Analysis Of Resistance-Associated Genetic Characteristic From Subtype B, CRF01_AE And CRF07_BC Isolates Prevailing In China

Since 1990s,Antiretroviral Therapy(ART) has dramatically changed the clinical outcome of AIDS,leading to decreased AIDS-related mortality and morbidity. However,ART cannot completely eradicate HIV from the body,results in long-term toxicity and eventually leads to the emergence of drug-resistant HIV strains under the drug pressure in vivo,which was considered a major cause of treatment failure.HIV-1 genome differs by 10%to 30%between subtypes of M group.Amino acid sequence diversity in the pol gene is 10%to 15%between different subtypes,which may influence the pattern of drug resistance in different subtypes.HIV-1 genotypic drug resistance testing is an effective tool for the surveillance of HIV-1 drug resistant strains.These testing results can be used in the choice of antiretroviral regimen.However,the benefit of genotyping is limited by the need to interpret the mutation pattern in order to obtain a prediction regarding susceptibility to each antiretroviral drug.There are different genotypic HIV drug resistance interpretation systems currently available,which are mostly constructed based on data for clade B viruses.Subtype B,CRF01_AE and CRF07_BC are prevailing in China but little information is available on non-B subtypes to date.It becomes more and more important to study resistance-associated genetic characteristic of subtype B, CRF01_AE and CRF07_BC isolates in China and evaluate the prediction efficiency of different genotypic drug resistance interpretation systems.In this study,Protease and reverse transcriptase sequences were available from 122 subtype B,117 CRF01_AE and 107 CRF07_BC isolates from drug-naive patients in Henan,Anhui,Sichuan,Hunan,Guangxi,Yunnan and Xinjiang provinces.Protease and reverse transcriptase sequences were also available from 107 subtype B and 67 CRF07_BC isolates from treated HIV-1 infected individuals in Henan and Xinjiang provinces.It showed that of the total 99 amino acids of protease,polymorphisms were found to be more than 50%at 5 codons(E35D,L63P,I72V,V77I and I93L) in subtype B,at 5 codons(I13V,E35D,M36I,H69K and L89M) in CRF01 AE,and at 4 codons (E35D,D60E,L63P and I93L) in CRF07_BC.Of the first 270 amino acids of reverse transcriptase,polymorphisms were found to be more than 50%at 3 codons(I135V, S162C and T200A) in subtype B,at 12 codons(E6D,T39K,K43E,D123S,Q174K, D177E,I178M,T200I,Q207A,R211S,K238R and V245E) in CRF01_AE,and at 8 codons(V35T,E36A,T39D,S48T,V60I,D121Y,KI22E and V245Q) in CRF07_BC.There were 3 secondary mutations in amino acid position 10,58 and 71 of protease in 3 subtypes prevailing in China.Although secondary mutations do not significantly alter the susceptibility of the PIs,these mutations,which exist before the emergence of a primary mutation,may alter the rate of the development of drug resistance or the subsequent evolution of mutations.The amino acid substitution K238R of reverse transcriptase in CRF01_AE may influence the drug resistance evolution.The increased genetic barrier was calculated for V75I(CRF01_AE) and K/R238N (CRF01_AE),and the decreased genetic barrier was calculated for V106M (CRF07_BC) compared with those of subtype B.The same genetic barrier was calculated for the other mutations between subtypes.This study found few differences between subtypes in the calculated genetic barrier for evolution to major drug-resistance-associated substitutions,which imply that subtype diversity might have little influence on the patterns of resistance substitutions that will emerge.The emergence of V106M in patients harboring clade CRF07_BC infections will be a matter of concern because cross-resistance to all NNRTIs occur as a result of this mutation.Only NVP and EFV can be chose in all NNRTIs in China,so we should be aware of the V106M mutation and its potential impact on therapy outcome in CRF07_BC patients.We found that H221Y,L228R and L228H were new resistance-associated mutations in subtype B and CRF07_BC isolates.All of three mutations were correlated with novel Y181C mutation.H221Y was also correlated with novel K103N mutation.The H221Y,L228R and L228H may be associated with the specific use of NVP.Variable prediction of antiretroviral treatment outcome by HIVDB,ANRS and Rega genotypic drug resiatance interpreting systems was observed in subtype B and CRF07_BC patients.Higher levels of interpreting discordance were observed for predictions of NNRTIs than for predictions of NRTIs susceptibility.The discordance could be attributed to specific mutations,including E44A/D,V118I,T69N,K238T, Y181C and M184V,which always have the interactions with other mutations.The mutations found here should be further investigated as to whether they contribute to differences in resistance and therapy response between subtypes prevailing in China.The HIVDB genotypic drug resistance interpreting system can be used to predict therapy response of subtype B and CRF07_BC patients in China.The Rega system should be an important complernent to HIVDB especially the presence of complicated mutation patterns.There exists,therefore,an urgent need for standardization of genotypic drug resistance interpreting system for HIV-1 genotyping.