A Molecular Epidemiological Study On HIV/AIDS Patients Of Han Nationality From Chongqing, China

Background:The HIV/AIDS epidemic remains a significant global problem because drug resistances occur so frequently and no effective preventive vaccine is available. Currently there are an estimated 33 million people living with HIV/AIDS and this number is growing rapidly, especially in developing countries where approximately 90% of the total patients lives. In Asia, an estimated 4.9 million [3.7 million–6.7 million] people were living with HIV in 2007, including 440 000 [210 000–1.0 million] people who became newly infected in the past year. Approximately 300 000 [250 000–470 000] patients died from AIDS-related illnesses in 2007. Chongqing, a municipal city in southwest China, has a population of more than 31 million. The first HIV-1 infected case from Chongqing was reported in 1993, by the end of September, 2008, up to 5033 individuals were reported as HIV-1 positive, the dominant HIV-1 subtype in Chongqing is CRF07_BC.Since 1980s, HIV/AIDS related research has been a worldwide hotspot, including virology, mechanisms of pathogenesis, mechanisms of transmission, epidemiology, pharmacotherapy, preventive vaccines, behavior intervention, etc. Molecular epidemiology of HIV/AIDS could provide with information of genetic markers for susceptibility and disease progression in the population, facilitating researches on pathogenesis mechanisms, population susceptibility, antiretroviral drugs and preventive vaccines.Human Leukocyte Antigen(HLA)plays an important role in human immune system, is associated with disease susceptibility and prognosis. Molecular epidemiology on HIV/AIDS revealed that host genetic backgrounds including diversity of HLA genes were associated with susceptibility/ resistance to HIV-1 infection, had a variety of effects on disease progression. Investigations on Caucasoids and Africans, who exposed to HIV-1 subtype B or C, confirmed the association of HLA with HIV/AIDS. Regardless of their geographical origin and ethnic backgrounds, HLA-B*27 and B*57 alleles were associated with delay of AIDS progression, while B*35 and Cw*04 alleles could accelerate disease progression. An increased risk for HIV infection was suggested in individuals carrying HLA-B40 and HLA-DR2, based on observations in south India. In China, a population genetic epidemiological investigation indicated that individuals with HLA-B*46 allele were susceptible to HIV infection, HLA-A*3601, Cw*14 and Cw*0304 alleles could delay disease progression in Yi people, Sichuan. Another investigation on 43 HIV-1 infected patients, who had a history of paid plasma donation, revealed HLA-Bw6 homozygotes accelerated AIDS progression, while HLA-Bw4 homozygotes had a protective role in disease progression.The association of HLA alleles/haplotypes with HIV/AIDS has been gained worldwide attention, however, limited data were available in Asia. Previous results have demonstrated significant differences in distribution of HLA alleles/haplotypes in populations from different regions or different ethnic groups, indicating geographic features should be considered in observation and analysis, as well as in study design of specific treatment and prevention.This study explored potential roles of HLA genetic markers in HIV-1 infection and progression in Chongqing, providing with clues for HIV/AIDS treatment and prevention.Methods:1. Prevalence survey: 769 subjects of HIV/AIDS infected patients were recruited in this study. Preliminary and follow-up investigations were conducted by Chongqing CDC. General information of this population were collected by data-searching and follow-up investigations.2. An survey of HLA allele distribution in HIV/AIDS population: we performed polymerase chain reaction analysis with sequence-specific primer (PCR-SSP) methods for 2-digital HLA class I (A, B) and II (DRB1) genotyping in a cohort of 549 HIV/AIDS individuals, 2475 HIV negative individuals from the same Han ethnic group of Chongqing as population control. We analyzed frequencies of HLA-A, B, DRB1 alleles and performed Hardy-Weinberg test with Arlequin ver.2.000 software and estimated the frequencies of 2-locus and 3-locus haplotypes. The respective frequencies and the distribution of HLA alleles and haplotypes were compared between these two groups using Epi info 2002 and SPSS 14.0. 3. Association study of HLA-A, B, DRB1 alleles with HIV-1 infection: we performed polymerase chain reaction analysis with sequence-specific oligonucleotide probes (PCR-SSO) methods based on Luminex IS Fluoroanalyzer for 4-digital HLA class I (A, B) and II (DRB1) genotyping in a cohort of 759 HIV/AIDS individuals , 358"exposed-uninfected"individuals from Chongqing Han, China as control. The frequencies of HLA-A, B, DRB1 alleles and haplotypes of two groups were analyzed and estimated with Arlequin ver.2.000 software. The association of HLA alleles with HIV-1 infection susceptibility or resistance was evaluated by using Epi info 2002 and SPSS 14.0. The statistical analysis was the same as Methods 2.4. Association study of HLA-A, B, DRB1 alleles with AIDS: 216 subjects with AIDS-defining symptoms and CD4 counts below 200 were recruited in the AIDS patient group, another 474 subjects with a stable CD4 count of no less than 200 cells/mm3 were defined as asymptomatic individuals and were enrolled in the HIV seropositive group. The frequencies of HLA-A, B, DRB1 alleles and haplotypes of two groups were analyzed and estimated with Arlequin ver.2.000 software. The association