[Strain differences of intra-species immunogenic activity of Streptococcus pneumoniae antigen components]

Study intra-species immunogenic activity of antigenic protein-polysaccharide components of S. pneumoniae.

Antigenic components of serotype 3, 6A, 6B, 14, 10A, 18A, 19A, 19F, 23F and unencapsulated S. pneumoniae strains were obtained by water extraction method. Synthetic hexasaccharide--corresponding to the structure of S. pneumoniae serotype 14 capsule polysaccharide repeated unit chain fragment was used as a reference preparation. Molecular mass of antigenic components was determined in SDS-electrophoresis. Antibody titers in blood sera of immunized mice were evaluated by solid-phase EIA method. Protective activity of preparations was studied in mice after 2 immunizations with consequent infection by virulent S. pneumoniae serotype 3 and 6B strains.

Preparations from serotype 6A, 6B, 14, 19A, 19F, 23F strains in reaction with anti-microbial sera were characterized by cross serologic activity (IgG titers of 1200 - 12 800). The lowest serologic activity was detected in S. pneumoniae serotype 3 and unencapsulated strain preparations. Conjugate of synthetic hexasaccharide and bovine serum albumin interacted only with homologous antimicrobial sera up to titers of 600 +/- 89.4 and did not react with sera against serotypes 19A and 19E Cross serologic activity of preparations is probably determined by the presence of protein fractions that were detected in SDS-electrophoresis. This is confirmed by high intra-species cross protective activity of preparations from serotype 6B and 10 A strains that protect 90 - 100% of mice from infection by heterologous S. pneumoniae strains.

Use of strains with cross antigenic and protective activity for production of immunogenic protein-containing fractions with the aim of enchanting and broadening specter of protective activity of vaccine preparations that are constructed based on capsule polysaccharides of S. pneumoniae is appropriate.