Abstract
Infectious bovine rhinotracheitis (IBR) and bovine viral diarrhea (BVD) are among the most common viral infections causing significant economic losses in livestock production. The efficacy of inactivated vaccines against these diseases is largely determined by the choice of an adjuvant system that ensures the formation of a pronounced and long-lasting immune response. The aim of this study was to comparatively evaluate the physical stability, safety, and immunogenicity of an experimental associated inactivated vaccine against IBR and BVD formulated with various commercial Montanide® adjuvants to substantiate the choice of the optimal adjuvant system. Experimental vaccines formulations were prepared based on inactivated virus-containing suspensions of the IBR virus strain “R-93” and the BVD virus strain “OregonC24V” using Montanide ISA 70 VG, Montanide ISA 61 VG, and Montanide GEL 01 PR adjuvants. The physical stability of the vaccines was assessed using an accelerated thermostability test, while safety and immunogenicity were assessed in a rabbit model following a single intramuscular immunization, with determination of virus-neutralizing antibody (VNA) titers in a neutralization test. All studied vaccines maintained physical stability for 10 days of incubation, did not cause clinically significant local adverse reactions, and were well tolerated. The highest VNA titers to both viruses were observed in the groups immunized with vaccines formulated with Montanide ISA 70 VG and Montanide GEL 01 PR, while antigens without adjuvant induced a less pronounced humoral immune response. This comprehensive evaluation supported the selection of Montanide ISA 70 VG as the optimal adjuvant for the domestic associated inactivated vaccine against IBR and BVD.