Abstract
Environmental shedding of genetically manipulated microorganisms is an issue impeding the development of new live vaccines. We have investigated the immunogenicity of a number of novel
Salmonella enterica
serotype Typhimurium oral vaccine candidates that express the fragment C (TetC) component of tetanus toxin and harbor combinations of additional mutations in genes
shdA
,
misL
, and
ratB
that contribute to the persistence of serotype Typhimurium's colonization of the intestine. Serotype Typhimurium
aroA
(TetC) derivatives harboring additional mutations in either
shdA
or
misL
or combinations of these mutations exhibited a marked decrease in shedding of the vaccine strain in the feces of orally vaccinated mice. However, equivalent levels of anti-TetC and anti-
Salmonella
lipopolysaccharide immunoglobulin G (IgG), IgG1, IgG2a, and IgA were detected in sera of the vaccinated but not of the control mice. Cellular immune responses to TetC were detected in all vaccinated mice, regardless of the presence of the additional mutations in
shdA
or
misL
. Further, immunization with serotype Typhimurium
aroA
candidate vaccines harboring
shdA
and
misL
afforded complete protection against challenge with a virulent strain of serotype Typhimurium.