Intercontinental dispersal of HIV-1 subtype B associated with transmission among men who have sex with men in Japan

Using molecular transmission networks to understand the epidemic characteristics of HIV-1 CRF08_BC across China

HIV-1 CRF08_BC has become a major epidemic in heterosexuals and intravenous drug users (IDUs) in southern China. In order to evaluate the trends of its epidemic and facilitate targeted HIV prevention, we constructed the genetic transmission networks based on its pol sequences, derived from the National HIV Molecular Epidemiology Survey. Through retrospective network analysis, to study the epidemiological and demographic correlations with the transmission network. Of the 1,829 study subjects, 639 (34.9%) were clustered in 151 transmission networks. Factors associated with increased clustering include IDUs, heterosexual men, young adults and people with lower education (P < 0.05 for all). The IDUs, MSM, young adult and person with low education had more potential transmission links as well (P < 0.05 for all). The most crossover links were found between heterosexual women and IDUs, with 30.9% heterosexual women linked to IDUs. The crossover links heterosexual women were mainly those with middle age and single (P < 0.001). This study indicated that the HIV-1 CRF08_BC epidemic was still on going in China with more than one third of the infected people clustered in the transmission networks. Meanwhile, the study could help identify the active CRF08_BC spreader in the local community and greatly facilitate précising AIDS prevention with targeted intervention.

Using molecular transmission networks to understand the epidemic characteristics of HIV-1 CRF08_BC across China

HIV-1 CRF08_BC has become a major epidemic in heterosexuals and intravenous drug users (IDUs) in southern China. In order to evaluate the trends of its epidemic and facilitate targeted HIV prevention, we constructed the genetic transmission networks based on its pol sequences, derived from the National HIV Molecular Epidemiology Survey. Through retrospective network analysis, to study the epidemiological and demographic correlations with the transmission network. Of the 1,829 study subjects, 639 (34.9%) were clustered in 151 transmission networks. Factors associated with increased clustering include IDUs, heterosexual men, young adults and people with lower education (P < 0.05 for all). The IDUs, MSM, young adult and person with low education had more potential transmission links as well (P < 0.05 for all). The most crossover links were found between heterosexual women and IDUs, with 30.9% heterosexual women linked to IDUs. The crossover links heterosexual women were mainly those with middle age and single (P < 0.001). This study indicated that the HIV-1 CRF08_BC epidemic was still on going in China with more than one third of the infected people clustered in the transmission networks. Meanwhile, the study could help identify the active CRF08_BC spreader in the local community and greatly facilitate précising AIDS prevention with targeted intervention.

Sun, sea and sex: a review of the sex tourism literature

Background

Sex tourism is defined as travel planned specifically for the purpose of sex, generally to a country where prostitution is legal. While much of the literature on sex tourism relates to the commercial sex worker industry, sex tourism also finds expression in non-transactional sexual encounters. This narrative review explores current concepts related to travel and sex, with a focus on trans-national sex tourism.

Methods

The PubMed database was accessed to source relevant literature, using combinations of pertinent search terms. Only articles published in the English language were selected. Reference lists of published articles were also examined for relevant articles.

Results

With regard to preferred destinations, South/Central America and the Caribbean were more likely to receive tourists looking for casual sex. Longer duration of travel, travelling alone or with friends, alcohol or drug use, being younger and being single were factors associated with higher levels of casual sex overseas. The majority of literature retrieved on sex workers focused on risk behaviours, sexually transmitted infections (STI), mobility of sex workers and how these factors affected their lives. Sex tourists require better access to effective methods of preventing HIV, such as pre-exposure prophylaxis, and better education on HIV prevention. Drugs and alcohol play a major role as risk factors for and cofactors in casual sexual behaviour while abroad.

Conclusions

Travellers need to be informed of the increased risks of STI before travel. They should be aware of the local prevalence of STIs and the risks associated with their sexual practices when they travel, including engaging with commercial sex workers, having unprotected sexual intercourse and becoming victims of sexual violence.

