Abstract
This study aimed to evaluate the immunogenicity of a recombinant Mycobacterium smegmatis vaccine expressing the CMX fusion protein, composed of immunodominant epitopes Ag85C, HspX and MPT51 of Mycobacterium tuberculosis, which are important mycobacteria virulence factors. A group of Nelore heifers, with age between 10 to 12 months, tuberculin skin test (TST) negative were immunized with four doses of the recombinant vaccine mc2-CMX (M. smegmatis- Ag85C- MPT51- HspX) during a period of one year. Before each immunization, blood was collected to obtain sera for antibody analysis. Serological analysis demonstrated that mc2-CMX was able to induce a humoral response with increased levels of specific IgG antibodies against CMX, despite minimum antibody levels detected for Ag85C, MPT51 or HspX individual recombinant antigens. However, there was no significant increase in specific CD4+ IFN-γ positive T cells. Lymphadenomegaly was observed in superficial cervical lymph nodes adjacent to the site of vaccination among mc2-CMX vaccinated bovines and the histopathological analysis demonstrated follicular hyperplasia without inflammatory infiltrate or granuloma. Animals remained negative for the TST until the end of the experiments, showing no cross- reactivity with the recombinant vaccine and tuberculin proteins. We discuss the potential of mc2-CMX to induce immune response in cattle.
