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The features of individual fragments of IgA1 protease of Neisseria meningitidis serogroup B during the formation of immunity to bacterial infections in animals and humans were studied. The antibodies to the immunogenic regions of the studied proteins are also detected in mice infected with some bacterial pathogens and in humans with bacterial meningitis. A region of IgA1 protease was identified that is not capable of producing antibodies during immunization of animals, but that detects homologous antibodies in the blood of humans and animals recovered from bacterial infections. It has been suggested that this fragment plays a regulatory role in the process of immunogenesis.

Immunization of mice with recombinant IgA1 protease of Neisseria meningitidis or several structural derivatives thereof protects the animals infected with a variety of deadly pathogens, including N. meningitidis serogroups A, B, and C and 3 serotypes of Streptococcus pneumonia. In sera of rabbits immunized with inactivated pneumococcal cultures, antibodies binding IgA1-protease from N. meningitidis serogroup B were detected. Thus, the cross-reactive protection against meningococcal and pneumococcal infections has been demonstrated in vivo. Presumably it indicates the presence of common epitopes in the N. meningitidis IgA1 protease and S. pneumoniae surface proteins.

We studied immunogenicity of two recombinant proteins FR.9 and FR.11-3 created on the basis of fragments of the primary structure of N. meningitidis IgA1 protease with different molecular weights containing different sets of T and B epitopes. The proteins actively protect animals infected with live virulent culture of meningococci, serogroups A, B, and C. Analysis of CD4+, CD8+, and CD19+ lymphocyte populations in mouse blood showed predominant contribution of different cell populations to the formation of immune response to different proteins. Injection of FR.11-3 protein to animals did no affect the immunoregulatory index, hence, this protein can be used for creation of immunologically safe vaccine preparation.

Four recombinant proteins, MA28–P1004LEH6, ME135–H328LEH6, MW329–H622LEH6 and MH835–P1004LEH6, were prepared based on the genomic sequence of IgA1 protease from Neisseria meningitidis serogroup B strain H44/76. The immunogenic and protective properties of these proteins were studied in a mouse model. The predicted T- and B-epitopes located in the N-terminal part of amino acid sequence of this enzyme are very important for the formation of effective protection against meningococci of the three main epidemic serogroups A, B, and C. The small-sized recombinant protein having the sequence ME135–H328LEH6 (molecular weight 23367 Da) appears to be as protective against meningococci of the tested serogroups as the high molecular MA28–P1004LEH6 (molecular weight 109019 Da), the latter being a large-sized analog of full-length IgA1 protease. These proteins can be promising candidates for a polyvalent meningococcal vaccine.

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.

The study of enzymatic and protective properties of recombinant IgA1 protease in active and mutant form showed that active form of IgA1 protease exhibited species - and type-specificity for mouse and human immunoglobulins. Mutant form, which did not exhibit enzymatic activity, had protective properties against meningococcal infection, induced by meningococcus serogroup A, B and C protecting the mice from lethal infection by living virulent culture of heterologous serogroups of meningococcus. Obtained results make it possible to consider IgA1 protease as a perspective preparation at the stages of development of polyvalent vaccine for protection the people from meningococcal infection of various etiology.NIssledovanie fermentativnykh i protektivnykh svoĭstv rekombinantnoĭ IgA1 proteazy v aktivnoĭ i mutantnoĭ formakh pokazalo, chto aktivnaia forma IgA1 proteazy kharakterizuetsia vidovoĭ i tipovoĭ spetsifichnost'iu v otnoshenii immunoglobulinov myshi i cheloveka. Mutantnaia forma, ne obladaia fermentativnoĭ aktivnost'iu, proiavliala protektivnye svoĭstva v otnoshenii meningokokkovoĭ infektsii, vyzyvaemoĭ meningokokkami serogrupp A, V i S, zashchishchaia mysheĭ ot letal'nogo zarazheniia zhivoĭ virulentnoĭ kul'turoĭ geterologichnykh serogrupp meningokokka. Poluchennye rezul'taty pozvoliaiut rassmatrivat' IgA1 proteazu v kachestve perspektivnogo preparata pri sozdanii polivalentnoĭ vaktsiny dlia zashchity cheloveka ot meningokokkovoĭ infektsii razlichnoĭ étiologii.

