illustrative purposes only, since various changes and modifications within the substance and scope of the invention will become apparent to those skilled in the art from this detailed specification. Brief description of the figures The following figures form part of this specification and are included to further illustrate certain aspects of the present invention. The invention may be better understood by referring to one or more of these figures in conjunction with the detailed specification of the specific embodiments presented above. Figure 1: Hypothetical proteins of E. chaffeensis analyzed by the ELISA method. Figure 2: Candidates for Immunodiagnostics of E. chaffeensis showing an OD of at least 0.3 based on the ELISA test. Figure 3: Hypothetical E. chaffeensis protein test using several HME-positive sera (6 serum samples in total) per protein. Figures 4A to 4B: Expression and immunoreactivity analysis of hypothetical E. chaffeensis proteins. (Figure 4A) Recombinant expression of 17 hypothetical E. chaffeensis proteins by IVTT was detected by spot immunoblotting with anti-His-tagged antibody. CTL, the negative control. (Figure 4B) Immunoreactivity analysis of recombinant hypothetical E. chaffeensis proteins by ELISA with serum from a patient with HME (No. Sandra). The patient serum did not recognize the control protein. Figure 5: Immunoreactivity of 15 hypothetical E. chaffeensis proteins and comparison with 3 TRPs by ELISA. IVTT products reacted with a panel of sera from 10 patients with HME. Normal human serum did not recognize these proteins. Figures 6A to 6B: Conformational immunoreactivity of hypothetical proteins from E. chaffeensis IVIA / t / ZUZ I / U1 UU I z recombinants, (Figure 6A) Comparison of the immunoreactivity of the hypothetical recombinant proteins under denaturing conditions and the TRPs detected by ELISA with a panel of sera from 10 patients with HME. (Figure 6B) Immunoreactivity of overlapping synthetic peptides encompassing 3 hypothetical proteins from E. chaffeensis, determined by ELISA with serum from a patient with HME (No. Sandra). Figure 7: Immunoreactivity of E. canis orthologs of hypothetical E. chaffeensis immunoreactive proteins by ELISA. The recombinant proteins reacted with sera from 10 dogs infected with E. canis. Serum from a normal dog did not recognize these proteins. TRP19 was included for comparison of immunoreactivity. Description of the illustrative modalities In some modalities, an immunoreactive polypeptide (e.g., in Table 1, Table 2, Table 3, Ecaj_0919, Ecaj_0073, Ecaj_0104, and / or Ecaj_0663) described herein may be used as a diagnostic or prophylactic tool for the detection of or immunization against Ehrlichia infection. In particular, the immunoreactive polypeptides described herein may be useful in solution-phase assays or in assays in which the isolated immunoreactive polypeptide is immobilized on a support substrate surface. Alternatively, an immunoreactive polypeptide described herein may be included in a vaccine formulation to induce a protective immune response in a subject, or an immune response against Ehrlichia chaffeensis or Ehrlichia canis.One or more immunoreactive polypeptides can be immobilized on a surface by covalent bonding, encapsulation, or adsorption using methods generally known in the art, and may include the use of crosslinkers, capture molecules, and the like, to which the peptides can be coupled, conjugated, or crosslinked. As shown in the examples below, high-throughput scopes were combined, including bioinformatics analysis to predict antigenicity, in vitro transcription and translation to express proteins in their native conformation, and ELISA to identify a group of immunoreactive E. chaffeensis proteins with unknown function. The complete E. chaffeensis proteome (n=1156) was analyzed using the ANTIGENpro protein antigenicity diagnostic test, which identified 250 proteins with a high antigenicity score (>0.695). Hypothetical proteins (n=93; 35 of 93 <22 kDa) present in this highly antigenic group were investigated in this study, and almost half (n=45) reacted at low to high levels with antibodies in the serum of a patient or a dog infected with E. chaffeensis.chaffeensis; however, 15 proteins were consistently immunoreactive with a panel of patient sera, including six at a high level comparable to the well-defined major immunoreactive TRPs. Most (10 / 15) of these novel immunoreactive proteins were small (<22 kDa) or contained previously diagnosed transmembrane domains. Notably, the immunoreactivity of these proteins was predominantly conformation-dependent, as denaturation significantly affected antibody recognition. In addition, E. canis orthologs (n=12) also reacted with sera from E. canis-infected dogs, including two proteins with immunoreactivity comparable to the “gold standard” TRP19. These proteins could be used, for example, in various modalities, to diagnose ehrlichiosis or to generate an immune response against E. chaffeensis or E.canis in a mammalian subject, such as a human or a dog. I. Immobilized Immunoreactive Polypeptides In some embodiments, an immunoreactive polypeptide provided herein (e.g., in Table 1, Table 2, Table 3, Ecaj_0919, Ecaj_0073, Ecaj_0104, or Ecaj_0663) can be immobilized on the surface of a solid support or substrate. For example, the immunoreactive polypeptide can be immobilized directly or indirectly by coupling, crosslinking, adsorption, encapsulation, or any other method known in the art. By way of non-limiting example, the adsorption of an immunoreactive polypeptide disclosed herein to a well in a microtiter plate or to a membrane can be achieved by contacting the peptide, in a suitable buffer solution, with the surface of the well for an appropriate period of time.The contact time may vary with temperature, but it is usually between one hour and one day when using an amount of peptide ranging from approximately 50 ng to approximately 1 mg, and preferably approximately 250-700 ng or approximately 450-550 ng. In some modalities, an immunoreactive polypeptide disclosed herein is covalently linked to a support substrate by first reacting the support with a reagent that will chemically react with both the support and a functional group (i.e., a cross-link), such as a hydroxyl or amino group, on the peptide. For example, an immunoreactive polypeptide may be cross-linked to a surface through an amine or carboxyl group at each end of the peptide, and a peptide may be cross-linked through a group at each end of the polypeptide (i.e., head-to-tail cross-linked). Such peptomers (i.e., head-to-tail cross-linked or otherwise immobilized peptides) can be used with current diagnostic and therapeutic methods. Several support substrates for the immobilization of polypeptides are known in the art and can be used with an immunoreactive polypeptide described herein, formed from materials such as, for example, latex, polystyrene, nylon, nitrocellulose, cellulose, silica, agarose, inorganic polymers, lipids, proteins, sugars, or magnetic resin. A person skilled in the art may select the support substrate that is suitable for a given application. In particular embodiments of the present invention, a support substrate may be a reaction chamber, a microplate well, a membrane, a filter, paper, an emulsion, a bead, a microbead, a microsphere, a nanocrystal, a nanosphere, a test strip, a card, a glass slide, a microscope slide, a lateral flow apparatus, a microchip, a comb, a silica particle, a magnetic particle, a nanoparticle, or a self-assembling monolayer. II. Detectably Labeled Immunoreactive Polypeptides An immunoreactive polypeptide (e.g., in Table 1, Table 2, Table 3, Ecaj_0919, Ecaj_0073, Ecaj_0104, or Ecaj_0663) can be conjugated or bound to a detectable tag such as, for example, a radioactive isotope, a non-radioactive isotope, a particle tag, a fluorescent tag, a chemiluminescent tag, a paramagnetic tag, an enzyme tag, or a tag ML / E / Zuzi / un yy iz colorimetric. The detectably labeled polypeptide can be used, for example, in diagnostic or prophylactic compositions and methods. In certain embodiments, the polypeptide portion of the detectably labeled immunoreactive polypeptide can be immobilized on a support substrate surface. In other embodiments, the detectable label can be used to immobilize the detectably labeled immunoreactive peptide to a support substrate surface. As used herein, the “detectable tag” is a compound and / or element that can be detected due to its specific functional properties and / or chemical characteristics, the use of which allows the detection of the peptide to which it is attached and / or additional quantification if desired. In some modalities, the detectable tag is a photoluminescent probe, such as a fluorophore or a nanoparticle, such as, for example, a strontium aluminate nanoparticle (for example, see Paterson et al., 2014). Exemplary labels include, but are not limited to, a particulate label such as colloidal gold, a radioactive isotope such as astatine, chromium, chlorine, codalto, codalto, gallium, hydrogen, iodine, indium, iron, phosphorus, rhenium, selenium, sulfide, technetium-99, technetium-99m, or yttrium, a colorimetric label such as dinitrodencene, dansyl chloride, dabsyl chloride, and any azo, cyanine, or triazine dyes or chromophores disclosed in U.S. Patents 5,470,932, 5,543,504 or 6,372,445, all of which are incorporated herein by reference; a paramagnetic label such as chromium (III), manganese (II), iron (III), iron (II), cobalt (II),nickel (II), copper (II), neodymium (III), samarl (III), ytterbium (III), gadolinium (III), vanadium (II), terbium (III), dysprosium (III), holmium (III) or erbium (III), a fluorescent tag such as Alexa 350, Alexa 430, AMCA, BODIPY 630 / 650, BODIPY 650 / 665, BODIPY-FL, BODIPY-R6G, BODIPY-TMR, BODIPY-TRX, Cascade Blue, Cy3, Cy5, 6-FAM, fluorescein isothiocyanate, HEX, 6-JOE, Oregon Green 488, Oregon Green 500, Oregon Green 514, Pacific Blue, REG, rhodamine green, rhodamine red, renografin, ROX, TAMRA, TET, tetramethylrhodamine, and / or Texas Red and Lucifer Yellow, an enzyme tag such as urease, luciferase, alkaline phosphatase, (horseradish) hydrogen peroxidase or glucose oxidase or a chemiluminescent label such as luminol, phthalizidine dione or others disclosed in any of U.S. Patents 4,373,932, 4,220,450, 5,470,723 and U.S. Patent Application 2007 / 0264664, all of which are incorporated herein by reference. III. Methods for producing an immunoreactive polypeptide An immunoreactive polypeptide of the present modalities can be produced using in vitro transcription and translation (IVTT) methods, recombinantly using various cell types (e.g., bacterial cells, mammalian cells, E. coli, yeast cells, insect cells, etc.), or in some cases, synthesized (e.g., using solid-phase synthesis). In some modalities, IVTT and synthetic methods can offer certain advantages over recombinant techniques, as the resulting polypeptides can be produced in highly pure forms without contaminating the bacteria or other proteins that could lead to false-positive reactions when recombinant proteins are used. Consequently, IVTT and synthetic methods have the advantage of lacking many of the costly and labor-intensive purification procedures often associated with recombinant proteins. ΜΛ / Ε / ζυζΊ / un yy iz with the recombinant methodologies. Various approaches to intravenous transfusion technology (IVTT) are known in this technique and can be used in different modalities. IVTT generally involves cell-free methods for the production or synthesis of a protein from DNA. Cell-free systems for protein production can utilize, for example, E. coli extract, protozoan extracts, yeast extracts, human cell extract, wheat germ extract, mammalian extracts, extracts from cultured human cell lines, rabbit reticulocyte lysate, insect cell extract, or reconstituted and purified E. coli components.A variety of commercially available kits exist, for example, RTS (FivePrime, San Francisco, CA), Expressway™ (Life Technologies), high-throughput S30 T7 (Promega), one-step human IVT (Thermo Scientific), WEPRO® (CelIFree Sciences), coupled TNT® (Promega), RTS CECF (5 PRIME), coupled TNT® (Promega), Retic lysate IVT™ (Life Technologies), TNT® T7 (Promega), EasyXpress Insect kit (Qiagen / RÍN A), PURExpress® (New England Biolabs), and PURESYSTEM® (BioComber). Such methods can be used to incorporate non-natural amino acids into proteins, if required. Cell-free expression systems that can be used in various modalities are also described, for example, in Zemella et al., 2015. An isolated immunoreactive protein as described herein can be produced in several ways using an appropriate method known in organic chemistry techniques. For example, peptides can be produced using one of the established solid-phase peptide synthesis techniques, such as those of Merrifield, Carpino, or Atherton [Atherton and Sheppard, 1989]. In some embodiments, peptides can be synthesized using equipment for automated peptide synthesis that is widely available from commercial suppliers such as Perkin Elmer (Foster City, CA), or the peptide can be chemically synthesized using solution-phase techniques such as those described in Carpino et al., 2003 or U.S. Patent Application 2009 / 0005535.In some modalities, shorter peptides or proteins can be synthesized, for example, using solid-phase peptide synthesis (SPPS), solid-phase t-Boc peptide synthesis, or solid-phase Fmoc peptide synthesis. In some embodiments, an immunoreactive protein as described herein can be prepared recombinantly from a nucleic acid encoding the peptide. This nucleic acid can be operationally linked to an expression vector. By way of non-limiting example, an immunoreactive protein can be expressed from a vector and isolated from the growth medium of a host cell comprising the vector. In some embodiments, the immunoreactive protein can be produced in a cell-free system from a nucleic acid encoding the peptide. An immobilized immunoreactive protein, as described herein, can be conjugated, crosslinked, or adsorbed, directly or indirectly, onto the surface of a support substrate. In some embodiments, an immunoreactive protein or peptide immobilized on a support substrate can be synthesized. It is anticipated that virtually any known protein or peptide immobilization method that does not impact the structure or function of the described peptides can be used to immobilize an immunoreactive protein or peptide as described herein.For example, peptide immobilization can be accomplished using a crosslinking or conjugating agent, such as methyl-p-hydroxybenzimidate, N-succinimidyl-3-(4-hydroxyphenyl)propionate, using sulfosuccinimidyl 4-(N-maleimidomethyl)cyclohexane-1-carboxylate (sSMCC), N-[maleimidocaproyloxy]sulfosuccinimidide ester (sEMCS), N-maleimidobenzoyl-N-hydroxysuccinimide ester (MBS), glutaraldehyde, 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide (EDCI), bis-diazobenzidine (BDB), or N-acetyl homocysteine ​​thiolactone (NAHT), and others disclosed in any of U.S. Patents 5,853,744, 5,891,506, 6,210,708, 6,617,142, 6,875,750, 6,951,765, 7,163,677 and 7,282,194, each incorporated herein by reference.Immunoreactive proteins can be conjugated directly and indirectly with any of the commercially available support substrates that have surface coatings comprising crosslinkers, coupling agents, thiol or hydroxyl derivatizing agents, carboxyl or amine reactive groups such as maleic anhydride (e.g., Pierce Immunotechnology Catalog and Handbook, in A12-A13, 1991). In some embodiments, a protein of the invention can also be immobilized using metal chelating complexation, employing, for example, an