Indoleamine 2,3-dioxygenase variants

Abstract

Indoleamine 2,3-dioxygenase (IDO) is a heme-binding enzyme involved in pathophysiological processes including, but not limited to, antimicrobial and antitumor defense, neuropathology, immunoregulation, and antioxidant activity. Aspects of the disclosure relate to variants of IDO that comprise one or more amino acid variations relative to a wild-type IDO and / or that are connected to a synthetic polymer, such as poly (ethylene glycol). Embodiments of the disclosure provide variant IDOs that have improved properties, such as resistance to oxidative conditions, protein solubility, lower propensity to aggregate in vivo, increased half-life in the circulatory system upon administration to a subject, increased binding to a cell or tissue, or any combination thereof. Accordingly, IDO variants of the disclosure can be administered to a subject in need thereof, such as a subject having, suspected of having, or at risk of developing a disease, disorder, or condition, such as one associated with inflammation.

Description

[0001]INDOLEAMINE 2,3-DIOXYGENASE VARIANTS RELATED APPLICATIONS The application claims the benefit under 35 U.S.C. 119(e) of U.S. Provisional Application number 63 / 551,503 filed February 8, 2024, 63 / 710,871 filed October 23, 2024, and 63 / 711,097 filed October 23, 2024, which are incorporated by reference in their entirety. REFERENCE TO AN ELECTRONIC SEQUENCE LISTING The content of the electronic sequence listing (U119770242WO00-SEQ-PRW.xml; Size: 42,114 bytes; and Date of Creation: February 7, 2025) is herein incorporated by reference in its entirety. FEDERALLY SPONSORED RESEARCH This invention was made with government support under Grant No(s). R01 AI171045 and R01 DK129690, awarded by the National Institutes of Health, and Grant No. 1743432, awarded by the National Science Foundation. The government has certain rights in the invention. BACKGROUND OF INVENTION Indoleamine 2,3-dioxygenase (IDO) is a heme-binding enzyme involved in tryptophan catabolism and implicated in certain pathophysiological processes. SUMMARY OF INVENTION Aspects of the disclosure relate to variants of indoleamine 2,3-dioxygenase (IDO) that have improved properties, such as resistance to oxidative conditions, protein solubility, lower propensity to aggregate in vivo, increased half-life in the circulatory system upon administration to a subject, increased binding to a cell or tissue (e.g., a target cell or tissue), and, at least in some aspects, combinations thereof. In some aspects, the disclosure relates to an IDO variant comprising: a hydroxyl-bearing amino acid at one or more positions corresponding to a cysteine in a wild-type IDO selected from the group consisting of: cysteine 85; cysteine 112; cysteine 129; cysteine 159; cysteine 206; cysteine 272; cysteine 308; and cysteine 335; a peptide or protein fused to the N-terminus 12084414.1 of the IDO; a peptide or protein fused to the C-terminus of the IDO; or any combination thereof. In some embodiments, the one or more positions in the wild-type IDO comprise at least two positions selected from the group consisting of: cysteine 85; cysteine 112; cysteine 129; cysteine 159; cysteine 206; cysteine 272; cysteine 308; and cysteine 335. In some embodiments, the one or more positions in the wild-type IDO comprise: cysteine 112, cysteine 159, and cysteine 308; or cysteine 112, cysteine 159, cysteine 206, and cysteine 308. In some embodiments, each hydroxyl-bearing amino acid at the one or more positions are independently selected from a serine or a threonine. In some embodiments, the heterologous cysteine is a modified cysteine. In some embodiments, the modified cysteine comprises a synthetic polymer (e.g., PEG). In some embodiments, the IDO variant comprises a fusion to: a galectin; a soluble peptide; a self- assembling peptide; a linker; an antibody or a fragment thereof; an Fc domain, a secretion signal or secretion tag; or any combination thereof. In some embodiments, the IDO variant is capable of being glycosylated or is glycosylated with monomeric or polymeric glycosides. In some embodiments, the IDO variant is fused to an amino acid sequence that is at least 75% identical to any one of SEQ ID NOs: 15-37. In some embodiments, the IDO variant comprises an amino acid sequence that is at least 75% identical to any one of SEQ ID NOs: 1-37. In some aspects, the disclosure relates to nucleic acids (e.g., vectors, such as plasmids) comprising a nucleotide sequence encoding an IDO variant described herein. The disclosure also relates to cells (e.g., mammalian cells, such as human cells) comprising an IDO variant and / or a nucleic acid encoding an IDO variant. In addition, the disclosure relates to compositions (e.g., pharmaceutical compositions) comprising an IDO variant, a nucleic encoding an IDO variant, a cell comprising an IDO variant, and / or a cell comprising a nucleic acid encoding an IDO variant. Any of the IDO variants, nucleic acids, cells, and / or compositions described herein can also be comprised in a kit described herein. In some embodiments, a method comprises administering the IDO variant to a subject in need thereof. In some embodiments, the subject is a mammal (e.g., a human). In some embodiments, the subject is characterized as having, suspected of having, or at risk of developing a disease, a disorder, or a condition described herein. In other embodiments, a method comprises contacting the IDO variant or a nucleic acid encoding the IDO variant with one or more cells (e.g., mammalian cells, such as human cells). In other aspects, the disclosure relates to method comprising contacting an IDO with a synthetic molecule comprising a functional group capable of forming at least one bond between 12084414.1 the IDO and the synthetic molecule. In some embodiments, the IDO is an IDO variant comprising a hydroxyl-bearing amino acid at one or more positions corresponding to a cysteine in a wild-type IDO selected from the group consisting of: cysteine 85; cysteine 112; cysteine 129; cysteine 159; cysteine 206; cysteine 272; cysteine 308; and cysteine 335; a cysteine that is heterologous to a wild-type IDO; a peptide or protein fused to the N-terminus of the IDO; a peptide or protein fused to the C-terminus of the IDO; or any combination thereof. In some embodiments, the synthetic molecule comprises a synthetic polymer (e.g., a synthetic polymer comprising polyethylene glycol (PEG)). In some embodiments, the functional group is capable of reacting with a sulfhydryl group (e.g., a functional group comprising maleimide). In some embodiments, the at least one bond comprises a covalent bond. In some embodiments, the IDO or the variant thereof has been contacted with one or more agents capable of reducing a sulfhydryl group prior to being contacted with the synthetic molecule. In some embodiments, the method further comprises expressing the IDO or the variant thereof in one or more cells and / or purifying the IDO or the variant thereof prior to the contacting with the synthetic molecule. BRIEF DESCRIPTION OF DRAWINGS FIGs. 1A-1G show non-limiting embodiments of indoleamine 2,3-dioxygenase (IDO) variants. FIG. 1A shows a schematic of an IDO variant comprising a cysteine-to-hydroxyl- bearing amino acid (e.g., serine or threonine) substitution at one, two, three, or four of the indicated positions. FIG. 1B shows a schematic of an IDO variant comprising a peptide (e.g., a soluble peptide or linker), a galectin, a self-assembling peptide (assembly peptide), or a combination thereof which are fused to the IDO variant (e.g., at the N-terminus and / or the C- terminus). FIG. 1C shows a schematic of an IDO variant comprising a heterologous cysteine residue and / or a peptide (e.g., a soluble peptide or linker) comprising a heterologous cysteine residue that, at least in some embodiments, can be used to conjugate the IDO variant to a synthetic polymer. FIG. 1D shows a schematic of a method for producing a PEGyalted IDO variant. FIG. 1E shows a schematic of a method for producing an assembly comprising five IDO variants formed via fusion to a self-assembling peptide (coiled-coil forming peptide sequence). FIG. 1F shows a CATCH hydrogel comprising oppositely charged peptides that, when combined, co-assemble into a nanofiber-based hydrogel (left panel) and the use of CATCH peptides for whole protein functionalization (right panel). FIG. 1G shows a schematic of an IDO variant comprising an Fc domain. 12084414.1 FIG. 2 shows non-limiting embodiments of cysteines in a wild-type IDO that can be mutated to produce an IDO variant. FIGs. 3A-3C show representative results obtained from analyses of IDO variants comprising cysteine mutations. IDO-Tri = IDO variant comprising C112S, C159S, and C308S mutations and IDO-Tetra = IDO variant comprising C112S, C159S, C206S, and C308S mutations. FIG. 3A shows results obtained from IDO enzymatic activity analyses of IDO variants. FIG. 3B shows results obtained from SDS-PAGE analysis of purified IDO variants. FIG. 3C shows results obtained from IDO enzymatic activity analyses of IDO variants. FIG. 4 shows representative obtained results from SDS-PAGE analyses of IDO variants comprising cysteine mutations prior to being subjected to PEGylation. IDO-Tri = IDO variant comprising C112S, C159S, and C308S mutations and IDO-Tetra = IDO variant comprising C112S, C159S, C206S, and C308S mutations. FIG. 5 shows representative results obtained from analyses of free maleimide in samples comprising IDO variants comprising cysteine mutations and the IDO enzymatic activity of PEGylated IDO variants comprising cysteine mutations. IDO-Tri = IDO variant comprising C112S, C159S, and C308S mutations and IDO-Tetra = IDO variant comprising C112S, C159S, C206S, and C308S mutations. FIG. 6 shows representative results obtained from analyses of the IDO enzymatic activity of PEGylated IDO variants (PEG-IDO) subjected to molar titration and incubation for 6 hours at 4oC. FIG. 7 shows representative results obtained from analyses of the IDO enzymatic activity of PEGylated IDO variants (PEG-IDO) subjected to molar titration and incubation for 48 hours at 4oC. FIG. 8 shows representative results obtained from analyses of the IDO enzymatic activity of an assembly of five IDO variants formed via fusion to co-assembling peptides (IDO- 5). FIG. 9 shows representative results obtained from dynamic light scattering analyses of an assembly of five IDO variants formed via fusion to co-assembling peptides (IDO-5) and PEGylated IDO variants (PEG-IDO). FIG. 10 shows representative results obtained from pharmacokinetic analyses of an assembly of five IDO variants formed via fusion to co-assembling peptides (IDO-5) and PEGylated IDO variants (PEG-IDO) following injection into mouse subjects. 12084414.1 FIG. 11 shows representative results obtained from western blot analyses of an assembly of five IDO variants formed via fusion to co-assembling peptides (penta-IDO) and PEGylated IDO variants (PEG-IDO) following injection into mouse subjects. Blood samples were collected from subjects at 96 (left panel) and 144 hours (right panel) after injection prior to being subjected to western blot analysis. FIG. 12 shows SDS PAGE gel of CATCH-IDO purified from E. coli. FIGs. 13A-13B show CATCH-IDO is active in the CATCH gel. FIGs. 14A-14E show decreased LPS-induced responses in dendritic cells. FIGs. 14A- 14B show CATCH-IDO gels decrease LPS-induced inflammatory cytokine secretion by dendritic cells, IL-12. FIG. 14C-14D show CATCH-IDO gels decrease LPS-induced inflammatory gene expression in dendritic cells. FIG. 14E shows CATCH-IDO gels decrease LPS-induced inflammatory cytokine secretion by dendritic cells, IL-6. FIG. 15A-15B show CATCH gels extend the local residence time of active enzyme in vivo. FIG. 16 shows a non-limiting example of a method for analyzing suppression of localized LPS-induced inflammation and pain in vivo following administration of CATCH-IDO gels. DETAILED DESCRIPTION OF INVENTION The disclosure relates to variants (alternatively referred to as mutants) of the anti- inflammatory enzyme, indoleamine 2,3-dioxygenase (IDO). Variant IDOs of the disclosure can have improved properties relative to a wild-type IDO, such as resistance to oxidative conditions, protein solubility, lower propensity to aggregate in vivo, increased half-life in the circulatory system upon administration to a subject, increased binding to a cell or tissue (e.g., a target cell or tissue), or any combination thereof. Thus, IDO variants of the disclosure can be administered to a subject, such as for the purposes of reducing, preventing, or ameliorating inflammation in the subject. In some embodiments, an IDO variant comprises one or more amino acid variations at surface-exposed residues, such as cysteine residues in a wild-type IDO that are sensitive to oxidation. In some embodiments, the cysteine residues in the wild-type IDO protein comprises one or more of cysteine 85, cysteine 112, cysteine 129, cysteine 159, cysteine 206, cysteine 272, 12084414.1 cysteine 308, or cysteine 335. In some embodiments, the cysteine residues are mutated to comprise one or more hydroxyl-bearing amino acid residues (see, e.g., FIGs. 1A-1C), such as serine or threonine. In some embodiments, an IDO variant comprises a serine or a threonine residue at amino acid positions corresponding to cysteine 112, cysteine 159, and cysteine 308 in wild-type IDO. In some embodiments, an IDO variant comprises a serine or a threonine