Coreceptor Tropism Research Articles

SHIVA - a web application for drug resistance and tropism testing in HIV.

BackgroundDrug resistance testing is mandatory in antiretroviral therapy in human immunodeficiency virus (HIV) infected patients for successful treatment. The emergence of resistances against antiretroviral agents remains the major obstacle in inhibition of viral replication and thus to control infection. Due to the high mutation rate the virus is able to adapt rapidly under drug pressure leading to the evolution of resistant variants and finally to therapy failure.ResultsWe developed a web service for drug resistance prediction of commonly used drugs in antiretroviral therapy, i.e., protease inhibitors (PIs), reverse transcriptase inhibitors (NRTIs and NNRTIs), and integrase inhibitors (INIs), but also for the novel drug class of maturation inhibitors. Furthermore, co-receptor tropism (CCR5 or CXCR4) can be predicted as well, which is essential for treatment with entry inhibitors, such as Maraviroc. Currently, SHIVA provides 24 prediction models for several drug classes. SHIVA can be used with single RNA/DNA or amino acid sequences, but also with large amounts of next-generation sequencing data and allows prediction of a user specified selection of drugs simultaneously. Prediction results are provided as clinical reports which are sent via email to the user.ConclusionsSHIVA represents a novel high performing alternative for hitherto developed drug resistance testing approaches able to process data derived from next-generation sequencing technologies. SHIVA is publicly available via a user-friendly web interface.

Tyrosine-sulfated V2 peptides inhibit HIV-1 infection via coreceptor mimicry

Tyrosine sulfation is a post-translational modification that facilitates protein-protein interaction. Two sulfated tyrosines (Tys173 and Tys177) were recently identified within the second variable (V2) loop of the major HIV-1 envelope glycoprotein, gp120, and shown to contribute to stabilizing the intramolecular interaction between V2 and the third variable (V3) loop. Here, we report that tyrosine-sulfated peptides derived from V2 act as structural and functional mimics of the CCR5 N-terminus and potently block HIV-1 infection. Nuclear magnetic and surface plasmon resonance analyses indicate that a tyrosine-sulfated V2 peptide (pV2α-Tys) adopts a CCR5-like helical conformation and directly interacts with gp120 in a CD4-dependent fashion, competing with a CCR5 N-terminal peptide. Sulfated V2 mimics, but not their non-sulfated counterparts, inhibit HIV-1 entry and fusion by preventing coreceptor utilization, with the highly conserved C-terminal sulfotyrosine, Tys177, playing a dominant role. Unlike CCR5 N-terminal peptides, V2 mimics inhibit a broad range of HIV-1 strains irrespective of their coreceptor tropism, highlighting the overall structural conservation of the coreceptor-binding site in gp120. These results document the use of receptor mimicry by a retrovirus to occlude a key neutralization target site and provide leads for the design of therapeutic strategies against HIV-1.

Deep Sequencing of the HIV-1 env Gene Reveals Discrete X4 Lineages and Linkage Disequilibrium between X4 and R5 Viruses in the V1/V2 and V3 Variable Regions

HIV-1 requires the CD4 receptor and a coreceptor (CCR5 [R5 phenotype] or CXCR4 [X4 phenotype]) to enter cells. Coreceptor tropism can be assessed by either phenotypic or genotypic analysis, the latter using bioinformatics algorithms to predict tropism based on the env V3 sequence. We used the Primer ID sequencing strategy with the MiSeq sequencing platform to reveal the structure of viral populations in the V1/V2 and C2/V3 regions of the HIV-1 env gene in 30 late-stage and 6 early-stage subjects. We also used endpoint dilution PCR followed by cloning of env genes to create pseudotyped virus to explore the link between genotypic predictions and phenotypic assessment of coreceptor usage. We found out that the most stringently sequence-based calls of X4 variants (Geno2Pheno false-positive rate [FPR] of ≤2%) formed distinct lineages within the viral population, and these were detected in 24 of 30 late-stage samples (80%), which was significantly higher than what has been seen previously by using other approaches. Non-X4 lineages were not skewed toward lower FPR scores in X4-containing populations. Phenotypic assays showed that variants with an intermediate FPR (2 to 20%) could be either X4/dual-tropic or R5 variants, although the X4 variants made up only about 25% of the lineages with an FPR of <10%, and these variants carried a distinctive sequence change. Phylogenetic analysis of both the V1/V2 and C2/V3 regions showed evidence of recombination within but very little recombination between the X4 and R5 lineages, suggesting that these populations are genetically isolated. Primer ID sequencing provides a novel approach to study genetic structures of viral populations. X4 variants may be more prevalent than previously reported when assessed by using next-generation sequencing (NGS) and with a greater depth of sampling than single-genome amplification (SGA). Phylogenetic analysis to identify lineages of sequences with intermediate FPR values may provide additional information for accurately predicting X4 variants by using V3 sequences. Limited recombination occurs between X4 and R5 lineages, suggesting that X4 and R5 variants are genetically isolated and may be replicating in different cell types or that X4/R5 recombinants have reduced fitness.