organic chelating agent such as diethylenetriaminepentaacetic acid anhydride (DTPA); EDTA; N-chloro-o-toluenesulfonamide; and / or antibody-linked tetrachloro-3α-6α-diphenylglycoryl-3 (U.S. Patent Nos. 4,472,509 and 4,938,948, each incorporated herein by reference). Proteins and peptides can also be immobilized by coupling to other peptides or condensation groups immobilized on a surface or present in an immobilization buffer solution such as glutaraldehyde or periodate. They can also be prepared conjugated with fluorescent tags in the presence of such agents or by reaction with an isothiocyanate.A peptide can be attached to a surface by conjugation, crosslinking, or binding to an affinity-binding agent such as biotin, streptavidin, a polysaccharide such as an alginate, a lectin, and the like. In general, regardless of the preparation method or immobilization state, the immunoreactive proteins described herein are preferably prepared in a substantially pure form. Preferably, the immunoreactive proteins are at least approximately 80% pure, more preferably at least approximately 90% pure, and most preferably at least approximately 99% pure. IV. Functional Biological Equivalents Preferred immunoreactive polypeptides or their analogues bind specifically or preferably to an antibody specific to Ehrlichia chaffeensis or Ehrlichia canis. Whether, or to what extent, a particular immunoreactive polypeptide, or its analogue, can bind to an antibody specific to E. chaffeensis can be assessed using an in vitro assay, such as, for example, an enzyme-linked immunosorbent assay (ELISA), immunoblotting, immunoprecipitation, radioimmunoassay (RIA), immunostaining, latex agglutination, indirect hemagglutination assay (IHA), complement fixation, indirect immunofluorescence assay (IFA), nephelometry, or other assays. ML / E / ζυζΊ / un yy iz flow cytometry, chemiluminescence assay, lateral flow immunoassay, U-capture assay, mass spectrometry assay, particle-based assay, inhibition assay and / or avidity assay. An immunoreactive polypeptide of current formulations can be modified to contain amino acid substitutions, insertions, and / or deletions that do not alter its interactions with the binding regions of anti-Ehrlichia antibodies. A biologically functional equivalent of an immunoreactive polypeptide derived from an Ehrlichia protein could be a molecule possessing similar or desirable characteristics, namely, the binding of Ehrlichia-specific antibodies. As a non-limiting example, certain amino acids can be substituted for other amino acids in an immunoreactive polypeptide described herein without appreciable loss of interactive capability, as demonstrated by the binding of antibodies without detectable changes.Therefore, an immunoreactive polypeptide described herein (or a nucleic acid encoding such a polypeptide) that is modified in sequence and / or structure, but whose utility or biological activity remains unchanged, is considered to be within the scope of these embodiments. The immunoreactive polypeptide may have, for example, at least 90%, 95%, or 99% sequence identity with a wild-type E. chaffeensis polypeptide, and in some embodiments, the immunoreactive protein may have 1, 2, 3, 4, 5, or more amino acid substitutions, insertions, and / or deletions compared to the corresponding wild-type E. chaffeensis or E. canis polypeptide. Furthermore, it is well understood by those skilled in the art that inherent in the definition of a biologically equivalent functional peptide is the concept that there is a limit to the number of changes that can be made within a defined portion of the molecule while maintaining an acceptable level of equivalent biological activity. Biologically equivalent functional polypeptides are therefore defined herein as those peptides in which some, but not most or all, of the amino acids may be substituted. Of course, a plurality of different peptides with different substitutions can be readily prepared and used according to the invention. The person in the field is also aware that when certain residues are shown to be particularly important for the biological or structural properties of a peptide—for example, residues in specific epitopes—these residues generally cannot be interchanged. It is anticipated that a mutation in an immunoreactive peptide or polypeptide described herein could result in a loss of species specificity and, in turn, reduce the usefulness of the resulting peptide for use in the methods of the modalities presented. Accordingly, polypeptides that are antigenic (for example, that bind specifically to anti-Ehrlichia antibodies) and comprise conservative amino acid substitutions are included in the modalities presented. Conservative substitutions are the least likely to drastically alter the activity of a protein.A “conservative amino acid substitution” refers to the substitution of one amino acid for a chemically similar amino acid, i.e., the substitution of nonpolar amino acids for other nonpolar amino acids; substitution of polar amino acids for other polar amino acids, acid residues for other acidic amino acids, etc. ma / e / zuzi / un yy i ¿ Amino acid substitutions, such as those that can be used to modify an immunoreactive polypeptide disclosed herein, are generally based on the relative similarity of amino acid side-chain substituents, such as their hydrophobicity, hydrophilicity, charge, size, and the like. An analysis of the size, shape, and type of amino acid side-chain substituents reveals that arginine, lysine, and histidine are all positively charged residues; that alanine, glycine, and serine are of similar size; and that phenylalanine, tryptophan, and tyrosine all have generally similar shapes. Accordingly, based on these considerations, arginine, lysine, and histidine; alanine, glycine, and serine; and phenylalanine, tryptophan, and tyrosine are defined herein as biologically functional equivalents. The invention also includes isoforms of the immunoreactive polypeptides of E. chaffeensis disclosed herein. An isoform contains the same number and types of amino acids as an E. chaffeensis polypeptide as described herein, but the isoform has a different molecular structure. The isoforms contemplated by the present embodiments are those that have the same properties as a polypeptide as described herein. Non-standard amino acids can be incorporated into proteins by chemical modification of existing amino acids or by de novo synthesis of a polypeptide described herein. A non-standard amino acid refers to an amino acid that differs in chemical structure from the twenty standard amino acids encoded by the genetic code, and a variety of non-standard amino acids are well known in the art. In selected embodiments, the present invention incorporates a chemical derivative of an immunoreactive polypeptide described herein. “Chemical derivative” refers to a peptide having one or more residues chemically derivatized by reaction of a functional side group and retaining biological activity and utility. Such derivatized polypeptides include, for example, those in which free amino groups have been derivatized to form specific salts or have been derivatized by alkylation and / or acylation, p-toluenesulfonyl groups, carbobenzoxy groups, t-butyloxycarbonyl groups, chloroacetyl, formyl, or acetyl groups, among others. Free carboxyl groups may be derivatized to form organic or inorganic salts, methyl and ethyl esters, or other types of esters or hydrazides, and preferably amides (primary or secondary).Chemical derivatives may include polypeptides comprising one or more naturally occurring amino acids derived from the twenty standard amino acids. For example, serine can be substituted with 4-hydroxyproline, and ornithine can be substituted with lysine. It should be noted that all amino acid residue sequences are represented in this document by formulas whose left-to-right orientation is in the conventional amino-to-carboxyl-terminus direction. Furthermore, it should be noted that a hyphen at the beginning or end of an amino acid residue sequence indicates a peptide bond to an additional sequence of one or more amino acid residues. The amino acids described above are preferred in the L-isomeric form. However, residues in the D-isomeric form may be substituted with any L-amino acid residue, provided that the protein retains the desired functional properties described herein. μλ / ε / zuzi / un yy i ¿ According to the standard protein nomenclature, the abbreviations for amino acid residues are known in the technique. In addition to the biological functional equivalents discussed above, it is envisaged that structurally similar compounds can be formulated to mimic key parts of an immunoreactive peptide described herein. Such compounds, which may be termed peptidomimetics, can be used in the same manner as the immunoreactive peptides described herein and are therefore also functional equivalents. Methods for generating specific structures are disclosed, for example, in Mizuno et al., 2017, as well as in U.S. patents 5,446,128; 5,710,245; 5,840,833; 5,859,184; 5,440,013; 5,618,914; and 5,670,155. V. Methods for detecting Ehrlichia infection Ehrlichiosis in humans generally refers to infections caused by obligate intracellular bacteria in the family Anaplasmataceae, primarily in the genera Ehrlichia and Anaplasma. Most cases of human ehrlichiosis (HE) are caused by three distinct species: Ehrlichia chaffeensis, the most important of these (Dumler et al., 2007). Ehrlichia infections in animals are also called ehrlichiosis, along with a variety of diseases caused by a diverse group of genera including Ehrlichia, Anaplasma, Neorickettsia, and Cowdria (Dumler et al., 2007). Ehrlichia infections are mainly maintained in monocytes or granulocytes and studies have shown that antibodies play an essential role in the immune response to Ehrlichia infection (Feng and Walker, 2004; Winslow et al., 2003; Winslow et al., 2000; Yager et al., 2005). Accordingly, selected embodiments of the present invention provide methods for detecting antibodies that bind specifically to an Ehrlichia organism in a sample. One such method involves contacting an isolated Ehrlichia immunoreactive polypeptide (e.g., from Tables 1, 2, and 3, Ecaj_0919, Ecaj_0073, Ecaj_0104, or Ecaj_0663) with the test sample under conditions that permit the formation of peptide-antibody complexes and the detection of these complexes. In these embodiments, the detection of peptide-antibody complexes indicates that antibodies specific to an Ehrlichia organism are present in the test sample, and the absence of peptide-antibody complexes indicates that antibodies specific to an Ehrlichia organism are not present in the test sample. In multiple modalities, the detection of an immunoreactive polypeptide disclosed herein bound to an Ehrlichia-specific antibody (i.e., a peptide-antibody complex) can be achieved using an enzyme-linked immunoassay (e.g., non-competitive or competitive ELISA), a radioimmunoassay, immunoprecipitation, a fluorescence immunoassay, a chemiluminescent assay, an immunoblotting assay, a lateral flow assay, a flow cytometry assay, a mass spectrometry assay, a latex agglutination, an indirect hemagglutination (IHA) assay, a complement fixation, an inhibition assay, an avidity assay, a reagent strip test, or a particle-based assay. In some preferred modalities, the peptide-antibody complexes described herein are detected using a ΜΛ / Ε / ζυζΊ / an yy iz enzyme-linked immunoassay, a lateral flow assay or a particle-based assay. As used herein, a sample is any sample that comprises or is suspected of comprising antibodies. Preferably, the sample is whole blood, sputum, serum, plasma, saliva, cerebrospinal fluid, or urine. In some modalities, the sample is a blood, serum, or plasma sample obtained from a subject or patient. Ehrlichiosis, caused by infection with Ehrlichia chaffeensis in humans, presents with flu-like symptoms such as fever, chills, headache, and muscle aches. In more severe cases, nausea, loss of appetite, weight loss, abdominal pain, cough, diarrhea, and altered mental status may also occur. Ehrlichiosis in humans is potentially fatal. In dogs, ehrlichiosis is often caused by the bacterium Ehrlichia chaffeensis or Ehrlichia canis and progresses through three phases: an acute phase, a subclinical phase, and a chronic phase. The acute phase typically lasts for weeks after infection and presents with symptoms similar to those of human ehrlichiosis, such as fever, lethargy, loss of appetite, difficulty breathing, and joint pain and stiffness. It can also include more severe symptoms such as anemia, depression, bruising, and enlarged lymph nodes, liver, and spleen. The subclinical phase can persist for years and is most often asymptomatic, although antibodies against Ehrlichia antigens may be detected.The chronic phase of Ehrlichia infection typically presents with recurring symptoms such as weight loss, anemia, neurological dysfunction, hemorrhage, eye inflammation, leg edema, and fever, and exhibits a blood profile that often leads to a misdiagnosis of leukemia. An Ehrlichia infection that progresses to the chronic stage is usually fatal. The nonspecific symptoms of Ehrlichia infection and their resemblance to mild and severe influenza symptoms make diagnosing Ehrlichiosis in humans and dogs difficult. Diagnosis can be further hampered by current laboratory testing procedures for Ehrlichia infection, which are not point-of-care tests—meaning the tests are not available in most hospitals, clinics, and medical or veterinary practices where a patient might receive treatment. Accordingly, selected embodiments of the present invention provide methods for identifying an Ehrlichia infection in a mammalian subject. Such a method may involve contacting a sample from the subject with an isolated immunoreactive polypeptide described herein (e.g., from Table 1, Table 2, Table 3, Ecaj_0919, Ecaj_0073, Ecaj_0104, or Ecaj_0663) under conditions that allow peptide-antibody complexes to form and be detected. In these embodiments, the detection of peptide-antibody complexes is an indication that the subject has an Ehrlichia infection. The Ehrlichia organism may be either Ehrlichia chaffeensis or Ehrlichia canis. In some embodiments, the subject is a human or a dog.As with other methods described in this document, the detection step can be achieved using any appropriate type of assay known in the art and can preferably be achieved using a lateral flow assay or an ELISA. μλ / ε / zuzi / un yy iz The terms “subject” and “patient” are used interchangeably in this document and may refer to a mammal, especially a human or a dog. In certain contexts, a “subject” or “patient” refers to a mammalian Ehrlichia host (i.e., an animal infected with an Ehrlichia organism). An Ehrlichia host may be, for example, a human or non-human primate, bovine, canine, caprine, guinea pig, crow, spiny-tailed, equine, feline, goat, hare, rabbit, lupine, murine, ovine, porcine, frog, vulpine, and the like, including livestock, zoological specimens, exotic animals, as well as companion animals, pets, and any animal under the care of a veterinarian. A subject may or may not be infected with an Ehrlichia organism, and a subject may be a mammal suspected of being infected with an Ehrlichia organism. Without wishing to be bound to any particular theory, the immunoreactive Ehrlichia polypeptides described herein each comprise at least a portion of a major Ehrlichia epitope that explains species-specific immunogenicity in humans and animals. The term “epitope” is used herein to denote the portion of an immunogenic substance that is specifically