Immunomodulation of T-cell responses with Vibrio cholerae O135 capsular polysaccharide and its protein conjugate, novel cholera vaccine study models

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 (R2 = 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.