We investigated the involvement of TLR signaling in the induction of humoral and cell-mediated immune responses (CMIR) following oral and intramuscular (IM) immunization with Dukoral (killed whole-cell V. cholerae and cholera toxin B subunit, CTB) or its components by using TLR-2-, TLR-4-, MyD88- and Trif-deficient mice. We show that wild type and all groups of TLR-deficient mice generated similar levels of V. cholerae- and CTB-specific IgG1and IgG2c serum antibodies, fecal IgA antibodies and agglutinating antibodies, following oral immunization with Dukoral or CTB alone. However, IM immunization with Dukoral or CTB alone required MyD88 signaling for the induction of CTB-specific IgG1and IgG2c serum antibodies. In addition, our results show that CD4+ T-cell and CD19+ B-cell proliferation, maturation of DCs in response to vaccine components, as measured by CD80, CD86, CD40, and MHCII expression, and cytokine secretion including IFN-g occurred in a MyD88-dependent manner in response to V. cholerae or CTB stimulation. In contrast, in response to CTB stimulation, Trif negatively regulated both CD4+ T-cell and CD19+ B-cell proliferation. Overall, our results suggest that despite the impaired ability of MyD88-/- DCs to mature, humoral responses, following oral immunization with Dukoral, occurred independently of TLR signaling, while CMIR were TLR-dependent. However, TLR-independence is lost in the generation of humoral responses when the vaccine is administered parenterally.
- Copyright © 2013 by The American Association of Immunologists, Inc.