The immune protection induced by a serine protease from the Trichinella spiralis adult administered as DNA and protein vaccine.

Trichinellosis is caused by Trichinella spiralis (T. spiralis), which is an important public health problem. In this study, a gene encoding a serine protease from adult worms of T. spiralis (Ts-Adsp) was screened from a cDNA library of adult worms and was cloned and expressed in a prokaryotic expression system. The gene Ts-Adsp was subcloned into the eukaryotic expression vector pcDNA3.1(+), which was named pcDNA3.1(+)-Adsp. Previous studies have found that recombinant Ts-Adsp protein (rTs-Adsp) can elicit partial protection against T. spiralis infection in mice. Our aim was to explore the protective effect of combining a DNA vaccine with the rTs-Adsp protein against T. spiralis. One week after the last vaccination, the serum and spleen were obtained. The levels of IgG, IgG1 and IgG2a and cytokine production in serum and spleen cells were analyzed. The results showed that the levels of humoral and cell-mediated immune responses increased in the pcDNA3.1(+)-Adsp/rTs-Adsp group mice and demonstrated that a Th1/Th2 mixed immune response was induced by pcDNA3.1(+)-Adsp/rTs-Adsp after vaccination. Moreover, mice vaccinated with pcDNA3.1(+)-Adsp/rTs-Adsp displayed a 69.50% reduction in muscle larvae burden. This study suggested that mixed immunity could improve the muscle larvae reduction rate.