residue at amino acid positions corresponding to cysteine 112, cysteine 159, cysteine 206, and cysteine 308 in wild-type IDO. However, in other embodiments, one or more of the cysteine residues are mutated to a residue that is not serine or threonine, such as a polar amino acid (e.g., an amide-bearing amino acid, such as asparagine or glutamine), a charged amino acid (e.g., an acidic amino acid or anionic amino acid, such as aspartate or glutamate, or a basic amino acid or cationic amino acid, such as arginine, lysine, or histidine), or a hydrophobic amino, such as glycine, alanine, valine, leucine, methionine, isoleucine, phenylalanine, tyrosine, tryptophan, proline, phenylalanine, or tyrosine. In some embodiments, an IDO variant comprises at least one cysteine residue which is mutated to a serine or threonine residue and at least one cysteine residue which has been mutated to a residue that is not serine or a threonine. In some embodiments, an IDO variant comprises one or more heterologous peptides or heterologous proteins that are connected (e.g., fused through a covalent bond) to an IDO protein (e.g., wherein the IDO variant comprises a wild-type IDO amino acid sequence or an IDO amino acid sequence comprising one or more mutations (e.g., a substitution at one or more positions comprising cysteine in wild-type IDO) relative to a wild-type IDO amino acid sequence). In some embodiments, one or more heterologous peptides or heterologous proteins are connected (e.g., fused through a covalent bond) to an IDO variant (see, e.g., FIGs. 1A-1C and 1G). In some embodiments, a heterologous peptide or heterologous protein is connected to the N-terminus and / or the C-terminus of an IDO variant. In some embodiments, a heterologous peptide or heterologous protein comprises a linker. In some embodiments, a heterologous peptide or heterologous protein comprises a self-assembling peptide. In some embodiments, a heterologous peptide or heterologous protein comprises a sequence of polar and aprotic amino acids which can be repeated in an IDO variant (e.g., repeated 1-20 times, such as 5, 8, 10, or 12 times), such as a soluble peptide described herein. In some embodiments, a heterologous protein comprises a galectin, such as galectin-3 (Gal3). In some embodiments, a heterologous protein or heterologous peptide comprises a glycosyltransferase recognition sequence. 12084414.1 In some embodiments, an IDO variant comprises a cysteine residue which is heterologous to wild-type IDO, such as a cysteine residue which has been inserted into the amino acid sequence of the IDO variant or a substitution of a residue in IDO which has been mutated to comprise the heterologous cysteine. In some embodiments, a heterologous cysteine residue is used for site-specific conjugation of a synthetic polymer, such as poly(ethylene glycol) (PEG) onto an IDO variant. In some embodiments, conjugating a synthetic polymer onto an IDO variant improves properties that are useful for administering an IDO variant to a subject. For example, in some embodiments, conjugating a synthetic polymer (e.g., PEG) onto an IDO variant improves protein solubility, prevents protein aggregation, increases protein half-life in vivo (e.g., in the circulatory system of a subject), increased binding to a cell or tissue (e.g., a target cell or tissue), or any combination thereof. Further aspects of the disclosure relate to methods. In some embodiments, methods of producing IDO variants described herein are provided. In some embodiments, a method of producing an IDO variant comprises expressing recombinant IDOs in cells (see, e.g., FIGs. 1D- 1F) from a nucleic acid (e.g., a vector, such as a plasmid) encoding IDO or a variant thereof. In some embodiments, methods comprise subjecting recombinant IDOs expressed from cells to one or more conditions and / or purification steps to produce an IDO variant. The one or more conditions and / or purification steps can include those that are useful for generating PEGylated IDO variants and / or IDO variants that form assemblies comprising a plurality of IDO variant molecules that are connected (e.g., fused covalently) to self-assembling peptides. Methods provided by the disclosure also relate to administering IDO variants or assemblies thereof to a subject (e.g., a mammalian subject, such as a human subject) in need thereof. In some embodiments, a subject is characterized as a having, suspected of having, or at risk of developing a disease, a disorder, or a condition. In some embodiments, the disease, disorder, or condition is associated with increased inflammation in the subject including, but not limited to, cancer, an inflammatory disorder, an infectious disease, an autoimmune disease, or a neurological disease or disorder. In some embodiments, administration of an IDO variant or assembly (e.g., a complex, or a composition thereof, formed by proteins comprising an IDO variant, which can include a gel, such as a hydrogel) thereof can be used to treat a subject in need thereof, such as a subject having one or more symptoms or signs associated with increased inflammation or other disease, disorder, or condition described herein. 12084414.1 Methods of producing IDO variants described herein can be used to generate compositions (e.g., pharmaceutical compositions) comprising IDO variants or assemblies thereof. Compositions and kits comprising IDO variants are further provided herein. The disclosure also provides compositions and kits that can be used to produce IDO variants or assemblies thereof. In some embodiments, a composition (e.g., a pharmaceutical composition) or a kit described herein can be used to administer an IDO variant or an assembly thereof (e.g., a complex, or a composition thereof, formed by proteins comprising an IDO variant, which can include a gel, such as a hydrogel) to a subject. Indoleamine 2,3-Dioxygenase Variants Indoleamine 2,3-dioxygenase (IDO) is a heme-binding enzyme that catalyzes the first and rate-limiting step in tryptophan catabolism to N-formyl-kynurenine. IDO acts on multiple tryptophan substrates including D-tryptophan, L-tryptophan, 5-hydroxy-tryptophan, tryptamine, and serotonin. IDO is also involved pathophysiological processes including, but not limited to, antimicrobial and antitumor defense, neuropathology, immunoregulation, and antioxidant activity. In humans, IDO comprises 403 amino acids which fold into a small domain and a large domain. Molecular modeling analyses indicate that the large domain comprises the catalytic binding pocket which comprises a heme molecule that is involved in the IDO enzymatic activity. A non-limiting example of a human wild-type IDO amino acid sequence is set forth in SEQ ID NO: 1 below: MAHAMENSWTISKEYHIDEEVGFALPNPQENLPDFYNDWMFIAKHLPDLIESGQLRERVEKLNML SIDHLTDHKSQRLARLVLGCITMAYVWGKGHGDVRKVLPRNIAVPYCQLSKKLELPPILVYADCV LANWKKKDPNKPLTYENMDVLFSFRDGDCSKGFFLVSLLVEIAAASAIKVIPTVFKAMQMQERDT LLKALLEIASCLEKALQVFHQIHDHVNPKAFFSVLRIYLSGWKGNPQLSDGLVYEGFWEDPKEFA GGSAGQSSVFQCFDVLLGIQQTAGGGHAAQFLQDMRRYMPPAHRNFLCSLESNPSVREFVLSKGD AGLREAYDACVKALVSLRSYHLQIVTKYILIPASQQPKENKTSEDPSKLEAKGTGGTDLMNFLKT VRSTTEKSLLKEG (NCBI Ref. Seq.: NP_002155.1; SEQ ID NO: 1) The human IDO gene is located on chromosome 8 at positions 39.9-39.93 Mb. A non- limiting example of a human IDO gene sequence is set forth in SEQ ID NO: 2 below: ACTGAGGGGCACCAGAGGAGCAGACTACAAGAATGGCACACGCTATGGAAAACTCCTGGACAATC AGTAAAGAGTACCATATTGATGAAGAAGTGGGCTTTGCTCTGCCAAATCCACAGGAAAATCTACC TGATTTTTATAATGACTGGATGTTCATTGCTAAACATCTGCCTGATCTCATAGAGTCTGGCCAGC TTCGAGAAAGAGTTGAGAAGTTAAACATGCTCAGCATTGATCATCTCACAGACCACAAGTCACAG CGCCTTGCACGTCTAGTTCTGGGATGCATCACCATGGCATATGTGTGGGGCAAAGGTCATGGAGA TGTCCGTAAGGTCTTGCCAAGAAATATTGCTGTTCCTTACTGCCAACTCTCCAAGAAACTGGAAC TGCCTCCTATTTTGGTTTATGCAGACTGTGTCTTGGCAAACTGGAAGAAAAAGGATCCTAATAAG 12084414.1 CCCCTGACTTATGAGAACATGGACGTTTTGTTCTCATTTCGTGATGGAGACTGCAGTAAAGGATT CTTCCTGGTCTCTCTATTGGTGGAAATAGCAGCTGCTTCTGCAATCAAAGTAATTCCTACTGTAT TCAAGGCAATGCAAATGCAAGAACGGGACACTTTGCTAAAGGCGCTGTTGGAAATAGCTTCTTGC TTGGAGAAAGCCCTTCAAGTGTTTCACCAAATCCACGATCATGTGAACCCAAAAGCATTTTTCAG TGTTCTTCGCATATATTTGTCTGGCTGGAAAGGCAACCCCCAGCTATCAGACGGTCTGGTGTATG AAGGGTTCTGGGAAGACCCAAAGGAGTTTGCAGGGGGCAGTGCAGGCCAAAGCAGCGTCTTTCAG TGCTTTGACGTCCTGCTGGGCATCCAGCAGACTGCTGGTGGAGGACATGCTGCTCAGTTCCTCCA GGACATGAGAAGATATATGCCACCAGCTCACAGGAACTTCCTGTGCTCATTAGAGTCAAATCCCT CAGTCCGTGAGTTTGTCCTTTCAAAAGGTGATGCTGGCCTGCGGGAAGCTTATGACGCCTGTGTG AAAGCTCTGGTCTCCCTGAGGAGCTACCATCTGCAAATCGTGACTAAGTACATCCTGATTCCTGC AAGCCAGCAGCCAAAGGAGAATAAGACCTCTGAAGACCCTTCAAAACTGGAAGCCAAAGGAACTG GAGGCACTGATTTAATGAATTTCCTGAAGACTGTAAGAAGTACAACTGAGAAATCCCTTTTGAAG GAAGGTTAATGTAACCCAACAAGAGCACATTTTATCATAGCAGAGACATCTGTATGCATTCCTGT CATTACCCATTGTAACAGAGCCACAAACTAATACTATGCAATGTTTTACCAATAATGCAATACAA AAGACCTCAAAATACCTGTGCATTTCTTGTAGGAAAACAACAAAAGGTAATTATGTGTAATTATA CTAGAAGTTTTGTAATCTGTATCTTATCATTGGAATAAAATGACATTCAATAAATAAAAATGCAT AAGATATATTCTGTCGGCTGGGCGCGGTGGCTCACGCCTGTAATCCCAGCACTTTGGGAGGCCGA GGCGGGCGGATCACAAGGTCAGGAGATCGAGACCATCTTGGCTAACACGGTGAAACCCCGTCTCT ACTAAAAATACAAAAAATTAGCCGGGCGCGGTGGCGGGCACCTGTAGTCCCAGCTACTCGGGAGG CTGAGGCAGGAGAATGGCGTGAACCTGGGAGGCGGAGCTTGCAGTGAGCCAAGATTGTGCCACTG CAATCCGGCCTGGGCTAAAGAGCGGGACTCCGTCTCAAAAAAAAAAAAAAAAAGATATATTCTGT CATAATAAATAAAAATGCATAAGATATAA (NCBI Ref. Seq.: NM_002164.6; SEQ ID NO: 2) In some embodiments, an IDO variant comprises one or amino acid variations relative to a wild-type IDO (e.g., wherein the one or more amino acid variations are relative to the amino acid sequence set forth in SEQ ID NO: 1 or wherein the one or more amino acid variations are relative to an amino acid sequence encoded by the nucleotide sequence set forth in SEQ ID NO: 2). Non-limiting examples of amino acid variations include substituted amino acids, inserted amino acids, and deleted amino acids. In some embodiments, an amino acid variation comprises a modified amino acid, such as a chemically modified amino acid. In some embodiments, a modified amino acid is a biotinylated amino acid. In some embodiments, a modified amino acid is a glycosylated amino acid. In some embodiments, a glycosylated amino acid is glycosylated with a monomeric glycoside or a polymeric glycoside. In some embodiments, an IDO variant comprises one or more monomeric glycosides and / or one or more polymeric glycosides. In some embodiments, an IDO variant comprises at least one amino acid substitution. In some embodiments, the at least one amino acid substitution is at a position comprising cysteine in the wild-type IDO protein. In some embodiments, the position comprising cysteine in the wild-type IDO protein is cysteine 85, cysteine 112, cysteine 129, cysteine 159, cysteine 206, cysteine 272, cysteine 308, or cysteine 335. Thus, in some embodiments, an IDO variant comprises a substitution (e.g., a substitution of a serine or threonine) at a position corresponding to cysteine 85, a position corresponding to cysteine 112 in the wild-type IDO, a position corresponding to cysteine 129 in the wild-type IDO, a position corresponding to cysteine 159 in 12084414.1 the wild-type IDO, a position corresponding to cysteine 206 in the wild-type IDO, a position corresponding to cysteine 272 in the wild-type IDO, a position corresponding to cysteine 308 in the wild-type IDO, and / or a position corresponding to cysteine 335 in the wild-type IDO (e.g., wherein the wild-type IDO comprises the amino acid sequence set forth in SEQ ID NO: 1 or the amino acid sequence encoded by the nucleotide sequence set forth in SEQ ID NO: 2). In some embodiments, an IDO variant comprises a serine at an amino acid position corresponding to cysteine 85. In some embodiments, an IDO variant comprises a serine at an amino acid position corresponding to cysteine 112. In some embodiments, an IDO variant comprises a serine at an amino acid position corresponding to cysteine 129. In some embodiments, an IDO variant comprises a serine at an amino acid position corresponding to cysteine 159. In some embodiments, an IDO variant comprises a serine at an amino acid position corresponding to cysteine 206 IDO. In some embodiments, an IDO variant comprises a serine at an amino acid position corresponding to cysteine 272. In some embodiments, an IDO variant comprises a serine at an amino acid position corresponding to cysteine 308. In some embodiments, an IDO variant comprises a serine at an amino acid position corresponding to cysteine 335. In some embodiments, an IDO variant comprises a threonine at an amino acid position corresponding to cysteine 85. In some embodiments, an IDO variant comprises a threonine at an amino acid position corresponding to cysteine 112. In some embodiments, an IDO variant comprises a threonine at an amino acid position corresponding to cysteine 129. In some embodiments, an IDO variant comprises a threonine at an amino acid position corresponding to cysteine 159. In some embodiments, an IDO variant comprises a threonine at an amino acid position corresponding to cysteine 206. In some embodiments, an IDO variant comprises a threonine at an amino acid position corresponding to cysteine 272. In some embodiments, an IDO variant comprises a threonine at an amino acid position corresponding to cysteine 308. In some embodiments, an IDO variant comprises a threonine at an amino acid position corresponding to cysteine 335. In some embodiments, an IDO variant comprises a plurality of amino acid variations relative to a wild-type IDO. As used herein, a “plurality of amino acid variations” refers to 2 amino acid variations or more. In some embodiments, the plurality of amino acid