HIV evolution and diversity in ART-treated patients

The molecular epidemiology of a dengue virus outbreak in Taiwan: population wide versus infrapopulation mutation analysis

Dengue virus (DENV) causes approximately 390 million dengue infections worldwide every year. There were 22,777 reported DENV infections in Tainan, Taiwan in 2015. In this study, we sequenced the C-prM-E genes from 45 DENV 2015 strains, and phylogenetic analysis based on C-prM-E genes revealed that all strains were classified as DENV serotype 2 Cosmopolitan genotype. Sequence analysis comparing different DENV-2 genotypes and Cosmopolitan DENV-2 sequences prior to 2015 showed a clade replacement event in the DENV-2 Cosmopolitan genotype. Additionally, a major substitution C-A314G (K73R) was found in the capsid region which may have contributed to the clade replacement event. Reverse genetics virus rgC-A314G (K73R) showed slower replication in BHK-21 and C6/36 cells compared to wildtype virus, as well as a decrease in NS1 production in BHK-21-infected cells. After a series of passaging, the C-A314G (K73R) mutation reverted to wildtype and was thus considered to be unstable. Next generation sequencing (NGS) of three sera collected from a single DENV2-infected patient at 1-, 2-, and 5-days post-admission was employed to examine the genetic diversity over-time and mutations that may work in conjunction with C-A314G (K73R). Results showed that the number of haplotypes decreased with time in the DENV-infected patient. On the fifth day after admission, two new haplotypes emerged, and a single non-synonymous NS4A-L115I mutation was identified. Therefore, we have identified a persistent mutation C-A314G (K73R) in all of the DENV-2 isolates, and during the course of an infection, a single new non-synonymous mutation in the NS4A region appears in the virus population within a single host. The C-A314G (K73R) thus may have played a role in the DENV-2 2015 outbreak while the NS4A-L115I may be advantageous during DENV infection within the host.

The cell biology of HIV-1 latency and rebound

Transcriptionally latent forms of replication-competent proviruses, present primarily in a small subset of memory CD4+ T cells, pose the primary barrier to a cure for HIV-1 infection because they are the source of the viral rebound that almost inevitably follows the interruption of antiretroviral therapy. Over the last 30 years, many of the factors essential for initiating HIV-1 transcription have been identified in studies performed using transformed cell lines, such as the Jurkat T-cell model. However, as highlighted in this review, several poorly understood mechanisms still need to be elucidated, including the molecular basis for promoter-proximal pausing of the transcribing complex and the detailed mechanism of the delivery of P-TEFb from 7SK snRNP. Furthermore, the central paradox of HIV-1 transcription remains unsolved: how are the initial rounds of transcription achieved in the absence of Tat? A critical limitation of the transformed cell models is that they do not recapitulate the transitions between active effector cells and quiescent memory T cells. Therefore, investigation of the molecular mechanisms of HIV-1 latency reversal and LRA efficacy in a proper physiological context requires the utilization of primary cell models. Recent mechanistic studies of HIV-1 transcription using latently infected cells recovered from donors and ex vivo cellular models of viral latency have demonstrated that the primary blocks to HIV-1 transcription in memory CD4+ T cells are restrictive epigenetic features at the proviral promoter, the cytoplasmic sequestration of key transcription initiation factors such as NFAT and NF-κB, and the vanishingly low expression of the cellular transcription elongation factor P-TEFb. One of the foremost schemes to eliminate the residual reservoir is to deliberately reactivate latent HIV-1 proviruses to enable clearance of persisting latently infected cells-the "Shock and Kill" strategy. For "Shock and Kill" to become efficient, effective, non-toxic latency-reversing agents (LRAs) must be discovered. Since multiple restrictions limit viral reactivation in primary cells, understanding the T-cell signaling mechanisms that are essential for stimulating P-TEFb biogenesis, initiation factor activation, and reversing the proviral epigenetic restrictions have become a prerequisite for the development of more effective LRAs.

HIV-1 envelope diversity and sensitivity to broadly neutralizing antibodies across stages of acute HIV-1 infection

We studied the relationship between viral diversity and susceptibility to broadly neutralizing antibodies (bNAbs) in longitudinal plasma and peripheral blood mononuclear cells from 89 people with HIV who initiated antiretroviral therapy (ART) during acute and early HIV-1 infection (AEHI). HIV-1 diversity and predicted bNAb susceptibility were comparable across AEHI. Diversity evolution was not observed during ART, suggesting (pro)viruses at initiation or during treatment may identify individuals with susceptible virus for bNAb interventional trials.

Potential Advantages of a Well-balanced Nutrition Regimen for People Living with Human Immunodeficiency Virus Type -1

This review underscores the important role of nutrition in enhancing the management of Human Immunodeficiency Virus type 1 (HIV-1). Highlighting the efficacy of dietary interventions, including, the importance of omega-3 fatty acids, vitamins D and B-12, and the Mediterranean diet, we delineate how these beneficial nutritional strategies can improve the effectiveness of combined antiretroviral therapy (cART), mitigate its side effects, and ameliorate metabolic disorders in people living with HIV-1 (PLWH). Our review advocates for the integration and implementation of personalized nutritional assessments into the care plan for PLWH, proposing actionable strategies for healthcare providers in HIV-1 field. Summarizing the current standing of the relevance of the nutritional and well-planned diet recommended for the PLWH and emphasizing on the future research directions, this review establishes a foundation for nutrition as a cornerstone in comprehensive HIV-1 management. Our review aims to improve patients' health outcomes and overall quality of life for PLWH.

Monocyte-derived macrophages contain persistent latent HIV reservoirs

The development of persistent cellular reservoirs of latent human immunodeficiency virus (HIV) is a critical obstacle to viral eradication since viral rebound takes place once anti-retroviral therapy (ART) is interrupted. Previous studies show that HIV persists in myeloid cells (monocytes and macrophages) in blood and tissues in virologically suppressed people with HIV (vsPWH). However, how myeloid cells contribute to the size of the HIV reservoir and what impact they have on rebound after treatment interruption remain unclear. Here we report the development of a human monocyte-derived macrophage quantitative viral outgrowth assay (MDM-QVOA) and highly sensitive T cell detection assays to confirm purity. We assess the frequency of latent HIV in monocytes using this assay in a longitudinal cohort of vsPWH (n = 10, 100% male, ART duration 5-14 yr) and find half of the participants showed latent HIV in monocytes. In some participants, these reservoirs could be detected over several years. Additionally, we assessed HIV genomes in monocytes from 30 vsPWH (27% male, ART duration 5-22 yr) utilizing a myeloid-adapted intact proviral DNA assay (IPDA) and demonstrate that intact genomes were present in 40% of the participants and higher total HIV DNA correlated with reactivatable latent reservoirs. The virus produced in the MDM-QVOA was capable of infecting bystander cells resulting in viral spread. These findings provide further evidence that myeloid cells meet the definition of a clinically relevant HIV reservoir and emphasize that myeloid reservoirs should be included in efforts towards an HIV cure.

The reservoir of latent HIV

The persistence of latent reservoir of the human immunodeficiency virus (HIV) is currently the major challenge in curing HIV infection. After HIV infects the human body, the latent HIV is unable to be recognized by the body’s immune system. Currently, the widely adopted antiretroviral therapy (ART) is also unble to eliminate it, thus hindering the progress of HIV treatment. This review discusses the existence of latent HIV vault for HIV treatment, its formation and factors affecting its formation, cell, and tissue localization, methods for detection and removing latent reservoir, to provide a comprehensive understanding of latent HIV vault, in order to assist in the future research and play a potential role in achieving HIV treatment.

