Cloning of the gene for cell-surface protein antigen A from Streptococcus sobrinus (serotype d)

A gene library of Strep. sobrinus B13N (serotype d) chromosomal DNA was constructed in Escherichia coli, with the bacteriophage vector lambda L47.1. A recombinant phage, lambda MDSM49, containing a 15.5 kb DNA insert, directed the expression of a 210 kDa antigenic protein. The recombinant 210 kDa protein was shown by Western blot analysis to be identical with cell-surface protein antigen A (spaA) from a serotype g strain. However, the restriction patterns of a subclone plasmid, pMD51, from lambda MDSM49 differed from those of serotype g strain. The cell-surface protein antigen I/II from serotype c Streptococcus mutans is a potential immunogen for vaccination against dental caries and corresponds to the spaA from serotype d and g strains. A recombinant clone, pDM51, will be a useful tool for serological and molecular biological studies. The recombinant spaA provides useful material for assessment of its diagnostic and immunogenic potential.