Background: Rabies remains a fatal zoonotic disease, necessitating effective and affordable vaccines. While current vaccines are effective, they require multiple doses and may not induce long-lasting immunity in all settings. The rabies virus glycoprotein (RABV-G) is the principal antigen responsible for eliciting virus-neutralizing antibodies, but its recombinant monomeric forms often suffer from poor immunogenicity due to misfolding and aggregation. Methods: A recombinant trimeric RABV-G ectodomain (rRABV-G-XVIII) was engineered by fusing it to a human collagen XVIII-derived trimerization domain. The protein was expressed in E. coli, purified under denaturing conditions, and refolded. Trimer formation was verified using size-exclusion chromatography. Mice were immunized with rRABV-G-XVIII, with or without adjuvant, and compared to a monomeric form (rRABV-GE). Antigen-specific antibody responses were measured by ELISA, neutralizing activity was assessed, and protective efficacy was evaluated via intracerebral challenge with the CVS-27 rabies strain. Results: rRABV-G-XVIII formed stable trimers and induced strong humoral immune responses, with high ELISA titers and virus-neutralizing activity comparable to an inactivated rabies vaccine. Mice immunized with rRABV-GE showed lower antibody responses and partial protection, which improved with adjuvant. All rRABV-G-XVIII-immunized mice were fully protected against rabies challenge, independent of adjuvant use. Conclusions: Stabilization of RABV-G in its native trimeric conformation markedly improves immunogenicity and protective efficacy. This approach offers a promising strategy for the development of rabies subunit vac-cines with simplified formulations and potential for cost-effective production in bacterial systems.

Immunoglobulin G (IgG) plays a key role in the body’s immune response, its high specificity to antigens and effectiveness in neutralizing pathogens make it a valuable tool in medical and scientific research. Horses are a source of significant amounts of IgG, but their purification to a level suitable for clinical or scientific use re[1]quires specialized methods. Development of chromatographic purification modes for immunoglobulin G (IgG) from the serum of horses hyperimmunized with rabies antigen will allow standardizing the technolo[1]gy in accordance with international quality and safety standards for the production and control of immunobiological medicines, vaccines and diagnostic test systems. Development of step-by-step modes and procedures for chromatographic purification of the serum of horses hyperimmunized with rabies antigen from the CVS-11 strain, with an assessment of the efficiency of the purification technology, protein yield and purity. The study used serological methods for obtaining and preparing serum from hyperimmunized horses, as well as biotechnological methods of gel filtration, ion exchange chromatography and subsequent electrophoresis. The practical significance of the study may allow developing technologies for obtaining immunobiological preparations based on immunoglobulins, and can be used in the fields of medicine, bio[1]technology and scientific research that require the use of highly purified immunoglobulins. According to the presented purification technology, immunoglobulins weighing 150 kDa were obtained, which under reducing conditions are divided into 2 light chains (28 kDa) and 2 heavy chains (55 kDa).