The Occurrence And Spread Of Dehong HIV-1 Recombinant Strain And Its Related Influencing Factors

Background:Dehong prefecture in Yunnan province is one of the earliest regions that HIV-1 circulating in our country.Many studies have shown that the current major epidemic strains of HIV-1 in China,such as B,CRF01_AE,CRF07_BC and CRF08 BC are spread to other provinces via Dehong.Therefore,Dehong is also considered as the gateway of the country's AIDS epidemic.Dehong,which is near the "Golden triangle" region,is bordering on three sides with Myanmar,except Lianghe County.IDU was the main ways of transmission of HIV-1 in the early age.Compared to the sexual transmission,intravenous injection is more advantageous to cause co-infection or superinfection within different subtypes.High proportion of recombinants in IDUs was reported.In this study,we sampled from youth under the age of 25 from 2009 to 2012.HIV-1 genotypes were analyzed.The occurrence and transmission of recombinant strains was assessed,and the relevant factors affecting the recombinants distribution was illustrated from the angle of epidemiology.We hope the suggestions we provide is effective and targeted for local HIV-1 control and prevention,thereby lowering the incidence of HIV-1.Methods:People under 25 years old were sampled form 2009 to 2012.Genotype of HIV-1,the signature of recombinants transmission and the related factors affecting recombinants distribution were study by subtyping,phylogenetic analyses,characteristic sites identification and statistic analyses.Results:1.HIV-1 genotype of young infections of Dehong.There were 205 young infections were enrolled from 2009 to 2012.Three fragments including gag,pol and near full-length genome were amplified.With each fragment,72,205 and 25 sequences were successf-ully sequenced,respectively.Phylogenetic and recombination pattern analyses were performed to identify the HIV-1 genotypes.Of all,BC recombinants were account for the most,with the proportion of 40.0%,followed by 01BC(19.5%),CRF01_AE(14.1%),C(10.2%),01C(4.9%),CRF08_BC(4.9%),B(4.4%),CRF07_BC(1.5%)and 01B(0.5%).With all recombinants,there were at least ? clusters which were named as potential circulating recombinant forms(pCRFs)after the definition of CRFs.pCRFs account for 26.3%of total samples,and the unique recombinant forms(URFs)accounts for 38.5%.2.The occurrence and transmission of recombinant strains.All pCRFs were subjected to NFLG amplification and at least one NFLG was successful amplified in each cluster.recombination patterns with accurate breakpoint sites were analyzed.In this study,we identified four novel CRFs named CRF57_BC,CRF62_BC,CRF64_BC and CRF65_cpx.By construction of maximum clade credibility(MCC)tree using Bayesian MCMC,we estimated the time of most recent common ancestor(tMRCA)of each new CRF.CRF57_BC:1998.6(95%HPD:1994.3-2003);CRF62_BC:2003.8(2000.4-2006.6);CRF64_BC:2001.1(1995.3-2005);CRF65_cpx:2004.2(2001-2006.9).Base on the model of Bayesian skyline plot,we reconstructed the circulating history of local recombinants.It predicted that there were two rapid growth stage in the history of Dehong epidemic form 1990 to 2010.The CRFs,as well as URFs,either circulating or elimination in these two period.Although the pCRFs have been in for a long time,the range of their spread is limited,except for pCRF4(CRF65_cpx),pCRF6 and pCRF9.The three pCRFs could co-cluster with sequence form other countries or regions,which means the ability of spreading outward.sequence alignment of recombinants showed that the identity of RNA dimerization initiation signal motif(GTGCAC)of Dehong recombinants may help the formation of heterologous RNA dimers in viral package process,which increase the possibility of second recombination3.Prediction of characteristic sites of recombinants circulating.The circulating pattern of CRF07_BC and BC recombinants of Dehong(DH_BC)were quite different.characteristic sites of DH_BC were predicted comparing to the background of CRF07_BC form Xinjiang and Sichuan province.Subtype B isolated form US and China and subtype C from Africa were used to eliminate the interference of subtype difference.Only when the site in DH_BC was different with all other subtype groups,the site can be consider as characteristic.By calculating the difference of entropy among these groups,42 sites were shown significant difference in diversity between DH_BC and all other