Multiple HIV-1 Genotypes Circulating Among College Students in Nanjing, China

College students are disproportionately affected by HIV-1 in China. However, little is known about the genetic characteristics of HIV-1 among this population. A molecular epidemiological investigation was conducted among the newly diagnosed antiretroviral therapy-naïve HIV-1-infected individuals during 2015-2019 in Nanjing city, China. The pol fragment (HXB2: 2,253-3,311) was obtained by HIV-1 RNA extraction and gene amplification, and subjected to genotyping, recombination analysis, and phylogenetic inference. A total of 945 pol sequences from 226 students and 719 nonstudents were successfully amplified. Multiple genotypes were identified in students, including CRF01_AE (37.66%), CRF07_BC (32.90%), CRF55_01B (5.63%), CRF68_01B (3.46%), CRF67_01B (3.03%), subtype B (1.73%), and CRF58_01B (1.30%) and unique recombinant forms (URFs) of 01C_like (7.08%), 0107_like (3.98%), 01BC_like (2.21%), and 01B_like (1.33%). The distribution of genotypes among students was similar to that among nonstudents. The estimated mean evolutionary rate of URFs was 2.89 × 10^-3 [95% Bayesian credible interval: 1.89-3.90] nucleotide substitutions/site/year. Approximately 64% (21/33) of URFs among students were located in three major clusters (0107_like, 01C_like 1, and 01C_like 2 clusters), which had recent time to the most recent common ancestors and low mean genetic distance, and presumably originated from Nanjing (posterior probability ≥0.99, state probability ≥0.9). Among 226 students with pol segments, the prevalence of primary and transmitted drug resistance mutations was 15.93% and 3.98%, respectively. The rapid evolution of multiple HIV-1 genotypes and high prevalence of URFs circulating among students in Nanjing emphasized the necessity of comprehensive surveillance for HIV-1 transmission among this population.

The Impact of Human Mobility on Regional and Global Efforts to Control HIV Transmission

HIV prevention and control methods are implemented on different scales to reduce the spread of the virus amongst populations. However, despite such efforts, HIV continues to persist in populations with a global incidence rate of 1.8 million in 2017 alone. The introduction of new infections into susceptible regional populations promotes the spread of HIV, indicating a crucial need to study the impact of migration and mobility on regional and global efforts to prevent HIV transmission. Here we reviewed studies that assess the impact of human mobility on HIV transmission and spread. We found an important role for both travel and migration in driving the spread of HIV across regional and national borders. Combined, our results indicate that even in the presence of control and preventive efforts, if migration and travel are occurring, public health efforts will need to remain persistent to ensure that new infections do not grow into outbreaks.

Transmission dynamics of HIV-1 subtype B strains in Indonesia

Human immunodeficiency virus type 1 (HIV-1) and acquired immunodeficiency syndrome (AIDS) represent a major public health concern in Indonesia. Although circulating recombinant form (CRF) 01_AE is a predominant subtype in Indonesia, HIV-1 subtype B (HIV-1B) is also widely prevalent. However, the viral genetic evolution, spatial origins, and patterns of transmission of HIV-1B in Indonesia remain unclear. In the present study, we described the evolutionary characteristics and spatial-temporal transmission networks of HIV-1B in Indonesia. To elucidate the epidemiological link between HIV-1B epidemics in Indonesia and those in the remainder of the world, we conducted phylogenetic analyses of HIV-1B strains in Indonesia. Based on the results obtained, at least three epidemic clades [the Indonesia, United States (US), and China clades] of HIV-1B were found to be prevalent in Indonesia. In order to identify the potential source and transmission route of Indonesian HIV-1B strains, we performed Bayesian analyses and constructed Maximum clade credibility trees of each clade. Although some HIV-1B strains in Indonesia were introduced from Thailand, the prevalent HIV-1B strains appeared to have been directly introduced from Europe or America. Indonesian HIV-1B may have spread via the main dispersal of pandemic HIV-1B strains via the US from the Caribbean region rather than being directly introduced from Africa.