Mechanistic Interplay between HIV-1 Reverse Transcriptase Enzyme Kinetics and Host SAMHD1 Protein: Viral Myeloid-Cell Tropism and Genomic Mutagenesis

Human immunodeficiency virus type 1 (HIV-1) reverse transcriptase (RT) has been the primary interest among studies on antiviral discovery, viral replication kinetics, drug resistance, and viral evolution. Following infection and entry into target cells, the HIV-1 core disassembles, and the viral RT concomitantly converts the viral RNA into double-stranded proviral DNA, which is integrated into the host genome. The successful completion of the viral life cycle highly depends on the enzymatic DNA polymerase activity of RT. Furthermore, HIV-1 RT has long been known as an error-prone DNA polymerase due to its lack of proofreading exonuclease properties. Indeed, the low fidelity of HIV-1 RT has been considered as one of the key factors in the uniquely high rate of mutagenesis of HIV-1, which leads to efficient viral escape from immune and therapeutic antiviral selective pressures. Interestingly, a series of studies on the replication kinetics of HIV-1 in non-dividing myeloid cells and myeloid specific host restriction factor, SAM domain, and HD domain-containing protein, SAMHD1, suggest that the myeloid cell tropism and high rate of mutagenesis of HIV-1 are mechanistically connected. Here, we review not only HIV-1 RT as a key antiviral target, but also potential evolutionary and mechanistic crosstalk among the unique enzymatic features of HIV-1 RT, the replication kinetics of HIV-1, cell tropism, viral genetic mutation, and host SAMHD1 protein.

HIV drug resistance in various body compartments

PURPOSE OF REVIEW

HIV drug resistance testing using blood plasma or dried blood spots forms part of international guidelines. However, as the clinical utility of assessing drug resistance in other body compartments is less well established, we review this for blood cells and samples from other body compartments.

RECENT EVIDENCE

Although clinical benefit is not clear, drug resistance testing in blood cells is often performed when patients with suppressed plasma viral loads require a treatment substitution. In patients with HIV neurocognitive disease, cerebral spinal fluid (CSF) drug resistance is rarely discordant with plasma but has nevertheless been used to guide antiretroviral drug substitutions. Cases with HIV drug resistance in genital fluids have been documented but this does not appear to indicate transmission risk when blood plasma viral loads are suppressed.

SUMMARY

Drug-resistant variants, which may be selected in tissues under conditions of variable adherence and drug penetration, appear to disseminate quickly, and become detectable in blood. This may explain why drug resistance discordance between plasma and these compartments is rarely found. Partial compartmentalization of HIV populations is well established for the CSF and the genital tract but other than blood plasma, evidence is lacking to support drug resistance testing in body compartments.

Genotypic and Phenotypic Diversity of the Replication-Competent HIV Reservoir in Treated Patients

In HIV infection, viral rebound after treatment discontinuation is considered to originate predominantly from viral genomes integrated in resting CD4⁺ T lymphocytes. Replication-competent proviral genomes represent a minority of the total HIV DNA. While the quantification of the HIV reservoir has been extensively studied, the diversity of genomes that compose the reservoir was less explored. Here, we measured the genotypic and phenotypic diversity in eight patients with different treatment histories. Between 4 and 14 (mean, 8) individual viral isolates per patient were obtained using a virus outgrowth assay, and their near-full-length genomes were sequenced. The mean pairwise distance (MPD) observed in different patients correlated with the time before undetectable viremia was achieved (r = 0.864, P = 0.0194), suggesting that the complexity of the replication-competent reservoir mirrors that present at treatment initiation. No correlation was instead observed between MPD and the duration of successful treatment (mean, 8 years; range, 2 to 21 years). For 5 of the 8 patients, genotypically identical viral isolates were observed in independent wells, suggesting clonal expansion of infected cells. Identical viruses represented between 25 and 60% of the isolates (mean, 48%). The proportion of identical viral isolates correlated with the duration of treatment (r = 0.822, P = 0.0190), suggesting progressive clonal expansion of infected cells during ART. A broader range of infectivity was also observed among isolates from patients with delayed viremia control (r = 0.79, P = 0.025). This work unveiled differences in the genotypic and phenotypic features of the replication-competent reservoir from treated patients and suggests that delaying treatment results in increased diversity of the reservoir.

IMPORTANCE In HIV-infected and effectively treated individuals, integrated proviral genomes may persist for decades. The vast majority of the genomes, however, are defective, and only the replication-competent fraction represents a threat of viral reemergence. The quantification of the reservoir has been thoroughly explored, while the diversity of the genomes has been insufficiently studied. Its characterization, however, is relevant for the design of strategies aiming the reduction of the reservoir. Here, we explored the replication-competent near-full-length HIV genomes of eight patients who experienced differences in the delay before viremia control and in treatment duration. We found that delayed effective treatment was associated with increased genetic diversity of the reservoir. The duration of treatment did not impact the diversity but was associated with higher frequency of clonally expanded sequences. Thus, early treatment initiation has the double advantage of reducing both the size and the diversity of the reservoir.

Digital Form for Assessing Dentists' Knowledge about Oral Care of People Living with HIV

Oral lesions are usually the first sign of HIV infection. The present study aimed to determine the level of the knowledge of dentists on the dental care needs of People Living with HIV (PLWH). This cross-sectional study was conducted between February and May 2021, in the Brazilian state of Pará, during which a total of 51 dentists received an anonymous digital form (Google^® Forms Platform) composed of four blocks of discursive, dichotomous, and multiple-choice questions. The questions referred to various aspects of the dental care needs of PLWH, together with data on the professional activities of the dentists. After signing the term of informed consent, the dentists were divided into six subgroups according to the time (in years) since completing their bachelor’s degree in dentistry. The data were presented as descriptive statistics and percentages, and then analyzed using the Kappa test. Most (70.6%; 36 of 51) of the dentists were female, the mean age of the dentists was 32.5 years, and a majority (80.2%) were based in the city of Belem; the mean time since graduation was 8.5 years, with 22 (43.1%) having more than 5 years of professional experience, and 31 (60.8%) having graduated from a private dental college. Just over half (51%) of the 51 dentists had completed graduate courses, and the most common dental specialty was orthodontics (19.6%). Most (74.5%) of the dentists work in the private sector, 38 (74.5%) claimed to have already provided oral care to PLWH, and 43 (84.3%) had access to specialist content on the oral care needs of PLWH. In terms of the knowledge of the dentists with regard to the oral care needs of PLWH, four of the ten diagnostic questions obtained more inadequate answers than expected, whereas the final two questions (11–45.1% and 12–31.4%) demonstrated that many of the dentists adopt unnecessary modifications in their oral care protocol for PLWH, due to a fear of contamination. Overall, our results demonstrate a frequent lack of knowledge, especially with regard to the oral healthcare needs of PLWH, which may account for many of the stigmas that persist in the dental care of this vulnerable group.

Impacts of HIV-1 Subtype Diversity on Long-Term Clinical Outcomes in Antiretroviral Therapy in Guangxi, China

BACKGROUND

Comprehensively estimating the impacts of HIV-1 subtype diversity on long-term clinical outcomes during antiretroviral therapy (ART) can help inform program recommendations.

METHODS

The HIV-1 sequence data and clinical records of 5950 patients from all 14 prefectures in Guangxi, China, during 2008-2020 were included. Evolutional trends of CD4+ T-lymphocyte count and viral load were explored, and the effects of HIV-1 subtypes on clinical outcomes were estimated by the Cox proportional hazards model. The polymorphisms involved in drug resistance mutation were analyzed.

