The immunogenic and protective activities of recombinant IgA1 serine protease obtained on the base of the genome DNA of N. meningitidis serogroup B strain H44/76 were studied. A several recombinant proteins of different molecular weights that are based on the full-length primary structure of the enzyme, taking into account the distribution of B- and T-epitopes, also were studied. In experiments on laboratory animals it was shown that a number of tested preparations demonstrate the immunogenic and protective activity to protect mice from lethal challenge with virulent strains of meningococcus serogroups A, B and C, thereby exhibiting polyvaccine properties. The protective role of antibodies against the IgA1 protease was shown when mice were infected by meningococccus serogroup B. The increase in antibodies to the meningococcal IgA1 protease into the blood of rabbits infected with different serotypes of pneumococci has been detected, indicating potential ability of the meningococcal IgA1 protease to generate protection against microbes the virulence of which is caused by IgA1protease.