Phylogenetic transmission clusters among newly diagnosed antiretroviral drug-naïve patients with human immunodeficiency virus-1 in Korea: A study from 1999 to 2012

Population-level phylogenetic patterns reflect both transmission dynamics and genetic changes, which accumulate because of selection or drift. In this study, we determined whether a longitudinally sampled dataset derived from human immunodeficiency virus (HIV)-1-infected individuals over a 14-year period (1999–2012) could shed light on the transmission processes involved in the initiation of the HIV-1 epidemic in Korea. In total, 927 sequences were acquired from 1999 to 2012; each sequence was acquired from an individual patient who had not received treatment. Sequences were used for drug resistance and phylogenetic analyses. Phylogenetic and other analyses were conducted using MEGA version 6.06 based on the GTR G+I parameter model and SAS. Of the 927 samples, 863 (93.1%) were classified as subtype B and 64 were classified as other subtypes. Phylogenetic analysis demonstrated that 104 of 927 patient samples (11.2%) were grouped into 37 clusters. Being part of a transmission cluster was significantly associated with subtype-B viruses, infection via sexual contact, and the infection of young males. Of all clusters, three (~8.1%) that comprised 10 individual samples (22.2% of 45 individuals) included at least one member with total transmitted drug resistance (TDR). In summary, HIV transmission cluster analyses can integrate laboratory data with behavioral data to enable the identification of key transmission patterns to develop tailored interventions aimed at interrupting transmission chains.

National and International Dimensions of Human Immunodeficiency Virus-1 Sequence Clusters in a Northern California Clinical Cohort

Background

Recent advances in high-throughput molecular epidemiology are transforming the analysis of viral infections.

Methods

Human immunodeficiency virus (HIV)-1 pol sequences from a Northern Californian cohort (NCC) of 4553 antiretroviral-naive individuals sampled between 1998 and 2016 were analyzed together with 140 000 previously published global pol sequences. The HIV-TRAnsmission Cluster Engine (HIV-TRACE) was used to infer a transmission network comprising links between NCC and previously published sequences having a genetic distance ≤1.5%.

Results

Twenty-five percent of NCC sequences were included in 264 clusters linked to a published sequence, and approximately one third of these (8.0% of the total) were linked to 1 or more non-US sequences. The largest cluster, containing 512 NCC sequences (11.2% of the total), comprised the subtype B lineage that traced its origin to the earliest North American sequences. Approximately 5 percent of NCC sequences belonged to a non-B subtype, and these were more likely to cluster with a non-US sequence. Twenty-two NCC sequences belonged to 1 of 4 large clusters containing sequences from rapidly growing regional epidemics: CRF07_BC (East Asia), subtype A6 (former Soviet Union), a Japanese subtype B lineage, and an East/Southeast Asian CRF01_AE lineage. Bayesian phylogenetics suggested that most non-B sequences resulted from separate introductions but that local spread within the largest CRF01_AE cluster occurred twice.

Conclusions

The NCC contains national and international links to previously published sequences including many to the subtype B strain that originated in North America and several to rapidly growing Asian epidemics. Despite their rapid regional growth, the Asian epidemic strains demonstrated limited NCC spread.

Phylogenetic and phylodynamic analyses of hepatitis C virus subtype 1a in Okinawa, Japan

Okinawa Island, located in Southern Japan, has a higher prevalence rate of hepatitis C virus subtype 1a (HCV-1a) infection than that in mainland Japan. Okinawa has a history of US military occupation after World War II. To elucidate the transmission history of HCV-1a in Okinawa, 26 whole-genome sequences were obtained from 29 patients during 2011-2016. Phylogenetic trees were reconstructed to identify the origin and characteristics of HCV-1a in Okinawa with epidemiological information. A phylogenetic tree based on whole-genome sequencing revealed that all of the samples were located below the US branches. Additionally, we identified one cluster comprised of 17 strains (Okinawa, n = 16; United States, n = 1). The majority of the patients in this cluster were people who inject drugs (PWID), indicating the presence of a people who inject drugs (PWID) cluster. Subsequently, Bayesian analyses were employed to reveal viral population dynamics. Intriguingly, a phylodynamic analysis uncovered a substantial increase in effective population size of HCV-1a from 1965 to 1980 and a slight increase in mid-2000, which were associated with an increase in illicit drug use in Okinawa. The estimated divergence time of the PWID cluster was 1967.6 (1964.2-1971.1). These findings suggest that HCV-1a was introduced into Okinawa from the United States in the late 1960s, coincident with the Vietnam War. Subsequently, HCV-1a might have spread among the Japanese population with the spread of injecting drug use. Our study provides an understanding of HCV transmission dynamics in Okinawa, as well as the key role of PWID in HCV transmission.

