Characteristics And Molecular Epidemiology Of HIV-1Infection Among Men Who Have Sex With Men (MSM) In Xi’an

Objective and significanceAcquired Immune Deficiency Syndrome (AIDS) is a sexually transmitted diseasecausing by Human Immunodeficiency Virus (HIV), which seriously affects human health.Xi’an is a low epidemic area of AIDS, where the first infected person was recorded in1992, and the first case of homosexual transmission of AIDS from men to men wasreported in2002. More than1700HIV/AIDS infections have been reported in Xi’an untilthe end of2012. Between2007and2012the proportion of homosexual transmission in thetotal HIV infections in Xi’an had increased from14.3%to56.7%, which have exceededthe ratio of drug-injection transmission and became the major route of transmission inXi’an. In this project the behavioral characteristics, syphilis infection and HIV-1subtypedistribution of HIV-infected men who have sex with men (MSM) will be investigated tostudy the molecular epidemiology in this population, which can be used for thedevelopment of AIDS prevention and control strategies in the future.MethodsAccording to the simple random sampling method,40%of HIV-infected men who have been verified as homosexual transmission by Xi’an Center for Disease Control andPrevention were selected as the objective of study. Excluding38individuals who refusedthe interview, there were a total of240individuals that could be used for analyses.1. Epidemiological investigation: Epidemiological questionnaire was carried out byface-to-face interviews. The main content includes general information, awareness rate ofAIDS, behavioral features, HIV counseling and testing, sexual and emotional orientations,etc.2. Laboratory test of syphilis: Two-step detection of syphilis antibody was conductedfor each investigated individual:(1) Preliminary screening: detection of specific antibodyof syphilis spirochete on all samples (ELISA);(2) Reexamination: detection ofnon-specific antibody of syphilis spirochete on ELISA-positive samples (TRUST). Onlypositive individual in the reexamination was judged as syphilis-positive.3. HIV-1subtype analysis: The plasma was isolated from5ml anticoagulantperipheral blood sampled of each investigated individual. Total RNA was extracted fromthe plasma. HIV-1GAG and ENV genes were amplified by nested RT-PCR and sequenced.The sequences were assembled and aligned with international reference sequences.Genetic divergences were calculated and phylogenetic trees were constructed in Mega5.2software.4. Statistical analyses on the collected data were performed in SPSS19.0software.The behavioral characteristics, syphilis infection and HIV-1subtype distribution ofHIV-positive MSM population were comprehensively analyzed. Chi-square test andvariance analysis were used in most cases, whereas P<0.05was considered as statisticallysignificant.Results1. Epidemiological survey revealed that young adults made up of the majority of240HIV-1-positive MSM investigated in this study, most of whom were at the ages of20-40(account for71.2%). Most of these MSM were Han Chinese (99.2%), unmarried (60.4%),well educated (79.2%with degrees of senior/vocational middle school or higher) anddistributed in more than10occupations such as commercial service, worker, student, teacher, cadre staff, houseworker/jobless and farmer. The awareness of AIDS was96.7%.Behavioral characteristics were complex:61.3%of investigated individuals had bisexualbehaviors, a mean number of5sex partners, and a low rate of condom use (20.4%);22.8%(13/57) of married objects did not use condom in sexual intercourse with the spouse afterinfection. All objects denied the history of drug use,10%of whom had history ofanaleptic/aphrodisiac use, and25%had history of blood donation;38.8%receivedperiodic tests of HIV antibody before infection; sexual or emotional orientations showedthat57.5%of the objects were homosexual,32.4%were bisexual,4.1%were heterosexual,and5.4%were uncertain.2. The positive rate of syphilis in HIV-1positive MSM objects was17.5%(42/240),which was significantly higher than that of the local HIV-negative MSM populationmonitored in2010-2012(c2=15.239, P<0.05).3.168of240HIV-1positive MSM samples were successfully amplified andsequenced, among which165samples produced consistent subtypes between GAG andENV sequences, including79CRF01_AE (47.0%),74CRF07_BC (44.0%) and12Bsubtypes (7.1%);3samples produced inconsistent subtypes between GAG and ENVsequences, including2CRF01_AE/A1(1.2%) and1CRF07_BC/CRF01_AE (0.6%). Bsubtype-infected individuals/patients had lower first-time CD4values than that of othertwo subtypes (F=5.801, P<0.05).The epidemic time of B, CRF01_AE and CRF07_BCsubtypes in MSM population in Xi’an were4-15,1-10and1-4years, respectively.ConclusionsA contradiction of knowledge and behavior is prevalent in HIV-infected MSMpopulation in Xi’an. This population has characteristis of bisexual behavior, multiplesexual partners, low rate of condom use and high rate of syphilis infection, etc.CRF01_AE, CRF07_BC and B subtypes are the dominant HIV-1subtypes in local MSM,among which CRF01_AE is preponderant. However, the infection of B subtype virus wasseverer and had the longest epidemic time in Xian. There are cross infection phenomenonbetween MSM, heterosexual and drug-user populations. The high rates of bisexual and intra/extramarital sexual behaviors make the MSM population become the connectionsbetween homosexual and heterosexual populations, as well as high risk and generalpopulations. Since MSM usually act covertly, the difficult points in the prevention andtreatment of AIDS in this population are how to find out these people and what measuresshould be taken to disrupt the connections. Moreover, the diverse sexual/emotionalorientations in MSM population lead to the complex interpersonal network, varied socialroles and unsafe sexual behaviors, which makes up of another difficult point in theprevention and treatment of AIDS.The prevention and control strategies for the MSM population should bestrengthened and improved hereafter. Pertinent and feasible measures should be taken tosuppress the prevalence of AIDS in this population, such as strengthening the publicity,education and behavior intervention, increasing the rate of condom use and promotingbehavioral change in MSM population, encouraging MSM to take periodic tests of HIVantibody in official institutions, reinforcing the professional ethical education and workingskills of AIDS-related employees in medical institutions to reduce the misgivings of MSMpopulation, diagnosing and treating syphilis according to the standard therapeutic methodas early as possible.