Brucella inactivated vaccine elicits immunity against B. melitensis infection in mice and guinea pigs.

BACKGROUND

Brucellosis is a zoonotic disease that poses a significant threat to both animal husbandry and public health. Currently available vaccines for brucellosis are all live attenuated forms, which carry the risk of potential infectivity and provide a relatively limited range of protection. In contrast, inactivated vaccines are perceived to exhibit poor protective efficacy and fail to elicit effective cellular immunity. This study aimed to comprehensively evaluate the efficacy of the Brucella inactivated vaccine (CF) with the objective of developing a safer and more effective candidate for brucellosis vaccination.

METHODS

Firstly, we evaluated the safety of CF in mice. Subsequently, we immunized mice with CF using various doses and methods, determining the optimal immunization dose and method through challenge testing. We evaluated the vaccine's immunogenicity by detecting the cellular and humoral immune levels induced by CF in mice, and assessed the vaccine's protective effect based on the post challenge organ bacterial load. Additionally, we evaluated the protective effects of dual doses and secondary immunization in guinea pigs.

RESULTS

The results indicate that CF is safe and non-toxic; it induced significant increases in specific IgG antibody levels against Brucella during the early stages and markedly enhanced the T cell immune response, thereby promoting a Th1-biased immune response in mice. Following the challenge, CF demonstrated protective efficacy comparable to that of the S2 vaccine against B. melitensis biovar 3 infection in mice. CF-immunized guinea pigs were able to resist infection by B. melitensis M28 and B. melitensis biovar 3.

CONCLUSIONS

In summary, CF significantly induces both humoral and cellular immunity in mice. This study reports for the first time that a safe and effective inactivated Brucella vaccine (CF) can induce cellular immune responses and effectively prevent animal brucellosis.