of HLA alleles with AIDS disease progression was analyzed by using Epi info 2002 and SPSS 14.0. The statistical analysis was the same as Methods 2.Results:1. Epidemiological characteristics of this HIV positive population : The characteristics of HIV epidemic in Chongqing were demonstrated by investigation of HIV/AIDS individuals of Chongqing Han population. Individuals aged from 18 to 49 were dominated, accounting for 88% of total. A gradual increase of young female patients was identified. Most HIV-1 seropositive individuals were infected via heterosexual transmission, a remarkable higher HIV infection rate was detected among men who have sex with men. Comparisons between the AIDS patient group and the HIV-1 infected group revealed significant differences in age and gender of the subjects enrolled in this study, more elder patients and more female patients were observed in the AIDS patient group than that from asymptomatic HIV positive individuals.2. Distribution of HLA alleles in HIV/AIDS individuals:The profile of HLA (A, B, DRB1) alleles of 549 HIV/AIDS individuals from Chongqing Han of China was obtained by PCR-SSP methods. The allele of A*11, A*02, A*24, B*46, B*40, B*15 and DRB1*09 are dominated in these subjects. Compared with population control, B*46, B*1501G (B62), B*67, B*37 and B*52 alleles were observed to have association with susceptibility to HIV-1 infection in this population. In addition, the haplotype analysis revealed that A*11-B*46, A*24-B*54 and A*01-B*37 for 2-locus, and A*11-B*46-DRB1*09, A*02-B*46-DRB1*08, A*11-B*4001G-DRB1*15, A*02-B*4001G-DRB1*04, A*11-B*46-DRB1*08 and A*02-B*4001G-DRB1*12 for 3-locus had significantly overrepresented in HIV/AIDS individuals, whereas A*11-B*1502G, A*11-B*1502G-DRB1*12 and A*33-B*58-DRB1*13 were underrepresented in them.3. Association of HLA-A, B, DRB1 alleles with HIV-1 infection: In this study, the distribution of 4-digit resolution HLA-A, B, DRB1 alleles and haplotypes of 759 HIV/AIDS individuals was obtained by PCR-SSO methods. The alleles of A*1101, A*0201, A*2402, B*4601, B*4001, B*1301, DRB1*0901, DRB1*1501, DRB1*1202 were observed to be relatively high in these subjects. The association analysis of HLA alleles with HIV-1 infection with"exposed-uninfected"individuals as control showed that individuals who have B*40 allele, and haplotypes containing B*40 were more likely to be risk to HIV-1 infection, while individuals who have B*3901, B*5101 alleles, and haplotypes containing B*3901, B*5101 and Bw4-Bw6 heterozygote showed resistant to HIV-1 infection. For HLA-Ⅱ, DRB1*0403 and DRB1*1101 may be the risk factor for HIV-1 infection. In addition, A*0101-B*3701, A*0101-B*3701-DRB1*1001 haplotypes and other common haplotypes maybe a risk factor of HIV-1 infection in this Chinese population.Results consistent with preliminary analyses: haplotypes containing B*37 and B*40 and other common haplotypes as risk factors. Results differing from previous analyses: protective roles of B*3901, B*5101, and haplotypes containing B*3901, B*5101 and Bw4-Bw6; risk factors such as DRB1*0403, DRB1*1101.4. Association of HLA-A, B, DRB1 alleles with AIDS progression : 690 HIV/AIDS individuals with records of CD4 counts were divided into two groups, 216 subjects with AIDS-defining symptoms and CD4 counts below 200 were recruited in the AIDS patient group, another 474 subjects with a stable CD4 count of no less than 200 cells/mm3 were defined as asymptomatic individuals and were enrolled in the HIV seropositive group. The association study of HLA alleles and AIDS disease between the AIDS patients and the HIV-1 infected individuals suggested the presence of B*3501 allele, A*2402-B*4801, common 2-locus and 3-locus haplotypes, HLA-A or B and Bw6-Bw6 homozygotes may predict bad disease outcome of HIV-1 infection, however, HIV-1 infected individuals who have B*5801 alleles, A*3303/1-B*5801 haplotype and Bw4-Bw6 heterozygote were more likely to be resistant to AIDS disease progression in this Chinese population.Conclusions in accordance with HIV-1 infection: risk factors of common haplotypes; conclusions differing from HIV-1 infection: risk factors such as B*3501 alleles and A*2402-B*4801 haplotypes, Bw6-Bw6 and HLA-A/B homozygotes, protective role of B*5801 allele and haplotypes containing B*5801.Significance and creativeness of this study:1. A distinct profile of HLA class I (A, B) and II (DRB1) alleles and haplotypes of HIV/AIDS individuals from Chongqing Han of China was observed. HLA polymorphism of the HIV-1 infected individuals and association with resistance or susceptibility to HIV-1 infection or AIDS disease was very helpful for exploring mechanisms of HIV-1 infection and vaccine design in this population.2. Our data indicated that haplotypes containing B*37 and B*40, other common haplotypes, DRB1*0403 and DRB1*1101 alleles were markers of HIV-1 susceptibility, and that B*3901 and B*5101 alleles, and haplotypes containing B*3901 and B*5101, Bw4-Bw6 genotype were protective markers for HIV-1 infection. Meanwhile, B*3501 allele and A*2402-B*4801 haplotype , common haplotypes, Bw6-Bw6,HLA-A/B homozygotes may accelerate AIDS progression. In contrast, B*5801 and haplotypes containing B*5801 may delay AIDS progression.3. The association of B*3701 allele, and haplotypes containing this alleles and A*2402-B*4801 haplotype with susceptibility to HIV-1 infection and disease progression has not been reported yet. The role of B*4601 in AIDS progression differed from known functions, suggesting the association of B*4601 may be of regional specificity.