David Pascual, Professor

Veterinary Molecular Biology P.O. Box 173610 Montana State University Bozeman, MT 59717 (406) 994-6244 dpascual@montana.edu

Research Interests

The focus of my laboratory is to understand the basic tenets of mucosal immunology and their application to improve targeted mucosal vaccine delivery. It is evident from our studies that not all mucosal tissues exhibit the same mucosal properties of the gut. In fact, these extra-intestinal mucosal tissues have components of both the mucosal and peripheral immune systems. Current studies are evaluating this relationship and how they may impact memory B cell responses. We have shown that the nasal-associated lymphoid tissue (NALT) and the various head and neck lymph nodes (HNLNs) express unique addressin patterns. Their high endothelial venules (HEVs) do not resemble Peyer's patch HEVs with the extensive presence of MAdCAM-1. Instead, the peripheral node addressin (PNAd) dominates these tissues, suggesting an alternative mode of mucosal lymphocyte homing.

Attenuated Salmonella vectors, adept at delivering vaccines to the Peyer’s patches, elicit T helper (Th) 1 cell (IFN-γ-dependent) immune responses to resolve 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 reveal 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 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.

Education

• B.S University of Florida, 1980, Microbiology
• M.S. University of Mississippi Medical Center, 1985, Microbiology
• Ph.D. University of Mississippi Medical Center, 1987, Microbiology

Professional Experience

• 1987-1990 Postdoctoral Fellow, Department of Physiology and Biophysics, University of Alabama at Birmingham
• 1990-1992 Research Instructor, Departments of Oral Biology and Microbiology, University of Alabama at Birmingham
• 1992-1995 Research Assistant Professor, Department of Oral Biology, University of Alabama at Birmingham
• 1995-1998 Assistant Professor, Veterinary Molecular Biology, Montana State University
• 1998-2005 Associate Professor, Veterinary Molecular Biology, Montana State University
• 2005-present Professor, Veterinary Molecular Biology, Montana State University

Recent Publications

1. Pascual, D.W.  Commentary: Vaccines are for dinner.  Proc. Natl. Acad. Sci., USA 104: 10757-10758, 2007.

2. Ochoa-Repáraz, J., Sentissi, J., Trunkle, T., and Pascual, D.W.  Attenuated Coxiella burnetii phase II causes a febrile response in IFN-γ-/- and TLR2-/- mice and protects against re-infection.  Infect. Immun. 75:5845-5858, 2007.

3. Pascual, D.W., Riccardi, C., and Csencsits, K.  Distal IgA immunity can be sustained by αEß7+ B cells in L-Selectin-/- mice following oral immunization.  Mucosal Immunol. 1:68-77, 2008.
4. Rynda, A., Maddaloni, M., Mierzejewska, D., Ochoa-Repáraz, J., Maslanka, T., Crist, K., Riccardi, C., Barszczewska, B., Fujihashi, K., McGhee, J.R., and Pascual, D.W.   Low-dose tolerance is mediated by the microfold cell ligand, reovirus protein σ1.  J. Immunol. 180: 5187-5200, 2008.

5. Pascual, D.W., Wang, X., Kochetkova, I., Callis, G., and Riccardi, C.  Absence of CD8+ lymphoid dendritic cell maturation in L-Selectin-/- respiratory compartment attenuates anti-viral immunity.  J. Immunol. 181: 1345-1356, 2008.

6. Ochoa-Repáraz, J., Rynda, A., Ascón, M.A., Yang, X., Kochetkova, I., Riccardi, C., Callis, G., Trunkle, T., and Pascual, D.W.  IL-13 production by regulatory T cells protects against experimental autoimmune encephalomyelitis (EAE) independently of autoantigen.  J. Immunol. 181: 954-968, 2008.

7. Kochetkova, I., Trunkle, T., Callis, G., and Pascual, D.W.  Vaccination without autoantigen protects against collagen II-induced arthritis via immune deviation and regulatory T cells.  J. Immunol. 181: 2741-2452, 2008.

8. Yamanaka, H., Hoyt, T., Yang, X., Golden, S., Bosio, C.M., Crist, K., Maddaloni, M., and Pascual, D.W.  A nasal IL-12 DNA vaccine co-expressing Yersinia pestis F1-V fusion protein confers protection against pneumonic plague.  Infect. Immun. 76: 4564-4573, 2008.

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