Data from: Vaccination method affects immune response and bacterial growth but not protection in the Salmonella Typhimurium animal model of typhoid

Understanding immune responses elicited by vaccines, together with immune
responses required for protection, is fundamental to designing effective
vaccines and immunisation programs. This study examines the effects of the
route of administration of a live attenuated vaccine on its interactions
with, and stimulation of, the murine immune system as well as its ability
to increase survival and provide protection from colonisation by a
virulent challenge strain. We assess the effect of administration method
using the murine model for typhoid, where animals are infected with S.
Typhimurium. Mice were vaccinated either intravenously or orally with the
same live attenuated S. Typhimurium strain and data were collected on
vaccine strain growth, shedding and stimulation of antibodies and
cytokines. Following vaccination, mice were challenged with a virulent
strain of S. Typhimurium and the protection conferred by the different
vaccination routes was measured in terms of challenge suppression and
animal survival. The main difference in immune stimulation found in this
study was the development of a secretory IgA response in orally-vaccinated
mice, which was absent in IV vaccinated mice. While both strains showed
similar protection in terms of challenge suppression in systemic organs
(spleen and liver) as well as survival, they differed in terms of
challenge suppression of virulent pathogens in gut-associated organs. This
difference in gut colonisation presents important questions around the
ability of vaccines to prevent shedding and transmission. These findings
demonstrate that while protection conferred by two vaccines can appear to
be the same, the mechanisms controlling the protection can differ and have
important implications for infection dynamics within a population.