groups with 4 sits in Gag,10 in Pol,6 in Env,3 in Vif,2 in Vpr,9 in Vpu,2 in Tat,4 in Rev and 2 in Nef.Some of them are in the CTL epitopes that associated with HLA alleles,of which are 200M and 368S in Gag,91E,125K,126K and 926K in Pol,61Y,791E and 805L in Env,31V in Vif,61 and 34Kin Vpu,and 133V in Nef.31Vin Vif and 133V in Nef showed lower entropy value than that of the corresponding sites of CRF07_BC.By comparing amino acid distribution frequency of the different protein locus,fifteen signature sites were found.Of all,R35K in Vpu and Y81F,H187Q in Nef are in the list of CTL epitopes that associated with HLA alleles.Thus,we presume that these mutations may HLA-associated escape.The mutation from R(in CRF07_BC)to K in position 35 of Vpu leads to the generation of RNA-and DNA-binding site,and the mutations of Y81F and H187Q cause the changes of protein tertiary structures.These changes in structure may result in the biological transmission abilities.4.Epidemiology factors that affecting recombinants distribution.In this study,205 young patients were enrolled.Youth from Dehong were mainly infected through heterosexual route(74.1%).Minority ethnic infections account for 59.5%of all,and people with HIV-1 tend to be in lower education level and most of them(74.6%)are farmers.More than a quarter of them are Myanmar nationalities indicating a wide range of population mobility.The distribution of different subtypes are significant different in ethnic(P<0.001),education level(P = 0.001),occupation(P = 0.01)and high-risk factor contact(P = 0.008).We divided subtypes into three categories(conventional strains,pCRFs and URFs)according to the circulating range.Multivariate logistic regression analyses showed that the distribution of URFs were positive related with lower education level(AOR:2.54,95%Cl:1.13-5.68)and residence(AOR Myanmar:3.43,1.29-9.12;AOR other county in Dehong:2.92,1.28-6.65).According to the AE related strains,the three categories were further divided into six categories:pure_AE(CRF01_AE),pure_BC(B,C,CRF07_BC and CRF08_BC),pCRFs_AE,pCRFs_BC,URFs_AE and URFs_BC.Chi-square analyses showed the distribution of subtypes were significant in sampling year(P = 0.019),ethnicity(P<0.001),education level(P<0.001),occupation(P = 0.028),residence(P = 0.002)and High-risk factor contact(P = 0.003),Multivariate logistic regression analyses demonstrated that compared to the distribution of CRF01_AE in Han,pure_BC(18.9,2.13-168.5)?pCRFs_BC(25.5,2.76-236.0),URFs_AE(10.0,1.02-98.0)and URFs_BC(18.2,2.06-160.5)were positive related with infections of Jingpo minority.Besides,URFs_BC also showed positive relationship with Dai minority(4,40,1.21-16.0).Comparing to the distribution of CRF01_AE in Mang City,URFs_BC was positive related with other counties in Dehong(4.68,0.76-13.9).It also indicated that the IDU infections have positive relationship with sex(AOR Male:27.25,5.77-128.6),marital status(AOR single:3.05,1.02-9.14),ethnicity(AOR Jingpo:8.65,2.21-33.12)and residence(AOR Myanmar:12.79,2.04-80.12)Conclusion:Heterosexual transmission is the most important factor of HIV-1 epidemic of youth of Dehong.The genotypes here are very complex,given that the high proportion of recombinants and URFs and pCRFs co-circulating.The phenomenon of high rates of recombinant strains in massive sexually transmitted popular is very rare in other countries and regions.The spread of recombinants are local limited,however,evidences of outward transmission are found.Thus,how to prevent the generation of URFs,prevent URFs strains to CRFs strain and CRFs strains spread to other regions is a great challenge for HIV-1 control and prevention in Dehong.By analyzing epidemiology factors that affecting recombinants distribution,we demonstrated that the distributions of recombinants are positive related with ethnicity,education level and residence.More attention should be paid to Jingpo minority in remote region of Dehong in IDUs to finally eliminate the generation of BC recombinants.Sexual transmission control may help block the transmission of AE related CRFs.In addition,collaborative prevention across border is needed to better control the local AIDS epidemic,especially in IDU population prevention.Only in this way,can we effectively prevent the spread of recombinant strains across the board,decrease the complexity of HIV-1 genotypes and,in turn,reduce the number of HIV-1 infected people.