variations in an IDO variant comprises 3, 4, 5, 6, 7, or 8 amino acid variations relative to a wild-type IDO. In some embodiments, the plurality of amino acid variations in an IDO variant comprises 2-4, 2-5, 5-10, 10-20, 20-30, 30-50, 50-100, or more amino acid variations relative to a wild-type IDO. In 12084414.1 some embodiments, the plurality of amino acid variations comprises one or more amino acid substitutions, one or more amino acid insertions, and / or one or more amino acid deletions relative to a wild-type IDO. In some embodiments, an IDO variant comprises a plurality of amino acid substitutions. In some embodiments, the plurality of substitutions comprises a plurality of cysteine residues that have been replaced with hydroxyl-bearing amino acids. In some embodiments, a hydroxyl- bearing amino acid is selected from a serine or a threonine. In some embodiments, the plurality of substitutions comprises a hydroxyl-bearing amino acid at two, three, four, or more of the following amino acid positions in a wild-type IDO: cysteine 85; cysteine 112; cysteine 129; cysteine 159; cysteine 206; cysteine 272; cysteine 308; and cysteine 335, wherein each hydroxyl-bearing amino acid in the plurality is selected from a serine or a threonine. In some embodiments, the plurality of substitutions comprises a plurality of cysteine residues that have been replaced with serine residues. In some embodiments, the plurality of substitutions in an IDO variant comprises any combination of at least two of: a serine at an amino acid position corresponding to cysteine 112 of the wild-type IDO; a serine at an amino acid position corresponding to cysteine 159 of the wild-type IDO; a serine at an amino acid position corresponding to cysteine 206 of the wild-type IDO; and a serine at an amino acid position corresponding to cysteine 308 of the wild-type IDO. In some embodiments, the plurality of substitutions in an IDO variant comprises any combination of at least three of: a serine at an amino acid position corresponding to cysteine 112 of the wild-type IDO; a serine at an amino acid position corresponding to cysteine 159 of the wild-type IDO; a serine at an amino acid position corresponding to cysteine 206 of the wild-type IDO; and a serine at an amino acid position corresponding to cysteine 308 of the wild-type IDO. In some embodiments, an IDO variant comprises a serine at an amino acid position corresponding to cysteine 112 of the wild- type IDO, a serine at an amino acid position corresponding to cysteine 159 of the wild-type IDO, and a serine at an amino acid position corresponding to cysteine 308 of the wild-type IDO. In some embodiments, an IDO variant comprises a serine at an amino acid position corresponding to cysteine 112 of the wild-type IDO, a serine at an amino acid position corresponding to cysteine 159 of the wild-type IDO, a serine at an amino acid position corresponding to cysteine 206 of the wild-type IDO, and a serine at an amino acid position corresponding to cysteine 308 of the wild-type IDO. In some embodiments, the plurality of substitutions comprises a plurality of cysteine residues that have been replaced with threonine 12084414.1 residues. In some embodiments, the plurality of substitutions in an IDO variant comprises any combination of at least two of: a threonine at an amino acid position corresponding to cysteine 112 of the wild-type IDO; a threonine at an amino acid position corresponding to cysteine 159 of the wild-type IDO; a threonine at an amino acid position corresponding to cysteine 206 of the wild-type IDO; and a threonine at an amino acid position corresponding to cysteine 308 of the wild-type IDO. In some embodiments, the plurality of substitutions in an IDO variant comprises any combination of at least three of: a threonine at an amino acid position corresponding to cysteine 112 of the wild-type IDO; a threonine at an amino acid position corresponding to cysteine 159 of the wild-type IDO; a threonine at an amino acid position corresponding to cysteine 206 of the wild-type IDO; and a threonine at an amino acid position corresponding to cysteine 308 of the wild-type IDO. In some embodiments, an IDO variant comprises a threonine at an amino acid position corresponding to cysteine 112 of the wild-type IDO, a threonine at an amino acid position corresponding to cysteine 159 of the wild-type IDO, and a threonine at an amino acid position corresponding to cysteine 308 of the wild-type IDO. In some embodiments, an IDO variant comprises a threonine at an amino acid position corresponding to cysteine 112 of the wild-type IDO, a threonine at an amino acid position corresponding to cysteine 159 of the wild-type IDO, a threonine at an amino acid position corresponding to cysteine 206 of the wild- type IDO, and a threonine at an amino acid position corresponding to cysteine 308 of the wild- type IDO. However, in other embodiments, an IDO variant comprises at least one cysteine-to- hydroxyl-bearing amino acid substitution described herein in addition to one or more cysteines (e.g., one or more of C85, C112, C129, C159, C206, C272, C308, or C335) that have been deleted or substituted for an amino acid which is not serine or threonine (e.g., an alanine, a polar amino acid, a charged amino acid, etc.). In some embodiments, an IDO variant comprises a cysteine residue which is heterologous to a wild-type IDO. As used herein, “a heterologous cysteine” is a cysteine which is inserted into an IDO variant or substituted for an amino acid residue that is found in wild-type IDO (see, e.g., the IDO amino acid sequence set forth in SEQ ID NO: 1 or the IDO amino acid sequence encoded by the nucleotide sequence set forth in SEQ ID NO: 2). In some embodiments, a heterologous cysteine is in an N-terminal region (e.g., amino acids 1-5, 5-10, 10-15, or 15-20) and / or in a C-terminal region (e.g., amino acids 380-385, 385-390, 390-395, or 395-403) of an IDO variant. In some embodiments, a heterologous cysteine is at the N-terminus and / or the C-terminus of an IDO variant. In some embodiments, a variant IDO comprises a 12084414.1 plurality of heterologous cysteines (e.g., 2, 3, 4, or more). In some embodiments, a heterologous cysteine is a modified cysteine (e.g., a chemically modified cysteine). In some embodiments, a heterologous cysteine is a chemically modified cysteine located at an amino acid position corresponding to cysteine 85, cysteine 112, cysteine 129, cysteine 159, cysteine 206, cysteine 272, cysteine 308, and / or cysteine 335 in wild-type IDO. In some embodiments, a heterologous cysteine is modified to comprise a synthetic polymer. Non-limiting examples of synthetic polymers include Polysarcosine, polysaccharides, polyvinyl pyrrolidone (PVP), Zwitterionic polymers, Poly(amino acid)-based lipopolymers, polymers comprising XTEN, Poly(thioglycidyl glycerol), poly(lactic-co-glycolic acid) (PLGA), polyvinyl alcohol (PVA), polyethylene oxide (PEO), poly(N-isopropylacrylamide) (PNIPAAm), poly(ethyleneimine) (PEI), poly(caprolactone) (PCL), poly(acrylic acid) (PAA), poly(methyl methacrylate) (PMMA), poly(ethylene glycol) (PEG), and combinations thereof. In some embodiments, the synthetic polymer comprises a hydrophilic polymer. In some embodiments, the synthetic polymer comprises poly(ethylene glycol) (PEG). In some embodiments, the synthetic polymer comprises a forked PEG chain and / or a Y-shaped PEG chain. In some embodiments, an IDO variant comprising a synthetic polymer (e.g., PEG) has a molecular weight of greater than 45 g / mol. In some embodiments, such as 45-260 g / mol, 46-150 g / mol, or 50-75 g / mol. In some embodiments, an IDO variant comprises one or more peptides and / or one or more proteins which are heterologous to a wild-type IDO. Non-limiting examples of peptides and / or proteins that are heterologous to a wild-type IDO include streptavidin and derivatives thereof, linkers, soluble peptides, self-assembling peptides, galectins (e.g., galectin-3), and combinations thereof. In some embodiments, an IDO variant which does not comprise a heterologous peptide or heterologous protein has a molecular weight of approximately 45 g / mol. In some embodiments, an IDO variant comprising a heterologous peptide or heterologous protein has a molecular weight of greater than 45 g / mol. In some embodiments, an IDO variant comprising a heterologous peptide and / or heterologous protein has a molecular weight of approximately 45-260 g / mol. In some embodiments, an IDO variant comprising a heterologous peptide and / or heterologous protein has a molecular weight of 46-150 g / mol. In some embodiments, an IDO variant comprising a heterologous peptide and / or heterologous protein has a molecular weight of 50-75 g / mol. 12084414.1 A heterologous peptide or heterologous protein will typically comprise at least 2 amino acids in length. In some embodiments, a heterologous peptide comprises 3-200 amino acids in length. In some embodiments, a heterologous peptide comprises 3-10, 10-25, 25-50, 50-75, 75- 100, 100-125, 125-150, or 150-200 amino acids in length. In some embodiments, a heterologous peptide comprises more than 200 amino acids in length. In some embodiments, a heterologous protein comprises 200 amino acids or more, such as 200-250, 250-300, 300-400, 400-500, or more amino acids in length. In some embodiments, an IDO variant comprises one or more glycosyltransferase recognition sequences. In some embodiments, a glycosyltransferase recognition sequence is capable of being glycosylated to comprise a monomeric glycoside or a polymeric glycoside. In some embodiments, a glycosyltransferase recognition sequence is capable of binding to an O- GlcNAc transferase (OGT). In some embodiments, a glycosyltransferase recognition sequence comprises an amino acid sequence of: APTYAP. In some embodiments, a glycosyltransferase recognition sequence is within the amino acid sequence of an IDO variant (e.g., wherein the glycosyltransferase recognition sequence is flanked by amino acids in the N- and C-terminal directions, such as wherein the glycosyltransferase recognition sequence is not comprised in an amino acid sequence at the N-terminus or the C-terminus). In some embodiments, a glycosyltransferase recognition sequence is comprised in an amino acid sequence fused at the N- terminus and / or C-terminus of the IDO variant (e.g., comprised in a heterologous peptide or protein described herein). In some embodiments, a heterologous peptide and / or heterologous protein comprises a linker. In some embodiments, the linker is fused to the N-terminus and / or the C-terminus of the IDO variant. In some embodiments, a linker comprises a combination of synthetic molecules, such as synthetic polymers, and amino acids. In some embodiments, a linker is at least one amino acid length. In some embodiments, a linker comprises any combination of the 20 naturally occurring amino acids. In some embodiments, a linker comprises 1-100 amino acids in length. In some embodiments, a linker comprises 2-5, 5-10, 10-20, 20-30, 30-40, 40-50, 50-60, 60-70, 70-80, 80-90, or 90-100 amino acids in length. In some embodiments, a linker comprises 2-25 amino acids in length. In some embodiments, a linker comprises 2-10 amino acids in length. In some embodiments, a linker comprises a heterologous cysteine described herein. In some embodiments, a linker is a flexible linker, such as a hydrophilic linker. In some embodiments, a linker is a Gly-Ser linker. In some embodiments, a linker comprises a sequence 12084414.1 comprising (X1X1X1X2)y, wherein X1and X2each correspond to respective amino acids. In some embodiments, X1 is glycine and X2 is serine. In some embodiments, X1 is serine and X2 is glycine. In some embodiments, a linker comprises the sequence (X1X1X1X2)y, wherein the sequence comprising X1X1X1X2is present a “y” number of times in the linker, wherein “y” is 1- 50 (e.g., 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 10-15, 15-20, 20-25, etc.). In some embodiments, a heterologous peptide or protein comprises a soluble peptide. In some embodiments, a soluble peptide comprises a sequence of one or more polar and one or more aprotic amino acids which can be repeated in an IDO variant. In some embodiments, a soluble peptide comprises a sequence of one or more polar amino acids and one or more aprotic amino acids that are repeated 1-20 times, such as 5, 8, 10, or 12 times. In some embodiments, each repeat comprises 10-15 amino acids. In some embodiments, a polar amino acid in a soluble peptide is selected from serine, threonine, cysteine, proline, asparagine, and glutamine. In some embodiments, an aprotic amino acid in a soluble peptide is selected from a hydrophobic amino acid (e.g., glycine, alanine, valine, leucine, methionine, isoleucine, phenylalanine, tyrosine, and tryptophan), or a polar amino acid (e.g., serine, threonine, cysteine, proline, asparagine, and glutamine). In some embodiments, 4-8 amino acids in a soluble peptide are continuous and comprise residues that form flexible structures, such as serine- and / or-glycine rich sequences. In some embodiments, the 4-8 amino acids are positioned C-terminally relative to a sequence of 5 amino acids that are each an aprotic amino acid. In some embodiments, an IDO variant comprises a soluble peptide that is N-terminally or C-terminally fused. In some embodiments, an IDO variant comprises a soluble peptide that is N-terminally or C-terminally fused via a linker. In some embodiments, a soluble peptide comprises a cysteine at its