Experimental evaluation of recombinant polypeptides as Streptococcus Group B vaccine

: Recombinant polypeptides corresponding to the conservative N-terminal area of Bac surface protein of group B streptococci (GBS) and having the human IgA binding-site were obtained and evaluated in terms of Immunogenic and protective properties. GBS strain 219, serotype 1 bc, served as the source of chromosomal DNA used for cloning. Three polypeptides P1, P5 and P6 were constructed. Polypeptides P1 and P5 with a molecular weight of 22 kD were coded by practically identical DNA fragments (685 nucleotide pairs) and differed in two aminoacids In their central part. Polypeptide P6 had a molecular weight of 35 kD, The fragment of recombinant Bac protein with a molecular weight of 35 kD was found to have protective properties: when used for the subcutaneous immunization of animals, it stimulated the development of immune response capable, in case of challenge, to induce accelerated elimination of streptococci and the prevention of the mice death. Recombinant fragment P6 of GBS protein Bac may be regarded as a candidate for inclusion into GBS-specific vaccine.