Molecular Characterization of HIV-1 Minority Subtypes in Hong Kong: A Recent Epidemic of CRF07_BC among the Men who have Sex with Men Population

AUTO-TUNE: SELECTING THE DISTANCE THRESHOLD FOR INFERRING HIV TRANSMISSION CLUSTERS

Molecular surveillance of viral pathogens and inference of transmission networks from genomic data play an increasingly important role in public health efforts, especially for HIV-1. For many methods, the genetic distance threshold used to connect sequences in the transmission network is a key parameter informing the properties of inferred networks. Using a distance threshold that is too high can result in a network with many spurious links, making it difficult to interpret. Conversely, a distance threshold that is too low can result in a network with too few links, which may not capture key insights into clusters of public health concern. Published research using the HIV-TRACE software package frequently uses the default threshold of 0.015 substitutions/site for HIV pol gene sequences, but in many cases, investigators heuristically select other threshold parameters to better capture the underlying dynamics of the epidemic they are studying. Here, we present a general heuristic scoring approach for tuning a distance threshold adaptively, which seeks to prevent the formation of giant clusters. We prioritize the ratio of the sizes of the largest and the second largest cluster, maximizing the number of clusters present in the network. We apply our scoring heuristic to outbreaks with different characteristics, such as regional or temporal variability, and demonstrate the utility of using the scoring mechanism's suggested distance threshold to identify clusters exhibiting risk factors that would have otherwise been more difficult to identify. For example, while we found that a 0.015 substitutions/site distance threshold is typical for US-like epidemics, recent outbreaks like the CRF07_BC subtype among men who have sex with men (MSM) in China have been found to have a lower optimal threshold of 0.005 to better capture the transition from injected drug use (IDU) to MSM as the primary risk factor. Alternatively, in communities surrounding Lake Victoria in Uganda, where there has been sustained hetero-sexual transmission for many years, we found that a larger distance threshold is necessary to capture a more risk factor-diverse population with sparse sampling over a longer period of time. Such identification may allow for more informed intervention action by respective public health officials.

Enhanced Cross-Reactive and Polyfunctional Effector-Memory T Cell Responses by ICVAX-a Human PD1-Based Bivalent HIV-1 Gag-p41 Mosaic DNA Vaccine

Vaccine-induced protective T cell immunity is necessary for HIV-1 functional cure. We previously reported that rhesus PD1-Gag-based DNA vaccination sustained simian-human immunodeficiency virus (SHIV) suppression by inducing effector-memory CD8⁺ T cells. Here, we investigated a human PD1-Gag-based DNA vaccine, namely, ICVAX, for clinical translation. PD1-based dendritic cell targeting and mosaic antigenic designs were combined to generate the ICVAX by fusing the human soluble PD1 domain with a bivalent HIV-1 Gag-p41 mosaic antigen. The mosaic antigen was cross-reactive with patients infected with B, CRF07/08_BC, and CRF01_AE variants. In mice, ICVAX elicited stronger, broader, and more polyfunctional T cell responses than mosaic Gag-p41 alone, and suppressed EcoHIV infection more efficiently. In macaques, ICVAX elicited polyfunctional effector-memory T cell responses that targeted multiple nonoverlapping epitopes of the Gag-p41 antigen. Furthermore, ICVAX manufactured following good manufacturing practices proved potent immunogenicity in macaques after biannual homologous vaccination, warranting clinical evaluation of ICVAX as an immunotherapy against HIV-1.

IMPORTANCE This study presents that ICVAX, a PD1-based DNA vaccine against HIV-1, could induce broad and polyfunctional T cell responses against different HIV-1 subtypes. ICVAX encodes a recombinant antigen consisting of the human soluble PD1 domain fused with two mosaic Gag-p41 antigens. The mosaic antigens cover more than 500 HIV-1 strains circulating in China including the subtypes B/B’, CRF01_AE, and CRF07/08_BC. In mice, ICVAX elicited stronger, broader, and more polyfunctional T cell responses, with better EcoHIV suppression than the nontargeting mosaic Gag-p41 DNA vaccine. Moreover, both lab-generated and GMP-grade ICVAX also elicited strong polyfunctional effector-memory T cell responses in rhesus macaques with good immunogenicity against multiple nonoverlapping epitopes of the Gag-p41 antigen. This study therefore highlights the great potential to translate the PD1-based DNA vaccine approach into clinical use, and opens up new avenues for alternative HIV-1 vaccine design for HIV-1 preventive and functional cure.

