| Trichinellosis is a serious parasitic zoonosis with worldwide distribution, which infect human and more than 150 species of mammals. The human tichinellosis 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 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 been diagnosed correctly and treated in time. Therefore, Trichinella spiralis (T.spiralis) becomes the first-checked parasite in the sanitary checks of Chinese meat food. It is very important and urgent for us to prevent and control trichinelosis. While the key to do like this is to build up a set of quick^ easy and highly specific test ways and use all kinds of effectively prevent measures to decrease the infectious rate of animals.There are not any satisfied diagnostic methods for this disease at present, and the clinical definite diagnosis relies on etiological test, but the rate of detect is low and it is not acceptable to patients. Scholars at home and abroad have carried out many studies on the immunodiagnosis of trichinellosis. Most of diagnostic antigens used in these studies are crude antigens of the ML of T.spiralis. When they were used for the immunodiagnosis of trichinellosis, the crude antigens could cross-react with sera from patients with other parasitic diseases, resulting in false-positive reactions. The methods above mentioned limit the early and punctual diagnosis oftrichinellosis.The research to immunoprophylaxis of trichinellosis demonstrates that T.spiralis has the obviously different antigenic components in different developmental stages and the structure of somatic body antigen is also extremely complex in the same stage, while T.spiralis has gradually formed immune-escaping during the chronically parasitic living. There is no good immunoprophylaxis effect with using the complicated somatic antigen which is very unstable at present and no breakthrough of in vitro culture of T.spiralis , which bring difficulties to prevention with normal immune methods in scales.With the development of technology of molecular biology, it is possible to express T.spiralis antigen in vitro. Compared with normal antigen, the genetic engineering antigen has the advantages of high-purity > singular component and easy produce in scales, which provide new methods for the immunodiagnosis and immunoprophylaxis of trichinellosis. The key to effective diagnosis and prophylaxis of trichinellosis is to obtain the high-specific and strong-protective antigenic gene. Of all the most effective measures is to build cDNA libraries of T.spiralis from which ideal antigenic gene are screened. Now studies on T.spiralis with genetic engineering method mainly focus on the antigen of ML. Because the stage of ML is the longest period of immune-escaping in the host, ML can have a parasitic life for a long time after encysting, then it is in the state of relative dormancy, metabolism is so low that it is unnecessary to express protein, the amount of mRNA is small, the effective recombinants of libraries are fewer, so it is difficult to screen the target gene. From the result of present publishing, the effect of antigen deduced by clones that are screened from ML cDNA libraries is not ideal. But the adult (AD) stage and newborn larvae (NBL) stage are two attacking stage, especially, 5-day-old adult (AD5) is the special stage in the life cycle of T.spiralis, its body contains lots ofnewborn larvae embryos and have few released. The stage of AD5 is transient and the metabolism is very vigorous. It is necessary to produce lots of stage-specific protein and the attacking-factors excreted are probable pathogenic factor and important protective antigen. It is sensitive to the immunity of host. So, by constructing high-qualified ADS cDNA libraries, the differently expressive and functional antigenic gene a...
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