Immunomodulation of T-cell responses withVibrio choleraeO135 capsular polysaccharide and its protein conjugate, novel cholera vaccine study models

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We studied T-cell immune responses to surface capsular polysaccharide (CPS) of Vibrio cholerae O135 and its protein conjugate. CPS and CPS-bovine serum albumin (BSA) activation and presentation are characterized with induced alterations in expression and upregulation of membrane antigens CD25, CD11b, CD16/32, MHCII and CD45 on blood- and spleen-derived T cells. Expression of the early activation marker CD25 revealed efficient CPS-BSA conjugate activation especially of CD4(+) CD3(+) and CD8(+) CD3(+) cells. Specific CPS-BSA-induced CD25(+) T-cell subsets in blood were observed after the first application, i.e. a 4.2-fold increase of CD4(+) CD25(+) and 7.6-fold increase of CD8(+) CD25(+) vs. preimmune levels was determined. The upregulation of surface antigens MHCII and CD45 involved in antigen presentation and cell activation of CD3(+) cells and their significant reciprocal correlation (R(2) =0.92) observed only with CPS-BSA conjugate suggested efficient T-cell dependency and presentation. The pattern of accelerated T-cell activation and engagement of T cells as antigen-presenting cells throughout CPS-BSA immunization contrary to CPS alone was also confirmed in CD4(+) /CD8(+) /CD3(+) splenic cells. The results revealed different T-cell antigen presentation and activation following administration of CPS and CPS-BSA conjugates, as supported also by evaluation of CD45, MHCII and CD25 expression on CD19(+) B cells.