The Characteristics Of HIV-1 Epidemic And Cross-border Molecular Transmission Network In Guangxi-vietnam Border Areas

ObjectiveGuangxi,located in the southwestern area of China,borders Vietnam.Guangxi is one of HIV/AIDS-hit areas in China.Along with the implementation of the "The Belt and Road" initiative,the communication and exchanges between Guangxi and Vietnam have been increasing in recnet years,which have created favorable conditions for the spread of infectious diseases such as HIV/AIDS.Therefore,using molecular transmission network and phylogenetic analysis,the aim of this study is to investigate the epidemic HIV-1 strains in Guangxi-Vietnam border areas,and to reveal the HIV-1 transmission network as well as transimission model in this region.We expect that the results of this study would be useful for guiding accurate prevention and improving intervention effect in this region.MethodsFrom 2016 to 2017,HIV/AIDS patients were collected by convenient sampling at some cities in Guangxi and four border provinces in Northern Vietnam.Demographic and behavioral information was obtained through questionnaires.Meanwhile,Peripheral venous blood samples were collected.HIV pro-viral DNA was extracted from PBMCs isolated from blood.HIV-1 pol region,containing reverse transcriptase and protease gene fragments,was amplified by PCR and then submitted to sequencing.The HIV pol gene sequences were submitted to the Los Alamos HIV Database for subtype analysis and phylogenetic tree construction.The bayesian phylogenetic tree was used to analyze the source of different subtypes.The molecular transmission network was constructed to analyze the transmission relationship and transmission risk of different virus strains,and to deduce the characteristics of high-risk transmission risk groups in the HIV transmission network in the border region between Guangxi and Vietnam.Result1.A total of 1170 subjects were enrolled in the study.Among them,853 patients were successfully collected,who had both sequences and epidemiological information.Of these subjects,most were male,married,farmer or jobless,with an average age of 43.0±11.0 years old.The Han nationality was the main nationality in Guangxi,while the Jing nationality was the main nationality in Northern Vietnam.2.In the border areas between Guangxi and the Northern Vietnam,HIV-1 CRF01_AE was the predominant subtype,accounting for 62.1%of all subtypes.Among them,214 Vietnamese samples were all HIV-1 CRF01_AE subtype.In Guangxi,CRF01_AE was also the predominant subtype,followed by CRF08_BC and then CRF07_BC.In addition,subtypes B,C and G were scattered in some cities of Guangxi.3.Two large clusters,cluster 1 and cluster 2 were identified in the ML tree by Phylogenetic tree analysis.Cluster 1 was mainly comprised of sequences from northern areas in Guangxi,and the cluster 2 was mainly comprised of sequences from border areas in Vietnam and southern cities in Guangxi.Using conditional screening,96 molecular transmission clades were obtained,among them,59.79%were found within Guangxi,30.93%within Northern Vietnam,and 9.38%were found in both Guangxi and Vietnam.4.Molecular transmission network showed that a total of 417 people were involved in network with an access rate of 48.89%,and gathered into 34 transmission clusters,composed of 2 to 126 people,respectively.The genetic network of HIV-1 in Guangxi-Vietnam border areas was highly clustered,and the distribution characteristics of each subtype were obvious.The cross-border cluster between Guangxi and Vietnam was comprised of 114 people,of which 39 samples were from Guangxi,but only 20 cases had potential transmission relationship with Vietnam,just accounting for 4.78%.The analysis of transmission risk degree indicated that,the characteristics of high-risk transmission population in the border region of Guangxi and Vietnam were those aged 30-49 years old,intravenous drug users,and those infected with CRF01_AE or CRF08_BC subtype.5.As for the source of HIV transmission,the constructed MCC tree indicated that,most Vietnamese strains in CRF01_AE-2 cluster originated from early strains in Vietnam,and few were introduced from Guangxi.In addition,most of the CRF07_BC strains prevalent in Guangxi originated from the early strains in Guangxi.Conclusions1.There was a HIV-1 cross-border transmission relationship between Guangxi and Northern Vietnam,which was established through CRF01_AE subtype strain.2.The cross-border HIV transmission relationship between Guangxi and Northern Vietnam was relatively weak,according the available data in this study.Furthermore,the hot spots of HIV transmission were limited to the Northern border of Vietnam and few border cities of Guangxi,including Chongzuo city,Fangchenggang city and Qinzhou city.3.The recent HIV-1 epidemic strains in Guangxi or Northern Vietnam were mainly from the early HIV-1 strains in their own areas,respectively.4.This study constructed a preliminary HIV-1 cross-border transmission model between Guangxi and Northern Vietnam,illustrating the mode of HIV-1 transmission between two areas.Furthermore,our study indicated that,HIV-1 CRF01_AE was first transmitted from Vietnam to the border areas of Guangxi,then prevailed in the border areas of Guangxi,and few strains transmitted back to the border areas of Vietnam from the southern areas of Guangxi.