HIV molecular network is a recently reported method for studying the transmission characteristics of HIV-infected people. Countries have used this method to conduct a large number of researches on transmission relations, transmission hotspots and epidemic surveillance for the purpose of providing evidence for precise AIDS intervention and control. At present, there are three major methods for constructing molecular networks in the world, i.e. genetic distance method based on pairwise alignment, phylogenetic node support method, and joint parameter method based on the two methods. This paper reviews the progress of the three methods for constructing HIV molecular network to study the transmission characteristics of HIV-infected patients, in order to provide data support for the prevention and control of HIV. Since the emergence of the molecular network method, Beijing, Shanghai, Zhejiang, Sichuan and other provinces in China have reported relevant research results using molecular network analysis, which provided scientific data for further precise AIDS prevention and control. Recent international studies have also predicted that molecular network based transmission cluster detection is expected to become a new method to stop AIDS epidemic.

Objective:To analyze the epidemiological characteristics of untreated 16-25 years old people living with HIV-1 (PLWH) in Dehong on the China-Myanmar border during 2009 to 2017, by using molecular network method and to provide references for precise prevention and reduction of the spread of HIV-1 in Dehong.Methods:Screening people living with HIV-1, collecting blood sample and separating plasma, extracting RNA were performed to amplify HIV-1 pol sequence, construct molecular network by HIV-TRACE program and conduct statistical analysis. Results:Among the 573 infected persons in the group, 319 were Chinese (55.67%), 254 were Burmese (44.33%); 351 were males (61%), and 222 were females (39%); 404 had heterosexual transmission (HET, 70.51%), 110 people injected drugs (PWID, 19.20%), 51 men had sex with men (MSM, 8.9%); genotypes included 252 unique recombinant forms (43.98%), and 222 had circular recombinant forms (39.02%), 76 had HIV-1 C (13.26%) and 23 HIV-1 B (4.01%) infection. The 83 molecular networks constructed through HIV-TRACE involved 250 PLWH, 49% were the China-Myanmar mixed network (41/83). Myanmar citizens were at high risk of accessing the China-Myanmar mixed network ( AOR=2.676, p=0.002). Chinese male PWID network assortativity is 0.34, Myanmar male PWID was 0.14, MSM was 0.12. Conclusions:There is a continuous risk of cross-border transmission of HIV-1 in Dehong on the China-Myanmar border; attention should be paid to the mixed transmission of MSM and Myanmar male PWID populations with other transmission routes.

Objective:To explore the resistance to protease inhibitors (PI), nucleoside reverse transcriptase inhibitors (NRTIs), non-nucleoside reverse transcriptase inhibitors (NNRTIs) and integrase inhibitors (INSTIs) of HIV-1 CRF55_01B and the transmission of drug-resistant strains among HIV-1 CRF55_01B infected patients before antiviral treatment in China.Methods:HIV-1 RNA was extracted from plasma samples of the patients infected with CRF55_01B in the national surveillance of HIV drug resistance before antiviral treatment in 2018. A 1 056 bp gene fragment of protease/reverse transcriptase (PR/RT) region and an 846 bp gene fragment of integrase (IN) region were obtained and sequenced. Drug resistance was analyzed by using all drugs included in the Stanford University HIV db Program, HIV-1 molecular network analysis was performed with software HIV-TRACE and polymorphism mutations of CRF55_01B integrase gene region were analyzed.Results:A total of 178 samples from 26 provinces, municipalities and autonomous regions in China were analyzed, and 170 sequences of CRF55_01B PR/RT region and 170 sequences of IN region of corresponding samples were obtained. The drug resistance rate was 15.3% (26/170). The drug resistance rates of PIs, NRTIs, NNRTIs and INSTIs were 1.2% (2/170), 1.2% (2/170), 15.3% (26/170), 0.6% (1/170), respectively. The level of drug resistance was mostly low. NNRTIs drug resistance mutations were mainly V179D/E co-appeared with other mutations, and 84.1% (143/170) of the infected patients carrying V179D/E alone showed potential drug resistance. INSTIs drug resistance mutation was G163R, and showed low resistance to EVG and RAL. The molecular network access rate was 30.0%(51/170)according to the 0.9% gene distance threshold. The resistant strains were transmitted between men with homosexual transmission and heterosexually transmitted people, and both carried resistant mutations E138G and V179E. In the integrase region, CRF55_01B and CRF01_AE and B subtypes showed high mutation frequency difference in 5 sites (T215A、G134N、I135V, K136R and L101I/V).Conclusions:Before antiviral treatment, CRF55_01B infected patients in China had a high resistance to NNRTIs. Strains carrying both E138G and V179E resistance mutations were transmitting in clusters. The prevalence of CRF55_01B integrase inhibitor resistant strains is low, but some genetic polymorphisms with high mutation rate in the integrase gene region have potential influence on drug sensitivity. The influence of drug resistance of new recombinant strains on antiviral therapy in China needs to be further monitored and analyzed.