RESULTS

Compared with patients with CRF07_BC, patients with CRF01_AE and CRF08_BC showed poor immunologic and virologic responses to antiretroviral therapy. Although the median expected time from ART initiation to virologic suppression for all patients was approximately 12 months, patients with CRF01_AE and CRF08_BC had a long time to achieve immune recovery and a short time to occur immunologic failure, compared with patients with CRF07_BC. Adjusted analysis showed that both CRF01_AE and CRF08_BC were the negative factors in immune recovery and long-term mortality. In addition, CRF08_BC was a negative factor in virologic suppression and a risk factor of virologic failure. This poor virologic response might result from the high prevalence of drug resistance mutation in CRF08_BC.

CONCLUSIONS

Compared with patients with CRF07_BC, patients with CRF01_AE could benefit more from immediate ART, and patients with CRF08_BC are more suitable for PI-based regimens. These data emphasize the importance of routine HIV-1 genotyping before ART, immediate ART, and personalized ART regimens to improve the prognosis for patients undergoing ART.

Predictors of Viral Non-Suppression among Patients Living with HIV under Dolutegravir in Bunia, Democratic Republic of Congo: A Prospective Cohort Study

The Democratic Republic of the Congo adopted the integrase inhibitor dolutegravir (DTG) as part of its preferred first-line HIV treatment regimen in 2019. This study aimed to identify predictors of viral non-suppression among HIV-infected patients under a DTG-based regimen in the context of ongoing armed conflict since 2017 in the city of Bunia in the DRC. We conducted a cohort study of 468 patients living with HIV under DTG in all health facilities in Bunia. We calculated the proportion of participants with an HIV RNA of below 50 copies per milliliter. About three in four patients (72.8%) in this cohort had a viral load (VL) of <50 copies/mL after 6–12 months. After controlling for the effect of other covariates, the likelihood of having non-suppression remained significantly lower among the 25–34 age group and self-reported naïve patients with a baseline VL of ≥50 copies/mL. The likelihood of having non-suppression remained significantly higher among those who were at advanced stages of the disease, those with abnormal serum creatinine, those with high baseline HIV viremia over 1000 copies/mL, and the Sudanese ethnic group compared to the reference groups. This study suggests that we should better evaluate adherence, especially among adolescents and economically vulnerable populations, such as the Sudanese ethnic group in the city of Bunia. This suggests that an awareness of the potential effects of DTG and tenofovir is important for providers who take care of HIV-positive patients using antiretroviral therapy (ART), especially those with abnormal serum creatinine levels before starting treatment.

New Approaches to Multi-Parametric HIV-1 Genetics Using Multiple Displacement Amplification: Determining the What, How, and Where of the HIV-1 Reservoir

Development of potential HIV-1 curative interventions requires accurate characterization of the proviral reservoir, defined as host-integrated viral DNA genomes that drive rebound of viremia upon halting ART (antiretroviral therapy). Evaluation of such interventions necessitates methods capable of pinpointing the rare, genetically intact, replication-competent proviruses within a background of defective proviruses. This evaluation can be achieved by identifying the distinct integration sites of intact proviruses within host genomes and monitoring the dynamics of these proviruses and host cell lineages over longitudinal sampling. Until recently, molecular genetic approaches at the single proviral level have been generally limited to one of a few metrics, such as proviral genome sequence/intactness, host-proviral integration site, or replication competency. New approaches, taking advantage of MDA (multiple displacement amplification) for WGA (whole genome amplification), have enabled multiparametric proviral characterization at the single-genome level, including proviral genome sequence, host-proviral integration site, and phenotypic characterization of the host cell lineage, such as CD4 memory subset and antigen specificity. In this review, we will examine the workflow of MDA-augmented molecular genetic approaches to study the HIV-1 reservoir, highlighting technical advantages and flexibility. We focus on a collection of recent studies in which investigators have used these approaches to comprehensively characterize intact and defective proviruses from donors on ART, investigate mechanisms of elite control, and define cell lineage identity and antigen specificity of infected CD4+ T cell clones. The highlighted studies exemplify how these approaches and their future iterations will be key in defining the targets and evaluating the impacts of HIV curative interventions.

Clonal Expansion of Infected CD4+ T Cells in People Living with HIV

HIV infection is not curable with current antiretroviral therapy (ART) because a small fraction of CD4+ T cells infected prior to ART initiation persists. Understanding the nature of this latent reservoir and how it is created is essential to development of potentially curative strategies. The discovery that a large fraction of the persistently infected cells in individuals on suppressive ART are members of large clones greatly changed our view of the reservoir and how it arises. Rather than being the products of infection of resting cells, as was once thought, HIV persistence is largely or entirely a consequence of infection of cells that are either expanding or are destined to expand, primarily due to antigen-driven activation. Although most of the clones carry defective proviruses, some carry intact infectious proviruses; these clones comprise the majority of the reservoir. A large majority of both the defective and the intact infectious proviruses in clones of infected cells are transcriptionally silent; however, a small fraction expresses a few copies of unspliced HIV RNA. A much smaller fraction is responsible for production of low levels of infectious virus, which can rekindle infection when ART is stopped. Further understanding of the reservoir will be needed to clarify the mechanism(s) by which provirus expression is controlled in the clones of cells that constitute the reservoir.

Characterizing the Relationship Between Neutralization Sensitivity and env Gene Diversity During ART Suppression

Although antiretroviral therapy (ART) successfully suppresses HIV-1 replication, ART-treated individuals must maintain therapy to avoid rebound from an integrated viral reservoir. Strategies to limit or clear this reservoir are urgently needed. Individuals infected for longer periods prior to ART appear to harbor more genetically diverse virus, but the roles of duration of infection and viral diversity in the humoral immune response remain to be studied. We aim to clarify a role, if any, for autologous and heterologous antibodies in multi-pronged approaches to clearing infection. To that end, we have characterized the breadths and potencies of antibody responses in individuals with varying durations of infection and HIV-1 envelope (env) gene diversity as well as the sensitivity of their inducible virus reservoir to broadly neutralizing antibodies (bNAbs). Plasma was collected from 8 well-characterized HIV-1+ males on ART with varied durations of active infection. HIV envs from reservoir-derived outgrowth viruses were amplified and single genome sequenced in order to measure genetic diversity in each participant. IgG from plasma was analyzed for binding titers against gp41 and gp120 proteins, and for neutralizing titers against a global HIV-1 reference panel as well as autologous outgrowth viruses. The sensitivity to bNAbs of these same autologous viruses was measured. Overall, we observed that greater env diversity was associated with higher neutralizing titers against the global panel and also increased resistance to certain bNAbs. Despite the presence of robust anti-HIV-1 antibody titers, we did not observe potent neutralization against autologous viruses. In fact, 3 of 8 participants harbored viruses that were completely resistant to the highest tested concentration of autologous IgG. That this lack of neutralization was observed regardless of ART duration or viral diversity suggests that the inducible reservoir harbors 'escaped' viruses (that co-evolved with autologous antibody responses), rather than proviruses archived from earlier in infection. Finally, we observed that viruses resistant to autologous neutralization remained sensitive to bNAbs, especially CD4bs and MPER bNAbs. Overall, our data suggest that the inducible reservoir is relatively resistant to autologous antibodies and that individuals with limited virus variation in the env gene, such as those who start ART early in infection, are more likely to be sensitive to bNAb treatment.