Defining HIV-1 transmission clusters based on sequence data

Understanding HIV-1 transmission dynamics is relevant to both screening and intervention strategies of HIV-1 infection. Commonly, HIV-1 transmission chains are determined based on sequence similarity assessed either directly from a sequence alignment or by inferring a phylogenetic tree. This review is aimed at both nonexperts interested in understanding and interpreting studies of HIV-1 transmission, and experts interested in finding the most appropriate cluster definition for a specific dataset and research question. We start by introducing the concepts and methodologies of how HIV-1 transmission clusters usually have been defined. We then present the results of a systematic review of 105 HIV-1 molecular epidemiology studies summarizing the most common methods and definitions in the literature. Finally, we offer our perspectives on how HIV-1 transmission clusters can be defined and provide some guidance based on examples from real life datasets.

Multiple introductions and onward transmission of HIV-1 subtype B strains in Shanghai, China

OBJECTIVE

To investigate the viral genetic evolution, spatial origins and patterns of transmission of HIV-1 subtype B in Shanghai, China.

METHODS

A total of 242 Shanghai subtype B and 1519 reference pol sequences were subjected to phylogenetic inference and genetic transmission network analyses.

RESULTS

Phylogenetic analysis revealed that subtype B strains circulating in Shanghai were genetically diverse and closely associated with viral sequence lineages in Beijing (76 of 242 [31.4%]), Central China (Henan/Hebei/Hunan/Hubei) (43 of 242 [17.8%]), Chinese Taiwan (20 of 242 [8.3%]), Japan (6 of 242 [2.5%]), and Korea (7 of 242 [2.9%]), suggesting multiple introductions into Shanghai from mainland China and Taiwan, Japan, and Korea. Interestingly, a monophyletic Shanghai lineage (SH-L) (36 of 242 [14.9%]) of HIV-1 subtype B most likely originated from an Argentine strain, transferred through Liaoning infected individuals. In-depth analyses of 195 Shanghai subtype B sequences revealed that a total of 37.9% (n = 74) sequences contributed to 35 transmission networks, whereof 33.8% (n = 25) of the sequences associated with infected individuals from other provinces.

CONCLUSIONS

Our new findings reflect the evolution complexity and transmission dynamics of HIV-1 subtype B in Shanghai, which would provide critical information for the design of effective prevention measures against HIV transmission.

Evolutionary Dynamics and Complicated Genetic Transmission Network Patterns of HIV-1 CRF01_AE among MSM in Shanghai, China

To explore the evolutionary dynamics and molecular transmission patterns of HIV-1 CRF01_AE in depth among men who have sex with men (MSM) in Shanghai, we constructed phylogenetic tree and genetic transmission networks based on 1, 152 pol sequences from MSM, 282 from other risk groups and 795 references. Phylogenetic analyses identified two distinct major CRF01_AE lineages and a Shanghai-based sub-lineage. The estimated tMRCAs for lineage 1 and 2 were 1996.0 (1992.9–1999.2) and 1997.8 (1994.3–2001.4), respectively. Of the 1, 152 MSM, 681 (59.1%) were identified as belonging to 241 separate networks. Of these 681 individuals in networks, 74.2% were linked to cases diagnosed in different years, 4.3% were linked to heterosexual women, and 0.7% were linked to persons who inject drugs. A total of 71 networks including 180 individuals diagnosed in Shanghai with the same domicile were found. Recent infection (P = 0.022) and sampling year after 2011 (P < 0.001) were significantly associated with potential transmission links among the networks. Besides, a significant transmission of viruses with drug resistant mutations at V179D/E were found in the networks. Given these findings, we propose that genetic transmission analysis is a useful tool in HIV intervention strategies to curb the spread of virus and promoting public health.