Epidemiological and phylogenetic analysis for non-B subtypes of human immunodeficiency virus type 1 in Busan, Korea

Recent data on non-B subtypes’ epidemiology among patients infected with human immunodeficiency virus-1 (HIV-1) in Korea are lacking. We aimed to assess the changing trends in the epidemiology of non-B subtypes of HIV-1 in Korea using phyloepidemiological analyses. We analyzed the demographic records and sequencing data obtained from genotypic drug resistance tests between 2005 and 2019 from 517 patients infected with HIV attending a tertiary care hospital in Busan, Korea. Subtyping and phylogenetic analyses with reference sequences were performed. Additionally, transmission clusters were identified via maximum-likelihood trees. Non-B subtypes accounted for 21.3% of the 517 sequences. CRF01_AE (52.7%) was the most common non-B subtype, followed by CRF02_AG (16.4%), A1 (11.8%), and C (5.5%). The prevalence of non-B subtypes decreased from 36.4 to 13.4% by 2009, while it increased to 27.4% between 2015 and 2019. Among patients with non-B subtypes, the proportion of overseas sailors decreased from 66.7 to 7.5%; contrarily, the proportion of men-who-have-sex-with-men (MSM) increased from 0 to 46.9% over the study period. We identified 8 transmission clusters involving non-B subtypes, with sizes ranging from 2 to 4 patients, including 3 clusters containing MSM. Our results highlight the changes in the epidemiological trends of non-B subtypes of HIV-1 in Korea.

HIV-1 genetic diversity and transmitted drug resistance among newly diagnosed HIV-1 individuals in Jiangmen, China

Jiangmen is one of the Guangdong-Hong Kong-Macao Greater Bay Areas with frequent commercial intercourse, which is responsible for human immunodeficiency virus type 1 (HIV-1) rapid circulation and genetic evolution for recent years. As a novel HIV-1 second-generation recombinant was previously reported in Jiangmen but the systematic molecular epidemiological investigation was still unknown. A retrospective study on HIV-1 genotypic characteristics and the emergence of transmitted drug resistance in this region was necessary. A total of 224 newly diagnosed HIV-positive cases were randomly selected in Jiangmen City of Guangdong Province between 2018 and 2019. The partial gag (1080 bp), pol (840 bp), and env (460 bp) genes were amplified using nested polymerase chain reaction followed by sequencing. The phylogenetic and recombination analysis as well as HIV-1 drug resistance were performed to surveillance. Sexual transmission was determined to be the major risk factor in Jiangmen. Phylogenetic analysis detected the genotypic distribution as follows: CRF01_AE (36.65%,70 of 191), CRF07_BC (32.46%, 62 of 191), CRF08_BC (4.71%, 9 of 191), CRF55_01B (5.24%, 10 of 191), CRF59_01B (3.14%, 6 of 191), subtype B (4.71%, 9 of 191), subtype C (1.05%, 2 of 191) as well as unique recombinant forms (12.04%, 23 of 191) consisted of seven recombinant patterns, which originated from multiple regions of China. Low-level prevalence of Surveillance Drug Resistance Mutations (2.1%) were predicted but drug-resistant mutations showed at a high level (15.4%) especially mutations in RT gene at position 179 were found to be the most frequent in the therapy-naïve population. Our study highlighted the critical importance of monitoring the emerge of recombinant strains among newly diagnosed HIV-1 individuals along with drug resistance regularly to prevent multi-channel introduction and breakout of new HIV strains.

The evolutionary and transmission characteristic of HIV-1 CRF07_BC in Nanjing, Jiangsu

To understand the epidemiology, evolutionary and transmission characteristics of HIV-1 CRF07_BC in Nanjing, China. One hundred and fifty-nine patients with HIV-1 CRF07_BC were recruited. DNA sequencing, phylogenetic analysis, and molecular transmission cluster analysis were conducted to determine the molecular epidemiology and evolutionary characteristics. Of these HIV-1-infected patients, 95.6% were male, and men who sex with men (76.7%) were the main transmission route. Only 34.0% of these cases were born in Nanjing, and most of them (64.8%) reported having multiple sex partners in the last 6 months. The maximum likelihood phylogenetic analyses of HIV-1 CRF07_BC revealed two lineages. Overall, 67.3% of Nanjing sequences were connected to at least one other individual distributed in 11 clusters, and the average degree was 21.2 with range (1-178). The clustered patients were more likely to be male. The time to a most recent common ancestor for the early HIV-1 CRF07_BC circulating in Nanjing was estimated to be 1998.71[1997.36-2001.07]. The mean estimated evolutionary rate for the epidemic cluster was slightly lower at 2.38[2.12-2.65]  ×  10-3 per site per year with the relaxed exponential clock model. HIV-1 CRF07_BC was transmitted into Nanjing more than 20 years ago from Yunnan and has become one of the most predominant subtypes with a higher evolutionary rate than before.