Phenotypic Coreceptor Tropism in Perinatally HIV-infected Youth Failing Antiretroviral Therapy.

Perinatally HIV-infected (PHIV) children and youth are often heavily treatment-experienced, with resultant antiretroviral resistance and limited treatment options. For those with virologic failure (VF), new agents such as CCR5 (R5) antagonists may be useful; however, reports of R5 antagonist susceptibility in children have mostly relied on genotypic testing, which may not accurately reflect the phenotypic tropism of the viral populations. We characterized phenotypic coreceptor usage among PHIV children and youth with VF on antiretroviral treatment to identify predictors of CXCR4 (X4) tropism which preclude R5 antagonist use. Plasma samples with >1000 HIV RNA copies/mL were obtained from 73 PHIV antiretroviral treatment-treated children and youth (age 9-21 years) enrolled in the multicenter Pediatric HIV/AIDS Cohort Study. Samples were analyzed using the Trofile phenotypic assay. Multiple logistic regression was performed to identify factors associated with detectable X4 tropism. Tropism results were obtained for 59 (81%) of the 73 children and youth; 32 (54%) had X4-tropism. Persistent viremia (≥80% of HIV RNA measurements >400 copies/mL) was associated with detectable X4 tropism (adjusted odds ratio: 6.6, 95% confidence interval: 1.4, 31.4), while longer cumulative nucleoside reverse transcriptase inhibitor use was associated with lower risk of X4 tropism (adjusted odds ratio: 0.6, 95% confidence interval: 0.5, 0.9). Using a phenotypic assay, >50% of PHIV children and youth with VF had X4 tropism, similar to that in experienced adults, and higher than the 30% reported for children using genotypic assays. Persistent viremia and shorter nucleoside reverse transcriptase inhibitor exposure are associated with X4-tropism in children and youth and may help target phenotypic testing to those most likely to benefit from R5 antagonist.

HIV coreceptor tropism determination and mutational pattern identification.

In the early stages of infection, Human Immunodeficiency Virus Type 1 (HIV-1) generally selects CCR5 as the primary coreceptor for entering the host cell. As infection progresses, the virus evolves and may exhibit a coreceptor-switch to CXCR4. Accurate determination coreceptor usage and identification key mutational patterns associated tropism switch are essential for selection of appropriate therapies and understanding mechanism of coreceptor change. We developed a classifier composed of two coreceptor-specific weight matrices (CMs) based on a full-scale dataset. For this classifier, we found an AUC of 0.97, an accuracy of 95.21% and an MCC of 0.885 (sensitivity 92.92%; specificity 95.54%) in a ten-fold cross-validation, outperforming all other methods on an independent dataset (13% higher MCC value than geno2pheno and 15% higher MCC value than PSSM). A web server (http://spg.med.tsinghua.edu.cn/CM.html) based on our classifier was provided. Patterns of genetic mutations that occur along with coreceptor transitions were further identified based on the score of each sequence. Six pairs of one-AA mutational patterns and three pairs of two-AA mutational patterns were identified to associate with increasing propensity for X4 tropism. These mutational patterns offered new insights into the mechanism of coreceptor switch and aided in monitoring coreceptor switch.

Statistical correlation of nonconservative substitutions of HIV gp41 variable amino acid residues with the R5X4 HIV-1 phenotype.