Genetic Analysis of HIV-1 in Japan: a Comprehensive Analysis of Donated Blood

In Japan, the number of human immunodeficiency virus (HIV)-1 infections remains relatively low; nevertheless, the annual incidence of HIV-1 infection has not decreased. New infections remain a great concern, and an improved understanding of epidemiological trends is critical for public health. The env C2V3 and pol sequences of HIV-1 RNA from 240 early (1996-2001) and 223 more recent (2010-2012) blood donations were used to compare the distribution of virus subtypes and to generate phylogenetic trees. Subtype B was clearly predominant in both early and more recent donations (both were 88.3%), and CRF01_AE was the second most common subtype. Phylogenetic analysis revealed a peculiar epidemiological transition. Compared to early subtype B isolates from 2 major endemic areas (Tokyo and Osaka), the more recent subtype B isolates formed fewer tight clusters in phylogenetic trees (from 8 to 2 clusters in Tokyo and 5 to zero clusters in Osaka). Furthermore, mixing of HIV-1 infections between these 2 endemic areas appear to increase. Analysis of phylogenetic trees suggested that local outbreaks have become smaller in Japan; however, intermixing of viral types between these 2 areas was more evident in the more recent samples.

Genetic diversity and transmission networks of HIV-1 strains among men having sex with men (MSM) in Lomé, Togo

Understanding the HIV epidemic in key populations is important. Today only scarce information is available on HIV-1 strains that circulate in men having sex with men (MSM) in sub-Saharan Africa. Here, we studied for the first time the genetic diversity of HIV-1 strains circulating in the MSM population in Lomé, the capital city from Togo. The overall subtype/CRF distribution in pol (protease and/or partial reverse transcriptase (RT)) among the 79 HIV-1 strains from MSM was as follows: CRF02_AG (72%, n=57), subtype G (2.5%, n=2), sub-subtype A3 (1.3%, n=1), and unique recombinant forms (URF) (24%, n=19). Among the 19 URFs four different mosaic structures were observed, annotated as URF1 to URF4. Fifteen sequences (URF1) had the same mosaic structure in pol (G/CRF02_AG) and could represent a new circulating recombinant form (CRF). Phylogenetic analysis of the RT sequences showed that there were several introductions of CRF02_AG strains in the MSM population, however half of the CRF02_AG and all URF1 strains formed a separate, well-supported cluster suggesting one major introduction of CRF02_AG in the MSM population followed by efficient transmission and emergence of a possible new CRF. At least 40% of the strains fell into recent transmission chains involving two to seven MSM. Comparison with >950 HIV-1 sequences from previous studies in Togo showed intermixing of the HIV-1 epidemics between MSM and the general population. Moreover, an HIV-1 strain from a recently HIV-1 infected male patient from Germany, fell within a cluster of HIV-1 strains from MSM from Togo, illustrating recent exchange between MSM from Africa and people from other geographic regions. With growing evidence of the importance of MSM in the dynamic of the HIV epidemic in Africa there is an urgent need for appropriate interventions to limit HIV transmission in this population group.

HIV-1 subtype B: Traces of a pandemic

Human migration is a major process that shaped the origin and dissemination of HIV. Within HIV-1, subtype B (HIV-1B) is the most disseminated variant and it is assumed to be the causative agent in approximately 11% of all cases of HIV worldwide. Phylogenetic studies have revealed that HIV-1B emerged in Kinshasa (Africa) and was introduced into the Caribbean region via Haiti in or around 1966 by human migration. After localized dispersion, the virus was brought to the United States of America via homosexual/bisexual contact around 1969. Inside USA, the incidence of HIV-1B infection increased exponentially and it became established in the population, affecting not only homosexual individuals but also heterosexual individuals and injecting drug users. Soon after, the virus was disseminated and became established in other regions, including Europe, Asia, Latin America, and Australia. Recent studies suggest that, in addition to this pandemic clade, several lineages have emerged from Haiti and reached other Caribbean and Latin American countries via short-distance dissemination. Different subtype B genetic variants have also been detected in these epidemics. Four genetic variants have been described to date: subtype B', which mainly circulates in Thailand and other Asian countries; a specific variant mainly found in Trinidad and Tobago; the GPGS variant, which is primarily detected in Korea; and the GWGR variant, which is mainly detected in Brazil. This paper reviews the evolution of HIV-1B and its impact on the human population.

