Recombinant Fim and OmpA1 Vaccines for Catfish Aeromonas Protection
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Solution Overview
Problem
Current vaccines against Aeromonas hydrophila, a pathogen causing significant disease outbreaks in farmed fish, do not provide adequate protection, and existing treatments are hindered by antibiotic resistance and the lack of a commercial vaccine.
Innovation Solution
Development of recombinant vaccines using fimbrial and outer membrane proteins (FimA, Fim, FimMrfG, FimOM, OmpA1, TonB-dependent receptor, and TbpA) from virulent Aeromonas hydrophila strains to stimulate protective immunity in catfish.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional antibiotics are used to treat Aeromonas hydrophila infection, then bacterial growth may be inhibited, but antibiotic resistance develops making treatment ineffective
Solution Approach 1:
The patent converts the harmful effect of antibiotic resistance into a beneficial alternative by developing vaccines that stimulate protective immunity without selecting for resistant bacteria. The recombinant protein vaccines provide a non-antibiotic treatment pathway that addresses the root cause (infection prevention) rather than symptoms (bacterial growth inhibition).
Solution Approach 2:
The vaccine applies preliminary protective action by stimulating the fish immune system in advance through recombinant protein administration. This preventive immunization creates immunity before infection occurs, eliminating the need for curative antibiotic treatment and avoiding the development of resistance.
2Reliability
If no commercial vaccine exists for Aeromonas hydrophila, then fish are unprotected against disease outbreaks, but developing new vaccines requires significant research and development resources
Solution Approach 1:
The patent segments the complex pathogen into specific protective antigens (recombinant proteins such as outer membrane proteins, fimbrial proteins, and capsule proteins). By identifying and utilizing only the essential protective antigens rather than whole-cell vaccines, the development process is simplified while maintaining effectiveness.
Solution Approach 2:
The patent uses recombinant DNA technology as an intermediary to produce purified bacterial proteins in heterologous expression systems. This intermediary approach allows for controlled production of specific antigens without requiring complex whole-bacteria cultivation and purification processes.
3Reliability
If recombinant protein vaccines are developed, then protective immunity can be stimulated, but protein expression and purification processes become complex
Solution Approach 1:
The patent creates copies of the target bacterial proteins by cloning their genes into expression vectors and producing them in heterologous systems such as E. coli or insect cells. This copying approach allows for scalable production of pure antigens without requiring large quantities of the actual pathogen.
Solution Approach 2:
The patent optimizes expression parameters including induction conditions, temperature, pH, and purification buffers to maximize protein yield and solubility. By systematically adjusting these parameters, the complex expression process is streamlined for efficient production of functional recombinant proteins.
Data Source
AI summary
Aeromonas hydrophila is a reemerging pathogen of channel catfish (Ictalurus punctatus); recent outbreaks from 2009 to 2014 have caused the loss of more than 12 million pounds of market size catfish in Alabama and Mississippi. Genome sequencing revealed a clonal group of A. hydrophila isolates with unique genetic and phenotypic features that is highly pathogenic in channel catfish. Comparison of the genome sequence of a representative catfish isolate (ML09-119) from this virulent clonal group with lower virulence A. hydrophila isolates revealed four fimbrial proteins unique to strain ML09-119. In this work, we expressed and purified four A. hydrophila fimbrial proteins (FimA, Fim, MrfG, and FimOM) and assessed their ability to protect and stimulate protective immunity in channel catfish fingerlings against A. hydrophila ML09-119 infection for vaccine development. Our results showed catfish immunized with FimA, Fim, FimMrfG, and FimOM exhibited 59.83%, 95.41%, 85.72%, and 75.01% relative percent survival, respectively, after challenge with A. hydrophila strain ML09-119. Bacterial concentrations in liver, spleen, and anterior kidney were significantly (p<0.05) lower in vaccinated fish compared to the non-vaccinated sham groups at 48 h post-infection. However, only the Fim immunized group showed a significantly higher antibody titer in comparison to the non-vaccinated treatment group (p<0.05) at 21 days post-vaccination. Altogether, Fim and FimMrfG recombinant proteins have potential for vaccine development against virulent A. hydrophila infection. Genomic subtraction revealed three outer membrane proteins present in strain ML09-119 but not in the low virulence reference A. hydrophila strain; the major outer membrane protein OmpAI (OmpA1), TonB-dependent receptor (TonB-DR), and transferrin-binding protein A (TbpA). Here, the genes encoding OmpAI, tonB-DR, and tbpA were cloned from A. hydrophila ML09-119 and were expressed into Escherichia coli. The purified recombinant OmpA, TonB-DR, and TbpA proteins had estimated molecular weights of 37.26, 78.55, and 41.67 kDa, respectively. Catfish fingerlings vaccinated with OmpA1, TonB-DR, and TbpA emulsified with non-mineral oil adjuvant were protected against the subsequent A. hydrophila ML09-119 infection with 98.59%, 95.59%, and 47.89% relative percent survival (RPS), respectively. Furthermore, the mean liver, spleen, and anterior kidney bacterial loads were significantly lower in catfish vaccinated with the OmpA1 and TonB-DR than the non-vaccinated control group. ELISA demonstrated that catfish immunized with OmpA1, TonB-DR, and TbpA produce significant antibody response by 21 days post-immunization. Therefore, data generated during the study suggest that OmpAI and TonB-DR proteins could be used as potential candidates for vaccine development against A. hydrophila epidemic strain infection. However, TbpA protein failed to provide such strong protection. Recombinant ATPase from A. hydrophila also showed promise as a vaccine antigen. A live attenuated vaccine was prepared that combined the advantages of a live attenuated vaccine (ESC-NDKL1 (ΔgcvPΔsdhCΔfrdA) mutant of Edwardsiella ictaluri) against enteric septicemia of catfish (ESC) and three immunogenic recombinant proteins (Fim, FimMrfg, and ATPase) against A. hydrophila infection. Our results showed channel catfish fingerlings immersion-vaccinated with ESC-NDKL1::pETfim, ESC-NDKL1::pETmrfG, and ESC-NDKL1::pETATPase exhibited 100%, 91.67%, and 100% percent survival after challenge with the A. hydrophila ML09-119, which was significantly less than non-vaccinated group (88.89% mortality). In a second study, Catfish immunized with NDKL1::pETfim, ESC-NDKL1::pETmrfG, ESC-NDKL1::pETATPase had significantly (p<0.05) lower mortalities than sham-vaccinated group.