intra-epithelial lymphocytes, expressing CD8 or T19, _Tcr ~6. All T subsets are found in the lamina propria, each with a preferential site. T cell numbers increase in jejunal lamina propria within 2 days of local challenge where they proliferate and differentiate. While most Tcr y6 + cells of sheep express

Conference Abstracts

T19, the enteric response involves increased numbers of 76 + T19- intra-epithelial cells, as well as CD8 ÷ cells. The number of dendritic cells expressing CD1 also increases in lamina propria and intra-epithelial compartments.

Safety assessment of Salmonella typhimurium live vectored vaccines

L.M. Henderson 1, N.E. foe 2, J.E. Mayfield 3, R. Curtiss 1114 and L.K. Schlater 1 1National Veterinary Services Laboratories, S & T, APHIS, USDA, PO Box 844, Ames, Iowa 50010, USA, 2National Animal Disease Center, ARS, USDA, Ames, Iowa 50010, USA, 3Iowa State University, Ames, Iowa 50010, USA, 4 Washington University, St Louis, Missouri 63130, USA

Salmonella typhimurium strains used as live carriers for foreign immunogens must be safety tested. This involves assessment of the effect of the foreign insert on survival and of the possibility for recombination of the construct with other bacteria, resulting in the creation of novel strains. We report the results of insertion and expression of the E. eoli K88 gene and the Brucella abortus superoxide dismutase (SOD) gene in a Acya Acrp Aasd

Salmonella typhimurium vector strain. These constructs are expected to provide a 'worst-case scenario' for safety assessment because they may effect colonization and/or survival of the vector strain. Changes in recombination potential, colonization of the host animal, and survival in the host animal and in macrophage culture resulting from the expression of these genes are reported.

Induction of cell mediated immune response using a chimeric flagellin vaccine

Naresh K. Verma, H. Kirk Ziegler and Gary K. Schoolnik Howard Hughes Medical Institute, Department of Microbiology & Immunolooy, Beckman Center, B239, Stanford University School of Medicine, Stanford, CA 94305, USA

Host-defense to intracellular microbial pathogens, including Salmonella typhi, Listeria monocytooenes, Mycobacteria tuber- culosis, many viruses and some protozoan parasites is conferred by the cellular immune system. Attenuated bacterial and viral strains that are known to stimulate a cellular immune response, have been proposed as vaccine vectors and some limited success has been achieved to date in this effort. Our study employs the use of model T cell epitopes for which corresponding T cell hybridomas and transgenic mice are available. An aro mutant

of Salmonella dublin was used and further modified for maximal intracellular delivery of T cell epitopes using chimeric flagella which have been engineered to express these epitopes on the surface of the organism. Such constructs were used to study antigen processing and presentation and their capacity to confer T cell epitope specific protection. Protective immunity was also assessed by challenging vaccine recipients with a 'chimeric' pathogen engineered to carry corresponding epitope.

An animal model to test a Helicobacter Pylori vaccine

A.W. Cripps, R.L. Clancy, M.L. Dunkley and P.W. Reinbott Hunter Area Pathology Service and the Auspharm Institute for Mucosal Immunology, Newcastle, NS W 2310, Australia

An animal model is being developed to test a vaccine against H. pylori, an organism associated with gastritis, duodenal ulcer, and non-ulcer dyspepsia, and to investigate the mechanisms of immunity to H. pylori in the gut. Rats were immunized intramuscularly (IM), intra-Peyers patch (IPP) and orally (OI) with various H. pylori vaccines. IM produced an enhanced IgG and IgA specific response in the serum but had no effect on the salivary antibody response. IPP gave an enhanced serum and saliva IgG and IgA response and the Peyers patch lymphocytes were demonstrated to have a

substantial proliferative response to a H. pylori antigen in vitro (stimulation index = 64 _+ 26) indicating that the gut mueosa is capable of mounting a vigorous immune response against to this organism. OI with live or paraformaldehyde-killed bacteria gave no significant enhancement of the serum or saliva anti-H. pylori antibody. OI with lyophilized H. pylori gave a small increase in serum antibody response. The enhancement of the mucosal antibody response by the addition of adjuvants is under investigation.

Vaccine, Vol. 10, Issue 4, 1992 275