Phylogenetic and Drug-Resistance Analysis of HIV-1 Sequences From an Extensive Paediatric HIV-1 Outbreak in Larkana, Pakistan

Introduction

In April 2019, an HIV-1 outbreak among children occurred in Larkana, Pakistan, affecting more than a thousand children. It was assumed that the outbreak originated from a single source, namely a doctor at a private health facility. In this study, we performed subtype distribution, phylogenetic and drug-resistance analysis of HIV-1 sequences from 2019 outbreak in Larkana, Pakistan.

Methods

A total of 401 blood samples were collected between April–June 2019, from children infected with HIV-1 aged 0–15 years recruited into a case-control study to investigate the risk factors for HIV-1 transmission. Partial HIV-1 pol sequences were generated from 344 blood plasma samples to determine HIV-1 subtype and drug resistance mutations (DRM). Maximum-likelihood phylogenetics based on outbreak and reference sequences was used to identify transmission clusters and assess the relationship between outbreak and key population sequences between and within the determined clusters. Bayesian analysis was employed to identify the time to the most recent common recent ancestor (tMRCA) of the main Pakistani clusters.

Results

The HIV-1 circulating recombinant form (CRF) 02_AG and subtype A1 were most common among the outbreak sequences. Of the treatment-naïve participants, the two most common mutations were RT: E138A (8%) and RT: K219Q (8%). Four supported clusters within the outbreak were identified, and the median tMRCAs of the Larkana outbreak sequences were estimated to 2016 for both the CRF02_AG and the subtype A1 clusters. Furthermore, outbreak sequences exhibited no phylogenetic mixing with sequences from other high-risk groups of Pakistan.

Conclusion

The presence of multiple clusters indicated a multi-source outbreak, rather than a single source outbreak from a single health practitioner as previously suggested. The multiple introductions were likely a consequence of ongoing transmission within the high-risk groups of Larkana, and it is possible that the so-called Larkana strain was introduced into the general population through poor infection prevention control practices in healthcare settings. The study highlights the need to scale up HIV-1 prevention programmes among key population groups and improving infection prevention control in Pakistan.

Intrapatient Development of Multi-Class Drug Resistance in an Individual Infected with HIV-1 CRF01_AE

The rapid expansion of access to antiretroviral therapy (ART) has led to the emergence of multi-class drug resistance (MDR) in people living with HIV (PLWH). However, the viral evolutionary dynamics of the development of MDR has not been well documented. For this study, plasma and peripheral blood mononuclear cells (PBMC) were longitudinally collected at different time points from a PLWH who suffered several periods of ART failure. Next generation sequencing (NGS) was used to analyze the distribution and percent of drug resistance mutations in PBMC and plasma. The results showed the gradual replacement of the wild type protease and integrase genotype by protease inhibitors (PI) and integrase strand transfer inhibitor (INSTI) drug resistant mutations when patient’s ART regimen was changed – driving the increase of genetic variability in HIV DNA. Sampling for this study was initiated after the patient was first diagnosed with ART failure, five years after ART treatment was first initiated. By that time, mutants resistant to the reverse transcriptase inhibitor nevirapine (NVP) had already replaced almost 100% of wild type. After the introduction of the protease inhibitor lopinavir/ritonavir (LPV/r) to the patient’s ART, resistant protease inhibitor (PI) mutants developed slowly. After one month, none were found in PMBC DNA; after sixteen months, less than 20% were mutants; and after three years (two months prior to the patient’s death) PI mutants were still under 50%. However, integrase strand transfer inhibitor (INSTI) mutations evolved much more quickly, replacing approximately 75% of the wild genotype in HIV DNA one year after addition of the integrase inhibitor raltegravir to the patient’s ART, and almost 100% after two years. In summary, our dataset provides the first analysis of the distribution and percent of drug resistance mutations in PBMC and plasma during the development of a four-class drug resistant HIV-1 CRF01_AE virion. The study also showed that months before drug resistant mutants could be found in plasma, NGS identified them in HIV DNA, demonstrating that this can be a very effective tool for early detection of the development of drug resistance.

Mathematical modeling of N-803 treatment in SIV-infected non-human primates

Immunomodulatory drugs could contribute to a functional cure for Human Immunodeficiency Virus (HIV). Interleukin-15 (IL-15) promotes expansion and activation of CD8⁺ T cell and natural killer (NK) cell populations. In one study, an IL-15 superagonist, N-803, suppressed Simian Immunodeficiency Virus (SIV) in non-human primates (NHPs) who had received prior SIV vaccination. However, viral suppression attenuated with continued N-803 treatment, partially returning after long treatment interruption. While there is evidence of concurrent drug tolerance, immune regulation, and viral escape, the relative contributions of these mechanisms to the observed viral dynamics have not been quantified. Here, we utilize mathematical models of N-803 treatment in SIV-infected macaques to estimate contributions of these three key mechanisms to treatment outcomes: 1) drug tolerance, 2) immune regulation, and 3) viral escape. We calibrated our model to viral and lymphocyte responses from the above-mentioned NHP study. Our models track CD8⁺ T cell and NK cell populations with N-803-dependent proliferation and activation, as well as viral dynamics in response to these immune cell populations. We compared mathematical models with different combinations of the three key mechanisms based on Akaike Information Criterion and important qualitative features of the NHP data. Two minimal models were capable of reproducing the observed SIV response to N-803. In both models, immune regulation strongly reduced cytotoxic cell activation to enable viral rebound. Either long-term drug tolerance or viral escape (or some combination thereof) could account for changes to viral dynamics across long breaks in N-803 treatment. Theoretical explorations with the models showed that less-frequent N-803 dosing and concurrent immune regulation blockade (e.g. PD-L1 inhibition) may improve N-803 efficacy. However, N-803 may need to be combined with other immune therapies to countermand viral escape from the CD8⁺ T cell response. Our mechanistic model will inform such therapy design and guide future studies.

Immune therapy may be a critical component in the functional cure for Human Immunodeficiency Virus (HIV). N-803 is an immunotherapeutic drug that activates antigen-specific CD8⁺ T cells of the immune system. These CD8⁺ T cells eliminate HIV-infected cells in order to limit the spread of infection in the body. In one study, N-803 reduced plasma viremia in macaques that were infected with Simian Immunodeficiency Virus, an analog of HIV. Here, we used mathematical models to analyze the data from this study to better understand the effects of N-803 therapy on the immune system. Our models indicated that inhibitory signals may be reversing the stimulatory effect of N-803. Results also suggested the possibilities that tolerance to N-803 could build up within the CD8⁺ T cells themselves and that the treatment may be selecting for virus strains that are not targeted by CD8⁺ T cells. Our models predict that N-803 therapy may be made more effective if the time between doses is increased or if inhibitory signals are blocked by an additional drug. Also, N-803 may need to be combined with other immune therapies to target virus that would otherwise evade CD8⁺ T cells.

HIV-1 Persistence in Children during Suppressive ART

There is a growing number of perinatally HIV-1-infected children worldwide who must maintain life-long ART. In early life, HIV-1 infection is established in an immunologically inexperienced environment in which maternal ART and immune dynamics during pregnancy play a role in reservoir establishment. Children that initiated early antiretroviral therapy (ART) and maintained long-term suppression of viremia have smaller and less diverse HIV reservoirs than adults, although their proviral landscape during ART is reported to be similar to that of adults. The ability of these early infected cells to persist long-term through clonal expansion poses a major barrier to finding a cure. Furthermore, the effects of life-long HIV persistence and ART are yet to be understood, but growing evidence suggests that these individuals are at an increased risk for developing non-AIDS-related comorbidities, which underscores the need for an HIV cure.

