Research On Molecular Epidemiology Of HIV-1 Among Entering Travelers At Main Ports In Southern Yunnan Province

As a serious threat to human health, AIDS is caused by infection human immunodeficiency virus （HIV）. According to the reports from Joint United Nations Program on HIV/AIDS （UNAIDS）, an estimated 35.3 （32.2-38.8） million people were living with HIV infection by the end of 2012.2.3 （1.9-2.7） million individuals were newly infected and 1.6 （1.4-1.9） million be of death for AIDS. In southern and Southeastern Asia, 270,000 （160,000-440,000） people were living with HIV infection. Thus, Southeast Asia has become one of the HIV-1 seriously threated regions in Asia. For its special geographic location, Yunnan was taken as the communicating hub between China and Southeast Asian countries and the epicenter of HIV-1 prevalence and furthermore the origin place of predominant HIV-1 subtypes and CRFs in China. Thus, understanding on the characteristics of HIV-1 molecular epidemiology and elucidation on HIV-1 evolution are very important for disease prevention and controlling. It may provide the significant information for the development of vaccine and treatment.Yunnan is located in Southeastern China. Geographically, Yunnan borders Myanmar, Laos and Vietnam and is situated on the drug trafficking routes by which heroin was transported into China from opium-producing "Golden Triangle" region. With the more frequent personnel exchanges and trading between China and Southeast Asia countries, entering travelers through ports of Yunnan is increasing. Meanwhile, this population also brings various pathogens and lead to the cross-border spreading of transmission diseases. The cross-border transmission of HIV-1 between China and Myanmar has been well documented. However, characteristics of HIV-1 epidemic among entering travelers through ports in southern Yunnan Province are far unclear. HeKou, DaLuo and MengKang ports were located at Honghe and Xishuangbanna prefectures along the border of southern Yunnan. Here, we have recruited the entering travelers at ports of Honghe and Xishuangbanna prefectures to describe the HIV-1 molecular epidemiology characteristics among this population.Between 2003 and 2012, a total of 326 entering travelers were recruited at main ports of south Yunnan province and determined to be HIV-1 infected. The serum samples from HIV-1-infected individuals were collected and viral RNA was extracted using the High Pure Viral RNA Kit. The RNA was subjected to reverse transcription and nested polymerase chain reaction （RT-Nested-PCR） to amplify the fragments of HIV-1 gag （1,155 base pairs, bp）, gag-prot （885bp） and partial RT genes （1,010bp）. When the overlapping sequences of 3 fragments were assembled, an interpretable sequence with a length of 2.6kb was obtained forl63 samples. Phylogenetic analyses based on these assembled sequences of the gag-RT gene （2.6kb） were performed using in MEGA version 6.0. It was showed that multiple subtypes of HIV-1 were distributed among these HIV-1-infected entering travelers, including 82 cases of CRF01_AE （50.3%）,38 cases of CRF08_BC （23.3%）,10 cases of CRF07_BC （6.1%）,2 cases of SGR₀708 （1.2%）,3 cases of subtype C （1.8%）,2 cases of subtype B （1.2%） and 26 cases couldn’t be classified into any known subtypes or recombinants, we temporally named as URFs （16%）. CRF01_AE was the predominant HIV-1 subtype, CRF08_BC, CRF07_BC, subtype C and B were listed to be circulating subsequently.The HIV transmission route was recorded for 111 individuals （34%） at interviewing, of them 100 was infected through sexual contact. It may lead to the major prevalence of CRF01_AE.As mentioned above,26 samples couldn’t be classified into any known HIV-1 subtypes or CRFs. To analyze their recombinant characteristics, bootscanning analyses were performed using the Simplot software. In the range of the gag-RT fragment （2.6 kb）, we have found multiple unique recombinant forms including 10 cases of B/C,5 cases of CRF08 BC/CRF07_BC,4 cases of CRF01_AE/C,3 cases of CRF01_AE/B,2 cases of CRF01_AE/CRF08 BC,1 case of C/Al and 1 case of CRF58₀1B/B/C. Furthermore, although these strains are the same recombinant forms, their recombinant structures maybe different. It was shown that these 7 kinds URF except C/Al and CRF58₀1B/B/C have only recombinant structure; other recombinant forms have two or more kinds of recombinant structures. The B/C have four kinds of recombinant structures, CRF08 BC/CRF07_BC share withtwo recombinant structures, CRF01_AE/C have four different recombinant structures, three recombinant structures were shared for CRF01 AE/B, and CRF01 AE/CRF08 BC have two recombinant structures. It is of worth that four recombinant structures of CRF01_AE/B, C/Al, CRF01_AE/CRF08_BC and CRF58₀1B/B/C haven’t been documented. The distribution of HIV-1 subtypes and recombinants are complex among entering travelers at ports in southern Yunnan.In summary, it was described that HIV-1 infection is very serious among entering travelersat ports in southern Yunnan. And a variety of HIV-1 subtypes, CRFs and URFs were co-circulated in this population. The entering traveler has played an important role in HIV-1 cross border transmission in Yunnan. The description on characteristics of HIV-1 molecular epidemic is definitely helpful for the understanding on HIV epidemic situation and predicting the prevalence trend, which may provide an important data for HIV-1 prevention and vaccine development.