Antibody Response to Neisseria Meningitidis Capsular Polysaccharide and Noncapsular Surface Antigens

Abstract

An indirect polysaccharide ELISA method that measured antibody response to Neisseria meningitidis capsular polysaccharide was modified to improve its sensitivity at high serum dilutions, to shorten the overall time of the assay procedure, and to decrease the background interference. The improved ELISA procedure was then used to study the antibody response of 261 sera from Upper Volta, Africa, to N. meningitidis group A capsular polysaccharide. An attempt was made to correlate group A capsular polysaccharide antibody levels of the Upper Volta sera to bactericidal and noncapsular protein antibody levels of the same sera. The polylysine precoat incubation time was shortened from 5 hours to 30 minutes along with a considerable decrease in background interference and an increase in sensitivity at high serum dilutions. No definite correlation could be seen between the bactericidal titers and the noncapsular protein and capsular polysaccharide antibody levels. A polysaccharide ELISA specifically aimed at IgM antibodies was used on some of the sera with promising results. It was concluded that either the wrong antigens were chosen to be assayed, or interference from some component of the test sera prevented the showing of a positive correlation. The ELISA procedure worked very well with the standard reference sera.