| Toxoplasma gondii is an obligate and intracelleular protozoan parasite which distributes over the world. It can result in Toxopalsmosis which infects both human beings and animals. Although infection of the adults is ususlly asymptomatic, primary infection during pregnancy can result in abortion, abnormality or death fetus. Toxoplasmosis is one of the common deadly causes in such patients of immunodeficiency as organic graft, malignant tumor, administering immumosuppressive and AIDS etc.Toxoplasmosis also causes mortality in domestic animals and poultry, which brings seriously economic damage to stockbreeding. So the preventation and therapy against Toxoplasma gondii is of importance to human health, eugenics and development of stockbreeding.Toxoplasmosis can be effectively treated with combination pyrimethamine plus sulfadiazine. However, there is a significant occurrence of adverse reactions to this therapy, especially among HIV-infected patients, which often results in discontinuation of therapy and relapse of disease. In pregnant women, therapy with pyrimethamine must be avoided during the first 16 weeks because of potential teratogenicity. These considerations are compelling arguments for the development of a vaccine against Toxoplasmosis. A great of basis research in this field has been made by foreign and native scholars for tens of years. Nucleic acid vaccine appeared after the attenuated active vaccine and the monovalent molecular vaccine. The nucleic acid vaccine is to clone gene encoding protective antigen into eukaryotic expressing plasmid, then the constructed recombinant plasmid is transferred into host cells directly, subsequently, the host cells express protective antigen protein by transcription and translation after ingesting plasmid. The nucleic acid vaccine has undermentioned advantages comparing with the others: firstly, it operates so easily that injecting only plasmid may do well and it expresses in vivo by eukaryotic system without purification in vitro; secondly, it cause CTL effct , which can kill the endophyte and virus; thirdly, the protein expressed from eukaryotic host cells resembles that of the native in construction and induces more effective immune response; fourthly, long-lasting immunity can be acquired only once ,which can avoid intricacy of repetitive inoculations in order to intensify immunity; Fifthly, nucleic acid vaccine can be prepared multivalent ones; the last, it is convenient to stock and transport. So nucleic acid vaccine technology has been focused on the research for vaccination of parasitogenic diseases. Malaria DNA vaccine has been approved to enter I,II period clinical experiment. The eukaryotic expressing plasmids of encoding ROP1, ROP2, SAG1, GRA4 et al genes of Toxoplasma gondii have been constructed presently . Vaccination to mice with those plasmids demonstrated to be a significant protection. Nucleic acid vaccine is also applied to preparation of antiserum and monoclonal antibody (McAb), and study for protective antigen of pathogen as well.The gene encoding Toxoplasma gondii dense granule antigen (GRA1) that is one of excreted-secreted antigens (ESA) has been demonstrated to be significant immunogenicity in the human and animals infection experiments. Identification of T cell epitopes wihin GRA1 by Dequesne et al showed that GRA1 gene was an excellent candidates. GRA1 protein of Toxoplsma gondii tachyzoites and bradyzoites as a diagnosis antigen during chronic infection is worth researching because infection of Toxoplasma gondii is usually recessive and chronic. There has been no report about GRA1 gene intron since Cesbron-Delauw et al first cloned the gene and demonstrated its molecular characterization in 1989.In the first experiment, the tachyzoites had been harvested from ascites of mice infected by inoculating RH strain through the intraperitonea, purifying tachyzoites and preparing genomic RNA. The 628bp –long GRA1 gene fragment expected was localized 613-1240bp of the original sequence. A pair of primers with XhoI and BamHI endonuclea...
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