Monoclonal antibodies against Neisseria Gonorrhoeae: serotyping and diagnostic applications
Coghill, Diane Vivien
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The aims of this study were (i) to investigate the value of newly developed monoclonal antibody coagglutination reagents for serotyping gonococci according to Protein I variation between strains; (ii) to determine if these or similar monoclonal antibodies could be used in an immunological method for the non -cultural detection of N. gonorrhoeae; and (iii) to produce monoclonal antibodies directed against gonococcal beta- lactamase and to examine their value in a non - cultural diagnostic test for penicillinase- producing gonococci.A total of 1201 gonococcal isolates, obtained from 967 patients attending a sexually transmitted diseases clinic in Edinburgh, were classified serologically using two independently developed panels, each of 14 monoclonal antibodies. The distribution of serogroups WI and WII /III was shown to be 51% and 49% respectively. Using a combination of the two panels of reagents, WI strains could be subdivided into 19 serovars and WII /III strains into 53 serovars: The individual panels recognised 7 (Ph) and 12 (GS) WI serovars and 22 (Ph) and 24 (GS) WII /III serovars. Temporal and geographical variations in serovar patterns were observed, illustrating the dynamic nature of the circulating gonococcal population. A statistically significant correlation between the WII /III serovar combination Bropyt /Back and homosexually acquired infection was found (P < 0.001). This serovar combination accounted for 57% of homosexually acquired infections compared with 3% and 0.8% of infections in heterosexual men and women. A statistically significant correlation between the WII /III serovar Bajk and concomitant rectal infection in women was found (0.05 > P > 0.02). This serovar accounted for 28% of women with genital and rectal infection compared with 17% of women in whom infection was restricted to the genital site. Statistically significant associations between serogroup WII /III and certain serovars and penicillin susceptibility were also observed. In addition to their value in correlating certain strains with particular anatomical sites and in predicting the antibiotic susceptibility of an isolate, these serovar studies proved valuable in tracing infected contacts.previously developed dot -blot immunoassay using polyclonal antisera raised against whole cell gonococci demonstrated poor sensitivity (26 %) in detecting gonococcal antigen in female cervical specimens: The specificity was 81.7 %. Replacement of polyclonal antisera with a panel of anti -Protein I monoclonal antibodies failed to improve the system, even though coagglutination reagents prepared with these antibodies had detected 99.7% of gonococcal strains.An immunoperoxidase staining technique was developed for the detection of gonococci directly in patient smears. An alternative panel of monoclonal antibodies developed for detection of gonococcal antigen was employed. Coagglutination reagents prepared using these antibodies had previously detected 97% of gonococcal strains. The sensitivity and specificity of this test when applied to 30 male urethral smears was 75% and 100% respectively. However, serovar analysis suggested that the incorporation of additional monoclonal antibodies to the panel would improve the sensitivity of this system.None of the hybridomas obtained from the fusions of myeloma cells and spleen cells from mice immunised with purified gonococcal beta -lactamase enzyme secreted antibodies specific for gonococcal beta -lactamase.It was concluded from this study that (i) the resolution achieved using two panels of monoclonal antibody coagglutination reagents was better than that achieved with either panel alone and increases the value of serotyping for the study of gonococcal epidemiology; (ii) a large variety of antigenic types of gonococci are circulating in the population at any one time and this antigenic pattern does not remain static, therefore constant surveillance of gonococcal strains will be necessary to ensure that immunological detection techniques remain effective; and (iii) the immun peroxidase assay using monoclonal antibodies against PrI has potential for use as an 'on- the -spot' test for the diagnosis of gonococcal infection.