Towards a Functional Cure of HIV-1: Insight Into the Chromatin Landscape of the Provirus

Despite potent combination antiretroviral therapy, HIV-1 infection persists due to irreversible integration of the virus in long-living cells of the immune system. The main focus of HIV-1 cure strategies has been on HIV-1 eradication, yet without great success so far. Therefore, HIV-1 remission or a functional cure, whereby the virus is silenced rather than eradicated, is considered as an alternative strategy. Elite controllers, individuals who spontaneously control HIV-1, may point us the way toward a functional HIV-1 cure. In order to achieve such a cure, a profound understanding of the mechanisms controlling HIV-1 expression and silencing is needed. In recent years, evidence has grown that the site of integration as well as the chromatin landscape surrounding the integration site affects the transcriptional state of the provirus. Still, at present, the impact of integration site selection on the establishment and maintenance of the HIV-1 reservoirs remains poorly understood. The discovery of LEDGF/p75 as a binding partner of HIV-1 integrase has led to a better understanding of integration site selection. LEDGF/p75 is one of the important determinants of integration site selection and targets integration toward active genes. In this review, we will provide an overview of the most important determinants of integration site selection. Secondly, we will discuss the chromatin landscape at the integration site and its implications on HIV-1 gene expression and silencing. Finally, we will discuss how interventions that affect integration site selection or modifications of the chromatin could yield a functional cure of HIV-1 infection.

Dynamics of HIV-1 quasispecies diversity of participants on long-term antiretroviral therapy based on intrahost single-nucleotide variations

OBJECTIVES

Human immunodeficiency virus (HIV) quasispecies diversity presents a large barrier to the eradication of HIV. The aim of this study was to investigate intrahost HIV quasispecies diversity and evolutionary patterns underpinning the mechanisms of viral pathogenesis during antiretroviral therapy (ART).

METHODS

Forty-five participants with HIV-1 infection were enrolled in a follow-up cohort for >84 months in 2004, and received a lamivudine-based first-line ART regimen. Blood samples were collected every 6 months to measure viral load and CD4⁺ cell count. Ultra-deep sequencing and phylogenetic analysis were used to characterize the dynamics governing quasispecies diversity of HIV-1 circulating between plasma RNA and cellular DNA of participants with treatment failure (TF, n = 20) or virologic suppression (VS, n = 25).

RESULTS

Analysis of the distribution of intrahost single-nucleotide variations (iSNVs) and their mutated allele frequencies revealed that approximately 65% of the quasispecies co-occurred in plasma HIV RNA and cellular DNA either before or after ART. The number and frequency of iSNVs are more representative of intrahost HIV diversity, and have better generalizability than phylogenetic inference by measurement of phylogenetic associations. Furthermore, drug-resistance-associated mutations (DRAMs) accumulated to high levels, dramatically increasing the DRAM-to-total-mutation ratio for TF patients. Linear regression analysis revealed that emergent mutations accumulated faster in TF patients compared with VS patients, at a rate of 0.02 mutations/day/kb.

CONCLUSIONS

Based on iSNV analysis, the results demonstrate the dynamics of intrahost HIV quasispecies diversity in patients on ART, and provide a novel insight into the persistence of HIV and development of DRAMs.

Epidemiological and Molecular Characteristics of HIV-1 Infection in a Sample of Men Who Have Sex With Men in Brazil: Phylogeography of Major Subtype B and F1 Transmission Clusters

This study describes human immunodeficiency virus 1 (HIV-1) prevalence, associated factors, viral genetic diversity, transmitted drug resistance (TDR), and acquired drug resistance mutations (DRM) among a population of 522 men who have sex with men (MSM) recruited by the respondent-driven sampling (RDS) method, in Goiânia city, the capital of the State of Goiás, Central-Western Brazil. All serum samples were tested using a four-generation enzyme-linked immunosorbent assay (ELISA), and reactive samples were confirmed by immunoblotting. Plasma RNA or proviral DNA was extracted, and partial polymerase (pol) gene including the protease/reverse transcriptase (PR/RT) region was amplified and sequenced. HIV-1 subtypes were identified by phylogenetic inference and by bootscan analysis. The time and location of the ancestral strains that originated the transmission clusters were estimated by a Bayesian phylogeographic approach. TDR and DRM were identified using the Stanford databases. Overall, HIV-1 prevalence was 17.6% (95% CI: 12.6–23.5). Self-declared black skin color, receptive anal intercourse, sex with drug user partner, and history of sexually transmitted infections were factors associated with HIV-1 infection. Of 105 HIV-1-positive samples, 78 (74.3%) were sequenced and subtyped as B (65.4%), F1 (20.5%), C (3.8%), and BF1 (10.3%). Most HIV-1 subtype B sequences (67%; 34 out of 51) branched within 12 monophyletic clusters of variable sizes, which probably arose in the State of Goiás between the 1980s and 2010s. Most subtype F1 sequences (n = 14, 88%) branched in a single monophyletic cluster that probably arose in Goiás around the late 1990s. Among 78 samples sequenced, three were from patients under antiretroviral therapy (ART); two presented DRM. Among 75 ART-naïve patients, TDR was identified in 13 (17.3%; CI 95%: 9.6–27.8). Resistance mutations to non-nucleoside reverse transcriptase inhibitors (NNRTI) predominated (14.7%), followed by nucleoside reverse transcriptase inhibitor (NRTI) mutations (5.3%) and protease inhibitor (PI) mutations (1.3%). This study shows a high prevalence of HIV-1 associated with sexual risk behaviors, high rate of TDR, and high genetic diversity driven by the local expansion of different subtype B and F1 strains. These findings can contribute to the understanding about the dissemination and epidemiological and molecular characteristics of HIV-1 among the population of MSM living away from the epicenter of epidemics in Brazil.

Embracing diversity: how can broadly neutralizing antibodies effectively target a diverse HIV-1 reservoir?

Genetic diversity in the latent proviral reservoir of HIV-1 infected individuals poses a challenge to cure strategies. It has become increasingly evident that diversity increases proportionally with length of active infection, and that functional and/or sterilizing cure strategies will need to overcome this obstacle in individuals who initiated antiretroviral therapy (ART) during chronic infection. Analyzing the results of analytic treatment interruption (ATI) has allowed for the evaluation of such therapeutic strategies in HIV+ individuals. Strategies to overcome the genetic diversity of the HIV-1 reservoir include antibody combinations, pre-screening individuals for bNAb sensitivity, focusing on low-diversity individuals as well as targeting host proteins.

No HIV-1 molecular evolution on long-term antiretroviral therapy initiated during primary HIV-1 infection

OBJECTIVE

Most studies about HIV-1 molecular evolution have shown the lack of viral evolution on effective antiretroviral therapy (ART), although controversial results have been documented. We therefore aimed to look for evidence of HIV-1 evolution in patients who initiated ART at the time of primary HIV-1 infection (PHI).

DESIGN

We included retrospectively 20 patients diagnosed at PHI, treated at the time of acute infection and with subsequent effective long-term suppressive ART (HIV viral load <20 copies/ml during at least 5 years without any blips).

METHODS

Longitudinal blood samples were deep sequenced using Illumina Miseq. Drug-resistance-associated mutations were retained at 2% cutoff and interpreted using the latest Agence Nationale de Recherches sur le Sida et les Hépatites Virales resistance algorithm. Viral evolution was established when temporal structure on maximum-likelihood phylogenetic tree and significant change over time of HIV-1 genetic diversity measured as the average pairwise distance was observed.