identified, recognized, and bound to an antibody or cell surface receptor of a host immune system that has mounted an immune response to the immunogenic substance, as determined by any method known in the art (see, for example, Geysen et al., 1984). Accordingly, a “species-specific” epitope is one that can be used to differentiate one species of the genus Ehrlichia from another. Specific modalities relate to the determination of whether a subject has been immunized against Ehrlichia or is actively infected with an Ehrlichia organism. In these modalities, the method comprises contacting a sample from a subject with at least one isolated immunoreactive polypeptide (e.g., from Table 1, Table 2, Table 3, Ecaj_0919, Ecaj_0073, Ecaj_0104, or Ecaj_0663) that is not a component of an Ehrlichia vaccine and detecting whether an antibody in the sample binds specifically to the isolated Ehrlichia immunoreactive polypeptide. According to the method, if an antibody in the sample binds specifically to the isolated Ehrlichia immunoreactive polypeptide, then the subject has an active Ehrlichia infection, and if an antibody does not bind specifically to the isolated Ehrlichia immunoreactive peptide, then the subject is either previously immunized with an Ehrlichia vaccine or is not infected with an Ehrlichia organism.An Ehrlichia organism can be an E. chaffeensis organism or an E. canis organism. An Ehrlichia immunoreactive polypeptide (e.g., from Tables 1, 2, 3, Ecaj_0919, Ecaj_0073, Ecaj_0104 or Ecaj_0663) can be used to bind an Ehrlichia-specific or E. chaffeensis-specific antibody using a variety of methods or kits.The specific binding between an antibody and an Ehrlichia polypeptide as disclosed herein can be assessed by any appropriate method known in the art, including but not limited to enzyme-linked immunosorbent assay (ELISA), non-competitive ELISA, competitive ELISA, immunoblotting, immunoprecipitation, radioimmunoassay (RIA), immunostaining, latex agglutination, indirect hemagglutination assay (IHA), complement fixation, indirect immunofluorescence assay (FA), nephelometry, flow cytometry assay, chemiluminescence assay, lateral flow immunoassay, U-capture assay, mass spectrometry assay, particle-based assay, inhibition assay, and avidity assay.Exemplary methods for detecting the binding of an Ehrlichia-specific antibody to an Ehrlichia immunoreactive polypeptide as described herein may include, for example, an ELISA performed in a microplate, a lateral flow assay performed using a test strip or lateral flow device, or a particle-based suspension multiplexing array assay using the Bio-Plex® system (Bio-Rad Laboratories, Hercules, CA, USA). A. ELISA In certain formulations, the detection of a peptide-antibody complex described herein is achieved using an enzyme-linked immunosorbent assay (ELISA). This assay can be performed by first contacting an immunoreactive Ehrlichia polypeptide (e.g., in Table 1, Table 2, Table 3, Ecaj_0919, Ecaj_0073, Ecaj_0104, or Ecaj_0663) immobilized on a solid support, commonly the well of a microtiter plate, with the sample, allowing peptide-specific antibodies within the sample to bind to the immobilized peptide. Subsequently, the unbound sample is removed from the immobilized peptide, and a detection reagent capable of binding to the immobilized antibody-polypeptide complex is added. The amount of detection reagent that remains unbound to the solid support is then determined using a method appropriate for the specific detection reagent. In some formulations, the detection reagent contains a binding agent (such as, for example, Protein A, Protein G, immunoglobulin, lectin, or free antigen) conjugated or covalently bound to a reporter group or tag. Exemplary reporter groups or tags include enzymes (such as horseradish peroxidase), substrates, cofactors, inhibitors, dyes, radioisotopes, luminescent groups, fluorescent groups, and biotin. Conjugation of the binding agent to the reporter group or tag can be achieved using standard methods known to technicians in the field. Common binding agents can also be purchased conjugated to a variety of reporter groups from many commercial sources (for example, Zymed Laboratories, San Francisco, CA; and Pierce, Rockford, IL). In one aspect of the present invention, the presence or absence of Ehrlichia-specific antibodies can be determined in the sample by comparing the level of a detected signal from a reporter group or label in the sample with the level of a signal corresponding to a control sample or predetermined cutoff value. In certain embodiments, the cutoff value may be the average mean signal obtained when the immobilized Ehrlichia immunoreactive polypeptide is incubated with samples from an uninfected subject. The cutoff value may be determined by a statistical method or a computer program. B. Lateral flow tests Lateral flow assays may also be referred to as immunochromatographic assays (ICS) or simply strip tests. In general, a lateral flow assay is a type of assay in which the test sample flows laterally along a solid substrate by capillary action, or alternatively, under fluidic control. These assays are typically inexpensive, require a very small amount (e.g., a drop) of sample, and can usually be performed reproducibly with minimal training. The cost-effectiveness and robustness of many lateral flow assay formats make this type of test ideal for identifying Ehrlichia infection (e.g., E. chaffeensis) at the point of care, which can be particularly important when the subject is, for example, a human or dog exhibiting detectable antibodies during the treatable acute phase of the infection. Exemplary lateral flow device formats include, but are not limited to, a test strip, a card, a chip, a microscope slide, and a cassette, and it is widely demonstrated in the art that the choice of format depends largely on the characteristics of a particular assay. Accordingly, lateral flow devices are now present in human and veterinary medicine and are quite varied, providing many options for the technologist typically trained to detect a peptide-antibody complex in a sample using a lateral flow assay (see any of U.S. Patents 7,344,893, 7,371,582, 6,136,610 and U.S. Patent Applications 2005 / 0250141 and 2005 / 0047972 or Koczula et al. (2016), each incorporated herein by reference).By way of non-limiting example, a sample from a subject suspected of having an Ehrlichia infection is applied to a lateral flow device comprising at least a sample zone and a binding zone. The sample may be a serum sample and may be drawn laterally from the sample zone to the binding zone, which comprises an Ehrlichia immunoreactive polypeptide described herein (e.g., from Table 1, Table 2, Table 3, Ecaj_0919, Ecaj_0073, Ecaj_0104, or Ecaj_0663) immobilized to a surface of the lateral flow device. In this example, the binding of the Ehrlichia immunoreactive polypeptide immobilized on the lateral flow device is an indication that Ehrlichia-specific antibodies are present in the subject sample, indicating an Ehrlichia infection in the subject, such as an E. chaffeensis or E. canis infection. In related modalities, an ELISA assay as described above can be performed in a rapid flow, lateral flow, or strip test format, where the antigen is immobilized on a membrane, such as a nitrocellulose membrane. In this continuous flow test, Ehrlichia antibodies within the sample bind to the immobilized Ehrlichia immunoreactive peptide as the sample passes through the membrane. A detection reagent, such as a gold-labeled protein, fluorophore, or chromophore, binds to the peptide-antibody complex as the solution containing the detection reagent flows through the membrane.The peptide-antibody complexes bound to the detection reagent can be detected, as appropriate for the detection reagent used (e.g., based on the presence or absence of a visibly detectable color or fluorescent label, a nanoparticle, a rare earth luminescent nanoparticle, a luminous nanoparticle, a strontium aluminate nanoparticle (e.g., see Paterson et al., 2014 and Wang et al., 2017, etc.). ML / E / ζυζΊ / un yy iz In one aspect, a continuous-flow ELISA can be performed in which one end of the membrane, on which an Ehrlichia immunoreactive peptide is immobilized (e.g., from Table 1, 2, or 3), can be immersed in a solution containing the sample, or the sample can be added to an area (i.e., a sample zone) at one end of the membrane. The sample migrates along the membrane through a region (i.e., a tide zone) comprising the detection reagent and flows into the area (i.e., a binding zone) comprising the immobilized Ehrlichia immunoreactive peptide. An accumulation of detection reagent in the binding zone indicates the presence of Ehrlichia-specific antibodies in the sample. Typically, a continuous-flow ELISA may include a detection reagent applied to a test strip in a pattern, such as a line, that can be visually read. As with other lateral-flow tests, the absence of such a pattern typically indicates a negative result. It is within the skill of a material technician to select an amount of Ehrlichia immunoreactive polypeptide for membrane immobilization that will produce a visually discernible pattern when the biological sample contains a level of antibodies sufficient to generate a positive signal in a standard-format ELISA. Preferably, the amount of peptide immobilized on the membrane ranges from approximately 25 ng to approximately 1 mg. C. Particle-based tests In general, particle-based assays utilize a capture-binding partner, such as an antibody or antigen in the case of an immunoassay, that coats the surface of particles, such as microbeads, crystals, chips, or nanoparticles. Particle-based assays can be effectively multiplexed or modified to test numerous variables of interest by incorporating fluorescently labeled particles or particles of varying sizes into a single assay, each coated or conjugated with one or more labeled capture-binding partners. The use of sensitive detection and amplification with particle-based assay platforms known in the art has resulted in numerous flexible and sensitive assay systems to choose from when performing a method described herein. For example, a particle multiplexing assay such as the Bio-Plex® Suspension Multiplexing Array Assay System available from Bio-Rad Laboratories, Inc.(Hercules, CA) and Luminez, Inc. (Austin, TX) may be useful for identifying Ehrlichia antibodies in a sample. In one aspect, the present invention involves immobilizing an isolated Ehrlichia immunoreactive polypeptide (e.g., from Table 1, Table 2, Table 3, Ecaj_0919, Ecaj_0073, Ecaj_0104, or Ecaj_0663) on a particle surface for use in a particle-based immunoassay. As described herein, methods for immobilizing peptides on support surfaces are well known in the art. In a preferred embodiment, a labeled immunoreactive polypeptide described herein is immobilized on a particle surface, and the peptide-particle complex is used in an ELISA or flow cytometry assay according to established protocols. VI. Composition of the Ehrlichia vaccine Previous work has shown that Ehrlichia proteins that induce antibody responses can provide protective immune responses; therefore, in some modalities, A protein from Ehrlichia provided herein (e.g., in Table 1, Table 2, Table 3, Ecaj_0919, Ecaj_0073, Ecaj_O104, or Ecaj_0663) may be included in a pharmaceutical composition such as a vaccine composition for administration to a mammalian or human subject. For example, protection against E. chaffeensis infection has been demonstrated with epitope-specific antibodies directed against OMP and TRP in in vitro and animal models (Kuriakose et al., 2012; L¡ et al., 2002; L¡ et al., 2001), demonstrating that Ehrlichia proteins that elicit strong antibody responses to linear epitopes are protective. In selected embodiments, it is envisaged that an immunoreactive Ehrlichia polypeptide (e.g., from Table 1, Table 2, Table 3, Ecaj_0919, Ecaj_0073, Ecaj_0104, or Ecaj_0663) may be included in a vaccine composition and administered to a subject (e.g., a human or dog) to induce a protective immune response in the subject that may prevent or substantially improve infection in the subject by an Ehrlichia organism such as Ehrlichia chaffeensis or Ehrlichia canis. A vaccine composition for pharmaceutical use in a subject may comprise an immunoreactive polypeptide from Table 1, 2, or 3 and a pharmaceutically acceptable vehicle. The phrases “pharmaceutical,” “pharmaceutically acceptable,” or “pharmacologically acceptable” refer to molecular entities and compositions that do not produce an adverse, allergic, or other adverse reaction when administered to an animal, such as, for example, a human, where appropriate. As used herein, “pharmaceutically acceptable vehicle” includes any and all solvents, dispersion media, coatings, surfactants, antioxidants, preservatives (e.g., antibacterial agents, antifungal agents), isotonic agents, absorption retardants, salts, preservatives, drugs, drug stabilizers, gels, binders, excipients, disintegrating agents, lubricants, sweetening agents, flavoring agents, colorants, similar materials, and combinations thereof, as would be known to a person skilled in the art (see, for example, Remington’s Pharmaceutical Sciences, 18th Ed.).Mack Printing Company, 1289-1329, 1990, incorporated herein by reference). Except to the extent that any conventional vehicle is incompatible with the active ingredient, its use is contemplated in the vaccine compositions of the present invention. As used herein, a “protective immune response” refers to a response of the immune system of a mammalian host to an Ehrlichia antigen that results in increased recognition of the antigen and antibody production by the mammalian host’s immune system following subsequent exposure to an Ehrlichia pathogen. A protective immune response can substantially reduce or prevent symptoms resulting from subsequent exposure to Ehrlichia chaffeensis or Ehrlichia canis. In some embodiments, a vaccine composition of the present invention may comprise an immunoreactive polypeptide (for example, having a sequence that has at least approximately 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, or 100% sequence identity with a polypeptide listed in Table 1 or, more preferably, in Table 2 or Table 3). In some embodiments, a vaccine composition comprising the immunoreactive polypeptide may be used. ΜΛ / Ε / ΖυΖΊ / un I z to induce a protective immune response against Ehrlichia chaffeensis or Ehrlichia canis (for example, in a human subject or dog). A medical technician will appreciate that the actual dose of a vaccine composition administered to an animal or human patient can be determined by physical and physiological factors such as body weight, severity of the condition, the type of disease being treated, prior or concurrent therapeutic interventions, patient idiopathic factors, and the route of administration. The physician responsible for administration will, in any case, determine the concentration of active ingredient(s) in a composition and the appropriate dose for the individual subject. In certain formulations, vaccine compositions may comprise, for example, at least approximately 0.1% of an Ehrlichia immunoreactive polypeptide (e.g., from Table 1, Table 2, Table 3, Ecaj_0919, Ecaj_0073, Ecaj_0104, or Ecaj_0663). In other formulations, the active compound may comprise from approximately 2% to approximately 75% of the unit weight, or from approximately 25% to approximately 60%, for example, and any range derived therefrom. As with many vaccine compositions, the frequency of administration, as well as the dosage, will vary among