[The relationship between the immunological efficacy of a dried meningococcal group-A polysaccharide vaccine and the molecular parameters of the group-A polysaccharide].

This work deals with the problem of relationship between the molecular parameters of group A meningococcal polysaccharide and its immunological effectiveness for laboratory animals and humans. The depolymerization of group A polysaccharide contained in the vaccine leads to a decrease in its capacity of inducing the production of hemagglutinating (19S and 7S) and bactericidal IgA antibodies in humans, as well as inducing an increase in the number of cells producing IgA antibodies in the spleen of immunized mice and the appearance of circulating IgA antibodies in their sera. As shown in this investigation, fully developed immune response to group A meningococcal vaccine may be achieved in humans only if the content of group A high-molecular polysaccharide in the vaccine is not less than 70%.

[Tolerance induction by the peroral administration of protein antigens].

The possibility of inducing systemic tolerance in animals by feeding them with ovalbumin and human serum was studied on mice, rats and rabbits. Antibodies to ovalbumin, human serum albumin and immunoglobulins (IgG, IgA, IgM) were determined by the passive hemagglutination test in the sera of the test and control animals after the second immunization made through a parenteral route. Tolerance to all the antigens under study was obtained in mice and rats, while in rabbits such feeding was found to produce the priming effect.