RESULTS

Emergences or disappearances of drug-resistance-associated mutations were detected in the blood cells during follow-up despite sustained virological control. In all patients, tree topologies showed an absence of segregation between sequences and blood viral populations from all time-points were intermingled. Comparison of the average pairwise distance showed the absence of significant viral diversity at the time of primary infection and afterwards during 5 years of full virological control under ART.

CONCLUSION

Despite a slight variation of minority resistance-associated mutation variants, there was no clear evidence of viral evolution during a prolonged period of time in this population of highly controlled adult patients treated at time of PHI.

A Stronger Transcription Regulatory Circuit of HIV-1C Drives the Rapid Establishment of Latency with Implications for the Direct Involvement of Tat

The magnitude of transcription factor binding site variation emerging in HIV-1 subtype C (HIV-1C), especially the addition of NF-κB motifs by sequence duplication, makes the examination of transcriptional silence challenging. How can HIV-1 establish and maintain latency despite having a strong long terminal repeat (LTR)? We constructed panels of subgenomic reporter viral vectors with varying copy numbers of NF-κB motifs (0 to 4 copies) and examined the profile of latency establishment in Jurkat cells. Surprisingly, we found that the stronger the viral promoter, the faster the latency establishment. Importantly, at the time of commitment to latency and subsequent points, Tat levels in the cell were not limiting. Using highly sensitive strategies, we demonstrate the presence of Tat in the latent cell, recruited to the latent LTR. Our data allude, for the first time, to Tat establishing a negative feedback loop during the late phases of viral infection, leading to the rapid silencing of the viral promoter.IMPORTANCE Over the past 10 to 15 years, HIV-1 subtype C (HIV-1C) has been evolving rapidly toward gaining stronger transcriptional activity by sequence duplication of major transcription factor binding sites. The duplication of NF-κB motifs is unique and exclusive to HIV-1C, a property not shared with any of the other eight HIV-1 genetic families. What mechanism(s) does HIV-1C employ to establish and maintain transcriptional silence despite the presence of a strong promoter and concomitant strong, positive transcriptional feedback is the primary question that we attempted to address in the present manuscript. The role that Tat plays in latency reversal is well established. Our work with the most common HIV-1 subtype, HIV-1C, offers crucial leads toward Tat possessing a dual role in serving as both a transcriptional activator and repressor at different phases of viral infection of the cell. The leads that we offer through the present work have significant implications for HIV-1 cure research.

Structural Biology of HIV Integrase Strand Transfer Inhibitors

Integrase (IN) strand transfer inhibitors (INSTIs) are recent compounds in the antiretroviral arsenal used against HIV. INSTIs work by blocking retroviral integration; an essential step in the viral lifecycle that is catalyzed by the virally encoded IN protein within a nucleoprotein assembly called an intasome. Recent structures of lentiviral intasomes from simian immunodeficiency virus (SIV) and HIV have clarified the INSTI binding modes within the intasome active sites and helped elucidate an important mechanism of viral resistance. The structures provide an accurate depiction of interactions of intasomes and INSTIs to be leveraged for structure-based drug design. Here, we review these recent structural findings and contrast with earlier studies on prototype foamy virus intasomes. We also present and discuss examples of the latest chemical compounds that show promising inhibitory potential as INSTI candidates.

Modeling the role of macrophages in HIV persistence during antiretroviral therapy

HIV preferentially infects activated CD4+ T cells. Current antiretroviral therapy cannot eradicate the virus. Viral infection of other cells such as macrophages may contribute to viral persistence during antiretroviral therapy. In addition to cell-free virus infection, macrophages can also get infected when engulfing infected CD4+ T cells as innate immune sentinels. How macrophages affect the dynamics of HIV infection remains unclear. In this paper, we develop an HIV model that includes the infection of CD4+ T cells and macrophages via cell-free virus infection and cell-to-cell viral transmission. We derive the basic reproduction number and obtain the local and global stability of the steady states. Sensitivity and viral dynamics simulations show that even when the infection of CD4+ T cells is completely blocked by therapy, virus can still persist and the steady-state viral load is not sensitive to the change of treatment efficacy. Analysis of the relative contributions to viral replication shows that cell-free virus infection leads to the majority of macrophage infection. Viral transmission from infected CD4+ T cells to macrophages during engulfment accounts for a small fraction of the macrophage infection and has a negligible effect on the total viral production. These results suggest that macrophage infection can be a source contributing to HIV persistence during suppressive therapy. Improving drug efficacies in heterogeneous target cells is crucial for achieving HIV eradication in infected individuals.

Compartmentalization and Clonal Amplification of HIV-1 in the Male Genital Tract Characterized Using Next-Generation Sequencing

Compartmentalization of HIV-1 between the systemic circulation and the male genital tract may have a substantial impact on which viruses are available for sexual transmission to new hosts. We studied compartmentalization and clonal amplification of HIV-1 populations between the blood and the genital tract from 10 antiretroviral-naive men using Illumina MiSeq with a PrimerID approach. We found evidence of some degree of compartmentalization in every study participant, unlike previous studies, which collectively showed that only ∼50% of analyzed individuals exhibited compartmentalization of HIV-1 lineages between the male genital tract (MGT) and blood. Using down-sampling simulations, we determined that this disparity can be explained by differences in sampling depth in that had we sequenced to a lower depth, we would also have found compartmentalization in only ∼50% of the study participants. For most study participants, phylogenetic trees were rooted in blood, suggesting that the male genital tract reservoir is seeded by incoming variants from the blood. Clonal amplification was observed in all study participants and was a characteristic of both blood and semen viral populations. We also show evidence for independent viral replication in the genital tract in the individual with the most severely compartmentalized HIV-1 populations. The degree of clonal amplification was not obviously associated with the extent of compartmentalization. We were also unable to detect any association between history of sexually transmitted infections and level of HIV-1 compartmentalization. Overall, our findings contribute to a better understanding of the dynamics that affect the composition of virus populations that are available for transmission.IMPORTANCE Within an individual living with HIV-1, factors that restrict the movement of HIV-1 between different compartments-such as between the blood and the male genital tract-could strongly influence which viruses reach sites in the body from which they can be transmitted. Using deep sequencing, we found strong evidence of restricted HIV-1 movements between the blood and genital tract in all 10 men that we studied. We additionally found that neither the degree to which particular genetic variants of HIV-1 proliferate (in blood or genital tract) nor an individual's history of sexually transmitted infections detectably influenced the degree to which virus movements were restricted between the blood and genital tract. Last, we show evidence that viral replication gave rise to a large clonal amplification in semen in a donor with highly compartmentalized HIV-1 populations, raising the possibility that differential selection of HIV-1 variants in the genital tract may occur.

Differences in HIV Markers between Infected Individuals Treated with Different ART Regimens: Implications for the Persistence of Viral Reservoirs

In adherent individuals, antiretroviral therapy (ART) suppresses HIV replication, restores immune function, and prevents the development of AIDS. However, ART is not curative and has to be followed lifelong. Persistence of viral reservoirs forms the major obstacle to an HIV cure. HIV latent reservoirs persist primarily by cell longevity and proliferation, but replenishment by residual virus replication despite ART has been proposed as another potential mechanism of HIV persistence. It is a matter of debate whether different ART regimens are equally potent in suppressing HIV replication. Here, we summarized the current knowledge on the role of ART regimens in HIV persistence, focusing on differences in residual plasma viremia and other virological markers of the HIV reservoir between infected individuals treated with combination ART composed of different antiretroviral drug classes.

