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Background: The development of therapies and vaccines for various diseases often necessitates the analysis of cellular immunity. However, unlike other rodents, the limited availability of reagents for Syrian hamsters restricts immunological analysis, particularly in the determination of serum effector molecules such as cytokines. In this study, we aim to produce and characterize the cytokines IFN-γ, TGF-β, IL-6, IL-10, and TNF-α from Syrian hamsters in recombinant form and to generate polyclonal antibodies against them in rats., Methods and Results: Cytokine transcript sequences were cloned into expression vectors in E. coli. Recombinant proteins were produced, purified through affinity chromatography, and characterized by Western blot using an anti-6xHis monoclonal antibody. Rats were immunized with the recombinant proteins to generate polyclonal antibodies (pAbs). These pAbs were characterized by Western blot and titrated by indirect ELISA. The recombinant cytokines rTNF-α, rIL-10, rIFN-γ, rTGF-β, and rIL-6 were produced and specifically recognized at their expected molecular weights of 22.3 kDa, 19.8 kDa, 18.9 kDa, 11.8 kDa, and 22.9 kDa. pAbs were produced and demonstrated the ability to specifically recognize their target proteins with titers of 409,600 (rIL-10), 204,800 (rTNF-α), 102,400 (rIL-10), 51,200 (rTGF-β), and 25,600 (rIFN-ɣ)., Conclusions: The reagents produced represent a starting point for developing immunoassays to detect hamster cytokines, facilitating the analysis of cellular immunity in this biomodel., (© 2024. The Author(s), under exclusive licence to Springer Nature B.V.)

Leptospirosis, a neglected zoonotic disease, is caused by pathogenic spirochetes belonging to the genus Leptospira and has one of the highest morbidity and mortality rates worldwide. Vaccination stands out as one of the most effective preventive measures for susceptible populations. Within the outer membrane of Leptospira spp., we find the LIC12287, LIC11711, and LIC13259 lipoproteins. These are of interest due to their surface location and potential immunogenicity. Thorough examination revealed the conservation of these proteins among pathogenic Leptospira spp.; we mapped the distribution of T- and B-cell epitopes along their sequences and assessed the 3D structures of each protein. This information aided in selecting immunodominant regions for the development of a chimeric protein. Through gene synthesis, we successfully constructed a chimeric protein, which was subsequently expressed, purified, and characterized. Hamsters were immunized with the chimeric lipoprotein, formulated with adjuvants aluminum hydroxide, EMULSIGEN®-D, Sigma Adjuvant System®, and Montanide™ ISA206VG. Another group was vaccinated with an inactivated Escherichia coli bacterin expressing the chimeric protein. Following vaccination, hamsters were challenged with a virulent L. interrogans strain. Our evaluation of the humoral immune response revealed the production of IgG antibodies, detectable 28 days after the second dose, in contrast to pre-immune samples and control groups. This demonstrates the potential of the chimeric protein to elicit a robust humoral immune response; however, no protection against challenge was achieved. While this study provides valuable insights into the subject, further research is warranted to identify protective antigens that could be utilized in the development of a leptospirosis vaccine. KEY POINTS: • Several T- and B-cell epitopes were identified in all the three proteins. • Four different adjuvants were used in vaccine formulations. • Immunization stimulated significant levels of IgG2/3 in vaccinated animals., (© 2024. The Author(s).)