Cross-reactive monoclonal antibodies for diagnosis of pneumococcal meningitis

Abstract

A diagnostic test for the detection of Streptococcus pneumoniae meningitis was developed using monoclonal antibodies (MAbs) to phosphocholine (PC) and non-PC determinants of pneumococcal teichoic acid. These MAbs do not recognize other bacteria that commonly cause meningitis. By using a dot blot assay, these MAbs were compared with a polyvalent pneumococcal capsular omniserum and an antiserum made to whole cells for their ability to detect pneumococci in infected spinal fluids. An immunoglobulin M (IgM) anti-PC antibody gave a positive reaction with 16 of 22 (73%) pneumococcal culture-positive spinal fluids. One false-positive result out of 45 pneumococcal culture-negative spinal fluids was also observed. D3114/63, an IgM MAb to non-PC determinants of teichoic acids, detected 15 of 22 of the pneumococcal culture-positive spinal fluids with one false-positive result. IgG2b and IgG3 anti-PC MAbs were less efficient than the IgM anti-PC MAb at detecting pneumococci in spinal fluids. Like the IgM anti-PC MAb, omniserum detected 73% of the culture-positive pneumococcal spinal fluids, with one false-positive result. The use of anti-PC or D3114/63 MAbs instead of a pooled serum such as omniserum has several advantages: (i) use of a single cross-reactive antibody rather than 83 pooled antibodies; (ii) possibility of a higher concentration of reactive antibody, which may increase the sensitivity of the test; (iii) a standardized antibody preparation; (iv) ease of preparation of the antibody; and (v) less expense.