Abstract:
AttenuatedSalmonella typhimurium strains are potential‘safe’ delivery vectors of an oral immunocontraceptive vaccine forthe European red fox (Vulpes vulpes). In the presentstudy, model bacterial (Escherichia coli heat-labileenterotoxin B subunit, LTB) and fox sperm (fSP10) antigens were expressed inS. typhimurium SL3261 (DaroA)under the control of the trc promoter. Adult femalefoxes were given three oral immunizations with SL3261 containing either LTB(SL3261/pLTB), fSP10 (SL3261/pFSP10) or a control plasmid (pKK233-2 orpTrc99A). All foxes raised serum (IgG) and vaginal (IgG and IgA) antibodiesagainst S. typhimurium lipopolysaccharide (LPS). Eachfox that received SL3261/pLTB raised high titre LTB-specific serum andvaginal IgG antibodies. However, only one of four foxes immunized withSL3261/pFSP10 raised an anti-fSP10 immune response, in the form of lowtitre serum and vaginal IgG antibodies. No vaginal IgA antibodies were raisedagainst either LTB or fSP10 in these experiments. The immune responses againstrecombinant LTB and fSP10 resulted chiefly from the initial dose of antigen inthe inocula and were minimally influenced by continuedin vivo antigen expression. This study demonstrates forthe first time in the female red fox that oralSalmonella can elicit specific systemic and reproductivetract antibodies against heterologous, recombinant proteins.