members of an animal or human population in ways predictable by a technician skilled in immunology. By way of a non-limiting example, pharmaceutical compositions and vaccines may be administered by injection (e.g., intracutaneous, intramuscular, intravenous, or subcutaneous), intranasally (e.g., by aspiration), or orally.Between 1 and 3 doses can be administered over a period of 1 to 36 weeks. Preferably, 2 doses are given at 34-month intervals, and booster vaccinations can be administered periodically thereafter. In some formulations, an “adequate dose” is an amount of an immunoreactive polypeptide that, when administered as described above, is capable of generating an immune response in an immunized patient sufficient to protect the subject from Ehrlichia infection upon subsequent exposure to Ehrlichia organisms. Generally, the amount of peptide present in an adequate dose (or produced in situ by the nucleic acid in a dose) can range from approximately 1 pg to approximately 500 mg per kg of host, typically from approximately 10 pg to approximately 10 mg, preferably from approximately 100 pg to approximately 1 mg, and most preferably from approximately 100 pg to approximately 100 micrograms. A vaccine composition of the present invention may comprise different types of vehicles depending on whether it is to be administered in solid, liquid, or aerosol form, and whether it needs to be sterile for routes of administration such as injection. A vaccine composition disclosed herein may be administered by intramuscular, intradermal, subcutaneous, intravenous, intra-arterial, intraperitoneal, intralesional, intracranial, intra-articular, intraprostatic, intrapleural, intratracheal, intranasal, intravitreal, intravaginal, intrarectal, intraperitoneal, intramuscular, topical, intratumoral, intramuscular, intraperitoneal, subconjunctival, intravesical, mucosal, intrapericardial, local, oral, intranasal, or by inhalation, injection, infusion, continuous infusion, lavage, or local perfusion.A vaccine composition may be administered to a subject via a catheter, in creams, in lipid compositions, by ballistic particle delivery, or by any other method or any combination thereof as would be known to a person skilled in the art (see, for example, Remington: The Science and Practice of Pharmacy, 21st Ed. Lippincott Williams and Wilkins 2005, incorporated herein by reference). Although any suitable vehicle known to those skilled in the art may be used in the vaccine compositions of this invention, the type of vehicle will vary depending on the mode of administration. For parenteral administration, such as subcutaneous injection, the vehicle preferably comprises water, saline solution, alcohol, a fat, a wax, or a buffer solution. For oral administration, any of the foregoing vehicles or a solid vehicle, such as mannitol, lactose, starch, magnesium stearate, sodium saccharin, talc, cellulose, glucose, sucrose, and magnesium carbonate, may be used. Biodegradable microspheres (e.g., polylactic galactide) may be employed as vehicles for the pharmaceutical compositions of this invention. Biodegradable microspheres are disclosed, for example, in U.S. Patents 4,897,268 and 5,075,109. Of particular interest in one aspect of the present invention is a vaccine composition that can be administered by microstructured ballistic or transdermal particle delivery. Microstructures as vaccine delivery vehicles are a desirable configuration for vaccine applications and are widely known in the art (e.g., U.S. Applications 5,797,898, 5,770,219, and 5,783,208 and U.S. Patent Application 2005 / 0065463). Such a vaccine composition formulated for ballistic particle delivery may comprise an immunoreactive polypeptide isolated from Tables 1, 2, or 3 immobilized on a support substrate surface. In these embodiments, a support substrate may include, but is not limited to, a microcapsule, a microparticle, a microsphere, a nanocapsule, a nanoparticle, a nanosphere, or a combination thereof. The microstructures or ballistic particles that serve as a support substrate for an Ehrlichia immunoreactive polypeptide described herein may be composed of biodegradable and non-biodegradable materials, and such support substrates may be composed of synthetic polymers, silica, lipids, carbohydrates, proteins, lectins, ionic agents, crosslinkers, and other microstructure components available in the art. The protocols and reagents for immobilizing a peptide of the invention on a support substrate composed of such materials are widely available commercially and in the art. In other embodiments, a vaccine composition comprises an immobilized or encapsulated immunoreactive polypeptide (e.g., from Table 1, Table 2, Table 3, Ecaj_0919, Ecaj_0073, Ecaj_0104, or Ecaj_0663) and a carrier substrate. In these embodiments, a carrier substrate may include, but is not limited to, a lipid microsphere, a lipid nanoparticle, an ethosome, a liposome, a niosome, a phospholipid, a sphingosome, a surfactant, a transferosome, an emulsion, or a combination thereof. The formation and use of liposomes and other lipid nano- and microcarrier formulations is generally known to those skilled in the art, and the use of liposomes, microparticles, nanocapsules, and the like has gained widespread use in the administration of ML / E / Zuzi / un yy iz therapeutic products (e.g., U.S. Patent 5,741,516, specifically incorporated herein in its entirety by reference). Several methods of liposome and liposome-like preparations as potential pharmaceutical vehicles have been reviewed, including peptide encapsulation (U.S. Patents 5,567,434; 5,552,157; ​​5,565,213; 5,738,868 and 5,795,587, each specifically incorporated herein in its entirety by reference). In addition to the methods of administration described herein, several alternative techniques for administering the disclosed vaccine compositions are also contemplated. By way of non-limiting example, a vaccine composition may be administered by sonophoresis (i.e., ultrasound), which has been used and described in U.S. Patent 5,656,016 to improve the rate and efficacy of drug penetration into and through the circulatory system; intraosseous injection (U.S. Patent 5,779,708); or feedback-controlled administration (U.S. Patent 5,697,899). Each of the patents in this paragraph is specifically incorporated herein by reference in its entirety. Any of a variety of adjuvants may be used in the vaccines of this invention to non-specifically enhance the immune response. Most adjuvants contain a substance designed to protect the antigen from rapid catabolism, such as aluminum hydroxide or mineral oil, and a non-specific stimulator of immune responses, such as lipid A, Bordetella pertussis, or Mycobacterium tuberculosis. Suitable adjuvants are commercially available, such as Freund's Incomplete Adjuvant and Freund's Complete Adjuvant (Difeo Laboratories, Detroit, Michigan) and Merck Adjuvant 65 (Merck and Company, Inc., Rahway, NJ). Other suitable adjuvants include alum, biodegradable microspheres, monophosphoryl lipid A, and quil A. A polypeptide can be formulated in a neutral composition or as a salt. Pharmaceutically acceptable salts include acid addition salts (formed from the free amino groups of the protein) derived from inorganic acids such as hydrochloric or phosphoric acid, or organic acids such as acetic, oxalic, tartaric, mandelic, and similar acids. Salts formed from free carboxyl groups can also be derived from inorganic bases such as sodium, potassium, ammonium, calcium, or ferric hydroxides, and organic bases such as isopropylamine, trimethylamine, histidine, procaine, and similar compounds. In any case, the composition may include several antioxidants to slow the oxidation of one or more components. Additionally, the prevention of microbial growth can be achieved through preservatives such as various antibacterial and antifungal agents, including, but not limited to, parabens (e.g., methylparabens, propylparabens), chlorobutanol, phenol, sorbic acid, thimerosal, or combinations thereof. Sterile injectable solutions are prepared by incorporating the required amount of active peptides into the appropriate solvent with several of the other ingredients listed above, as required, followed by sterilization by filtration. Dispersions are generally prepared by incorporating several sterilized active ingredients into a sterile vehicle containing the basic dispersion medium and / or the other ingredients. For sterile powders used in the preparation of sterile injectable solutions, suspensions, or emulsions, the preferred methods of preparation are vacuum drying or lyophilization techniques that produce a powder of the active ingredient plus any desired additional ingredients from a previously sterile, filtered liquid medium.The liquid medium should be adequately buffered if necessary, and the liquid diluent should be isotonic before injection with sufficient saline or glucose solution. This is particularly relevant for preparing highly concentrated compositions for direct injection, where the use of DMSO as a solvent is expected to result in extremely rapid penetration, releasing high concentrations of the active agents to a small area. The composition must be stable under manufacturing and storage conditions and must be protected from contamination by microorganisms, such as bacteria and fungi. It is desirable that endotoxin contamination be kept at a minimum safe level, for example, less than 0.5 ng / mg of protein. In particular modalities, prolonged absorption of an injectable composition can be achieved by using absorption-delaying agents in the compositions, such as aluminum monostearate, gelatin, or combinations thereof. Vil. Ehrlichia detection and vaccination kits Several embodiments of the present invention relate to kits for detecting antibodies in a sample that bind specifically to an Ehrlichia organism, such as E. chaffeensis or E. canis. The kits can be used for the diagnosis or identification of an Ehrlichia infection in a subject. In other embodiments, the invention provides kits for determining whether a subject has been immunized against Ehrlichia or is actively infected with an Ehrlichia organism. In still other embodiments, kits are provided for vaccinating a subject against Ehrlichia chaffeensis infection, and in some embodiments, it is anticipated that the composition can be used to provide a protective immune response against Ehrlichia canis infection. In selected embodiments, a kit of the present invention can be used to perform a method disclosed herein. For example, a kit may be suitable for detecting Ehrlichia antibodies in a sample, for identifying an individual infected with Ehrlichia, for determining whether a subject has been immunized against Ehrlichia or is actively infected with an Ehrlichia organism, or for vaccinating a subject against the Ehrlichia organism. In these modalities, one or more immunoreactive peptides (e.g., from Table 1, 2 or 3, or a polypeptide having at least approximately 95% or more sequence identity with a polypeptide from Table 1, 2 and 3; and / or Ecaj_0919, Ecaj_0073, Ecaj_0104, Ecaj_0663 or a polypeptide having at least approximately 95% or more sequence identity with Ecaj_0919, Ecaj_0073, Ecaj_0104, Ecaj_0663) may be included in the kit.The Ehrlichia immunoreactive polypeptide in the kit can be detectably labeled or immobilized on a surface of a support substrate included in the kit. The immunoreactive polypeptides can be provided in the kit, for example, in a suitable form, such as sterile, lyophilized, or both. The support substrate included in a kit of the invention can be selected according to the method to be performed. By way of non-limiting example, a support substrate can be a multi-well plate or microplate, a membrane, a filter, paper, an emulsion, a bead, a microbead, a microsphere, a nanobead, a nanosphere, a nanoparticle, an ethosome, a liposome, a niosome, a transferosome, a test strip, a card, a celluloid strip, a glass slide, a microscope slide, a biosensor, a lateral flow apparatus, a microchip, a comb, a silica particle, a magnetic particle, or a self-assembling monolayer. As appropriate for the method being performed, a kit may further comprise one or more apparatuses for administering a composition to a subject or for otherwise manipulating a composition of the invention. By way of non-limiting example, a kit may include an apparatus that is a syringe, a dropper, a ballistic particle applicator (e.g., the applicators described in U.S. Patents 5,797,898, 5,770,219, and 5,783,208 and U.S. Patent Application 2005 / 0065463), a spatula, a micro-object cover, a test strip holder or cover, and the like. A detection reagent for labeling a component of the equipment may optionally be included in equipment for performing a method of the present invention. In particular embodiments, the labeling or detection reagent is selected from the group comprising reagents commonly used in the art and including, without limitation, radioactive elements, enzymes, UV-absorbing molecules, and fluorophores such as fluorescein, rhodamine, auramine, Texas Red, AMCA Blue, and Lucifer Yellow. In other embodiments, a kit is provided comprising one or more containers and a BST protein agent already labeled with a detection reagent selected from a group comprising a radioactive element, an enzyme, a UV-absorbing molecule, and a fluorophore. In particular embodiments, the present invention provides a kit for detecting anti-Ehrlichia antibodies in a sample that can also be used to identify an Ehrlichia infection in a subject, and / or to determine whether a subject has been immunized against Ehrlichia or is actively infected with an Ehrlichia organism. Such a kit may comprise one or more immunoreactive polypeptides (e.g., Table 1, 2, or 3, or having at least approximately 95% sequence identity with a polypeptide of Table 1, 2, or 3; Ecaj_0919, Ecaj_0073, Ecaj_0104, or Ecaj_0663), and the peptides may be labeled and detectably immobilized on one or more support substrates included in the kit. In some embodiments, a kit comprises an immunoreactive polypeptide from Table 1, 2, or 3, or having approximately 95% or more sequence identity with the polypeptide in Table 1, 2, or 3. In some embodiments, a kit comprises an immunoreactive polypeptide comprising or consisting of Ecaj_0919, Ecaj_0073, Ecaj_0104, or Ecaj_0663. The peptides may be immobilized on one or more separate lateral flow assay devices, such as nitrocellulose reagent strips. In these embodiments, each reagent strip may further comprise a detection reagent, for example, a chromophore-labeled protein A. Such a kit may further comprise one or more containers for sample material, one or more diluents for sample dilution, and one or more control indicator strips for comparison. ML / E / ζυζΊ / un yy iz When the reagents and / or components comprising a kit are provided in lyophilized form (lyophilized powder) or as a dry powder, the lyophilized powder or powder can be reconstituted by adding a suitable solvent. In particular embodiments, the solvent may be a sterile, pharmaceutically acceptable buffer solution and / or other diluent. It is anticipated that such a solvent may also be supplied as part of a kit. When the components of a kit are provided in one or more liquid solutions, the liquid solution may be, by way of example only, a sterile aqueous solution. The compositions may also be formulated as an administrative composition. In this case, the container may itself be a syringe, pipette, topical applicator, or similar device, from which the formulation can be applied to an affected area of ​​the body, injected into a subject, and / or applied or mixed with the other components of the kit. IV. Examples The following examples are included to show preferred embodiments of the invention. Those skilled in the art should appreciate that the techniques disclosed in the following examples represent the techniques discovered by the inventor that work well in the practice of the invention and can therefore be considered preferred embodiments thereof. However, those skilled in the art, in light of this disclosure, will appreciate that many changes can be made to the specific embodiments disclosed and still achieve a similar or comparable result without departing from the spirit and scope of the invention. Example 1 Identification and validation of immunoreactive proteins The proteins of Ehrlichia chaffeensis (Arkansas strain) were first evaluated for antigenicity using a bioinformatics approach with ANTIGENpro (scratch.proteomics.ics.uci.edu). All proteins were classified and separated based on their antigenicity score and function. The top 100 hypothesized proteins were cloned into the plVEX2.3d vector containing a His tag and expressed using an in vitro transcription / translation assay. The expressed proteins were captured using anti-His antibody-coated ELISA plates. Pre-coated His tag antibody plates (GenScript #L00440C) were blocked for 20 minutes at room temperature using blocking buffer (PBS (Thermo, cat. #37538) + 2% milk). The blocked plates were incubated overnight at 4°C with their respective hypothesized E. chaffeensis proteins.Labeled chaffeensis antibodies were diluted in dilution buffer (dilution buffer, starting block buffer (PBS) (Thermo, cat. #37538) + 2% milk + 0.05% Tween 20). The plates were washed 4 times with wash buffer (wash buffer, PBS + 0.05% Tween 20) and HME-positive sera diluted 1:500 were added to each well (100 pL) followed by gentle shaking at room temperature for 2 hours. The plates were subsequently washed 4 times and alkaline phosphatase-labeled rabbit anti-human IgG secondary antibody (H+L) was added to each well (100 pL, 1:10000 dilution) and incubated at room temperature for 1 hour with gentle shaking. The plates were washed 5 times and 100 pL of BluePhos Phosphatase Substrate (KPL, cat. #50-88-05 and 50-8806) was added to each well and incubated in the dark for 30 minutes at room temperature with gentle shaking. Optical density was measured at Aeso in a microplate reader (VERSAmax, Molecular Devices). The readings were analyzed using SoftMax Pro 6.5.1 software. A total of 100 hypothetical proteins from E. chaffeensis were analyzed by ELISA. Proteins with an optical density (OD) >0.3 by ELISA were further analyzed using multiple HME-positive sera (6 serum samples in total) (Figure 1). After analysis, proteins showing an OD >0.3 by ELISA with multiple sera were further analyzed (Figure 2). Proteins that showed 100% reactivity with all sera and had an OD >0.5 with at least 4 sera were designated as highly immunoreactive (Figure 3). Proteins that showed 100% reactivity with all sera tested, but with OD values ​​between 0.2 and 0.5 by ELISA, were designated as moderately immunoreactive (Figure 3). Proteins that did not react to at least 4 HME-positive serum samples were excluded. Example 2 Ehrlichia immunoreactive proteins containing transmembrane domains and conformation-dependent antibody epitopes Materials and methods Antigenicity prediction of E. chaffeensis proteins: The antigenicity of all E. chaffeensis proteins was predicted by SCRATCH Protein Predictor ANTIGENpro, a sequence-based, alignment-free diagnostic test for protein antigenicity. Predictions are made using a two-stage architecture based on multiple representations of the primary sequence and five machine learning algorithms. A final score (0–1) summarizes the resulting antigenic probability prediction; a higher score indicates a higher antigenic probability. PCR amplification of Ehrlichia genes: E. chaffeensis (Arkansas strain) or E. canis (Jake strain) was propagated and purified as previously described. Fractions containing bacteria were frozen and used for DNA preparation. Oligonucleotide primers for amplification of Ehrlichia gene fragments were designed manually or using PrimerSelect (Lasergene v13.0, DNAStar, Madison, W1) according to sequences in GenBank and synthesized (Integrated DNA Technologies, Coralville, Iowa). PCRs were performed using PCR HotMaster Mix (Eppendorf, Westbury, NY) with E. chaffeensis or E. canis genomic DNA as a template.The thermal cycling profile was: 95°C for 3 min, 30 cycles of 94°C for 30 s, alignment temperature (1°C less than the lowest primer Tm) for 30 s, and 72°C for the appropriate spread time (1 min / 1000 base pairs) followed by a 72°C spread for 10 min and a 4°C hold. Expression of recombinant E. chaffeensis proteins by in vitro transcription and translation (IVTT): E. chaffeensis protein expression was performed using the RTS 100 E. coli HY kit (5 PRIME, Germany) or the S30 T7 high-throughput protein expression system (Promega, ML / ιζ / ζυζΊ / un yy iz Madison, Wl), the cell-free protein synthesis system based on E. coli extract, which can produce high levels of recombinant protein in 1 h. Briefly, E. chaffeensis DNA sequences were cloned into the plVEX-2.3do pET-14b vector containing the T7 promoter / terminator and a 6His tag sequence, and the recombinant plasmid was mixed with an E. coli extract and a reaction premix containing all the components necessary for transcription and translation, such as T7 RNA polymerase and ribosomal machinery, followed by incubation at 30 °C for 4 h (for the PRIME 5 kit) or 37 °C for 1 h (for the Promega kit). Protein expression was confirmed by dot blot immunoblotting using a horseradish peroxidase (HRP)-labeled 6His-tagged antibody (Thermo Fisher).IVTT products were used directly for immunoreactivity analysis or purified using the MagneHis protein purification system (Promega). Expression and purification of recombinant orthologs of E. canis: All E. canis proteins were cloned and expressed by the pBAD / Thio-TOPO expression system (Invitrogen) and purified under natural or denaturing conditions using TALON metal affinity resin (Clontech) as described above. Synthetic peptides: For the E: chaffeensis proteins, the overlapping peptides were commercially synthesized by Bio-Synthesis (Lewisville, TX) or Biomatik (Wilmington, DE). All peptides were supplied as lyophilized powder and resuspended in molecular biology grade water (1 mg / mL). Antisera: Convalescent anti-E. chaffeensis dog serum was obtained from an experimentally infected dog (No. 2251). Sera from HME patients were donated by the Centers for Disease Control and Prevention (Atlanta, GA), Vanderbilt University (Nashville, TN), Washington State University (Pullman, WA), and St. Louis Children’s Hospital (St. Louis, MO). Anti-E. canis dog sera were obtained from dogs experimentally infected with E. canis as previously described or from naturally infected dogs from Focus Technologies (Cypress, CA). Gel electrophoresis and Western Blot: Purified recombinant proteins were separated by sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) and transferred to nitrocellulose, and Western Blot was performed as described above, except that primary dog ​​sera were diluted to 1:100, human sera were diluted to 1:200 and rabbit antisera were diluted to 1:1,000. Enzyme-linked immunosorbent assay (ELISA): ELISA was performed to determine the immunoreactivity of recombinant Ehrlichia proteins and synthetic peptides. For IVTT products, the His Tag Antibody Plate (GenScript, Piscataway, NJ) was used for specific recombinant protein binding. Briefly, ELISA plates were blocked with 100 pL of StartingBlock blocking buffer (Thermo Fisher) in 2% skim milk for 20 minutes and washed twice with 200 pL of phosphate-buffered saline containing 0.05% (v / v) Tween 20 (PBST, pH 7.2). The plates were coated with 50 pL of IVTT-expressed Ehrlichia proteins diluted (1:50) in dilution buffer (StartingBlock blocking buffer in milk). ML / E / Zuzi / un yy iz at 2% and Tween at 0.5%) were added to each well and incubated overnight at 4°C. The wells were washed five times with PBST. Human sera diluted (1:200) in dilution buffer were added to each well (50 pL) and incubated for 1 h. ELISA plates were washed five times and 50 pL of rabbit anti-human IgG (H+L) secondary antibody labeled with alkaline phosphatase (Abcam, Cambridge, MA) diluted (1:5,000) in dilution buffer were added and incubated for 1 h. After the final washes (5 x), the BluePhos phosphatase substrate (100 pL; Kirkegaard & Perry Laboratories, Gaithersburg, MD) was added and the plates were incubated in the dark for 30 min and the color development was determined on a VersaMax microplate reader (Molecular Devices, Sunnyvale, CA) in A650 and the data were analyzed by SoftmaxPro v7.0 (Molecular Devices).All incubations were performed at room temperature with gentle shaking unless otherwise specified. For synthetic peptides, the Nunc MaxiSorp plate (Thermo Fisher) was used, and ELISA was performed as previously described. Optical density (OD) readings represent the mean OD for three wells (± standard deviations) after subtracting the negative control reading. Because negative controls generally had raw readings of <0.08 OD, a positive sample threshold was set at >0.1 OD after subtracting the negative control reading, with 0.1–0.5 OD considered positive and >0.5 OD considered strongly positive. Indirect fluorescent antibody (IFA) assay: The antibody status of E. chaffeensis in sera from patients with HME and anti-E. canis antibody in serum from CME dogs was determined as previously described. Antigen slides were prepared from THP-1 cells infected with E. chaffeensis (Arkansas) or DH82 cells infected with E. canis (Jake). Sera were diluted twice in PBS, starting at 1:100. Statistics: The statistical difference between the experimental groups was assessed using the two-tailed Student's t-test, and significance was indicated by a P-value <0.05. Ehrlichia gene locus tag numbers: Genetic locus tag numbers for E. chaffeensis or E. canis proteins in this study were previously available from Integrated Microbial Genomes. Results Prediction of E. chaffeensis proteome antigenicity by ANTIGENpro: The antigenicity of all 1156 proteins of E. chaffeensis (Arkansas strain) was predicted using the ANTIGENpro SCRATCH protein diagnostic test. The results showed that the final antigenicity score of all E. chaffeensis proteins ranged from 0.01 to 0.969, with the top 250 proteins scoring above 0.695. Some important immunoreactive proteins in the list of the top 250 proteins included TRP47 (Ech_0166; rank no. 30; score = 0.908), TRP120 (Ech_0039; no. 100; score = 0.838), and p28 (Ech_1144; no. 158; score = 0.776), indicating the efficiency and validity of ANTIGENpro's antigenicity prediction. Among these 250 E. chaffeensis proteins, 93 proteins, including TRP47, were noted as hypothetical with no putative function by the IMG database.This study focuses on these 93 hypothetical proteins, which were named A1-A93 proteins according to antigenicity score (from highest to lowest), with. ML / E / ζυζΊ / un yy iz TRP47 as protein A23 (Table 6). Immunoreactivity analysis of hypothetical E. chaffeensis proteins: To analyze immunoreactive proteins, we used the in vitro transcription and translation (IVTT) system to express 93 hypothetical E. chaffeensis proteins (A1–A93) that were among the top 250 antigenic proteins predicted by ANTIGENpro. A total of 90 protein genes were successfully cloned into the IVTT vector and expressed. To confirm expression, 17 proteins were randomly selected and detected by dot blot immunoblotting using an anti-His tag antibody. Expression of all proteins was detectable, despite differential expression levels, with protein A83 showing the lowest expression (Figure 4A). The negative control protein expressed by IVTT was not detectable. The other three proteins (A3, A67, and A92) were not expressed due to unsuccessful cloning.The immunoreactivity of the 90 expressed proteins was examined by ELISA using serum from a patient with HME (#Sandra), who had an IFA-detectable E. chaffeensis antibody (titer 1:1600) that has been effectively used in our previous publication. In total, 45 (50%) proteins reacted with the patient's serum (OD > 0.1), and nine (10%) proteins reacted strongly with the patient's serum (OD > 0.5), including A4, A5, A21, A23, A34, A54, A63, A75, and A77 (Figure 4B). These 45 proteins were therefore considered candidates for novel immunoreactive E. chaffeensis proteins and were investigated further. The anti-E. chaffeensis dog or patient serum did not recognize the negative control protein expressed by IVTT (crude OD < 0.08). Determination of the immunoreactivity of 45 hypothetical E. chaffeensis proteins: To determine and compare the immunoreactivity of these 45 novel immunoreactive proteins from E. chaffeensis, ELISA was performed using a panel of sera from 10 patients with HME who had antibodies against E. chaffeensis detectable by IFA (titers from 1:100 to 3200). We found that 14 (31%) of the 45 proteins were recognized by the sera of 10 patients, and 15 (33%) proteins were recognized by at least eight sera. All 15 of these proteins reacted strongly with at least three patient sera (OD>0.5), and 11 (24%) proteins reacted strongly with at least six sera, demonstrating that these 15 proteins were novel immunoreactive proteins from E. chaffeensis (Figure 5). All patient sera failed to recognize the negative control expressed by IVTT (crude OD<0.08). To compare the immunoreactivity of the new immunoreactive proteins of E.In addition to identifying the major immunoreactive TRPs of E. chaffeensis, we cloned and expressed TRP32, TRP47, and TRP120 by IVTT and used sera from 10 patients with HME to detect TRP immunoreactivity. The results showed that, consistent with our previous publications, all three TRPs reacted strongly with most patient sera, and TRP32 and TRP120, in particular, reacted strongly with nine and eight patient sera, respectively (Figure 5). Some proteins, such as A56, A62, A77, A50, A19, and A51, reacted strongly with antibodies in most patient sera at a level comparable to the TRPs, and were therefore considered major immunoreactive proteins of E. chaffeensis. Table 4 lists 15 immunoreactive proteins of E. chaffeensis and their characteristics, with the range of immunoreactivity predicted by the reactions with patient sera.Furthermore, we found that, of these 15 proteins, 10 (67%) were small in size. ML / E / ζυζΊ / un yy iz (< 22 kDa) and 10 (67%) were predicted as membrane proteins by the TMHMM 2.0 server, suggesting that these novel immunoreactive proteins from Ehrlichia are predominantly small membrane proteins. Determination of the conformational immunoreactivity of new immunoreactive proteins from E. chaffeensis: To determine the conformation dependence of the immunoreactivity of new immunoreactive proteins from E. chaffeensis, we compared the immunoreactivity of native proteins (IVTT products) with that of denatured proteins (IVTT products treated with urea) by ELISA with sera from 10 patients with HME.After denaturation, three novel immunoreactive proteins, including A19, A51, and A83, did not react with any patient sera; six proteins, including A56, A6, A77, A50, A73, and A36, reacted only weakly with 1–3 patient sera; five proteins, including A14, A63, A34, A9, and A42, still reacted with most patient sera, but at a substantially lower level compared to native IVTT proteins; protein A25 still reacted strongly with serum from patient #2, but did not react with any other sera. However, the immunoreactivity of three