Research On Molecular Epidemiology Among HIV Positive People Aged Over 50 In Yuxi, Yunnan Province

ObjectiveThis study was designed aimed at revealing the features of HIV-1 genotype/subtype distribution among HIV positive cases aged over 50 in Yuxi, Yunna province. The study was also designed to explore the biologic features of HIV-1 and the evolution of HIV in Yuxi among people aged over 50 years old and to provide basis for HIV prevention among people aged over 50.MethodsPeople living with AIDS who infected HIV after 50 years old were investigated up to the end of August,2014. The epidemic characteristics of HIV were investigated while blood specimens were collected. Plasmas were separated from blood specimen and nucleic acids （RNA of HIV-1） were abstracted by RNA abstraction kits. Target DNA fragments amplified by RT-PCR and nest-PCR, and the PCR products were sequenced. Gene sequences were spliced by SeqMan software. Phylogenetic and genetic distance analysis were conducted by MEGA software, recombinant analysis were conducted by SimPlot software. HIV-1 cellular co-receptors were predicted by R5/X4-pred online software. All the epidemic data from HIV positive cases aged over 50 were analysed by SPSS software. Epidemic mapping and analysis of spatial distribution were conducted by Epi Info and GeoDa software.ResultsA total 173 HIV positive cases over aged 50 were investigate.108 cases of which were male （62.4%）, and 65 cases of which were female （37.6%）. The average age of HIV infected were 57.6±7.9 and it showed a concentration of aged in the age group of 50-60 （112,64.7%）. Occupational distribution concentrated in farmers （117, 66.7%）.122 cases of HIV infections/AIDS patients were married, which accounted 64.7% in the all cases. Among all the HIV infections/AIDS patients, most of them were Han people （130,75.1%）, and the minority nationalities mainly included Yi people （19,11.0%）. The majority of HIV infections/AIDS patients just only received primary education, which accounted for 45.1% among all the cases. Among all the HIV infections/AIDS patients aged over 50,123 cases of which reported non-marriage heterosexual contact history, accounted for 71.1% of all. Almost all the HIV infected patients infected HIV by heterosexual contact, which accounted for 93.1% of all the 173 cases of the infections. And there were 66 cases of HIV infected patients reported their spouses infected HIV, accounted for 38.2% of all the HIV infections.154 cases of HIV infections did not report the history of other sex-transmitted diseases, accounted 89.0% of all. The average degree of first CD4-cell count after HIV infected was 373.8±236.8/mm3, and it showed a concentration of CD4-cell degree in the group of less than 300/mm3 （102,58.9%）. There were 127 cases of HIV infected patients had been received the treatment of antiviral therapy, which accounted 73.4% of all the 173 case of HIV infections/AIDS patients.48 towns from all the 9 counties of Yuxi had HIV positive cases （including HIV infections and AIDS patients） aged over 50 reported, and the top 5 counties with HIV/AIDS reported was Yunjing, Tonghai, Xinping, Hongta and Huaning. All of the 9 counties had less cases of HIV/AIDS reported before the year of 2009, and the cases of HIV/AIDS scattered at the areas of each county. The numbers of HIV/AIDS reported cases had been increasing since the year of 2009 in each county. Spatial autocorrelation analysis suggested the general spatial distribution model of HIV/AIDS among people aged over 50 was disperse, and there also existed spatial clusters of HIV/AIDS since 2012 in Yuxi. Up to the end of August 2014, there were 9 hot spot towns of HIV/AIDS detected by local spatial autocorrelation Gi* cluster mapping analysis, and these towns mainly clustered in the southwest counties （Yuanjiang and Xinping county） of Yuxi.In this research,100 pieces of effective HIV-1 target gene sequences were obtained, and the success rate of nucleic acids abstraction and amplification was 57.8%. The total 100 cases of HIV/AIDS that gene sequences obtained were similar to the total HIV positive cases aged over 50 on the epidemic and spatial distribution features, which could preferably reflect and represent the molecular epidemic features of HIV positive cases aged over 50 in Yuxi.37 pieces of CRF07_BC subtype HIV-1 strains were detected, which accounted for 37.0% of all the 100 specimens.50 pieces of CRF08_BC subtype strains were detected, accounted 50.0% of all.6 pieces of C type strains were detected, accounted for 6.0% of all.2 pieces of CRF₀1B subtype and 3 pieces of CRF01_AE subtype strains were detected, which accounted 2% and 3% respectively, while 2 pieces of other new recombinants strains were found. Generally, CRF08_BC subtype strains were the predominant circulating HIV-1 strains that epidemic in Yuxi among different groups of HIV positive people who aged over 50, while CRF07_BC subtype strains were the predominant HIV-1 strains among Yi and Dai people.The difference of HIV-1 genotypes among different ethnic groups were statistical significant （x2=66.982, Fisher’s P=0.048）. CRF08_BC subtype strains were mainly clustered and epidemic in the east of Yuxi, and CRF07_BC subtype strains were mainly clustered in the southwest of Yuxi. Genetic distance analysis indicated that genetic distance of CRF07_BC, CRF08_BC and C type strains were less than CRF01_AE and CRF₀1B subtypes both in gaglenv gene regions, which suggested CRF07_BC, CRF08_BC and C type strains may be imported later than CRF01_AE and CRF₀1B subtypes strains, and CRF07_BC, CRF08_BC and C type strains may be epidemic for a short time relatively. According to the different clusters of CRF07_BC and CRF08_BC subtype strains on the phylogenetic trees, we deduced that the epidemic of CRF07_BC subtype strains among people aged over 50 originated from Xinping county in the early time probably, and it had been spread to other regions in Yuxi gradually. And the epidemic of CRF08_BC subtype strains among people aged over 50 maybe perhaps originated from Tonghai county in the early time, and it also had been spread to other regions gradually.The prediction of cellular co-receptor showed that 83 （89.2%） pieces of strains may use CCR5 co-receptor to infect target cells, while 10 pieces of strains perhaps used CXCR4 co-receptor. The difference of co-receptor types among different genotype strains were statistical significant（x2=23.805, Fisher’s P<0.001）. Most of CRF07_BC, CRF08_BC and C type strains used CCR5 type co-receptor while most CRF01_AE and CRF₀1B subtype strains used CXCR4 co-receptor.ConclusionsHIV epidemic situation among people aged over 50 years old were serious and it had been increasing gradually during recent years in Yuxi. HIV epidemic among people aged over 50 showed temporal and spatial features, HIV/AIDS mainly distributed in the towns and counties that with high economic levels. The mainly transmission model of HIV among people aged over 50 were still the heterosexual contact and marital sexual contact. Most of them had been accessed the period of AIDS with low CD4 cell degree when the HIV infection confirmed.CRF08_BC subtype strains had become the predominant HIV-1 strains among people aged over 50 years old. Different genotypes/subtypes of HIV-1 strains circulated in different regions and different ethnic groups of people among people aged over 50 in Yuxi. CRF07_BC and CRF08_BC subtype strains had different epidemic features of time. CRF08_BC subtype strains imported later than CRF07_BC subtype strains and circulated in a short time, though it was the predominant circulating strains.The genotypes/subtypes of HIV-1 strains were abundant in Yuxi among HIV positive people aged over 50, comprehensive intervention and prevention should be strengthened, and intervention for HIV positive people also need to be strengthened that avoid the transmission between different groups of people and to avoid new recombinants strains formed in the course of transmission.