Immunodiagnosis of group-A streptococci by latex agglutination assays with monoclonal or monospecific polyvalent antibodies

Abstract

Seven clones of murine monoclonal antibodies specific for group-A streptococci were generated. All of them were of IgM isotypes and recognized trypsinized as well as nontrypsinized group-A streptococci and polysaccharide. These were devoid of reactivity with streptococci-B, -C, -G and Staphylococcus aureus. Polyclonal antibodies against group-A polysaccharide (APS) were also raised in rabbits by linking APS to bovine serum albumin, and rendered monospecific by adsorption. Latex agglutination assays were developed employing both types of antibodies. The assay employing monospecific polyvalent antibodies had a sensitivity of 12.5 ng APS/ml as compared to 1 microgram APS/ml for latex sensitized with monoclonal antibodies. Both assays were specific, as no agglutination was observed with polysaccharides obtained from streptococci-B, -C, -G, Staph. aureus, Cornybacterium diptheriae, Candida albicans, Candida spp., Morexella catarrhalis, Klebsiella pneumoniae, Pseudomonas aeruginosa, Escherichia coli, Streptococcus agalactiae, Strep. pneumoniae. Salmonella typhi and S. paratyphi A and B. Throat swabs from children obtained in duplicate, when tested for the presence of streptococci-A, showed a good correlation of the results obtained by latex agglutination assay with the microbial culture test and serogrouping.