well-defined major immunoreactive TRPs, including TRP32, TRP47, and TRP120, was not substantially reduced after denaturation, consistent with our earlier conclusion that TRPs contain major continuous epitopes (Figure 6A).Therefore, our result indicated that the immunoreactivity of most of these new immunoreactive proteins from E. chaffeensis was conformation-dependent and most of the epitopes of these proteins were discontinuous. Synthetic peptides were also used to confirm whether the novel immunoreactive proteins of E. chaffeensis contain the linear epitope. Overlapping polypeptides were synthesized to cover the sequence of the 15 novel immunoreactive proteins of E. chaffeensis, except for A83 and A36. All peptides were 20–25 amino acids long (except for the last peptide, which covered the C-terminus of each protein), and six amino acids overlapped with each other. Serum from one patient (#Sandra) was used to react all peptides by ELISA. One peptide (A14-2) for protein A14 reacted weakly with the patient's serum, while four peptides (A63-3, 5, 12, and 21) for protein A63 reacted weakly, and one peptide (A63-11) reacted strongly with the patient's serum. Two peptides (A34-14 and 15) for the A34 protein reacted weakly and one peptide (A34-1) reacted strongly with the patient's serum.All synthetic peptides for other proteins did not react with the patient's serum, suggesting that most of these novel immunoreactive proteins from E. chaffeensis do not contain a linear epitope, consistent with our ELISA data with native and denatured IVTT products (Figure 6B). Immunoreactivity of E. canis orthologs of hypothetical immunoreactive proteins of E. chaffeensis: Because we have found several pairs of E. chaffeensis / E. canis orthologs, such as TRP19 / TRP32, TRP36 / TRP47, TRP75 / TRP95 and TRP120 / TRP140, which are the two major immunoreactive proteins of Ehrlichia, the E. canis orthologs of the A1-A93 proteins of E. chaffeensis were analyzed. A total of 25 E. canis orthologs of E. chaffeensis protein A with immunoreactivity were found, as identified in Figure 1. These E. canis orthologs were expressed and purified from E. coli, and a Western blot analysis showed that 12 selected E. canis orthologs reacted with an anti-E. canis dog serum (No. 2995) (data not shown). The immunoreactivity of these 12 E. canis orthologs was further determined and compared with TRP19, a well-documented major immunoreactive protein of E.E. canis was tested by ELISA using a panel of sera from 10 dogs with CME (Figure 7). We found that the proteins Ecaj_0919 and Ecaj_0073 reacted strongly with the sera from 10 dogs as TRP19; therefore, these two proteins were considered the main immunoreactive proteins of E. canis. The proteins Ecaj_0104, Ecaj_0663, and Ecaj_0881 reacted strongly with most of the sera from 10 dogs, and seven other proteins also reacted with most of the dog sera, so all 12 E. canis orthologs of the E. chaffeensis proteins are immunoreactive (Figure 7). However, the conserved ortholog pairs of E. chaffeensis and E. canis do not necessarily have equivalent immunoreactivity (Table 4 and Table 5). Table 5 shows a list of 12 E. canis orthologs of hypothetical immunoreactive proteins from E. chaffeensis, ranked by immunoreactivity detected by ELISA with sera from CME dogs.In total, 6 out of 12 (50%) proteins have a small size (< 22 kDa). In these experiments, E. chaffeensis proteins exhibiting immunoreactivity with sera from patients with HME or dogs with CME were identified, including 15 E. chaffeensis proteins and 12 E. canis orthologs. Notably, many of the novel major immunoreactive Ehrlichia proteins were found to contain transmembrane domains. Previously, the major continuous antibody epitopes of TRPs had been mapped to the central TR region in all TRPs, indicating that Ehrlichia TR domains are targets of the host's humoral immune response. The association of these transmembrane domains with the host immune response is interesting and unique and, to the inventors' knowledge, has not been described with respect to any other pathogen; however, the specific role of these domains in Ehrlichia pathobiology or immunity remains unknown. Interestingly, most of the new major immunoreactive proteins of E. chaffeensis were found to be small proteins containing a conformational epitope. A few conformational epitopes have been mapped to TRPs, and the host response to continuous major epitopes on immunodominant Ehrlichia proteins is strong, suggesting the absence of dominant conformational epitopes. Without wishing to commit to any particular theory, this could be due to previous methods used for protein identification, such as SDS-PAGE and Western blot, during which small proteins are easily depleted from the regular gel, and proteins generally lose their conformation after denaturation. Consequently, there may be other conformational epitopes associated with previously identified major immunoreactive proteins that went undetected. Similarly, the further identification of orthologous E. proteins...canis expressed by IVTT could provide more conformational epitopes. Furthermore, the inventors observed that the conserved orthologous pairs from E. chaffeensis and E. canis do not necessarily have equivalent immunoreactivity, suggesting that homologous proteins may play different roles in Ehrlichia. Some novel orthologous pairs from ML / E / ζυζΊ / un yy iz E. chaffeensis and E. canis are major immunoreactive proteins, such as Ech_0846 (A56) and Ecaj_0242, Ech_1053 (A77) and Ecaj_0846. In contrast, the proteins Ecaj_0919 and Ecaj_0073 reacted strongly with the sera of 10 dogs as TRP19, but other orthologs Ech_1147 (A2) and Ech_0122 (A78) were not identified as major immunoreactive proteins. Similarly, the proteins Ech_0535 (A14) and Ech_0181 (A73) reacted with the sera of 10 patients, but their orthologs Ecaj_0500 and Ecaj_0122 were not identified as major immunoreactive proteins (Table 5 and Table 6). In addition, some important novel immunoreactive proteins of the Ech_0700 (A50) and Ech_0578 (A62) proteins of E. chaffeensis do not have orthologs in E. canis. ivia / t / zuz i / un yy iz Table 4. List of 15 hypothetical E. chaffeensis proteins classified by immunoreactivity detected by ELISA with sera from patients with HME. Classification Protein Ech Tag No. Antigenicity Score MW (kDa) Predicted Membrane Protein E. canis Ortholog (Tag No.) 1 A77 1053 0.762 22 + 0846 2 A62 0578 0.797 21 - - 3 A56 0846 0.828 19 + 0242 4 A19 0745 0.919 13 - 0324 5 A50 0700 0.845 21 - - 6 A51 0607 0.811 38 - 0434 7 A14 0535 0.927 21 - 0500 8 A63 0716 0.790 41 + 0347 9 A34 0252 0.874 40 + - 10 A9 0722 0.944 21 + - 11 A42 0240 0.856 18 + - 12 A25 0531 0.904 20 + - 13 A83 0715 0.747 61 + 0348 14 A73 0181 0.769 12 + 0122 15 A36 0807 0.864 34 + 0271 Table 5. List of 12 E. canis orthologs of the hypothetical immunoreactive proteins of E. chaffeensis classified by immunoreactivity detected by ELISA with sera from CME dogs. Classification Protein (Ecaj Tag No.) Antigenicity Score PM (kDa) Predicted Membrane Protein E. chaffeensis Ortholog (Tag No.) E. chaffeensis Protein 1 0919 0.840 13 - 1147 A2 2 0073 0.887 10 - 0122 A78 3 0104 0.392 48 + 0159 A76 4 0663 0.818 33 - 0345 A47 5 0881 0.904 38 - 1103 A55 6 0507 0.664 55 - 0526 A88 7 0312 0.897 21 - 0763 A38 8 0324 0.921 14 - 0745 A19 9 0434 0.880 26 - 0607 A51 10 0242 0.669 20 - 0846 A56 11 0347 0.756 40 + 0716 A63 12 0846 0.576 22 + 1053 A77 ML / E / ZuZ / UI yy I z Table 6. List of 93 hypothetical proteins from E. chaffeensis (Arkansas) with potential antigenicity predicted by ANTIGENpro (antigenicity score > 0.695). Label No. Ech Antigenicity Score Size (AA) 1 0187 0.969 563 2 1147 0.964 126 3 0247 0.958 302 4 0261 0.956 264 5 0255 0.950 338 6 0253 0.950 189 7 0865 0.949 302 8 1152 0.949 185 9 0722 0.945 190 10 0246 0.944 275 11 0257 0.943 226 12 0609 0.935 301 13 0601 0.929 374 14 0535 0.928 186 15 0251 0.928 205 16 0576 0.924 98 17 0150 0.923 672 18 1037 0.920 1231 19 0745 0.920 118 20 0864 0.918 330 21 0825 0.917 380 22 0113 0.909 793 23 0166 (TRP47) 0.908 285 24 0862 0.907 403 25 0531 0.905 175 26 0285 0.895 181 27 0744 0.889 157 28 0612 0.888 208 29 0879 0.885 815 30 0147 0.885 193 31 0611 0.880 229 32 1036 0.880 750 33 0525 0.879 666 34 0252 0.875 364 35 0118 0.873 30 36 0807 0.864 334 37 0348 0.862 202 38 0763 0.860 165 39 0106 0.858 713 40 1154 0.857 135 41 0120 0.857 213 42 0240 0.857 158 43 1148 0.854 142 44 0243 0.853 293 45 0284 0.852 1016 46 0115 0.851 203 47 0345 0.850 294 48 0878 0.847 409 49 1021 0.845 219 50 0700 0.845 192 51 0607 0.844 322 52 0377 0.843 104 53 0549 0.842 195 54 0614 0.839 231 55 1103 0.830 223 56 0846 0.828 171 57 0199 0.823 213 58 0108 0.819 825 59 0551 0.811 191 60 1027 0.804 34 61 0663 0.802 202 62 0578 0.798 185 63 0716 0.790 367 64 0778 0.786 1132 65 1013 0.785 203 66 0398 0.781 121 67 0991 0.779 710 68 0927 0.775 34 69 0949 0.773 31 70 0259 0.773 118 71 0704 0.771 248 72 0256 0.770 72 73 0181 0.769 103 74 0297 0.769 272 75 0388 0.768 293 ml / e / zuzi / ui yy i ¿ 76 0159 0.767 507 77 1053 0.763 193 78 0122 0.758 126 79 0593 0.758 382 80 0698 0.758 200 81 0079 0.756 134 82 0986 0.752 179 83 0715 0.748 551 84 0279 0.747 41 85 0836 0.737 1201 86 0281 0.716 179 87 0276 0.716 184 88 0526 0.715 495 89 0478 0.704 172 90 0126 0.704 334 91 0866 0.703 330 92 0945 0.699 1349 93 0767 0.695 621 ML / E / zyzΙ / un yy iz All the methods disclosed and claimed herein can be performed and executed without undue experimentation in light of this disclosure. Although the compositions and methods of this invention have been described in terms of preferred embodiments, it will be evident to those skilled in the art that variations may be applied to the methods and to the steps or sequence of steps of the method described herein without departing from the concept, spirit, and scope of the invention. More specifically, it will be evident that certain agents that are chemically and physiologically related may be substituted for the agents described herein, while achieving the same or similar results. All such substitutes and similar modifications evident to those skilled in the art are deemed to be within the spirit, scope, and concept of the invention as defined in the appended claims. References The following references, insofar as they provide exemplary procedural details or other details supplementing those set forth herein, are incorporated herein specifically by reference. United States Patent 4,373,932 United States Patent 4,220,450 United States Patent 4,897,268 United States Patent 4,472,509 United States Patent 4,938,948 United States Patent 5,075,109 United States Patent 5,440,013 United States Patent 5,446,128 United States Patent 5,470,723 United States Patent 5,470,932 United States Patent 5,543,504 United States Patent 5,552,157 United States Patent 5,565,213 United States Patent 5,567,434 United States Patent 5,618,914 United States Patent 5,656,016 United States Patent 5,670,155 United States Patent 5,697,899 United States Patent 5,738,868 United States Patent 5,741,516 United States Patent 5,770,219 United States Patent 5,779,708 United States Patent 5,783,208 United States Patent 5,795,587 United States Patent 5,797,898 United States Patent 5,840,833 United States Patent 5,853,744 United States Patent 5,859,184 United States Patent 5,891,506 United States Patent 5,929,237 United States Patent 6,136,610 United States Patent 6,210,708 United States Patent 6,372,445 United States Patent 6,617,142 United States Patent 6,875,750 United States Patent 6,951,765 United States Patent 7,163,677 United States Patent 7,282,194 United States Patent 7,344,893 United States Patent 7,371,582 United States Patent Application 2005 / 0047972 United States Patent Application 2005 / 0065463 United States Patent Application 2005 / 0250141 United States Patent Application 2007 / 0264664 IVIA / t / ZUZ I / ​​UI yy I z United States Patent Application 2009 / 0005535 Carpino etal., Org. Proc. Res. Dev., 7(1)28-37, 2003. Dumler et al., Clin. I infected. Dis., 45:S45-S51,2007. Feng and Walker, Infect. Immun., 72:966-971,2004. Fishbein et al., Human ehrlichiosis in the United States, 1985 to 1990. AnnlntemMed 120:736-743, 1994. Geysen et al., Proc. Nati. Academic Sci. USA, 81(13):3998-4002, 1984. He et al., Vaxign: the first web-based vaccine design program for reverse vaccinology and applications for vaccine development. J Biomed Biotechnol 2010:297505, 2010. Hotopp et al., Comparative genomics of emerging human ehrlichiosis agents. PLoS Genet 2:e21, 2006. Kuriakose et al., Ehrlichia chaffeensis transcriptome in mammalian and arthropod hosts reveáis differential gene expression and post transcriptional regulation. PLoS One 6:e24136, 2011. Kuriakose et al., Molecular basis of antibody mediated immunity against Ehrlichia chaffeensis involves species-specific linear epitopes in tándem repeat proteins. Microbes Infect 14:1054-1063, 2012. L¡ and Winslow, Survival, replication, and antibody susceptibility of Ehrlichia chaffeensis outside of host cells. Infectlmmun 71:4229-4237, 2003. L¡ et al., Antibodies highly effective in SCID mice during infection by the intracellular bacterium Ehrlichia chaffeensis are of picomolar affinity and exhibit preferential epitope and isotype utilization. Jlmmunol 169:1419-1425, 2002. L¡ eí al., Outer membrane protein-specific monoclonal antibodies protect SCID mice from fatal infection by the oblígate intracellular bacterial pathogen Ehrlichia chaffeensis. Jlmmunol 166:1855-1862, 2001. Lin et al., Global proteomic analysis of two tick-borne emerging zoonotic agents: Anaplasma phagocytophilum and Ehrlichia chaffeensis. Front Microbiol 2:24, 2011. Magnan et al., High-throughput prediction of protein antigenicity using protein microarray data. Bioinformatics 26:2936-2943, 2010. McBride and Walker, Progress and obstacles in vaccine development for the ehrlichioses. Expert Rev Vaccines 9:1071-1082, 2010. Mizuno et al., Chemistry.23(58):14394-14409, Oct 17 2017. Nandi et al., CD4 T-cell epitopes associated with protective immunity induced following vaccination of mice with an ehrlichial variable outer membrane protein. Infectlmmun 75:5453-5459., 2007. Glano etal., Human monocytotropic ehrlichiosis, Missouri. EmerglnfectDis 9:1579-1586, 2003. Paparone et al., Ehrlichiosis with pancytopenia and ARDS. New Jersey Med 92:381 -385, 1995. Paterson et al., Anal Chem. 86(19):9481 -8, Oct 7; 2014. Pierce Immunotechnology Catalog and Handbook, at A12-A13, 1991 Racine et al., IgM production by bone marrow plasmablasts contributes to long-term protection against intracellular bacterial infection. J Immunol 186:1011 -1021,2011. ivia / t / zuz i / un yy i z Sotomay et al., Animal model of fatal human monocytotropic ehrlichiosis. AmJPath 158:757-769, 2001. The Science and Practice of Pharmacy, 21stEd. Lippincott Williams and Wilkins, 2005 Walker and Dumler, Human monocytic and granulocytic ehrlichioses. Discovery and diagnosis of emerging tick-borne infections and the critical role of the pathologist. [Review] [50 reís]. Archives of Pathology & Laboratory Medicine 121:785-791,1997. Walker etal., Ehrlichia chaffeensis: a prevalent, life-threatening, emerging pathogen. Trans Am Clin Climatol Assoc 115:375-382; discussion 382-374, 2004. Winslow etal., Ann. NYAcad. Sci., 990:435-443, 2003. Winslow etal., Infect. Immun., 68:2187-2195, 2000. Winslow et al., Infection of the laboratory mouse with the intracellular pathogen Ehrlichia chaffeensis. Infectlmmun 66:3892-3899, 1998. Yager etal., Infect. Immun., 73:8009-8016, 2005. Zemella etal., Cell-Free Protein Synthesis: Pros and Cons of Prokaryotic and Eukaryotic Systems. Chembiochem.;16(17):2420-2431,2015. IVIA / t / ZUZ I UU I z