Impact of Suboptimal APOBEC3G Neutralization on the Emergence of HIV Drug Resistance in Humanized Mice

HIV diversification facilitates immune escape and complicates antiretroviral therapy. In this study, we take advantage of a humanized-mouse model to probe the contribution of APOBEC3 mutagenesis to viral evolution. Humanized mice were infected with isogenic HIV molecular clones (HIV-WT, HIV-45G, and HIV-ΔSLQ) that differ in their abilities to counteract APOBEC3G (A3G). Infected mice remained naive or were treated with the reverse transcriptase (RT) inhibitor lamivudine (3TC). Viremia, emergence of drug-resistant variants, and quasispecies diversification in the plasma compartment were determined throughout infection. While both HIV-WT and HIV-45G achieved robust infection, over time, HIV-45G replication was significantly reduced compared to that of HIV-WT in the absence of 3TC treatment. In contrast, treatment responses differed significantly between HIV-45G- and HIV-WT-infected mice. Antiretroviral treatment failed in 91% of HIV-45G-infected mice, while only 36% of HIV-WT-infected mice displayed a similar negative outcome. Emergence of 3TC-resistant variants and nucleotide diversity were determined by analyzing 155,462 single HIV reverse transcriptase gene (RT) and 6,985 vif sequences from 33 mice. Prior to treatment, variants with genotypic 3TC resistance (RT-M184I/V) were detected at low levels in over a third of all the animals. Upon treatment, the composition of the plasma quasispecies rapidly changed, leading to a majority of circulating viral variants encoding RT-184I. Interestingly, increased viral diversity prior to treatment initiation correlated with higher plasma viremia in HIV-45G-infected animals, but not in HIV-WT-infected animals. Taken together, HIV variants with suboptimal anti-A3G activity were attenuated in the absence of selection but displayed a fitness advantage in the presence of antiretroviral treatment.IMPORTANCE Both viral (e.g., RT) and host (e.g., A3G) factors can contribute to HIV sequence diversity. This study shows that suboptimal anti-A3G activity shapes viral fitness and drives viral evolution in the plasma compartment in humanized mice.

Dynamics of HIV DNA reservoir seeding in a cohort of superinfected Kenyan women

A reservoir of HIV-infected cells that persists despite suppressive antiretroviral therapy (ART) is the source of viral rebound upon ART cessation and the major barrier to a cure. Understanding reservoir seeding dynamics will help identify the best timing for HIV cure strategies. Here we characterize reservoir seeding using longitudinal samples from before and after ART initiation in individuals who sequentially became infected with genetically distinct HIV variants (superinfected). We previously identified cases of superinfection in a cohort of Kenyan women, and the dates of both initial infection and superinfection were determined. Six women, superinfected 0.2–5.2 years after initial infection, were subsequently treated with ART 5.4–18.0 years after initial infection. We performed next-generation sequencing of HIV gag and env RNA from plasma collected during acute infection as well as every ~2 years thereafter until ART initiation, and of HIV DNA from PBMCs collected 0.9–4.8 years after viral suppression on ART. We assessed phylogenetic relationships between HIV DNA reservoir sequences and longitudinal plasma RNA sequences prior to ART, to determine proportions of initial and superinfecting variants in the reservoir. The proportions of initial and superinfection lineage variants present in the HIV DNA reservoir were most similar to the proportions present in HIV RNA immediately prior to ART initiation. Phylogenetic analysis confirmed that the majority of HIV DNA reservoir sequences had the smallest pairwise distance to RNA sequences from timepoints closest to ART initiation. Our data suggest that while reservoir cells are created throughout pre-ART infection, the majority of HIV-infected cells that persist during ART entered the reservoir near the time of ART initiation. We estimate the half-life of pre-ART DNA reservoir sequences to be ~25 months, which is shorter than estimated reservoir decay rates during suppressive ART, implying continual decay and reseeding of the reservoir up to the point of ART initiation.

During HIV infection, a reservoir of long-lived latently infected cells is established that persists during antiretroviral therapy (ART) and is the source of virus replication after treatment cessation. A better understanding of when viruses enter the HIV reservoir (reservoir seeding) will aid efforts to target these long-lived HIV infected cells during their establishment. We studied women infected at two different times with two genetically distinct HIV strains (called superinfection), and assessed the genetic relationship between sequences of the HIV strains that circulated throughout infection (pre-ART HIV RNA sequences) and the HIV strains that persisted in reservoir cells (HIV DNA sequences during ART). We estimated when HIV DNA sequences entered the reservoir by identifying the time the most genetically related HIV RNA sequence was detected. In most cases we observed that viruses in the reservoir included both the initial and superinfecting lineages, suggesting reservoir seeding occurs throughout HIV infection. However, the majority of HIV sequences entered the reservoir near the time of ART initiation, suggesting that novel strategies that aim to reduce reservoir size should focus on times immediately prior to ART.

New Frontiers in Measuring and Characterizing the HIV Reservoir

A cure for HIV infection remains elusive due to the persistence of replication-competent HIV proviral DNA during suppressive antiretroviral therapy (ART). With the exception of rare elite or post-treatment controllers of viremia, withdrawal of ART invariably results in the rebound of viremia and progression of HIV disease. A thorough understanding of the reservoir is necessary to develop new strategies in order to reduce or eliminate the reservoir. However, there is significant heterogeneity in the sequence composition, genomic location, stability, and expression of the HIV reservoir both within and across individuals, and a majority of proviral sequences are replication-defective. These factors, and the low frequency of persistently infected cells in individuals on suppressive ART, make understanding the reservoir and its response to experimental reservoir reduction interventions challenging. Here, we review the characteristics of the HIV reservoir, state-of-the-art assays to measure and characterize the reservoir, and how these assays can be applied to accurately detect reductions in reservoir during efforts to develop a cure for HIV infection. In particular, we highlight recent advances in the development of direct measures of provirus, including intact proviral DNA assays and full-length HIV DNA sequencing with integration site analysis. We also focus on novel techniques to quantitate persistent and inducible HIV, including RNA sequencing and RNA/gag protein staining techniques, as well as modified viral outgrowth methods that seek to improve upon throughput, sensitivity and dynamic range.

Combined HIV-1 sequence and integration site analysis informs viral dynamics and allows reconstruction of replicating viral ancestors

Understanding HIV-1 persistence despite antiretroviral therapy (ART) is of paramount importance. Both single-genome sequencing (SGS) and integration site analysis (ISA) provide useful information regarding the structure of persistent HIV DNA populations; however, until recently, there was no way to link integration sites to their cognate proviral sequences. Here, we used multiple-displacement amplification (MDA) of cellular DNA diluted to a proviral endpoint to obtain full-length proviral sequences and their corresponding sites of integration. We applied this method to lymph node and peripheral blood mononuclear cells from 5 ART-treated donors to determine whether groups of identical subgenomic sequences in the 2 compartments are the result of clonal expansion of infected cells or a viral genetic bottleneck. We found that identical proviral sequences can result from both cellular expansion and viral genetic bottlenecks occurring prior to ART initiation and following ART failure. We identified an expanded T cell clone carrying an intact provirus that matched a variant previously detected by viral outgrowth assays and expanded clones with wild-type and drug-resistant defective proviruses. We also found 2 clones from 1 donor that carried identical proviruses except for nonoverlapping deletions, from which we could infer the sequence of the intact parental virus. Thus, MDA-SGS can be used for "viral reconstruction" to better understand intrapatient HIV-1 evolution and to determine the clonality and structure of proviruses within expanded clones, including those with drug-resistant mutations. Importantly, we demonstrate that identical sequences observed by standard SGS are not always sufficient to establish proviral clonality.