N-terminus or C-terminus. In some embodiments, the cysteine comprises a synthetic polymer described herein. In some embodiments, a heterologous peptide and / or heterologous protein comprises a self-assembling peptide. As used herein, a “self-assembling peptide” refers to peptides that form interactions in the presence of one or more other self-assembling peptide molecules which promote them to adopt ordered, larger scale structures, such as granules, particles, etc. Non- limiting examples of self-assembling peptides that can be used in embodiments of the disclosure include those which have been described previously in WO2018 / 067660, US20210107943, WO2022 / 225987, and WO2023 / 201370 which are incorporated by reference herein for their disclosures related to self-assembling peptide structure, making self-assembling peptides, and 12084414.1 methods of administering self-assembling peptides (e.g., administration of self-assembling peptides to cells and / or subjects). In some embodiments, self-assembling peptides interact to form coiled coils, beta meanders, beta-alpha beta motifs, beta hairpins, Greek key motifs, beta solenoids (e.g., structures comprising beta rolls and / or beta helices, such as parallel beta helices), and / or psi- loop motifs. Non-limiting examples of tools which are useful for prediction of protein structure and may be used to model peptides, polypeptides, and / or proteins comprising self-assembling peptides described herein include AlphaFold, Rossetta, I-TASSER, Robetta, Phyre2, RaptorX, and SWISS-MODEL. The interactions which drive a spontaneous assembly of self-assembling peptides into ordered, larger scale structures can include any combination of intermolecular and intramolecular interactions, such as electrostatic interactions, hydrophobic interactions, hydrogen bonding, van der Waals interactions, pi-pi stacking, etc. In some embodiments, a self- assembling peptide comprises an arrangement of amino acids that adopt ordered structures which are stabilized by interactions involving the side chains of amino acids in the self- assembling peptide. Accordingly, the disclosure also provides for “assemblies” comprising a plurality of IDO variants, wherein at least two of the IDO variants in the plurality comprise a self-assembling peptide. In some embodiments, an assembly comprising a plurality of IDO variants comprises at least two IDO variants. In some embodiments, an assembly comprising a plurality of IDO variants comprises 2, 3, 4, 5, or more IDO variants. In some embodiments, an assembly comprises a plurality of IDO variants, wherein the IDO variants in the assembly stack in an end- end manner or in a side-side manner through the self-assembling peptides that they are connected to. In some embodiments, an IDO variant comprises one or more (e.g., 2, 3, or more) self-assembling peptides which can be connected to the IDO variant directly or indirectly (e.g., via a linker described herein) at the N-terminus and / or the C-terminus. A self-assembling peptide can also be connected to an IDO variant via a covalent and / or a non-covalent linkage at an amino acid side chain (e.g., a cysteine residue) present in the IDO variant amino acid sequence. For example, in some embodiments, an assembly comprises a complex formed by proteins comprising an IDO variant (e.g., wherein the IDO variant is fused to a self-assembly peptide, such as a peptide described in Table 1), or a composition thereof, which can include a gel, such as a hydrogel. 12084414.1 A self-assembling peptide will typically comprise at least 3 amino acids in length. In some embodiments, a self-assembling peptide comprises 3-100 amino acids in length. In some embodiments, a self-assembling peptide comprises 3-5, 5-8, 8-11, 11-15, 15-20, 20-25, 25-30, 30-35, 40-45, 45-50, 50-60, 60-70, 70-80, 80-90, or 90-100 amino acids in length. In some embodiments, a self-assembling peptide comprises more than 100 amino acids in length. In some embodiments, a first self-assembling peptide can interact with a second self-assembling peptide that is of the same length or a different length. In some embodiments, a self-assembling peptide comprises repeat sequences that drive folding events (e.g., via phase separation), wherein hydrophobic moieties in the self-assembling peptide (e.g., the side chains of aromatic amino acids, such as a phenylalanine and tryptophan) are positioned in three-dimensional space so that they form hydrophobic interactions, van der Waals interactions, pi-pi stacking interactions, or any combination thereof. In some embodiments, the repeat sequences drive folding events (e.g., via phase separation), wherein hydrophilic moieties in the self-assembling peptide (e.g., the side chains of hydrophilic amino acids, carbonyl groups in the peptide backbone, and amine groups in the peptide backbone) are positioned in three-dimensional space so that they form electrostatic interactions, hydrogen bonds, van der Waals interactions, or any combination thereof. In some embodiments, the repeat sequences comprise flexible and / or hydrophilic segments (e.g., segments that are serine- and / or glycine-rich) of sequences which promote folding of self-assembling peptides into a conformation that pushes hydrophobic side chains into close physical proximity. In some embodiments, the repeat sequences drive folding events such that the self-assembling peptide adopts a three-dimensional conformation comprising an interior and / or exterior aspect (or face) of the molecule which is substantially hydrophobic and a separate interior and / or exterior aspect (or face) of the molecule which is substantially hydrophilic. In some embodiments, the repeat sequences comprise polar, aprotic amino acid residues. In some embodiments, the repeat sequences are repeated in the self-assembling peptide 1, 2, 3, 4, 5, 6, 7, 8, or 9 times. In some embodiments, the repeat sequences are repeated in the self-assembling peptide 10 times or more. In some embodiments, a self-assembling peptide is a charge-complementary peptide. In some embodiments, a charge-complementary peptide is a positive peptide or a negative peptide comprising one or more charge-complementary segments. In some embodiments, a co- assembling peptide comprises a core sequence of alternating hydrophobic and hydrophilic residues. The “core sequence” refers to a charged (e.g., either positive or negative) segment of 12084414.1 amino acids comprising either at least two hydrophobic residues which flank a cationic or anionic residue or a hydrophobic residue flanked by at least one cationic or anionic residue and a hydrophilic residue (e.g., either polar or charged) (see, e.g., Table 1). Thus, both a hydrophobic core component and a charged core component, provided by the appropriate residues comprising the side chain chemistries, promote peptide assembly. As such, the core structure must be sufficiently hydrophobic and charged. In some embodiments, the other residues found in the N- terminal and / or C-terminal direction of the core structure may be cationic or anionic to further promote self-assembly. In some embodiments, one core sequence is found in a positive and / or negative peptide. In some embodiments, a positive peptide and / or a negative peptide may comprise two, three, four, or more core sequences. In some embodiments, a positive peptide and / or a negative peptide comprise more than one core sequence comprising the same amino acid arrangements (e.g., a positive peptide with a core sequence of KFK and KFK). In some embodiments, a positive peptide and / or a negative peptide comprise more than one core sequence comprising different amino acid arrangements (e.g., a positive peptide with a core sequence of KFK and QFK). In some embodiments, more than one core sequence is found in a positive and / or negative peptide located adjacent to each other in the primary sequence. In some embodiments, more than one core sequence is found in a positive and / or negative peptide and separated by one or more (e.g., two, three, four, or more) residues. In some embodiments, a core sequence comprises one or more amino acids which are located N-terminal to the core sequence and / or C-terminal to the core sequence. In some embodiments, a core sequence comprises 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, or more amino acids which are located N-terminal to the core sequence and / or C-terminal to the core sequence. In some embodiments, a core sequence is flanked by sequences in the N-terminal and C-terminal direction (e.g., with an equal or non- equal number of amino acids flanking it in the N-terminal and C-terminal direction). In some embodiments, the flanking sequences may be the same sequence or different sequences. In some embodiments, however, a core sequence is found at the N-terminus, the C-terminus, or both termini. In some embodiments, an IDO variant comprises a heterologous protein or peptide (e.g., wherein the heterologous protein or peptide is connected, such as via fusion, to the N-terminus and / or C-terminus of the IDO amino acid sequence) to promote binding of the IDO to another protein or peptide (e.g., a protein or peptide located on the surface of a cell, such as a cell located in a tissue of a subject including, but not limited to, a target tissue for delivery of the 12084414.1 IDO). In some embodiments, an IDO variant comprises an antibody or fragment thereof (e.g., an antigen-binding fragment thereof, an Fc domain, and / or a secretion signal or secretion tag) (e.g., wherein the antibody or fragment thereof derived from a human or mouse antibody). In some embodiments, an IDO variant comprises a single-chain variable fragment (scFv) or antigen- binding fragment thereof. In some embodiments, an IDO variant comprises a humanized antibody or antigen-binding fragment thereof. In some embodiments, an IDO variant comprises a chimeric antibody or antigen-binding fragment thereof. In some embodiments, an IDO variant comprises a monoclonal antibody or antigen-binding fragment thereof. In some embodiments, an IDO variant comprises a polyclonal antibody or antigen-binding fragment thereof. In some embodiments, an IDO variant comprises a single-domain antibody or antigen-binding fragment thereof. In some embodiments, an IDO variant comprises a VHH region. In some embodiments, an IDO variant comprises a VH region and / or VL region. In some embodiments, an IDO variant comprises an immunoglobulin (e.g., an immunoglobulin selected from IgM, IgD, IgG3, IgG1, IgA1, IgG2, IgG4, IgE, and IgA2 or an immunoglobulin selected from IgM, IgD, IgG3, IgG1, IgG2b, IgG2a, IgE, and IgA) or a fragment thereof (e.g., an antigen-binding fragment thereof, an Fc domain, and / or an secretion signal or secretion tag). In some embodiments, an IDO variant comprises an IgG1 Fc domain (e.g., an IgG1 Fc domain derived from human or mouse). In some embodiments, an IDO variant comprises an IgG2a Fc domain. In some embodiments, a heterologous protein or peptide comprises a secretion signal or secretion tag (e.g., an immunoglobulin secretion signal or secretion tag, such as an IgG1 secretion signal or secretion tag). In some embodiments, a heterologous protein comprises a galectin. In some embodiments, a galectin is galectin-3 (Gal-3). In some embodiments, an IDO variant comprises a galectin that is N-terminally or C-terminally fused. In some embodiments, an IDO variant comprises a galectin that is N-terminally or C-terminally fused via a linker. In some embodiments, an IDO variant comprises an amino acid sequence having one or more mutations (e.g., one or more substitutions, one or more deletions, and / or one or more insertions) (e.g., 2, 3, 4, 5, 6, 7, 8, 9, 10-15, 15-20, 20-25, 25-30, 30-40, or more than 40 amino mutations) relative to an amino acid sequence described herein (see, e.g., the amino acid sequences in Table 1). In some embodiments, an IDO variant comprising one or more mutations relative to an amino acid sequence described herein comprises an amino acid sequence having at least 75% (e.g., 75-80%, 80-85%, 85-90%, 90-95%, or 95-100%) sequence identity to an amino 12084414.1 acid sequence described herein (see, e.g., the amino acid sequences in Table 1) (e.g., wherein the IDO variant comprises an amino acid sequence having at least 75%-99% identity to any one of the amino acid sequences set forth in SEQ ID NOs 1-37, such as an IDO variant comprising one or more mutations (e.g., one or more substitutions, one or more deletions, and / or one or more insertions) relative to any of SEQ ID NOs: 1-37, or wherein the IDO variant comprises any one of the amino acid sequence set forth in SEQ ID NOs 1-37). In some embodiments, an IDO variant comprises an amino acid sequence having at least 75% identity to a wild-type IDO, such as a wild-type IDO comprising the amino acid sequence of SEQ ID NO: 1. In some embodiments, an IDO variant comprising an amino acid sequence having at least 75% identity to a wild-type IDO can comprise one or more amino acid variations at a position comprising cysteine in the wild-type IDO (see, e.g., the bolded positions in SEQ ID NO: 1 in Table 1). In some embodiments, an IDO variant comprising an amino acid sequence having at least 75% identity to a wild-type IDO can comprise a plurality of amino acid variations at positions (e.g., 2, 3, 4, or more) comprising cysteine in the wild-type IDO (see, e.g., the bolded positions in SEQ ID NO: 1 in Table 1). In some embodiments, an IDO variant comprises an amino acid sequence having at