The Role Of Syphilis And Syphilis Testing In The HIV-lepidemic Among Men Who Have Sex With Men

Objectives:To distinguish the role of men who have sex with men(MSM)with or without syphilis testing in HIV-1 transmission.Furthermore,we also sought to determine the risk factors associated with HIV/syphilis co-infection in a newly diagnosed HIV-infected MSM cohort and to address the role of syphilis in affecting HIV immunodeficiency progression particularly in the context of HIV-1 diversity.Methods:HIV-1 transmission clusters were constructed using HIV-1 pol sequences from 729 newly diagnosed HIV-infected MSM from 2008 to 2012 in Guangzhou,China.Follow-up examinations were done every 3-6 months from 2008 to 2015.China’s National Free Antiretroviral Treatment Program provides free-of-charge care to HIV-infected subjects including consulting,CD4 cell measurements every 3-6 months,and antiretroviral therapy(ART)in those with CD4 cell counts<350 cells/mm3.The role of MSM in the HIV-1 transmission networks was determined by a node influence measurement and centrality analysis.Factors associated with syphilis testing,and syphilis/HIV co-infection were confirmed by Logistic regression analysis.Factors associated antiviral treatment initiation and treatment response were analyzed by Cox regression.Results:Among HIV-infected MSM,56.7%did not test for syphilis at the time of HIV-1 diagnosis.MSM without syphilis testing was a specific sub-group of MSM with bigger closeness centrality and clustering coefficient than the recipients of syphilis testing(P<0.001),indicating their central position in the HIV-1 transmission networks.The median degree and radiality within HIV-1 transmission networks as well as the median K shell scores were also greater for MSM without syphilis testing(P<0.001),suggesting their relatively greater contribution in transmitting HIV-1 than the receipts of syphilis testing.The MSM without syphilis testing usually did not disclose their occupation or were more likely to be unemployed or to take non-skilled jobs,to have a history of sexually transmitted infections(STIs)and to be AIDS patients when diagnosed with HIV-1 infection(P<0.05).Multivariable Cox regression analysis indicated that syphilis testing per se did not promote the engagement of ART(P=0.233)or affect the speed of CD4+T cell count recovery after treatment(P=0.256).In addition,logistic analysis indicated that patients with syphilis-HIV co-infection were more likely to be older with the adjusted odds ratio(aOR)of 2.48(95%CI:1.28-4.80)for ages between 31-40 years and 3.20(1.11-9.22)for≥40 years when compared to 16-30 years.Compared to CRF01_AE,the aOR for the patients infected with HIV-1 CRF07_BC was 2.14(95%CI:1.01-4.53).Co-infection of HIV and syphilis was associated with lower baseline CD4+cell counts(0.45,95%CI:0.22-0.94),but was not associated with HIV disease progression(HR:1.03;95%CI,0.86-1.23)based on Kaplan-Meier analysis.Conclusions:HIV-1 transmission networks analysis reveals that the HIVinfected MSM who refuse syphilis screening at the time of HIV-1 diagnosis are a specific group and play important role in HIV-1 transmission.Although syphilis testing per se may not relate to the enhanced HIV-1 transmission and did not promote linkage to HIV-1 care,phylogenetic analysis of HIV-1 sequences identifies syphilis testing as a proxy marker for the subjects with important role in the HIV-1 transmission.Therefore,specific prevention and intervention targeting MSM without syphilis testing during HIV-1 care are urgently needed.Our study also indicated that co-infection of syphilis and HIV among MSM was more common in older people infected with HIV1 CRF07_BC in China.Co-infection of syphilis might not affect HIV-related immunodeficiency progression in the context of HIV-1 diversity.Our results provide new evidence about the interaction of syphilis and HIV and could contribute to evidence-based policy making for precise intervention of HIV-1 epidemic particularly among the key sub-populations.