[Preliminary study on congenital transmission of Trichinella spiralis in mice].

OBJECTIVE: To study congenital transmission of Trichinella spiralis in mice and observe the protection of anti-Trichinella antibodies from the infected dams to challenge infection. METHODS: According to the gestation (fertilization), the Kunming mice were divided into two groups: the infected group after gestation and the gestated group after infection. New-born mice were cut into small pieces to separate the larvae within 1 day after birth. One-day-old offspring born to normal dams were nursed by the infected dams, slaughtered after 21 days and examined for the larvae. Serum anti-Trichinella antibody level in offspring born to the infected dams was assayed by ELISA at different time after birth, and its immune protection against challenge infection was studied. RESULTS: Out of 6 offspring born to the dams infected at 7 days after fertilization, two were found to be infected. Among other female mice which were first infected with T. spiralis and then gestated, only the offspring born to the dams fertilized at 8 and 22 days after infection were found to be infected, the infection rate of offspring was 20% (2/10) and 25%(2/8) respectively. All larvae recovered from the young were non-encapsulated. The cross-fostering experiment showed that none of 30 offspring born to normal dams were found to be infected. The serum antibody positive rate in 27 offspring born to the infected dams at 1,7,24, and 40 days after birth was 100%, 100%, 77.8% and 14.8%, respectively. The worm reduction rate in the offspring 40 days after birth was 62.0% after challenge infection. The worm reduction rate in mice in which sera from the offspring born to the infected dams were passively transferred was 55.7%, there was a significant difference (P<0.01) compared to the control group. CONCLUSION: A transplacental transmission of T. spiralis is revealed in mice. Anti-Trichinella antibodies from the infected dams may partially protect the young from challenge infection.

Expression of DNA vaccine against Trichinella spiralis in Chinese hamster ovary cells.

OBJECTIVE: To observe the in vitro expression of DNA vaccine (recombinant eukaryotic expression plasmid pcDNA3-TspE1) encoding a Mr 31,000 antigen of Trichinella spiralis in Chinese hamster ovary (CHO) cells and analyze the antigenicity of the products expressed. METHODS: The recombinant plasmid pcDNA3-TspE1 was transfected into CHO cells by using cationic lipids (Lipofectamine 2000). The positive cell clones were screened by the selective antibiotic G418. The expressed products were identified by RT-PCR, IFAT, SDS-PAGE and Western blotting. RESULTS: The results of RT-PCR amplification showed that there was one band with 876 bp in CHO cells transfected with pcDNA3-TspE1 and no any bands in CHO cells transfected with the empty plasmid pcDNA3. The IFAT demonstrated that the pcDNA3-TspE1 transfected CHO cells reacted with sera from mice immunized with the recombinant fusion protein and from mice infected with T. spiralis, the bright yellow green fluorescence staining appeared in the transfected CHO cells. The pcDNA3 transfected and un-transfected CHO cells exhibited as orange color. The results of SDS-PAGE showed that there was one band with Mr 31,000 in culture supernatant of CHO cells transfected with pcDNA3-TspE1. Western blotting confirmed that the band with Mr 31,000 could be recognized by sera from mice immunized with the recombinant fusion protein, from rabbits immunized with T. spiralis muscle larval soluble antigens, from mice infected with T. spiralis and from patients with trichinellosis. Conclusion The mammalian CHO cells were transfected by the recombinant plasmid pcDNA3-TspE1, and the TspE1 gene of T. spiralis was expressed in the transfected CHO cells. The proteins expressed are secreted into cell culture supernatants and show the antigenicity of T. spiralis.