ORAL IMMUNIZATION WITH THE SALIVA-BINDING REGION OF STREPTOCOCCUS-MUTANS AGI II GENETICALLY COUPLED TO THE CHOLERA-TOXIN-B SUBUNIT ELICITS T-HELPER-CELL RESPONSES IN GUT-ASSOCIATED LYMPHOID-TISSUES/

Mice immunized intragastrically (i.g.) with a genetically constructed chimeric protein consisting of the saliva-binding region (SBR) of Stre ptococcus mutans AgI/II coupled to cholera toxin (CT) A2 and B subunit s (CTA2/B) develop serum immunoglobulin G (IgG) and mucosal IgA antibo dy responses against AgI/II that are enhanced by the coadministration of CT as an adjuvant, To investigate the development of antigen-specif ic T cells in the gut-associated lymphoid tissues, mice were immunized i.g. with SBR, SBR-CTA2/B, or SBR-CTA2/B plus CT, AgI/II-specific T c ells in Peyer's patches (PP), mesenteric lymph nodes (MLN), and spleen were assayed by lymphoproliferation and flow cytometry for the expres sion of T-cell surface markers, and cytokine mRNA expression was evalu ated by reverse transcription-PCR, T cell responses were consistent wi th antibody responses but were detectable after the first immunization , Proliferative responses of PP and MLN cells upon stimulation with Ag I/II in vitro were low and delayed in mice given SBR alone, and these cells displayed a mixed type 1 and 2 (or Th0) pattern of cytokine expr ession, Immunization with SBR-CTA2/B resulted in greater AgI/II-specif ic proliferative responses in PP cells and an increase in the proporti on of CD4+ T cells, Coadministration of CT with SBR-CTA2/B led to grea ter proliferative responses especially in the MLN cells, which then sh owed an increase in CD4+ cells, Immunization with SBR-CTA2/B (with or without CT) skewed the cytokine expression pattern in PP and MLN cells toward Th2. The results indicate that T helper cells were induced in gut-associated lymphoid tissues by i.g. immunization with SBR-CTA2/B, concomitantly with and prior to the appearance of circulating and muco sal antibodies.