[The immunomodulating capacity of Shigella flexneri 2A bacteria that have lost their invasiveness plasmid].

An immunosuppressive effect produced by live microbial cells of S. flexneri virulent plasmid-carrying strain 2a 516 (pSF 140-) was shown in relation to the formation of splenic cells producing antibodies to heterologous antigen (sheep red blood cells). This effect was most pronounced at an early period (days 4-7) after the infection of mice.

[The role of the outer membrane proteins, determined by the Shigella flexneri invasiveness plasmid, in inducing cellular immune reactions].

Fractions of S.flexneri 2a 516 outer membrane proteins determined by plasmid pSF140 have been shown to possess immunomodulating activity and to be capable of influencing the intensity of hematopoiesis, manifested by the stimulation of endocolony formation, the increase of the amount of splenic colony-forming units in the marrow, the increase of the pool of proliferating splenic colony-forming units of the marrow and their intensive migration into the blood. Outer membrane proteins have been shown to produce an immunostimulating effect on the functional activity of effector B-lymphocytes shortly after their injection.

[A morphological evaluation of the harmlessness of noninvasive recombinant Shigella strains].

The interaction of Shigella recombinant strains (with attenuating chromosomal mutations, with transposon-neutralized plasmid gene mutations, the hybrids of both strains), incapable of inducing keratoconjunctivitis in guinea pigs, with cells Hep-2 and enterocytes in the ligated loop of the small intestine of rabbits was studied. These strains retained, to varying extent, pronounced adhesiveness, but practically lost their invasiveness (though in Peyer's patches the translocation of bacteria by M-cells was observed) and cytotoxicity, as well as their capacity to multiply in epithelial cells and to cause destructive inflammation in the intestine. According to these criteria of evaluation, morphological investigations confirm the safety of the recombinant shigellae under study.

[A morphological evaluation of the protective properties of noninvasive recombinant strains of Shigella].

In 2-3 weeks after the oral immunization of rabbits, made in one or two administrations, with attenuated two-marker S. dysenteriae 1 strain VS-12 and recombinant S. dysenteriae VS-12/S.