IMMNOGENETIC ANALYSIS OF SCHISTOSOMIASIS JAPONICA IN CHINA

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Along Yangzhe River in China, Schistosomiasis japonica is still endemic. we have been estimating the efficiency of the mass-therapy on the prevalence of several targeted villages in Jiangxi. We observed that there were two categories, resistant and susceptible, in the levels of re-infection. Our final goal of this study is to clarigy the host factors which determine their susceptiblity.Method. Zhuxi village is located on the northern shore of Poyang Lake in Xingzi County, Jiangxi Province. Transmission occurs mainly during the flood season which usually begins in mid-May and goes through October. The life of the community is based on substance agriculture. Fishing is also important in this area. The reinfection study began from March to December 1995. In the beginning of study, before mass chemotherapy, all villagers at home were asked to give a stool specimen and duplicate 41.7mg Kato thick smears were examined quantitatively for S.japonicum eggs. Then, in Dec.1995, reinfection rate a … More nd intensity were examined for those subjects. Meanwhile, venous blood samples were collected twice at the same time as stool examinations. Nanshan is an islet endemic village, which located in the center of Poyang Lake, of Xinjian county, Jiangxi Province. The infection rate of Nanshan from 1991 to 1994 were 30.4%, 33.4%, 20.7%, 17.2% resoectively. Agriculture and fishing are the main income of this village. In February 1997, a retrospective study was designed to select subjects who are relative susceptible or resistant to reinfection based on a five-year Kato-Katz records (1990-1994).Results We have categorized two groups in the subjects in Zhuxi and Nanshan by using egg count record. For Zhuxi, the resistant should have less than 100 eggs in both exams. For Nanshan, the resistant should not have any positive egg count during 5 years period. Then we have typed them for their HLA-DRB1 alleles as shown in Table 1. Compared with the resistant individuals, normal people had higher frequency of HLA-DRB1^<**>0301 (Odds Ratio=4.13,95% Confidence Interval =1.31-13.0) and HLA-DRB1^<**>1201 (OR=3.80,95%CI=1.02-d14.2). Therefor, those two allels are associated with susceptibility to re-infection. Those associations are not significant after the Bonferroni correction, so it would be necesary to increase the number of the subjects to confirm the association. We are planning to expand the field and to analyze other polymorphic genetic loci that relate the immune responsiveness. Less