State Research Center — Institute of Immunology, Moscow, Russia
The immunochemical purity of S.typhi polysaccharide antigens, obtained in earlier studies, was analyzed, viz. lipopolysaccharide (O-LPS) and 3 samples of Vi-antigen differing in the degree of purification: Vi-antigen obtained by cetavlon sedimentation (Ct-Vi), Vi-antigen obtained by chromatographic purification (CP-Vi) and Vi-antigen obtained by triple cetavlon sedimentainon (3-Ct-Vi). These preparations were used in the study of immune response in typhoid fever patients from different regions. The immunological purity of Vi-antigens was evaluated by the level of their reactiveness in the immunoenzyme assay with background antibodies in the sera taken from healthy donors in a hyperendemic region (Dushanbe) and a nonendemic one (Moscow). The levels of preexisting antibodies to O-LPS and CP-Vi in Dushanbe were essentially higher than in Moscow. In the sera brought from Tajikistan O-LPS gave the maximum binding of antibodies (0.79 vs 0.56; 0.79 vs 0.3). At the same time the use of 3-Ct-Vi did not show significant differences between the levels of background anti-Vi antibodies in the sera from Dushanbe and the sera taken in Moscow. On the panel of sera from acute salmonellosis patients (in cases of S.enteritidis infection) the use of 3-Ct-Vi made it possible to find out an essential decrease in the number of false positive reactions (9.5% vs 28.5% for CP-Vi, vs 33.3% for O-LPS). To study the antibody response in typhoid fever patients, 3-Ct-Vi was used as the most antigenically pure preparation. The prevalence of the level of O-specific antibodies in comparison with response to 3-Ct-Vi-antigen (96.77 μg/ml vs 65.13 μg/ml).
Zh. Mikrobiol. (Moscow), 2003, No. 6, P. 56—60