Persistent HIV-1 Viremia on Antiretroviral Therapy: Measurement and Mechanisms

HIV-1 viremia persists at low-levels despite clinically effective antiretroviral therapy (ART). Here we review new methods to quantify and characterize persistent viremia at the single genome level, and discuss the mechanisms of persistence including clonal expansion of infected cells and tissue origins of viremia. A deeper understanding of how viremia persists on ART is critically important to the design of therapies to eliminate viremia and achieve a functional cure for HIV-1.

Potential impact of the antirheumatic agent auranofin on proviral HIV-1 DNA in individuals under intensified antiretroviral therapy: Results from a randomised clinical trial

Antiretroviral therapy (ART) is typically composed of a combination of three antiretroviral drugs and is the treatment of choice for people with human immunodeficiency virus type 1/acquired immune deficiency syndrome (HIV-1/AIDS). However, it is unable to impact on viral reservoirs, which harbour latent HIV-1 genomes that are able to reignite the infection upon treatment suspension. The aim of this study was to provide an estimate of the safety of the disease-modifying antirheumatic agent auranofin and its impact on the HIV-1 reservoir in humans under intensified ART. For this purpose, an interim analysis was conducted of three of the six arms of the NCT02961829 clinical trial (five patients each) with: no intervention, i.e. continuation of first-line ART; intensified ART (ART + dolutegravir and maraviroc); and intensified ART plus auranofin. Auranofin treatment was found to be well tolerated. No major adverse events were detected apart from a transient decrease in CD4⁺ T-cell counts at Weeks 8 and 12. Auranofin decreased total viral DNA in peripheral blood mononuclear cells compared with ART-only regimens at Week 20 (P = 0.036) and induced a decrease in integrated viral DNA as quantified by Alu PCR. Despite the limited number of patient-derived sequences available in this study, phylogenetic analyses of nef sequences support the idea that auranofin may impact on the viral reservoir. [ClinicalTrials.gov ID: NCT02961829].

Determinants of HIV-1 reservoir size and long-term dynamics during suppressive ART

The HIV-1 reservoir is the major hurdle to a cure. We here evaluate viral and host characteristics associated with reservoir size and long-term dynamics in 1,057 individuals on suppressive antiretroviral therapy for a median of 5.4 years. At the population level, the reservoir decreases with diminishing differences over time, but increases in 26.6% of individuals. Viral blips and low-level viremia are significantly associated with slower reservoir decay. Initiation of ART within the first year of infection, pretreatment viral load, and ethnicity affect reservoir size, but less so long-term dynamics. Viral blips and low-level viremia are thus relevant for reservoir and cure studies.

Here, Bachmann et al. provide data on long-term dynamics of the HIV-1 reservoir in 1,057 individuals on suppressive antiretroviral therapy and show that in 26.6% of individuals the reservoir increases. Viral blips and low-level viremia are significantly associated with a slower reservoir decay.

PCR Amplification Strategies Towards Full-length HIV-1 Genome Sequencing

The advent of next-generation sequencing has enabled greater resolution of viral diversity and improved feasibility of full viral genome sequencing allowing routine HIV-1 full genome sequencing in both research and diagnostic settings. Regardless of the sequencing platform selected, successful PCR amplification of the HIV-1 genome is essential for sequencing template preparation. As such, full HIV-1 genome amplification is a crucial step in dictating the successful and reliable sequencing downstream. Here we reviewed existing PCR protocols leading to HIV-1 full genome sequencing. In addition to the discussion on basic considerations on relevant PCR design, the advantages as well as the pitfalls of the published protocols were reviewed.

Determinants of the efficacy of HIV latency-reversing agents and implications for drug and treatment design

HIV eradication studies have focused on developing latency-reversing agents (LRAs). However, it is not understood how the rate of latent reservoir reduction is affected by different steps in the process of latency reversal. Furthermore, as current LRAs are host-directed, LRA treatment is likely to be intermittent to avoid host toxicities. Few careful studies of the serial effects of pulsatile LRA treatment have yet been done. This lack of clarity makes it difficult to evaluate the efficacy of candidate LRAs or predict long-term treatment outcomes. We constructed a mathematical model that describes the dynamics of latently infected cells under LRA treatment. Model analysis showed that, in addition to increasing the immune recognition and clearance of infected cells, the duration of HIV antigen expression (i.e., the period of vulnerability) plays an important role in determining the efficacy of LRAs, especially if effective clearance is achieved. Patients may benefit from pulsatile LRA exposures compared with continuous LRA exposures if the period of vulnerability is long and the clearance rate is high, both in the presence and absence of an LRA. Overall, the model framework serves as a useful tool to evaluate the efficacy and the rational design of LRAs and combination strategies.

Modeling HIV persistence and cure studies

PURPOSE OF REVIEW

To provide a summary of the contributions of mathematical modeling to understanding of HIV persistence during antiretroviral therapy.

RECENT FINDINGS

Although HIV persistence during therapy could be caused by continual viral replication or slow-decaying latent infection, most evidence points toward the latter mechanism. The latent reservoir is maintained by a balance of cell death, proliferation, and reactivation, and new methods to estimate the relative contributions of these rates use a wide range of experimental data. This has led to new quantitative predictions about the potential benefit of therapies such as latency-reversing agents or antiproliferative drugs.

SUMMARY

Results of these mathematical modeling studies can be used to design and interpret future trials of new therapies targeting HIV persistence.

Insight into treatment of HIV infection from viral dynamics models

The odds of living a long and healthy life with HIV infection have dramatically improved with the advent of combination antiretroviral therapy. Along with the early development and clinical trials of these drugs, and new field of research emerged called viral dynamics, which uses mathematical models to interpret and predict the time-course of viral levels during infection and how they are altered by treatment. In this review, we summarize the contributions that virus dynamics models have made to understanding the pathophysiology of infection and to designing effective therapies. This includes studies of the multiphasic decay of viral load when antiretroviral therapy is given, the evolution of drug resistance, the long-term persistence latently infected cells, and the rebound of viremia when drugs are stopped. We additionally discuss new work applying viral dynamics models to new classes of investigational treatment for HIV, including latency-reversing agents and immunotherapy.

Critical challenges and emerging opportunities in hepatitis C virus research in an era of potent antiviral therapy: Considerations for scientists and funding agencies

The development and clinical implementation of direct-acting antivirals (DAAs) has revolutionized the treatment of chronic hepatitis C. Infection with any hepatitis C virus (HCV) genotype can now be eliminated in more than 95% of patients with short courses of all-oral, well-tolerated drugs, even in those with advanced liver disease and liver transplant recipients. DAAs have proven so successful that some now consider HCV amenable to eradication, and continued research on the virus of little remaining medical relevance. However, given 400,000 HCV-related deaths annually important challenges remain, including identifying those who are infected, providing access to treatment and reducing its costs. Moreover, HCV infection rarely induces sterilizing immunity, and those who have been cured with DAAs remain at risk for reinfection. Thus, it is very unlikely that global eradication and elimination of the cancer risk associated with HCV infection can be achieved without a vaccine, yet research in that direction receives little attention. Further, over the past two decades HCV research has spearheaded numerous fundamental discoveries in the fields of molecular and cell biology, immunology and microbiology. It will continue to do so, given the unique opportunities afforded by the reagents and knowledge base that have been generated in the development and clinical application of DAAs. Considering these critical challenges and new opportunities, we conclude that funding for HCV research must be sustained.