Immune responses to a recombinant attenuated Salmonella typhimurium strain expressing a Taenia solium oncosphere antigen TSOL18.

A tapeworm, Taenia solium, remains a great threat to human health, particularly in developing countries. The life cycle of T. solium is thought to be terminated via vaccination of intermediate hosts. In this study, we constructed a recombinant attenuated Salmonella typhimurium live vaccine strain χ4558 expressing a TSOL18 antigen. SDS-PAGE and Western blot confirmed the expression of the interest protein and its antigenic property. The recombinant strain stably propagated in vitro, of which the growth was not reversely influenced by TSOL18 protein expressed. It was also shown that mice survived 10(12) CFU of S. typhimurium χ4558, while all mice infected with 10(7) CFU of the wild-type died within five days. The mouse experiment indicated that vaccine strain χ4558 induced a high titer of specific antibody for a long time. In contrast to the controls, the vaccinated mice had an obvious augment of CD4(+) and CD8(+) T lymphocytes and the percentage of helper CD4(+)/CD8(+) T lymphocytes was significantly increased (p<0.01). After oral administration, S. typhimurium χ4558 was first colonized mainly in the Peyer's patches and then predominantly in the mesenteric lymph nodes and spleens in the vaccinated mice. In addition, the high levels of specific anti-TSOL18 antibodies were also observed in pigs administrated with S. typhimurium χ4558. Collectively, these results demonstrate the possibility of use of an attenuated S. typhimurium strain as a vector to deliver protective antigens of T. solium.