Attenuated Salmonella vectors, adept at delivering vaccines to the PPs, elicit T helper (Th) 1 cell (IFN-γ-dependent) immune responses to resolve its infection. However, our studies show that we can obtain elevated Th2 cell (IL-4-dependent) immune responses, followed by a delayed onset of Th1 cells to colonization factor antigen I (CFA/I), from human enterotoxigenic Escherichia coli (ETEC). Subsequent studies revealed that proinflammatory cytokine production are abated suggesting this acts as an anti-inflammatory vaccine. Current studies are evaluating the efficacy of this vaccine against autoimmune diseases such as experimental autoimmune encephalomyelitis (EAE) and collagen-induced arthritis. Our recent findings show that this vaccine induces regulatory T cells, but the type of regulatory cell induced is disease-dependent. We are currently investigating how Salmonella-CFA/I stimulates the production of these regulatory T cells, and we are determining the involved dendritic cells that sustain these responses.
Effective treatments for multiple sclerosis (MS) are problematic due to its unknown etiology. Current work has adapted the rodent EAE model to test whether our tolerogen vaccine delivery platform, the reovirus adhesin, protein sigma 1 (pσ1), can improve mucosal auto-antigen uptake. We show that a single low-dose of pσ1-based vaccines induces tolerance and prevents or treats autoimmunity when applied mucosally. Our studies show that pσ1-mediated tolerance is IL-10-dependent via regulatory T cells. In addition, regulatory elements with the IL-4-producing CD25- CD4+ T cells have been found. Further work will determine the mechanisms used by pσ1 and to understand the involved dendritic cell subset(s) that stimulate regulatory T cells. Ultimately, these studies will determine the feasibility of using pσ1-based single-dose delivery system to prevent and/or treat autoimmune diseases.
One goal of our work is to improve and devise novel vaccine delivery systems by taking advantage of infectious agents' adhesins, particularly those that can target mucosal inductive tissues for the GI and respiratory tracts. We employ three vaccine delivery systems: the nonreplicating adenoviral vector for delivery into respiratory tissues, live attenuated Salmonella for delivery into the GI tract, and DNA formulations for both the respiratory and the GI tracts. The objectives for our studies include 1) to delineate the immune T and B cell responses to the vaccine; 2) to assess the type of CD4+ T cells elicited; and 3) to design vaccines to produce the desired T cell response. We are currently evaluating vaccine candidates for ETEC, Coxiella burnetii, Brucella, botulinum, and Yersinia pestis. The results of these research endeavors will ultimately have clinical, veterinary, and wildlife applications.