HEAT-SHOCK RESPONSE OF STREPTOCOCCUS-PNEUMONIAE - IDENTIFICATION OF IMMUNOREACTIVE STRESS PROTEINS

In order to investigate whether pneumococcal heat shock proteins (HSPs ) were major immunogens of humoral immune response, we first character ized the heat shock response of S. pneumoniae. Three HSPs, HSP62, HSP7 2 and HSP80, having an apparent molecular mass of 62, 72, and 80kDa, r espectively, were detected by labelling proteins synthesized with [S-3 5]methionine after a shift from 37 degrees C to 45 degrees C and fluor ography of SDS-polyacrylamide gels. Radioimmunoprecipitation and immun oblot analyses with mouse anti-pneumococcal sera revealed that HSP72 w as a major immunogen. S. pneumoniae HSP62 was another antigen which wa s precipitated by some immune sera. Anti-HSP72 antibodies appeared aft er the first immunization with S. pneumoniae antigens and subsequent i mmunization elicited a booster response. Monoclonal antibodies (MAbs) to pneumococcal HSP72 were produced and their specificities defined. T he epitopes reactive with four MAbs are highly conserved in S. pneumon iae since 20 out of 20 different strains were recognized by each indiv idual MAb. Western blot analysis revealed cross-reactivities with few nonpneumococcal strains. By N-terminal sequence analysis, the S. pneum oniae HSP72 was found to belong to the heat shock protein 70 family. T hat HSP72 is an important highly conserved antigen in S. pneumoniae sh ould provide a basis for further investigation of its physiological an d potential pathogenic role. (C) 1997 Academic Press Limited.