| Trichinella spiralis (T. spiralis) is one of the most widespread parasites which can infect human being and more than 150 species of other mammals. Trichinellosis caused by T. spiralis is a serious parasitic zoonosis with worldwide distribution, and is regarded as emerging or re-emerging disease. The global prevalence of the disease is difficult to evaluate but as many as 11 million people may be infected. More than 10 000 human cases with trichnellosis were reported by the International Commission on Trichinellosis (ICT) from 1995 to 1997 and about 10 000 porcine infections were reported by the Office International des Epizootic (OIE) in 1998. The human trichinellosis has been found in 17 provinces, cities and autonomous regions of China and many outbreaks of this disease have been occurred in recent years. Henan province is one of the high endemic areas of trichinellosis, and 7 outbreaks have occurred, which involved more than 400 patients only in Zhengzhou city. The mortality is from 3% to 30% if the patients with trichinellosis have not been diagnosed correctly and treated in time. Pork is the most common source of human trichinellosis in China. The increase incidence of human trichinosis in China was correlated to the increased infection rate of T. spiralis in pigs. An epidemiological survey on one million of pigs from 17 areas in Henan Province during 1990-1991, trichinellosis was found in 16 areas and the infection rate was 3.1% up to 15% while the infection rate of pigs was 0.44% and 0.86% in 1982 and 1984 respectively. It is very important and urgent for us to prevent and control trichinellosis. While one of the key measures to do like this is to use all kinds of effectively preventive measures to decrease the infections rate of animals, especially the pig. It is very important to develop and use trichinellosis vaccine, and its effect of immunoprophylacxis may decrease or avoid the infections of people and other animals.Scholars at home and abroad have carried out many studies on the immunoprophylacxisand immunodiagnosis of trichinellosis. Regarded as the first generation vaccine, the dead or attenuated vaccines of T.spiralis has shown the protective effect against trichinellosis. But most of antigens used in these studies are crude antigen of T. spiralis, such as somatic antigen, muscle larvae antigen, and component antigen, and so on. The antigenic components are extremely complex. There is no good immunoprophylaxis effect with using the complicated antigen, which is very unstable at present. Most important of all, with no breakthrough of T. spiralis culture in vitro, not enough antigen of T.spiralis were used to prevent trichinellosis in scales.With the development of technology of molecular biology, it is possible to express antigen of T. spiralis in vitro by the genetic engineering in scales. But the genetic engineering recombinant antigen which was regarded as second generation vaccine has some disadvantages, such as expressing fusion protein with unnatural conformation, being difficult to manage subsequently, and requiring addition of adjuvant which induce a local inflammatory reaction and so on. DNA vaccine of third generation vaccine has been shown to induce favorable immune response to a variety of viral, bacterial and parasitic antigens. In addition, they have been shown efficacy in treatment of tumor models. DNA vaccines induce a full spectrum of immune responses, including antibodies, T helper cells and cytolytic T cell. DNA vaccination has been shown favorable protection in experimental animals against some of parasities, such as Leishmania major, Toxoplasma gondii, Schistosoma japonicum, Plasmodium yoelii, Trypanosoma cruzii and so on. It brings to us a new desire for prevent trichinellosis. In recent years, some antigenic molecules of T. spiralis have been studies by several researchers. Arasu et al has cloned a cDNA gene , TspEl, which encodes 31kDa antigen of T. spiralis. This protein can eliminate the challenge infection of T.spiralis muscle larvae from the gastrointest...
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