Microbial capsular polysaccharides for many years provided a highly practical public health vaccines for preventing meningococcal, pneumococcal and Haemophilus influenza infection, and typhoid fever. Their application in the form of conjugates with protein carriers eliminate the gap in protection against these infections in children under one year. Extremely promising turned out offered us a new generation of vaccines, which have synthetic peptides conjugated to a meningococcal polysaccharide. Thus, new approaches to the solution of the problem of meningococcal disease vaccination serogroup B were open. In recent years, Russian researchers first suggested to use IgA1 protease (one of the major virulence factors of microbes and almost identical for mentioned below infections) for prevention of such diseases as meningococcal of all serogroups, pneumococcus and hemophilia infections. Patented processes for producing of the vaccine define domestic priority of its production and use.

IgA1-protease allocated from the culture N. meningitidis serogroup A. As original materials were used three different intermediate products of vaccine production: cultural fluid, cetavlon supernatant and cetavlon precipitate. IgA1-protease was used to evaluate their protectivity and immunogenity. It was shown, that isolated IgA1 protease from the meningococcus serogroup A is able to protect mice, infected by meningococcus serogroup B.

A method of the isolation and purification of IgA1 protease from a culture of Neisseria meningitidis serogroup A has been developed. Three inactivated intermediates of the production of the meningococcal vaccine, a culture liquid, as well as a supernatant and precipitate obtained by the precipitation of bacterial cells by cetavlon, served as a starting material. The purity of IgA1 protease was determined by SDS-PAGE. An immunoenzyme assay for determining the IgA1 protease activity has been developed. The yield of the enzyme with a specific activity of 0.5 to 4 million units/mg from 103 g of the cetavlon precipitate (40 l of culture liquid) was about 600 µg. It was shown that IgA1 protease isolated from serogroup A meningococcus is capable of protecting experimental animals (mice) infected with meningococcus of serogroup B.

Using the genome sequence of IgA1 protease of N. meningitidis of serogroup B, four recombinant proteins of different structure and molecular weight were constructed. These proteins were equal in inducing the formation of specific antibodies to IgA1 protease and had protective properties against meningococci. In the sera of immunized mice, anti-IgA1 protease antibodies were detected by whole-cell ELISA, which indicated the presence of IgA1 protease on the surface of these bacteria. We hypothesized that the protective properties of IgA1 protease-based antigens and IgA1 protease analogs could be realized not only via impairment of bacterium adhesion to the mucosa, but also via suppression of this pathogen in the organism. The presented findings seem promising for using these proteins as the basis for anti-meningococcus vaccine.

A new approach to estimation of IgA subclass levels and IgA1/IgA2 ratio using enzymatically active and inactive forms of Neisseria meningitidis IgA1 protease was developed.The approach was tested using the sera of healthy volunteers and patients with meningococcal meningitis. There was a significant increase in the IgA1 level in patients with meningitis (mean titer 1:1546 ± 352) compared to healthy volunteers (mean titer 1:546 ± 282), while the IgA2 content remained unchanged. The IgA1/IgA2 ratio was 6.3 for the healthy volunteers and 12.8 for patients with meningitis. IgA2 for the patients with meningitis and the healthy volunteers were almost unchanged, 1:86 ± 61 and 1:121 ± 46, respectively.The proposed method is economical and reliable and can be used for evaluation of IgA1 and IgA2 in clinical laboratories or for research purposes.

Recombinant proteins (M1K2–N963-LEH6, MA28–N963-LEH6 and ME135–H328-LEH6) have been created on the basis of the genome sequence of IgA1 protease of N. meningitidis serogroup B strain H44/76. It is revealed that, similarly to the native enzyme isolated earlier from N. meningitidis serogroup A strain A208, these proteins induce formation of animal protection against the infection with the virulent strain of meningococcus serogroup B. It is shown that these compounds are promising as a basis for a polyvalent anti-meningococcal vaccine.