BackgroundThe interaction of the envelope glycoprotein of HIV-1 (gp120/gp41) with coreceptor molecules has important implications for specific cellular targeting and pathogenesis. Experimental and theoretical evidences have shown a role for gp41 in coreceptor tropism, although there is no consensus about the positions involved. Here we analyze the association of physicochemical properties of gp41 amino acid residues with viral tropism (X4, R5, and R5X4) using a large set of HIV-1 sequences. Under the assumption that conserved regions define the complex structural features essential for protein function, we focused our search only on amino acids in the gp41 variable regions.MethodsGp41 amino acid sequences of 2823 HIV-1 strains from all clades with known coreceptor tropism were retrieved from Los Alamos HIV Database. Consensus sequences were constructed for homologous sequences (those obtained from the same patient and having the same tropism) in order to avoid bias due to sequence overrepresentation, and the variability (entropy) per site was determined. Comparisons of hydropathy index (HI) and charge (Q) of amino acid residues at highly variable positions between coreceptor groups were performed using two non-parametrical tests and Benjamini-Hochberg correction. Pearson’s correlation analysis was performed to determine covariance of HI and Q values.ResultsCalculation of variability per site rendered 58 highly variable amino acid positions. Of these, statistical analysis rendered significantly different HI or Q only for the R5 vs. R5X4 comparison at twelve positions: 535, 602, 619, 636, 640, 641, 658, 662, 667, 723, 756 and 841. The largest differences in particular amino acid frequencies between coreceptor groups were found at 619, 636, 640, 641, 662, 723 and 756. A hydrophobic tendency of residues 619, 640, 641, 723 and 756, along with a hydrophilic/charged tendency at residues 636 and 662 was observed in R5X4 with respect to R5 sequences. HI of position 640 covariated with that of 602, 619, 636, 662, and 756.ConclusionsVariability and significant correlations of physicochemical properties with viral phenotype suggest that substitutions at residues in the loop (602 and 619), the HR2 (636, 640, 641, 662), and the C-terminal tail (723, 756) of gp41 may contribute to phenotype of R5X4 strains.Electronic supplementary materialThe online version of this article (doi:10.1186/s12985-016-0486-6) contains supplementary material, which is available to authorized users.

HIV coreceptor tropism among patients with newly diagnosed infection

Introduction: Coreceptor tropism is the ability of human immunodeficiency virus (HIV) to use CCR5 or CXCR4 coreceptor to enter the host cell. Tropism depends on the structure of the surface glycoprotein, involved in binding molecules to receptor and coreceptor. Viruses that CCR5use are named R5, viruses that CXCR4 use are X4-tropic, and dual/mixed (DM) viruses use either of the two. During early stages of HIV infection,R5 strains are usually present and with the progression of HIV disease, frequency of X4 occurs. Aim: The aim of the study was to analyze the coreceptor tropism in newly diagnosed HIV infected patients. Material and methods: The study group included 26 patients with newly diagnosed HIV infection, in the hospital care from 2010 to 2012 at the Clinic for Infectious and Tropical diseases of the Clinical Center of Serbia. Upon RNA isolation from plasma, PCR amplification and DNA sequencing of the V3 loop of the env gene were performed. The sequences were used for prediction of the coreceptor tropism, using the Geno2pheno bioinformatics algorithms. Results: R5 and X4 tropism were detected in 21/26 (81%) and 5/26 (19%) patients, respectively. Five out of twenty-six patients (19.2%) were in the C3 clinical stadium of the disease, and all of them were infected with R5-tropic virus. Fourteen out of twenty-five patients (56%) were late presenters of HIV infection, where 12 (86%) of them were infected with R5-tropic virus. Conclusion: Our results imply that the majority of HIV strains in patients, with newly diagnosed infection in Serbia, are characterized by R5 tropism. However, the prevalence of X4 strains is not negligible, indicating late presentation of newly diagnosed patients, but also possibly implying increased virulence of the circulating strains. Considering that CCR5 antagonists would not be effective in 19% of studied patients, the prediction of coreceptor tropism is undoubtedly very important.

Co-Receptor Tropism Determined by Genotypic Assay in HIV-1 Circulating in Cuba

Introduction: R5-tropic viruses predominated at the time of initial HIV-1 infection and a switch to X4-tropic occurs in about 50% of patients in late-stage disease. Objective: To associate different variants of Cuban HIV-1 with the co-receptor use, and the implication for the use of co-receptor inhibitors. Methodology: Viral HIV-1 subtype was determined in 42 Cuban individuals using COMET V.2, Rega subtyping toolV.3 algorithms and phylogenetic analysis. Co-receptor tropism was predicted using the geno2pheno [co-receptor] algorithm. Additionally, all V3 loop HIV-1 Cuban sequences deposited previously at Los Alamos database were also analyzed for comparison of subtype and co-receptor tropism. Results: The most frequent subtypes detected were CRF20–23–24_BG (35.7%), subtypes B (33.3%) and CRF19_ cpx (14.3%) when pol and V3 regions were analyzed. Overall, 61.9% of the samples were R5 viruses and 14.3% were X4. Viruses CRF19_cpx were more often R5X4/X4 (5/6 samples, p=0.009) or X4 strains (3/6 samples, p=0.019). The additional analysis of 359 Cuban env sequences demonstrated that only 29.3% were X4 viruses. Interestingly, 43.6% of the CRF19_cpx were R5X4/X4 viruses, confirming the previous association (p=0.011). Characteristic amino acids in the V3 loop (V/T12, R13, Q18, V19, G22) were identified at higher frequencies in CRF19_cpx viruses than in subtype B (p<0.0001). Conclusion: CRF19_cpx is a genetic form with high proportion of X4-tropic viruses. This supports the increased pathogenicity of CRF19_cpx, potentially leading to rapid disease progression. The high frequency of X4 tropism in CRF19_cpx infected patients would imply that CCR5 antagonists could be ineffective in most of these patients.

