Abstract: Objective:To investigate the association of gene polymorphism of cytotoxic T lymphocyte-associated antigen 4 (CTLA-4) with drug users with HIV infection.Methods The A+49G transition polymorphism at position 49 (exon 1) and C-318T transition polymorphism at position 318 in promoter of the CTLA-4 gene were determined by polymerase chain reaction with sequence specific primers (PCR-SSP) method in 24 drug users,41 drug users with HIV Infection patients and 204 healthy controls.Results Compared with control group, in drug users group the frequency of C/C(12.50% VS 51.47%)( P<0.01) significantly reduced; in drug users with HIV infection group,no significant differences in the distribution of genotype and allele frequencies were observed in A+49G gene polymorphisms (p>0.05); however,there are significant differences in C-318T gene polymorphisms in drug users with HIV infection group(p<0.01),the frequency of C/T (68.3% VS 45.6%) and T/T（21.95% VS 2.94%）increased significantly,in contrast in C/C（9.76% VS 51.47%）significantly reduced. Compared with drug users group, no significant differences in the distribution of genotype and allele frequencies were observed in A+49G and C-318T gene polymorphisms (p>0.05) in drug users with HIV infection group.Conclusion There is close associativity between CTLA-4 Alleles and drug taking with HIV infection,in C-318T genotype, C/T and T/T were positively correlated with occurence of drug taking with HIV infection, but C/C was negatively correlated with it.

Key words: drug users with HIV infection , Cytotoxic T lymphocyte-associated antigen, Gene polymorphism, genotype