The International Dimension of the U.S. HIV Transmission Network and Onward Transmission of HIV Recently Imported into the United States

The majority of HIV infections in the United States can be traced back to a single introduction in late 1960s or early 1970s. However, it remains unclear whether subsequent introductions of HIV into the United States have given rise to onward transmission. Genetic transmission networks can aid in understanding HIV transmission. We constructed a genetic distance-based transmission network using HIV-1 pol sequences reported to the U.S. National HIV Surveillance System (n = 41,539) and all publicly available non-U.S. HIV-1 pol sequences (n = 86,215). Of the 13,145 U.S. persons clustered in the network, 457 (3.5%) were genetically linked to a potential transmission partner outside the United States. For internationally connected persons residing in but born outside the United States, 61% had a connection to their country of birth or to another country that shared a language with their country of birth. Bayesian molecular clock phylogenetic analyses indicate that introduced nonsubtype B infections have resulted in onward transmission within the United States.

HIV-1 CRF01_AE and Subtype B Transmission Networks Crossover: A New AE/B Recombinant Identified in Japan

The major circulating HIV-1 strains in Japan have been subtype B (B) followed by CRF01_AE (AE) in newly diagnosed HIV/AIDS cases. These two subtypes have distinct epidemiological characteristics; B predominates in men who have sex with men, while AE is observed mostly in heterosexuals engaging in high-risk sex. However, transmission networks of these two high-risk populations appear to be crossing over and diffusing. Here we report the emergence of previously unidentified HIV-1 AE/B recombinants in Japan. We initially identified 13 cases with discordant subtyping results with AE (gag MA)/B (pol PR-RT)/AE (env C2V3) by molecular phylogenetic analysis of 1,070 cases who visited Nagoya Medical Center from 1997 to 2012. Genetic characterization of full-length sequences demonstrated that they shared an identical recombinant structure, and was designated as CRF69_01B by the Los Alamos HIV National Laboratory. By reviewing gag, pol, and env sequences collected in the Japanese Drug Resistance HIV-1 Surveillance Network, we found five other CRF69_01B probable cases from different areas in Japan, suggesting that the strain is transmitted widely throughout the country. The time of the most recent common ancestor analyses estimated that CRF69_01B emerged between 1991 and 1995, soon after AE was introduced from neighboring countries in the mid-1990s. Understanding the current epidemic strains is important for the diagnosis and treatment of HIV/AIDS, as well as for the development of globally effective HIV vaccines.

Targeting HIV Prevention Based on Molecular Epidemiology Among Deeply Sampled Subnetworks of Men Who Have Sex With Men

BACKGROUND

Molecular epidemiology can be useful in identifying clusters of human immunodeficiency virus (HIV) transmission that can be targeted for prevention.

METHODS

Regular screening of 2000 men who have sex with men (MSM) in Beijing, China, for HIV infection every 2 months identified 179 primary infections (2007-2010). HIV-1 pol sequences were obtained and used to infer the transmission network and identify transmitted drug resistance (TDR) among these individuals. We evaluated the use of clinical and network information to target prevention efforts. Prevention efficiency was calculated as the number of infections saved per number of interventions.

RESULTS

This cohort was infected with HIV-1 subtype B (28%), circulating recombinant form (CRF)_01 AE (53%), and CRF_07 BC (16%). The overall rate of TDR was low (5%), but the rate of clustering was high (64%), suggesting deep sampling of the subnetwork. Provision of a theoretically high-efficacy intervention like antiretroviral therapy to all participants had a prevention efficiency of 23%. The efficiency of targeting prevention based on lower CD4 counts (<200 cells/mL, <350 cells/mL, or <500 cells/mL) and higher viral loads (>100 000 copies/mL and >50 000 copies/mL) was between 10% and 18%. The efficiency of targeting prevention based on number of network connections was much higher (30%-42%). For example, treating the 33 participants with ≥5 connections in 2009 would have theoretically prevented 14 infections in 2010 (42% prevention efficiency).

CONCLUSIONS

Regular HIV testing of MSM in Beijing can deeply sample the local transmission subnetwork, and targeting prevention efforts based on network connectivity may be an efficient way to deliver prevention interventions.