Previous studies showed that crude antigens from Trichinella spiralis adult worms (AW) can be recognized by mouse infection sera at 8 days post infection. The aim of this study was to identify the early diagnostic antigenic bands in soluble proteins from T. spiralis AW by Western blot using early infection sera. The affecting factors of adult recovery were firstly observed in this study, and the results showed that the maximum number of adults was collected from small intestine when the female BALB/c mice were orally infected with 4000 ML and sacrificed at 3 days post infection. The results of Western blot analysis showed that seven protein bands (31, 35.1, 39, 40.6, 41.9, 47 and 50.6 kDa) could be recognized by early infection sera as early as at 8-10 days post infection, and were strongly reacted with mouse infection sera at 11-12 days post infection. Our results suggested that the seven protein bands of T. spiralis AW soluble proteins might be the early expressed antigens during the intestinal stage of Trichinella infection and therefore have potential value for the early diagnosis of trichinellosis.

A putative serine protease of T. spiralis (TsSP) was expressed in Escherichia coli and its potential as a diagnostic antigen was primarily assessed in this study. Anti-Trichinella IgG in serum samples from T. spiralis different animal hosts (mice, rats, pigs and rabbits) were detected on Western blot analysis with rTsSP. Anti-Trichinella antibodies were detected in 100% (30/30) of experimentally infected mice by rTsSP-ELISA. Cross-reactions of rTsSPELISA were not found with sera from mice infected with other parasites (S. erinaceieuropaei, S. japonicum, C. sinensis, A. cantonensis and T. gondii) and sera from normal mice. There was no statistical difference in antibody detection rate among mice infected with the encapsulated Trichinella species (T. spiralis, T. nativa, T. britovi, and T. nelsoni) (P>0.05). The results of rTsSP-ELISA showed that serum specific antibody IgG in mice infected with 100 or 500 T. spiralis muscle larvae (ML) were detectable early at 7-8 dpi, but not detected by ML ES antigen-ELISA prior to 10-12 dpi. Specific anti-Trichinella IgG was detected in 100% (18/18) of infected pigs by rTsSP-ELISA and ES-ELISA, but no specific antibodies was not detected in 20 conventionally raised normal pigs by two antigens. The results showed the rTsSP had the potential for early serodiagnosis of animal Trichinella infection, however it requires to be assayed with early infection sera of swine infected with Trichinella and other parasites.