Claims

1. A method for detecting antibodies that bind specifically to an Ehrlichia organism in a test sample, comprising: (a) contacting an isolated polypeptide from Table 1, Table 2 or Table 3 or a polypeptide having at least 95% sequence identity with it, with the test sample, under conditions that allow the formation of peptide-antibody complexes; (b) detecting the peptide-antibody complexes; wherein the detection of the peptide-antibody complexes is an indication that antibodies specific to an Ehrlichia organism are present in the test sample, and wherein the absence of the peptide-antibody complexes is an indication that antibodies specific to an Ehrlichia organism are not present in the test sample.

2. The method according to claim 1, wherein the polypeptide is selected from the group consisting of a polypeptide from Table 2.

3. The method according to claim 1, wherein the polypeptide is selected from the group consisting of a polypeptide from Table 3.

4. The method according to any of claims 1 to 3, wherein the Ehrlichia organism is an Ehrlichia chaffeensis organism.

5. The method according to any of claims 1 to 3, wherein the detection step comprises performing an enzyme-linked immunoassay, a radioimmunoassay, an immunoprecipitation, a fluorescence immunoassay, a chemiluminescent assay, an immunoblotting assay, a lateral flow assay, a flow cytometry assay, a multiplex immunoassay, a mass spectrometry assay, or a particle-based assay.

6. The method according to claim 5, wherein the detection step comprises a lateral flow assay or an enzyme-linked immunoassay, wherein the enzyme-linked immunoassay is an ELISA.

7. The method according to any of claims 1 or 4 to 6, wherein the isolated polypeptide is A77 (SEQ ID NO:22), A62 (SEQ ID NO:17), A56 (SEQ ID NO:16), A19 (SEQ ID NO:6), A50 (Ech_0700; SEQ ID NO: 28), A51 (SEQ ID NO:13), A14 (SEQ ID NO:4), A63 (SEQ ID NO:18), A34 (SEQ ID NO:9), A9 (SEQ ID NO:3) or A42 (Ech_0240; SEQ ID NO:11).

8. A method for identifying an Ehrlichia infection in a mammalian subject comprising: (a) contacting a biological sample from the subject with a polypeptide isolated from Table 1, Table 2 or Table 3 under conditions that allow the formation of peptide-antibody complexes; and (b) detecting the peptide-antibody complexes; wherein the detection of the peptide-antibody complexes is an indication that the subject has an Ehrlichia infection.

9. The method according to claim 8, wherein the polypeptide is selected from the group consisting of Table 2.

10. The method according to claim 8, wherein the polypeptide is selected from the group consisting of Table 3.

11. The method according to any of claims 8 to 10, wherein the detection MLE / E / ζυζΊ / un yy iz comprises performing an enzyme-linked immunoassay, a radioimmunoassay, an immunoprecipitation, a fluorescence immunoassay, a chemiluminescent assay, an immunoblotting assay, a lateral flow assay, a flow cytometry assay, a multiplex immunoassay, a test strip test, or a particle-based assay.

12. The method according to claim 8, wherein the subject is a human.

13. The method according to claim 8, wherein the subject is a dog.

14. The method according to any of claims 8 or 11 to 13, wherein the isolated polypeptide is A77 (SEQ ID NO:22), A62 (SEQ ID NO:17), A56 (SEQ ID NO:16), A19 (SEQ ID NO:6), A50 (Ech_0700; SEQ ID NO: 28), A51 (SEQ ID NO:13), A14 (SEQ ID NO:4), A63 (SEQ ID NO:18), A34 (SEQ ID NO:9), A9 (SEQ ID NO:3) or A42 (Ech_0240; SEQ ID NO:11).

15. An isolated polypeptide comprising a sequence from Table 1, Table 2 or Table 3, wherein the isolated peptide is immobilized on a surface of a support substrate.

16. The method according to claim 15, wherein the polypeptide is selected from the group consisting of Table 2.

17. The method according to claim 15, wherein the polypeptide is selected from the group consisting of Table 3.

18. The peptide according to any of claims 15 to 17, wherein the support substrate comprises latex, polystyrene, nylon, nitrocellulose, cellulose, silica, agarose or magnetic resin.

19. The peptide according to any of claims 15 to 18, wherein the support substrate is a reaction chamber, a well, a membrane, a filter, paper, an emulsion, a bead, a microbead, a test strip, a card, a glass slide, a lateral flow apparatus, a microchip, a comb, a silica particle, a magnetic particle, a nanoparticle, or a self-assembling monolayer.

20. The peptide according to any of claims 15 to 19, wherein the peptide is comprised in a kit.

21. The peptide according to any of claims 15 to 19, wherein the peptide is produced via peptide synthesis or in vitro transcription and translation (IVTT).

22. The peptide according to claims 15 to 19, wherein the peptide is produced by recombinant means.

23. The method according to any of claims 15 or 18 to 22, wherein the isolated polypeptide is A77 (SEQ ID NO:22), A62 (SEQ ID NO:17), A56 (SEQ ID NO:16), A19 (SEQ ID NO:6), A50 (Ech_0700; SEQ ID NO: 28), A51 (SEQ ID NO:13), A14 (SEQ ID NO:4), A63 (SEQ ID NO:18), A34 (SEQ ID NO:9), A9 (SEQ ID NO:3) or A42 (Ech_0240; SEQ ID NO:11).

24. An isolated polypeptide comprising a sequence from Table 1, Table 2 or Table 3, wherein the isolated peptide is covalently linked to a detectable tag.

25. The polypeptide according to claim 24, wherein the polypeptide is selected from the group consisting of Table 2.

26. The polypeptide according to claim 24, wherein the polypeptide is selected from the ML / E / ζυζΊ / un yy iz group consisting of Table 3.