least 75% identity to an IDO variant set forth in any one of SEQ ID NOs: 3- 14. In some embodiments, an IDO variant comprising an amino acid sequence having at least 75% identity to a wild-type IDO can comprise a linker, a self-assembling peptide, or a combination thereof. In some embodiments, the self-assembling peptide is a charge- complementary peptide (e.g., a positive peptide of any one of SEQ ID NOs: 15-21 or a negative peptide of any one of SEQ ID NOs: 22-26) that can spontaneously assemble in the presence of its cognate charge-complementary peptide (e.g., a negative peptide). In some embodiments, a self-assembling peptide in an IDO variant comprises at least 75% identity to any one of SEQ ID NOs: 15-26 such that the hydrophobic component, the charged component, and / or the polar component of the core sequence is substituted relative to any one of SEQ ID NOs: 15-26 (e.g., see the non-limiting examples of core sequences in Table 1). In some embodiments, a self- assembling peptide comprises the sequence set forth in SEQ ID NO: 27. In some embodiments, an IDO variant comprises the amino acid sequence of any one SEQ ID NOs: 3-14. In some embodiments, an IDO variant comprises a linker (see, e.g., any one of the amino acid sequences set forth in SEQ ID NOs: 30, 31, 35, or 36). In some embodiments, an IDO variant comprises a heterologous peptide or heterologous protein comprising the sequence of any one of SEQ ID NOs: 15-37. However, in other embodiments, an IDO variant may comprise the sequence of a 12084414.1 wild-type IDO in addition to comprising one or modified amino acids that are linked to a synthetic polymer described herein. Table 1. Non-limiting Examples of Sequences Corresponding to IDO Variants 12084414.1 12084414.1 12084414.1 12084414.1 12084414.1 12084414.1 Compositions In some aspects, the disclosure relates to compositions. In some embodiments, a composition comprises an IDO variant described herein or any assembly thereof. In some embodiments, a composition comprises a nucleic acid described herein. In some embodiments, a composition comprises a cell or cell population described herein. Pharmaceutical compositions of the disclosure may be suitable for treatment regimens and thus administered to a subject via a variety of methods described herein. Such compositions may be formulated for use in a therapy, such as, in the amelioration, prevention, and / or treatment of a disease, disorder, or condition for which an IDO variant comprised in the composition is therapeutic, such as a disease, disorder, or conditions associated with inflammation. Compositions described herein can be administered to a subject, such as human or non-human subjects, a cell in situ, a cell ex vivo, a cell derived from a subject, or a biological sample (e.g., one derived from a subject). In some embodiments, a composition that can be administered to a subject comprises an IDO variant or an assembly thereof in an amount of 0.1 ng / kg of a subject’s bodyweight to 100 mg / kg of a subject’s bodyweight. In some embodiments, a composition that can be administered to a subject comprises an IDO variant or an assembly thereof in an amount of less than 100 mg / kg of a subject’s bodyweight, such as 50-75 mg / kg, 25-50 mg / kg, 10-25 mg / kg, 1-10 mg / kg, 750-1000 ug / kg, 500-750 ug / kg, 250-500 ug / kg, 1-250 ug / kg, 500-1000 ng / kg, or 1-500 ng / kg. In some embodiments, a composition comprises a pharmaceutical excipient. Pharmaceutically acceptable excipients (excipients) are substances other than a therapeutic agent 12084414.1 (e.g., an IDO variant) that are intentionally included in a delivery system (e.g., an assembly comprising a plurality of IDO variants). In some embodiments, excipients do not exert or are not intended to exert a therapeutic effect. In some embodiments, a pharmaceutically acceptable excipient may be an inert substance. In some embodiments, a pharmaceutically acceptable excipient may not be an inert substance. Non-limiting examples of excipients include, but are not limited to, absorption enhancers, anti-adherents, anti-foaming agents, anti-oxidants, binders, buffering agents, carriers, coating agents, colors, delivery enhancers, delivery polymers, dextran, dextrose, diluents, disintegrants, emulsifiers, extenders, fillers, flavors, glidants, humectants, lubricants, oils, polymers, preservatives, saline, salts, solvents, sugars, suspending agents, sustained release matrices, sweeteners, thickening agents, tonicity agents, vehicles, water- repelling agents, and wetting agents. In some embodiments, a composition further comprises additional components commonly found in pharmaceutical compositions, such as anti-pruritics, astringents, local anesthetics, or anti-inflammatory agents (e.g., antihistamine, diphenhydramine). In some embodiments, the composition is provided in a solvent or dispersion medium containing, for example, water, ethanol, polyol (for example, glycerol, propylene glycol, and liquid polyethylene glycol), and suitable mixtures thereof. A composition may also contain adjuvants such as preservatives, wetting agents, emulsifying agents, and dispersing agents. Methods Methods of Producing IDO Variants In some embodiments, a method comprises contacting an IDO or a variant thereof with a synthetic molecule. In some embodiments, a synthetic molecule comprises a synthetic polymer. Non-limiting examples of synthetic polymers include Polysarcosine, polysaccharides, polyvinyl pyrrolidone (PVP), Zwitterionic polymers, Poly(amino acid)-based lipopolymers, polymers comprising XTEN, Poly(thioglycidyl glycerol), poly(lactic-co-glycolic acid) (PLGA), polyvinyl alcohol (PVA), polyethylene oxide (PEO), poly(N-isopropylacrylamide) (PNIPAAm), poly(ethyleneimine) (PEI), poly(caprolactone) (PCL), poly(acrylic acid) (PAA), poly(methyl methacrylate) (PMMA), poly(ethylene glycol) (PEG), and combinations thereof. In some embodiments, the synthetic polymer comprises a hydrophilic polymer. In some embodiments, the synthetic polymer comprises poly(ethylene glycol) (PEG). In some embodiments, the synthetic polymer comprises a forked PEG chain and / or a Y-shaped PEG chain. In some 12084414.1 embodiments, a synthetic molecule comprises a functional group capable of forming at least one bond between the IDO and the synthetic molecule. In some embodiments, the at least one bond comprises a covalent bond and / or a non-covalent bond (e.g., via interactions involving van der waals interactions, pi-pi interactions, hydrophobic interactions, hydrogen bonding, ionic bonds, etc., or any combination thereof). In some embodiments, a functional group comprises an amino acid-reactive cross linker. In some embodiments, the functional group is capable of reacting with a group in an amino acid side chain, such as an amino group, a sulfhydryl group, a hydroxyl group, an imidazole group, an indole group, a guanidinium, a carboxylic acid group, etc. In some embodiments, an amino acid cross-linker is capable of forming a bond with a heterologous cysteine in an IDO variant cysteine. In some embodiments, a functional group comprises an ester functional group, such as N-hydroxy succinimidyl (NHS) esters or a functional group in succinimidyl valeric acid (SVA). In some embodiments, a functional group comprises acrylate or methacrylate. In some embodiments, a functional group comprises n-acetylgalactosamine. In some embodiments, the functional group is capable of reacting with a sulfhydryl group. In some embodiments, the functional group comprises maleimide. In some embodiments, a method comprises contacting an IDO or a variant thereof with PEG comprising a functional group. In some embodiments, the IDO variant comprises a heterologous cysteine. In some embodiments, PEG comprises an ester functional group, acrylate, methacrylate, n-acetylgalactosamine, cyanuric chloride activated PEG, PEG comprising aldehyde groups, succinimidyl PEG derivatives (e.g., those comprising succinate, carbonate, etc. or derivatives thereof), PEG comprising benzotriazole carbonate, PEG comprising phenyl carbonate PEG, PEG comprising carbonylimidazole, or PEG comprising thiazolidine-2-thione. In some embodiments, a method comprises contacting an IDO or a variant thereof with PEG comprising an amine group and a transglutaminase. In some embodiments, a method comprises contacting an IDO or a variant thereof with PEG-maleimide. In some embodiments, a method comprises contacting an IDO variant comprising a heterologous cysteine with PEG-maleimide. In some embodiments, the heterologous cysteine is located at the N-terminus and / or the C-terminus. In some embodiments, the heterologous cysteine is positioned within a linker connected to the IDO variant. In some embodiments, an IDO or a variant thereof has been contacted with one or more reducing agents (e.g., dithiothreitol (DTT), β-mercaptoethanol, tris(2-carboxyethyl)phosphine (TCEP), reduced glutathione (GSH), iodoacetamide, other phosphines, etc., or a combination thereof) prior to 12084414.1 being contacted with PEG-maleimide. In some embodiments, PEGylation comprises incubating IDO or a variant thereof for at least one hour (e.g., 1-96 hours, such as 1-4 hours, 4-12 hours, 12-24 hours, 24-48 hours, etc.) in the presence of PEG-maleimide and an appropriate buffer. In some embodiments, PEGylation occurs at a temperature between 1-37oC (e.g., at 4oC). In some embodiments, PEGylation comprises molar titration. In some embodiments, molar titration comprises using PEG (e.g., PEG-maleimide) to IDO or a variant thereof at a ratio of about 1:1, 2:1, 5:1, 10:1, 25:1, 50:1, 100:1 or more. In some embodiments, quantitative PEGylation comprises a ratio of about 100:1 PEG-maleimide to IDO or a variant thereof and a longer reaction time (e.g., longer than 12, 16, 18, or 24 hours). In some embodiments, unreacted PEG- maleimide is removed following IDO PEGylation. In some embodiments, a PEGylated IDO variant may be further subjected to one or more purification steps and analytical assays (e.g., SDS-PAGE, enzymatic analyses, etc.) prior to being contacted with a cell or used to formulate a composition described herein. In some embodiments, a method comprises expressing an IDO or a variant thereof. In some embodiments, expressing an IDO or a variant thereof comprises introducing a nucleic acid (e.g., a vector, such as a plasmid) encoding the IDO or the variant thereof into one or more cells, such as a cell population. In some embodiments, cells expressing an IDO or a variant thereof may be bacterial cells, mammalian cells, fungal cells, or plant cells. In some embodiments, the nucleotide sequence may be codon optimized for expression in the cell or cell population that will be engineered to express the IDO or the IDO variant. In some embodiments, the nucleotide sequence encoding the IDO or the IDO variant is operably linked to one or more regulatory sequences. In some embodiments, the cell or cell population comprises a glycosyltransferase, such as an O-GlcNAc Transferase (OGT). In some embodiments, a method comprises purifying an IDO or a variant thereof. In some embodiments purifying an IDO or a variant thereof comprises chromatography (e.g., affinity chromatography, size exclusion chromatography, ion exchange chromatography, high performance liquid chromatography, etc.), dialysis, ultrafiltration, magnetic affinity purification, protein precipitation (e.g., via treatment with salts, organic chemicals, etc.), or any combination thereof. In some embodiments, an IDO variant is purified before and / or after being contacted with a synthetic molecule comprising a functional group (e.g., PEG-maleimide). In some embodiments, an IDO variant may be contacted with one or more cells after it has been subjected to one or more rounds of purification. In some embodiments, one or more assays are 12084414.1 performed on the cells that were contacted with the IDO variant, such as western blot, IDO enzymatic activity assays, microscopy, etc., or a combination thereof to detect changes in the cells as a result of being contacted with the IDO variant. In some embodiments, a method comprises generating a solution by mixing a sample of IDO variants under conditions that promote interactions between self-assembling peptides that are connected to the IDO variants. In some embodiments, the conditions are selected to promote assembly of the IDO variants into large order structures comprising a plurality of IDO variants. In some embodiments, the solution is a neutral aqueous solution. In some embodiments, the solution has a pH ranging from about 6.5 to about 8.5 (e.g., 6.5-7.0, 7.0-7.5, 7.5-8.0, or 8.0-8.5). In some embodiments, the solution comprises a source of divalent cations, such as CaCl2, MgCl2, ZnCl2, MnCl2, CuCl2, CoCl2, CdCl2, BaCl2, SrCl2, YbCl2, NiCl2, PbCl2, AgNO3, Hg(Hg(CN)2), Pt (K2PtCl4). In some embodiments, the concentration of divalent cations in the solution comprises 1-1000 mM (e.g., 1-100 mM, 100-250 mM, 250-500 mM, or 500-1000 mM). In some embodiments, an IDO variant comprising a charge-complementary peptide is used to produce an assembly of IDO variants. In some embodiments, a method comprises mixing a sample of IDO variants comprising a positive peptide and a sample of IDO variants comprising a negative peptide. In some embodiments, the IDO variants comprising the positive peptide, the IDO variants comprising the negative peptide, or both are provided at a concentration of about 0.5 µM to 30 mM. In some embodiments, the concentration of the IDO variants comprising the positive peptide and / or the IDO variants comprising the negative peptide is about 1-50 µM, 50-150 µM, 150-500 µM, 500-1000 µM, 1-5 mM, 5-10 mM, or 10-30mM. In some embodiments, the solution comprises a non-ionic crowding agent, such as PEG (e.g., PEG1550, PEG2000, PEG3350, PEG6000, or PEG20000) or Tween (e.g., Tween 20, Tween 80, or Triton-X 114). In some embodiments, PEG is present in the neutral aqueous solution at a concentration of 50-300µM (e.g., 50-100µM, 100-200µM, or 100-300µM). In some embodiments, PEG is present in the neutral aqueous solution at a concentration greater than or equal to 200 mg / mL (e.g., 200-800 mg / mL). In some embodiments, Tween 20 is present in the neutral aqueous solution at a concentration of about 0.06mM (e.g., 0.055 mM, 0.056 mM, 0.057 mM, 0.058 mM, 0.059 mM, 0.060 mM, 0.061 mM, 0.062 mM, 0.063 mM, or 0.064 mM). In some embodiments, Tween 80 is present in the neutral aqueous solution at a concentration of about 0.012mM (e.g., 0.010mM, 0.011mM, 0.012mM, 0.013mM, or 0.014mM). In some embodiments, Triton-X 114 is present in the neutral aqueous solution at a concentration of about 12084414.1 0.2mM (e.g., 0.15mM, 0.16mM, 0.17mM, 0.18mM, 0.19mM, 0.2mM, 0.21mM, 0.22mM, 0.23mM, or 0.24mM). In some embodiments, the concentrations of IDO variants comprising the positive peptide and the IDO variants comprising the negative peptide in the solution are equal. However, in other embodiments, the IDO variants comprising the positive peptide are provided in the solution in molar excess relative to the IDO variants comprising the negative peptide. In some embodiments, the concentration ratio of the positive IDO variant comprising the positive peptide to the IDO variant comprising the negative peptide may be about 5000:1, 4000:1, 3000:1, 2000:1, 1000:1, 900:1. 