Intranasal immunogenicity of a Δcya Δcrp-pabA mutant of Salmonella enterica serotype Typhimurium for the horse

The aim of this study was to investigate the intranasal immunogenicity for the horse of a Delta cya Delta crp-pabA mutant (MGN-707) of Salmonella enteric a serotype Typhimurium (S. tryphimurium). MGN-707 caused no sign of disease, was not detected in feces and a single administration induced strong Salmonella-specific serum and nasal mucosal antibody responses. All ponies had made strong salmonella specific serum IgGa. IgGb. IEA and IgM antibody responses by day 25 after the first immunization. IgM responses to salmonella lipopolysaccharide (LPS) were short lived whereas salmonella specific serum IgGa and IgGb persisted at high levels in all ponies until 83 and 140 days, respectively. Specific nasal mucosal antibody responses dominated by IEA and IgM were evident by day 25 in all ponies except one in which only specific IgGa and IgGb were evident. Specific nasal mucosal IgA persisted in most ponies until day 69. A second immunization on day 140 boosted antibody responses, and stimulated a strong nasal mucosal IgA response in the pony that failed to make an IgA response after primary immunization. At the termination of the experiment, IgA and IgGb dominated jejunal antibody responses whereas vaginal responses were mainly IgA. The latter response unequivocally confirms the existence of a common mucosal immune system in equids. The results: indicate that a S. typhimurium Delta cya Delta crp-pabA mutant has potential as an intranasal vaccine against salmonellosis in the horst. (C) 2001 Elsevier Science Ltd, All rights reserved.