Construction and immunological assessment of Salmonella typhimurium expressing fox sperm LDH-C4

Abstract

This study examined immune responses of foxes to oral doses of recombinantSalmonella typhimurium expressing fox sperm-specificlactate dehydrogenase (fLDH). The cDNA for fLDH was cloned into the expressionplasmid pKK233&middot; 2 (pKKfLDH).Salmonella typhimuriumaroA<emph type="7">-(SL3261) was transformed with either the pKK233&middot;2 plasmid alone (SpKK)or the pKKfLDH construct (SpKfLDH). The fLDH expressed by SpKfLDH retainedenzymatic activity and was recognized by human LDH-C4-specific antibody. MaleEuropean red foxes (Vulpes vulpes) were given an initialoral dose of 1 &times; 10<emph type="7">11 cfu of either SpKK (control,n = 3) or SpKfLDH (test, n= 6), followed four weeks later with a further dose of 1 &times;10<emph type="7">11 cfu. Antibodies to Salmonellalipopolysaccharide (LPS-04) and fLDH were measured in plasma and saliva foreight consecutive weeks after the initial doses. Both LPS-04 IgG- andIgA-specific antibodies as well as fLDH-specific IgG antibodies were detectedin plasma and saliva. However, there was a marked fLDH-specific IgA responsein saliva consistent with induction of the common mucosal immune system. Theantibody measurements demonstrated the feasibility of using recombinantSalmonella as an oral vaccine to elicit gameteantigen-specific mucosal immune responses in foxes.