800:1, 700:1, 600:1, 500:1, 400:1, 350:1, 300:1, 250:1, 200:1, 150:1, 100:1, 95:1, 90:1, 85:1, 80:1, 75:1, 70:1, 65:1, 60:1, 55:1, 50:1, 45:1, 40:1, 35:1, 30:1, 25:1, 20:1, 15:1, 10:1, 9:1, 8:1, 7:1, 6:1, 5:1, 4:1, 3:1, or 2:1 or any intervening ratio therein. In some embodiments, the IDO variants comprising the positive peptide are provided in molar excess relative to the IDO variants comprising the negative peptide. In some embodiments, the concentration ratio of the IDO variant comprising the negative peptide to the IDO variant comprising the positive peptide may be about 5000:1, 4000:1, 3000:1, 2000:1, 1000:1, 900:1. 800:1, 700:1, 600:1, 500:1, 400:1, 350:1, 300:1, 250:1, 200:1, 150:1, 100:1, 95:1, 90:1, 85:1, 80:1, 75:1, 70:1, 65:1, 60:1, 55:1, 50:1, 45:1, 40:1, 35:1, 30:1, 25:1, 20:1, 15:1, 10:1, 9:1, 8:1, 7:1, 6:1, 5:1, 4:1, 3:1, 2:1, or any intervening ratio therein. Methods of Administration In some embodiments, a method comprises administering an IDO variant or an assembly thereof described herein to a subject. In some embodiments, a subject is a mammalian subject. In some embodiments, a subject is a non-human subject, such as a primate, a mouse, a rat, a pig, a dog, a cat, etc. In some embodiments, a subject is a human subject. In some embodiments, a subject is characterized as having one or more mutations in a gene encoding IDO. In some embodiments, a subject is characterized as having, suspected of having, or at risk of developing a disease, a disorder, or a condition. In some embodiments, the disease, disorder, or condition is associated with increased inflammation in one or more tissues in the subject. In some embodiments, a subjected is characterized as having, suspected of having, or at risk of developing a cancer, an inflammatory disorder, an infectious disease, an autoimmune disease, or a neurological disease or disorder. In some embodiments, a subjected is characterized as having, suspected of having, or at risk of developing a condition associated with increased 12084414.1 pain. In some embodiments, a condition associated with increased pain is also associated with cancer, an inflammatory disorder, an infectious disease, an autoimmune disease, or a neurological disorder. Non-limiting examples of signs or symptoms experienced by a subject characterized as having, suspected of having, or at risk of developing a condition associated with pain include neuropathic pain, central pain, deafferentation pain, chronic pain, acute pain, inflammatory pain, joint pain, arthritic pain, lumbosacral pain, musculoskeletal pain, lower back pain, neck pain, visceral pain, and the like. In some embodiments, an IDO variant or an assembly thereof can be administered after one or more signs or symptoms of a disease, a disorder, or a condition have developed or have been observed in a subject. In other embodiments, administration of an IDO variant or an assembly thereof can be performed in the absence of signs or symptoms of a disease, a disorder, or a condition. Administration of an IDO variant or an assembly thereof may also be continued after symptoms have resolved, for example, to delay or prevent recurrence. In some embodiments, administration of an IDO variant or an assembly thereof achieves one, two, three, four, or more of the following effects, including, for example: (i) reduction or amelioration the severity of a disease, a disorder, or a condition or a symptom associated therewith; (ii) reduction in the duration of a symptom associated with a disease, disorder, or condition; (iii) protection against the progression of a disease or disorder or symptom associated therewith; (iv) regression of a disease, disorder, or condition or symptom associated therewith; (v) protection against the development or onset of a symptom associated with a disease, disorder, or condition; (vi) protection against the recurrence of a symptom associated with a disease; (vii) reduction in the hospitalization of a subject; (viii) reduction in the hospitalization length; (ix) an increase in the survival of a subject with a disease; (x) a reduction in the number of symptoms associated with a disease, disorder, or condition; (xi) an enhancement, improvement, supplementation, complementation, or augmentation of the prophylactic or therapeutic effect(s) of another therapy. In some embodiments, administration of an IDO variant or an assembly thereof is performed intravenously, subcutaneously, intraocularly, intravitreally, parenterally, subcutaneously, intravenously, intra-cerebroventricularly, intramuscularly, intracranially, intrathecally, orally, intraperitoneally, or by direct injection to one or more cells, tissues, or organs. In some embodiments, direct injection is performed concurrently with a surgical procedure or interventional procedure. In some embodiments, an IDO variant or an assembly 12084414.1 thereof is administered to a subject through only one administration route. In some embodiments, multiple administration routes may be exploited (e.g., serially, or simultaneously) for administration of an IDO variant or an assembly thereof to a subject. In some embodiments, when multiple administrations of an IDO variant are performed, the time between each administration can be the same or different. In some embodiments, an IDO variant administered to a subject has a half-life in the circulatory system of a subject that is increased relative to a wild-type IDO administered under the same conditions. In some embodiments, the half-life can be increased by hours (e.g., 4 hours, 8 hours, 12 hours, or more), days (1 days, 2 days, 3 days, 4 days, 5 days, 6 days, or more), or weeks (e.g., 1-2 weeks, 2-3 weeks, or more). In some embodiments, a polymer assembly is administered to a subject in an effective amount. In some embodiments, an effective amount is a “therapeutically effective amount” which refers to an amount sufficient to provide a therapeutic benefit in the treatment of a disease, disorder, or condition or to delay or minimize one or more symptoms associated with the disease, disorder, or condition. In some embodiments, a therapeutically effective amount means an IDO variant or an assembly thereof alone or in combination with other therapies which provides a therapeutic benefit in the treatment of the disease, disorder, or condition. In some embodiments, a therapeutically effective amount is between 0.1 ng / kg of a subject’s bodyweight to 100 mg / kg of a subject’s bodyweight. In some embodiments, a therapeutically effective is amount is less than 100 mg / kg of a subject’s bodyweight, such as 50-75 mg / kg, 25-50 mg / kg, 10-25 mg / kg, 1-10 mg / kg, 750-1000 ug / kg, 500-750 ug / kg, 250-500 ug / kg, 1-250 ug / kg, 500- 1000 ng / kg, or 1-500 ng / kg. Kits In some aspects, the disclosure relates to kits comprising an IDO variant or an assembly thereof described herein. In some embodiments, kit comprise a nucleic acid described herein. In some embodiments, a cell or a cell population described herein. In some embodiments, a kit comprises a compositions described herein, such as one that can be used for administration to a subject. In some embodiments, a kit comprises a nucleic acid encoding a wild-type IDO and / or a wild-type IDO protein for production of an IDO variant or an assembly thereof. Accordingly, kits provided by the present disclosure may comprise any or all of the materials necessary for producing and / or administering an IDO variant or an assembly thereof. 12084414.1 In some embodiments, the kits described herein may include one or more containers housing components for performing the methods described herein, and optionally instructions for use. In some embodiments, the components may be prepared sterilely, packaged in a syringe, and shipped refrigerated. Alternatively, in some embodiments, they may be housed in a vial or other container for storage. In some embodiments, a second container may have other components prepared sterilely. Alternatively, in some embodiments, the kits may include the active agents premixed and shipped in a vial, tube, or other container. In some embodiments, the kits may also include other components, depending on the specific application, for example, containers, cell media, salts, buffers, reagents, syringes, needles, a fabric, such as gauze, for applying or removing a disinfecting agent, disposable gloves, a support for the agents prior to administration, etc. In some embodiments, each component of the kits, where applicable, may be provided in liquid form (e.g., in solution) or in solid form, (e.g., a dry powder). In some embodiments, some of the components may be reconstitutable or otherwise processible (e.g., to an active form), for example, by the addition of a suitable solvent or other species (for example, water), which may or may not be provided with the kit. In some embodiments, a kit further comprises a set of instructions for carrying out the methods described herein. As used herein, “instructions” can define a component of instruction and / or promotion, and typically involve written instructions on or associated with packaging of this disclosure. In some embodiments, instructions also can include any oral or electronic instructions provided in any manner such that a user will clearly recognize that the instructions are to be associated with the kit, for example, audiovisual (e.g., videotape, DVD, etc.), Internet, and / or web-based communications, etc. In some embodiments, the written instructions may be in a form prescribed by a governmental agency regulating the manufacture, use, or sale of pharmaceuticals or biological products, which can also reflect approval by the agency of manufacture, use or sale for animal administration. As used herein, “promoted” includes all methods of doing business including methods of education, hospital and other clinical instruction, scientific inquiry, drug discovery or development, academic research, pharmaceutical industry activity including pharmaceutical sales, and any advertising or other promotional activity including written, oral, and electronic communication of any form, associated with this disclosure. 12084414.1 EXAMPLES Example 1: Characterizations of IDO Variants Comprising Cysteine-to-Serine Substitutions IDO variants comprising cysteine mutations (“IDO-Tri” comprising C112S, C159S, and C308S mutations and “IDO-Tetra” comprising C112S, C159S, C206S, and C308S mutations) were produced. Purified IDO variants were obtained at a yield of 557 ug of IDO-Tri and 631 ug of IDO-Tetra post-SEC75. The IDO variants were then subjected to IDO enzymatic analyses (FIGs. 3A-3B). Further results from analyses of IDO variant activities are shown in FIG. 3C. Then, IDO-Tri and IDO-Tetra variants were reacted at 4oC overnight in the presence of 10k polyethylene glycol (PEG) at 1:1, 2:1, and 10:1 molar ratios of IDO variant:PEG (FIG. 4). Higher levels of free maleimide were observed in samples comprising IDO-Tri relative to samples comprising IDO-Tetra. No change in IDO enzymatic activity was observed following PEGylation of the IDO variants (FIG. 5). Example 2: Characterizations of IDO Variants with Increased Hydrodynamic Radii Compositions comprising IDO variants with increased hydrodynamic radii were generated. Briefly, recombinant IDO was expressed in bacterial cells, and purified IDO protein was then reacted with PEG-maleimide to PEGylate surface-accessible cysteines (“PEG-IDO”) via molar titration and incubation for 6 hours or 48 hours at 4oC. In addition, IDO proteins were fused to a self-assembling peptide and expressed and purified in a similar manner as stated above that spontaneously forms coiled-coils in the presence of other self-assembling peptides without PEG-maleimide reaction. Assemblies of the IDO variants were produced to comprise five IDO variants with each IDO variant being fused to a self-assembling peptide (“IDO-5” alternatively referred to as “Penta-IDO”). IDO enzymatic activity analyses showed differences between wild-type IDO and PEG- IDO (FIGs. 6-7) and no differences between wild-type IDO and IDO-5 (FIG. 8). Dynamic light scattering analyses of IDO-5 and PEG-IDO indicated IDO-5 was monodisperse and had a hydrodynamic size sufficient to avoid renal clearance (FIG. 9). Compositions comprising the IDO variants were then injected into mouse subjects. Following injection, blood samples were collected at specific time points to analyze IDO variant levels in circulation via western blot. PEG-IDO showed a half-life of 21.2 hours in circulation while IDO-5 levels were stable at 48 hours post-injection (FIG. 10). Further analyses showed detection of IDO-5 in blood (via Western) at 144 hours post-injection (FIG. 11). 