Intranasal immunogenicity of a Deltacya Deltacrp-pabA mutant of Salmonella enterica serotype Typhimurium for the horse.

The research article investigates the potential of a certain type of Salmonella enterica mutation (MGN-707) as a nasal vaccine for horses. Administered once, it induced strong, specific responses from serum and nasal mucosal antibodies without causing any diseases or appearing in feces.

Objective and Methodology

• The primary purpose of this research was to explore the potential of a Salmonella enterica serotype Typhimurium (S. typhimurium) mutant named MGN-707 that loses Cya, Crp, and PabA as an intranasal vaccine candidate for horses.
• The experimental approach was to administer the MGN-707 mutant to horses, observe its effect on the animals, and closely monitor the immune response.

Findings

• Administration of MGN-707 did not provoke any diseases, nor was it detected in horse feces.
• The mutant prompted strong Salmonella-specific responses from serum and nasal mucosal antibodies, with distinct outcomes seen across different antibody types (IgGa, IgGb, IgA, IgM).
• All horses showed significant Salmonella-specific serum IgGa, IgGb, IgA, and IgM antibody responses by day 25 after initial immunization.
• While responses to Salmonella’s Lipopolysaccharide (LPS) from IgM antibodies were short-lived, high levels of Salmonella-specific serum IgGa and IgGb endured in all horses until 83 and 140 days, respectively.
• Among the horses, specific nasal mucosal antibody responses were dominated by IgA and IgM, with one outlier showcasing only specific IgGa and IgGb.
• Despite this, most horses had persistent specific nasal mucosal IgA up to day 69.

Secondary Immunization Effects and Conclusion

• Secondary immunization at day 140 led to higher antibody responses and stimulated a robust nasal mucosal IgA response in the horse that didn’t have an IgA response after the first immunization.
• Upon concluding the experiment, IgA and IgGb were found to dominate jejunal antibody responses, while vaginal responses were primarily IgA.
• This vaginal reaction solidifies the existence of a common mucosal immune system in equids (horse family).
• The findings of this research suggest that the S. typhimurium Deltacya Deltacrp-pabA mutant (MGN-707) has potential to be further developed and used as an intranasal vaccine against salmonellosis in horses.