Monoclonal antibodies against Streptococcus pneumoniae detect epitopes on eubacterial ribosomal proteins L7/L12 and on streptococcal elongation factor Ts.

Two monoclonal antibodies (mAbs) designated 144,H-3 (IgG2a) and 218,C-5 (IgM) were produced after immunization of mice with two different heat-treated and sonicated pneumococcal strains. Western blotting, with solubilized proteins from different bacterial genera and from mammalian lymphocytes, showed that both mAbs reacted with a protein of approximately 12 kDa in all 66 strains of eubacteria examined, representing 27 different species. The 12 kDa protein was isolated by immunoaffinity chromatography. Subsequent preparative Western blotting enabled N-terminal amino acid sequence analysis by microsequencing. A high degree of amino acid sequence similarity with eubacterial ribosomal proteins L7/L12 was demonstrated. One of the mAbs (144,H-3) also cross-reacted in Western blotting with a 43 kDa protein, but only from streptococci. The 43 kDa protein carrying the common streptococcal epitope was isolated and sequenced in the N-terminal region. A high degree of amino acid sequence identity was found to elongation factor Ts from Escherichia coli.