12084414.1 Example 3: CATCH-IDO A fusion protein comprising indoleamine 2,3-dioxygenase (IDO) fused to a CATCH (Co-Assembly Tags based on CHarge complementarity) peptide tag (“CATCH-IDO”) was generated. The CATCH peptides comprised a pair of oppositely charged peptides (anionic “CATCH(−)” and cationic “CATCH(+)”) that do not self-assemble on their own due to strong electrostatic repulsion. However, when combined at equimolar ratios, the peptides co-assemble into β-sheet nanofibers due to charge complementarity. At higher concentrations these nanofibers can entangle to form hydrogels. The peptides are variants of the β-sheet fibrillizing peptide Q11. Fusion proteins, such as CATCH-IDO, can be expressed from recombinant DNA by E. coli and incorporated into these nanofibers, endowing them with functionality. When delivered exogenously, IDO has shown therapeutic benefit in pre-clinical models of inflammation. FIG. 12 shows SDS PAGE gel of CATCH-IDO purified from E. coli (theoretical molecular weight = 49519 kDa). FIGs. 13A-13B show CATCH-IDO is active in the CATCH gel. CATCH-IDO depleted tryptophan and generated NFK which was measured by absorbance at 321nm. IDO converts tryptophan to N-formlykynurenine (NFK), which can be measured spectroscopically by absorbance at 321nm. IDO with a CATCH(-) peptide tag fused to the N-terminus (CATCH- IDO) was expressed and recovered from E. coli. The ternary mixture of CATCH(+), CATCH(-), and CATCH-IDO forms gels that generate NFK when incubated with tryptophan and other reactants. The reaction velocity of the resultant gel was dependent on the dose of CATCH-IDO assembled into the gel. FIGs. 14A-14E show decreased LPS-induced responses in dendritic cells. FIGs. 14A- 14B show CATCH-IDO gels decrease LPS-induced inflammatory cytokine secretion by dendritic cells, IL-12. The activity of IDO, resulting in the depletion of tryptophan and generation of kynurenine metabolites, plays important roles in immune cell suppression and tolerance. CATCH-IDO gels were cultured with dendritic cells to determine if the gels can suppress lipopolysaccharide (LPS) induced inflammatory activation. Dendritic cells were generated from the bone marrow of mice, co-cultured with CATCH-IDO gels (or control treatments) for 24 hours, and then half of the groups were treated with LPS for 24 hours. The supernatants were then collected to measure secreted proinflammatory IL-12 by ELISA. The 12084414.1 soluble IDO, blank gel, and CATCH-IDO gel alone (without LPS) had no effect on IL-12 levels. LPS treatment increased levels of IL-12 as expected. Pre-treatment with soluble IDO and CATCH-IDO gels decreased the LPS-induced IL-12 secretion, while blank gels had no effect. CATCH-IDO gels decreased IL-12 secretion to a greater degree than soluble IDO. FIG. 14C- 14D show CATCH-IDO gels decrease LPS-induced inflammatory gene expression in dendritic cells. The same experimental setup as the previous data set was used here. However, instead of collecting the supernatant after LPS treatment, the cells were collected instead, and IL-6 gene expression was measured by qPCR. The soluble IDO, blank gels, and CATCH-IDO gels alone (without LPS) had no effect on IL-6 expression levels. LPS treatment increased levels of IL-6 as expected. Pre-treatment with soluble IDO and CATCH-IDO gels decreased the LPS-induced IL- 12 secretion, while blank gels had no effect. FIG. 14E shows CATCH-IDO gels decrease LPS- induced inflammatory cytokine secretion by dendritic cells, IL-6. FIG. 15A-15B show CATCH gels extend the local residence time of active enzyme in vivo. NanoLuc® luciferase (NL) is an enzyme that generate bioluminescence when it reacts with its substrate, furimazine. NL with a CATCH(-) peptide tag fused to the N-terminus (CATCH-NL) was expressed and recovered from E. coli. The ternary mixture of CATCH(+), CATCH(-), and CATCH-NL forms gels that emit blue bioluminescence in the presence of furimazine, while gels formulated without enzyme (empty gels) did not. Soluble CATCH-NL or CATCH-NL gels were injected into the hind paw of mice. Furimazine was injected and luminescence was measured. This was repeated over a 21-day time period. Within minutes after subcutaneous injection, greater local bioluminescence, indicative of a higher local NL dose, was observed from CATCH-NL immobilized in gels when compared to soluble CATCH-NL, likely because the gel reduced the convective forces acting on soluble enzyme that would push it through the tissue. Enzymatically active CATCH-NL gels were detectable at a subcutaneous injection site for up to 21 days, whereas soluble CATCH-NL injected into the same site was cleared within a day. This data demonstrated that the CATCH gel vehicle extended the local residence time of catalytically active enzyme in vivo. Example 4: Administration of CATCH-IDO Hydrogels FIG. 16 shows a non-limiting example of a method for analyzing suppression of localized LPS-induced inflammation and pain in vivo following administration of CATCH-IDO gels. The method can involve analyzing, for example, inflammatory cytokines, gene expression, 12084414.1 and mechanical sensitivity post-administration to a subject (e.g., a mammalian subject, such as a mouse). INCORPORATION BY REFERENCE The present application refers to various issued patent, published patent applications, scientific journal articles, and other publications, all of which are incorporated herein by reference. The details of one or more embodiments of the invention are set forth herein. Other features, objects, and advantages of the invention will be apparent from the Detailed Description, the Figures, the Examples, and the Claims. EQUIVALENTS While several inventive embodiments have been described and illustrated herein, those of ordinary skill in the art will readily envision a variety of other means and / or structures for performing the function and / or obtaining the results and / or one or more of the advantages described herein, and each of such variations and / or modifications is deemed to be within the scope of the inventive embodiments described herein. More generally, those skilled in the art will readily appreciate that all parameters, dimensions, materials, and configurations described herein are meant to be exemplary and that the actual parameters, dimensions, materials, and / or configurations will depend upon the specific application or applications for which the inventive teachings is / are used. Those skilled in the art will recognize, or be able to ascertain using no more than routine experimentation, many equivalents to the specific inventive embodiments described herein. It is, therefore, to be understood that the foregoing embodiments are presented by way of example only and that, within the scope of the appended claims and equivalents thereto, inventive embodiments may be practiced otherwise than as specifically described and claimed. Inventive embodiments of the present disclosure are directed to each individual feature, system, article, material, kit, and / or method described herein. In addition, any combination of two or more such features, systems, articles, materials, kits, and / or methods, if such features, systems, articles, materials, kits, and / or methods are not mutually inconsistent, is included within the inventive scope of the present disclosure. All definitions, as defined and used herein, should be understood to control over dictionary definitions, definitions in documents incorporated by reference, and / or ordinary meanings of the defined terms. 12084414.1 All references, patents and patent applications disclosed herein are incorporated by reference with respect to the subject matter for which each is cited, which in some cases may encompass the entirety of the document. The indefinite articles “a” and “an,” as used herein in the specification and in the claims, unless clearly indicated to the contrary, should be understood to mean “at least one.” The phrase “and / or,” as used herein in the specification and in the claims, should be understood to mean “either or both” of the elements so conjoined, i.e., elements that are conjunctively present in some cases and disjunctively present in other cases. Multiple elements listed with “and / or” should be construed in the same fashion, i.e., “one or more” of the elements so conjoined. Other elements may optionally be present other than the elements specifically identified by the “and / or” clause, whether related or unrelated to those elements specifically identified. Thus, as a non-limiting example, a reference to “A and / or B”, when used in conjunction with open-ended language such as “comprising” can refer, in one embodiment, to A only (optionally including elements other than B); in another embodiment, to B only (optionally including elements other than A); in yet another embodiment, to both A and B (optionally including other elements); etc. As used herein in the specification and in the claims, “or” should be understood to have the same meaning as “and / or” as defined above. For example, when separating items in a list, “or” or “and / or” shall be interpreted as being inclusive, i.e., the inclusion of at least one, but also including more than one, of a number or list of elements, and, optionally, additional unlisted items. Only terms clearly indicated to the contrary, such as “only one of” or “exactly one of,” or, when used in the claims, “consisting of,” will refer to the inclusion of exactly one element of a number or list of elements. In general, the term “or” as used herein shall only be interpreted as indicating exclusive alternatives (i.e., “one or the other but not both”) when preceded by terms of exclusivity, such as “either,” “one of,” “only one of,” or “exactly one of.” “Consisting essentially of,” when used in the claims, shall have its ordinary meaning as used in the field of patent law. As used herein in the specification and in the claims, the phrase “at least one,” in reference to a list of one or more elements, should be understood to mean at least one element selected from any one or more of the elements in the list of elements, but not necessarily including at least one of each and every element specifically listed within the list of elements and not excluding any combinations of elements in the list of elements. This definition also 12084414.1 allows that elements may optionally be present other than the elements specifically identified within the list of elements to which the phrase “at least one” refers, whether related or unrelated to those elements specifically identified. Thus, as a non-limiting example, “at least one of A and B” (or, equivalently, “at least one of A or B,” or, equivalently “at least one of A and / or B”) can refer, in one embodiment, to at least one, optionally including more than one, A, with no B present (and optionally including elements other than B); in another embodiment, to at least one, optionally including more than one, B, with no A present (and optionally including elements other than A); in yet another embodiment, to at least one, optionally including more than one, A, and at least one, optionally including more than one, B (and optionally including other elements); etc. It should also be understood that, unless clearly indicated to the contrary, in any methods claimed herein that include more than one step or act, the order of the steps or acts of the method is not necessarily limited to the order in which the steps or acts of the method are recited. In the claims, as well as in the specification above, all transitional phrases such as “comprising,” “including,” “carrying,” “having,” “containing,” “involving,” “holding,” “composed of,” and the like are to be understood to be open-ended, i.e., to mean including but not limited to. Only the transitional phrases “consisting of” and “consisting essentially of” shall be closed or semi-closed transitional phrases, respectively, as set forth in the United States Patent Office Manual of Patent Examining Procedures, Section 2111.03. It should be appreciated that embodiments described in this document using an open-ended transitional phrase (e.g., “comprising”) are also contemplated, in alternative embodiments, as “consisting of” and “consisting essentially of” the feature described by the open-ended transitional phrase. For example, if the disclosure describes “a composition comprising A and B”, the disclosure also contemplates the alternative embodiments “a composition consisting of A and B” and “a composition consisting essentially of A and B”. 12084414.1

