Outer membrane protein antigens in an enzyme-linked immunosorbent assay for Salmonella enteric fever and meningococcal meningitis.

Outer membrane protein preparations were obtained from strains of Salmonella and Neisseria meningitidis. Solubilized cell envelope (CE) fractions from S. typhi and Salmonella groups A, B, C, and E had very similar electrophoretic mobilities on polyacrylamide gel, and common antigens were demonstrated by immunodiffusion. CE appeared to be a more satisfactory antigen than the more purified preparation (T/TEI) in the enzyme-linked immunosorbent assay (ELISA) with sera from typhoid and paratyphoid patients. With either antigen, however, the presence of antibodies was demonstrated in acute- and vonvalescent-phase sera. In the case of N. meningitidis infections, the crude (STA) and the more purified antigens (T/TEI) were equally satisfactory, and a rise in antibody titer could easily be demonstrated with paired acute- and convalescent-phase sera. The ELISA appears to be a simple but highly sensitive test for the detection of antibodies by using outer membrane protein antigens.