27. The polypeptide according to any of claims 24 to 26, wherein the detectable tag is a fluorescent tag, a radioactive tag, an enzyme tag, or a luminescent nanoparticle.

28. The polypeptide according to claim 27, wherein the luminescent nanoparticle is a rare earth luminescent nanoparticle, a light particle, or a strontium alumina nanoparticle.

29. The polypeptide according to any of claims 24 to 28, wherein the polypeptide is comprised in a kit.

30. The polypeptide according to any of claims 24 to 29, wherein the polypeptide is produced via peptide synthesis or in vitro transcription and translation (IVTT).

31. The polypeptide according to any of claims 24 to 29, wherein the polypeptide is produced by recombinant means.

32. The method according to any of claims 24 or 27 to 31, wherein the isolated polypeptide comprises or consists of A77 (SEQ ID NO:22), A62 (SEQ ID NO:17), A56 (SEQ ID NO:16), A19 (SEQ ID NO:6), A50 (Ech_0700; SEQ ID NO: 28), A51 (SEQ ID NO:13), A14 (SEQ ID NO:4), A63 (SEQ ID NO:18), A34 (SEQ ID NO:9), A9 (SEQ ID NO:3) or A42 (Ech_0240; SEQ ID NO:11).

33. A kit comprising: (a) the isolated polypeptide according to any of claims 24 to 32, (b) an anti-dog or anti-human secondary antibody linked to a reporter molecule and (c) a suitable reagent for the detection of the reporter molecule.

34. The kit according to claim 33, wherein the peptide is immobilized on a membrane or a microtiter plate.

35. The kit according to any of claims 33 and 34, wherein the reporter molecule is selected from the group consisting of luciferase, horseradish peroxidase, a luminescent nanoparticle, P-galactosidase, and a fluorescent tag.

36. The kit according to claim 35, wherein the luminous nanoparticle is a strontium aluminum nanoparticle.

37. The kit according to any of claims 33 to 36, wherein the kit further comprises a dilution buffer solution for dog or human serum.

38. The kit according to any of claims 33 to 37, wherein the kit comprises a lateral flow immunoassay or a lateral flow immunochromatographic assay.

39. The kit according to any of claims 33 to 38, wherein the kit comprises an enzyme-linked immunosorbent assay (ELISA).

40. A method for inducing an immune response in a mammalian subject comprising administering to the subject an effective amount of a pharmaceutical preparation comprising a polypeptide from Table 1, Table 2 or Table 3.

41. The method according to claim 40, wherein the polypeptide is selected from the group consisting of Table 2 and Table 3. ivia / t / zuz i / un yy iz 42. The method according to any of claims 40 to 41, wherein the subject is a human.

43. The method according to any of claims 40 to 42, wherein the pharmaceutical preparation is administered subcutaneously, intramuscularly, nasally, by inhalation or aerosol administration, or intradermally.

44. The method according to any of claims 40 or 42 and 43, wherein the isolated polypeptide comprises or consists of A77 (SEQ ID NO:22), A62 (SEQ ID NO:17), A56 (SEQ ID NO:16), A19 (SEQ ID NO:6), A50 (Ech_0700; SEQ ID NO: 28), A51 (SEQ ID NO:13), A14 (SEQ ID NO:4), A63 (SEQ ID NO:18), A34 (SEQ ID NO:9), A9 (SEQ ID NO:3) or A42 (Ech_0240; SEQ ID NO:11).

45. A method for treating an Ehrlichia chaffeensis infection in a subject, comprising: (a) contacting a biological sample from the subject with a polypeptide isolated from Table 1, Table 2, or Table 3 under conditions that allow the formation of peptide-antibody complexes; (b) detecting the peptide-antibody complexes; wherein the detection of the peptide-antibody complexes is an indication that the subject has an Ehrlichia chaffeensis infection; and (c) administering a therapeutic compound to treat the Ehrlichia infection in the subject.

46. ​​The method according to claim 45, wherein the polypeptide is selected from the group consisting of Table 2.

47. The method according to claim 45, wherein the polypeptide is selected from the group consisting of Table 3.

48. The method according to any of claims 45 to 47, wherein the detection comprises performing an enzyme-linked immunoassay, a radioimmunoassay, an immunoprecipitation, a fluorescence immunoassay, a chemiluminescent assay, an immunoblotting assay, a lateral flow assay, a flow cytometry assay, a multiplex immunoassay, a test strip test, or a particle-based assay.

49. The method according to claim 45, wherein the subject is a dog.

50. The method according to claim 45, wherein the subject is a human.

51. The method according to any of claims 45 to 50, wherein the therapeutic compound is an antibiotic.

52. The method according to claim 51, wherein the antibiotic is doxycycline.

53. The method according to any of claims 45 or 48 to 52, wherein the isolated polypeptide is A77 (SEQ ID NO:22), A62 (SEQ ID NO:17), A56 (SEQ ID NO:16), A19 (SEQ ID NO:6), A50 (Ech_0700; SEQ ID NO: 28), A51 (SEQ ID NO:13), A14 (SEQ ID NO:4), A63 (SEQ ID NO:18), A34 (SEQ ID NO:9), A9 (SEQ ID NO:3) or A42 (Ech_0240; SEQ ID NO:11).

54. A method for detecting antibodies that bind specifically to an Ehrlichia organism in a test sample, comprising: a) contacting a polypeptide isolated from: Ecaj_0919, Ecaj_0073, Ecaj_0104, Ecaj_0663, or Ecaj_0881, more preferably Ecaj_0919, Ecaj_0073, Ecaj_0104, or Ecaj_0663, even more preferably Ecaj_0919, Ecaj_0073, Ecaj_0104, even more preferably Ecaj_0919 or Ecaj_0073; or a polypeptide having at least 95% sequence identity with the same, with the test sample, under conditions allowing the formation of peptide-antibody complexes; (b) detect peptide-antibody complexes;where the detection of peptide-antibody complexes is an indication that antibodies specific to an Ehrlichia organism are present in the test sample, and where the absence of peptide-antibody complexes is an indication that antibodies specific to an Ehrlichia organism are not present in the test sample.

55. The method according to claim 54, wherein the detection step comprises performing an enzyme-linked immunoassay, a radioimmunoassay, an immunoprecipitation assay, a fluorescence immunoassay, a chemiluminescent assay, an immunoblotting assay, a lateral flow assay, a flow cytometry assay, a multiplex immunoassay, a mass spectrometry assay, or a particle-based assay.

56. The method according to claim 55, wherein the detection step comprises a lateral flow assay or an enzyme-linked immunoassay, wherein the enzyme-linked immunoassay is an ELISA.

57. A method for identifying an Ehrlichia infection in a mammalian subject comprising: (a) contacting a biological sample from a subject with a polypeptide isolated from Ecaj_0919, Ecaj_0073, Ecaj_0104, Ecaj_0663 or Ecaj_0881, more preferably Ecaj_0919, Ecaj_0073, Ecaj_0104 or Ecaj_0663, even more preferably Ecaj_0919, Ecaj_0073, Ecaj_0104, even more preferably Ecaj_0919 or Ecaj_0073, under conditions allowing the formation of peptide-antibody complexes; and (b) detecting the peptide-antibody complexes; wherein the detection of the peptide-antibody complexes is an indication that the subject has an Ehrlichia infection.

58. The method according to claim 57, wherein the detection step comprises performing an enzyme immunoadsorption assay, a radioimmunoassay, an immunoprecipitation assay, a fluorescence immunoassay, a chemiluminescent assay, an immunoblotting assay, a lateral flow assay, a flow cytometry assay, a multiplex immunoassay, a test strip test, or a particle-based assay.

59. The method according to any of claims 57 to 58, wherein the subject is a dog.

60. An isolated polypeptide comprising a sequence of Ecaj_0919, Ecaj_0073, Ecaj_0104, Ecaj_0663, or Ecaj_0881, more preferably Ecaj_0919, Ecaj_0073, Ecaj_0104, or Ecaj_0663, even more preferably Ecaj_0919, Ecaj_0073, Ecaj_0104, even more preferably Ecaj_0919 or Ecaj_0073, wherein the isolated peptide is immobilized on a surface of a support substrate.

61. The peptide according to claim 60, wherein the support substrate comprises latex, polystyrene, nylon, nitrocellulose, cellulose, silica, agarose or magnetic resin.

62. The peptide according to any of claims 60 to 61, wherein the support substrate is a reaction chamber, a well, a membrane, a filter, paper, an emulsion, a bead, a microbead, a test strip, a card, a glass slide, a lateral flow apparatus, a microchip, a comb, a silica particle, a magnetic particle, a nanoparticle or a self-assembling monolayer.

63. The peptide according to any of claims 60 to 62, wherein the peptide is comprised in a kit.

64. The peptide according to any of claims 60 to 62, wherein the peptide is produced via peptide synthesis or in vitro transcription and translation (IVTT).

65. The peptide according to any of claims 60 to 62, wherein the peptide is produced by recombinant means.

66. An isolated polypeptide comprising a sequence of Ecaj_0919, Ecaj_0073, Ecaj_0104, Ecaj_0663, or Ecaj_0881, more preferably Ecaj_0919, Ecaj_0073, Ecaj_0104 or Ecaj_0663, even more preferably Ecaj_0919, Ecaj_0073, Ecaj_0104, even more preferably Ecaj_0919 or Ecaj_0073, wherein the isolated peptide is covalently linked to a detectable tag.

67. The polypeptide according to claim 66, wherein the detectable tag is a fluorescent tag, a radioactive tag, an enzyme tag, or a luminescent nanoparticle.

68. The polypeptide according to claim 67, wherein the luminescent nanoparticle is a rare earth luminescent nanoparticle, a light particle, or a strontium aluminate nanoparticle.

69. The polypeptide according to any of claims 66 to 68, wherein the polypeptide is comprised in a kit.

70. The polypeptide according to any of claims 66 to 69, wherein the polypeptide is produced via peptide synthesis or in vitro transcription and translation (IVTT).

71. The polypeptide according to any of claims 66 to 69, wherein the polypeptide is produced by recombinant means.

72. A kit comprising: (a) the isolated polypeptide according to any of claims 66 to 71, (b) an anti-human secondary antibody linked to a reporter molecule; and (c) a reagent suitable for the detection of the reporter molecule.

73. The kit according to claim 72, wherein the peptide is immobilized on a membrane or a microtiter plate.

74. The kit according to any of claims 72 to 73, wherein the reporter molecule is selected from the group consisting of luciferase, horseradish peroxidase, a luminescent nanoparticle, P-galactosidase, and a fluorescent tag.

75. The kit according to claim 74, wherein the luminous nanoparticle is a strontium aluminate nanoparticle.

76. The kit according to any of claims 72 to 75, wherein the kit further comprises a dilution buffer solution for dog or human serum.

77. The kit according to any of claims 72 to 76, wherein the kit comprises a lateral flow immunoassay or a lateral flow immunochromatographic assay.

78. The kit according to any of claims 72 to 77, wherein the kit comprises an enzyme-linked immunosorbent assay (ELISA).

79. A method for inducing an immune response in a mammalian subject comprising administering to the subject an effective amount of a pharmaceutical preparation comprising a polypeptide of Ecaj_0919, Ecaj_0073, Ecaj_0104, Ecaj_0663 or Ecaj_0881, more preferably Ecaj_0919, Ecaj_0073, Ecaj_0104 or Ecaj_0663, even more preferably Ecaj_0919, Ecaj_0073, Ecaj_0104, even more preferably Ecaj_0919 or Ecaj_0073.

80. The method according to claim 79, wherein the subject is a human.

81. The method according to any of claims 79 to 80, wherein the pharmaceutical preparation is administered subcutaneously, intramuscularly, nasally, by inhalation or aerosol administration, or intradermally.

82. A method for treating an Ehrlichia canis infection in a mammalian subject comprising: (a) contacting a biological sample from the subject with a polypeptide isolated from Ecaj_0919, Ecaj_0073, Ecaj_0104, Ecaj_0663 or Ecaj_0881, more preferably Ecaj_0919, Ecaj_0073, Ecaj_0104 or Ecaj_0663, even more preferably Ecaj_0919, Ecaj_0073, Ecaj_0104, even more preferably Ecaj_0919 or Ecaj_0073, under conditions allowing the formation of peptide-antibody complexes; (b) detecting the peptide-antibody complexes; wherein the detection of the peptide-antibody complexes is an indication that the subject has an Ehrlichia canis infection; and (c) administer a therapeutic compound to treat Ehrlichia infection in the subject.

83. The method according to claim 82, wherein the detection step comprises performing an enzyme-linked immunoassay, a radioimmunoassay, an immunoprecipitation, a fluorescence immunoassay, a chemiluminescent assay, an immunoblotting assay, a lateral flow assay, a flow cytometry assay, a multiplex immunoassay, a test strip test, or a particle-based assay.

84. The method according to claim 82, wherein the subject is a dog.

85. The method according to any of claims 82 to 84, wherein the therapeutic compound is an antibiotic.

86. The method according to claim 85, wherein the antibiotic is doxycycline.