Claims

CLAIMS What is claimed is:

1. An indoleamine 2,3-dioxygenase (IDO) variant comprising: (i) a hydroxyl-bearing amino acid at one or more positions corresponding to a cysteine in a wild-type IDO selected from the group consisting of: cysteine 85; cysteine 112; cysteine 129; cysteine 159; cysteine 206; cysteine 272; cysteine 308; and cysteine 335; (ii) a cysteine that is heterologous to a wild-type IDO; (iii) a peptide or protein fused to the N-terminus of the IDO; (iv) a peptide or protein fused to the C-terminus of the IDO; or (v) any combination of two or more of (i)-(iv).

2. The IDO variant of claim 1, wherein the one or more positions of (i) in the wild-type IDO comprise at least two positions selected from the group consisting of: cysteine 85; cysteine 112; cysteine 129; cysteine 159; cysteine 206; cysteine 272; cysteine 308; and cysteine 335.

3. The IDO variant of claim 1 or 2, wherein the one or more positions of (i) in the wild-type IDO comprise: (a) cysteine 112, cysteine 159, and cysteine 308; or (b) cysteine 112, cysteine 159, cysteine 206, and cysteine 308.

4. The IDO variant of claim 1 or 2, wherein each hydroxyl-bearing amino acid at the one or more positions of (i) are independently selected from a serine or a threonine.

5. The IDO variant of any one of claims 1-4, wherein the cysteine of (ii) is a modified cysteine.

6. The IDO variant of claim 5, wherein the modified cysteine comprises a synthetic polymer. 12084414.

17. The IDO variant of claim 6, wherein the synthetic polymer comprises polyethylene glycol (PEG).

8. The IDO variant of any one of claims 1-7, wherein the peptide or protein of (iii) or (iv) comprises at least one of: (a) a galectin; (b) a soluble peptide; (c) a self-assembling peptide; (d) a linker; (e) an antibody or a fragment thereof; (f) an Fc domain; (g) a secretion signal or secretion tag; or (h) any combination of two or more of (a)-(g).

9. The IDO variant of any one of claims 1-8, wherein IDO variant is capable of being glycosylated or comprises one or more monomeric glycosides and / or one or more polymeric glycosides.

10. The IDO variant of any one of claims 1-9, wherein the peptide or protein of (iii) or (iv) comprises an amino acid sequence that is at least 75% identical to any one of SEQ ID NOs: 15- 37.

11. The IDO variant of any one of claims 1-10, wherein the IDO variant comprises an amino acid sequence that is at least 75% identical to any one of SEQ ID NOs: 1-37.

12. A nucleic acid comprising a nucleotide sequence encoding the IDO variant of any one of claims 1-11.

13. A cell comprising the IDO variant of any one of claims 1-11 or the nucleic acid of claim 12. 12084414.

114. A composition comprising the IDO variant of any one of claims 1-11, the nucleic acid of claim 12, and / or the cell of claim 13.

15. A method comprising administering the IDO variant of any one of claims 1-11 to a subject in need thereof.

16. The method of claim 15, wherein the subject is a mammal.

17. A method comprising contacting the IDO variant of any one of claims 1-11 or the nucleic acid of claim 12 with one or more cells.

18. A method comprising contacting an indoleamine 2,3-dioxygenase (IDO) with a synthetic molecule, wherein the synthetic molecule comprises a functional group capable of forming at least one bond between the IDO and the synthetic molecule.

19. The method of claim 18, wherein the IDO is an IDO variant comprising: (i) a hydroxyl-bearing amino acid at one or more positions corresponding to a cysteine in a wild-type IDO selected from the group consisting of: cysteine 85; cysteine 112; cysteine 129; cysteine 159; cysteine 206; cysteine 272; cysteine 308; and cysteine 335; (ii) a cysteine that is heterologous to a wild-type IDO; (iii) a peptide or protein fused to the N-terminus of the IDO; (iv) a peptide or protein fused to the C-terminus of the IDO; or (v) any combination of (i)-(iv) 20. The method of claim 18 or 19, wherein: (a) the synthetic molecule comprises a synthetic polymer; (b) the functional group is capable of reacting with a sulfhydryl group; and / or (c) the at least one bond comprises a covalent bond.

21. The method of claim 20, wherein the synthetic polymer of (a) comprises polyethylene glycol (PEG) and / or the functional group of (b) comprises maleimide. 12084414.

122. The method of any one of claims 18-21, wherein the IDO has been contacted with one or more agents capable of reducing a sulfhydryl group prior to being contacted with the synthetic molecule.

23. The method of any one of claims 18-22, wherein the method further comprises expressing the IDO in one or more cells and / or purifying the IDO prior to the contacting the IDO with the synthetic molecule.

24. A kit comprising the IDO of any one of claims 1-11, the nucleic acid of claim 12, the cell of claim 13, and / or the composition of claim 14. 12084414.1

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