F-109 Antigenicity of the human immunodeficiency virus envelope on virions in solution by fluorescence correlation spectroscopy

The envelope glycoproteins on HIV particles are structurally heterogeneous, making it difficult to equate antigenicity with neutralization sensitivity. Efforts to address this question typically employ immobilized reagents and indirect measures of antibody interactions, which can produce inexact antigenicity profiles. Towards this, we applied a single molecule based approach using fluorescence correlation spectroscopy (FCS) that uses fluctuations in fluorescent signals to measure diffusion and reaction kinetics of fluorescently-labeled anti-envelope monoclonal antibodies (MAbs) as they attach to virions. Our method allows monitoring antibody-virion binding interaction with all reactants continuously in solution. FCS binding profiles of anti-envelope antibodies were determined using different virus types. Anti-gp120 MAbs against the 2G12 or b12 epitopes marking functional envelope structures potently neutralized CCR5-tropic JRFL and BaL pseudotyped viruses and exhibited efficient virion binding in solution. MAbs against various CD4-induced (CD4i) epitopes considered hidden on functional envelope structures exhibited limited binding to these pseudoviruses and were not neutralizing. Anti- gp41 MAb 2F5 neutralized both pseudoviruses despite limited virion binding. Overall our experimental data suggest that virion antigenicity in solution is not the only factor that might determine neutralization sensitivity. A variety of mechanisms may converge to produce the overall neutralizing profile of a given HIV variant, depending on variables such as envelope genotype, coreceptor tropism, and virus production method.

SAT-430 - Influence of HIV-1 Co-Receptor Tropism on Liver Fibrosis in HIV-Infected Patients

SAT-430 - Influence of HIV-1 Co-Receptor Tropism on Liver Fibrosis in HIV-Infected Patients

Characteristics and spread to the native population of HIV-1 non-B subtypes in two European countries with high migration rate.

BackgroundNon-B subtypes account for at least 50 % of HIV-1 infections diagnosed in Belgium and Luxembourg. They are considered to be acquired through heterosexual contacts and infect primarily individuals of foreign origin. Information on the extent to which non-B subtypes spread to the local population is incomplete.MethodsPol and env gene sequences were collected from 410 non-subtype B infections. Profound subtyping was performed using 5 subtyping tools and sequences of both pol and env. Demographic information, disease markers (viral load, CD4 count) and viral characteristics (co-receptor tropism) were compared between subtypes. Maximum likelihood phylogenetic trees were constructed and examined for clustering.ResultsThe majority of non-B infections were diagnosed in patients originating from Africa (55.8 %), individuals born in Western Europe represented 30.5 %. Heterosexual transmission was the most frequently reported transmission route (79.9 %), MSM transmission accounted for 12.2 % and was significantly more frequently reported for Western Europeans (25.7 % versus 4.3 % for individuals originating from other regions; p < 0.001). Subtypes A and C and the circulating recombinant forms CRF01_AE and CRF02_AG were the most represented and were included in the comparative analysis. Native Western Europeans were underrepresented for subtype A (14.5 %) and overrepresented for CRF01_AE (38.6 %). The frequency of MSM transmission was the highest for CRF01_AE (18.2 %) and the lowest for subtype A (0 %). No differences in age, gender, viral load or CD4 count were observed. Prevalence of CXCR4-use differed between subtypes but largely depended on the tropism prediction algorithm applied. Indications for novel intersubtype recombinants were found in 20 patients (6.3 %). Phylogenetic analysis revealed only few and small clusters of local transmission but could document one cluster of CRF02_AG transmission among Belgian MSM.ConclusionsThe extent to which non-B subtypes spread in the native Belgian-Luxembourg population is higher than expected, with 30.5 % of the non-B infections diagnosed in native Western Europeans. These infections resulted from hetero- as well as homosexual transmission. Introduction of non-B variants in the local high at risk population of MSM may lead to new sub-epidemics and/or increased genetic variability and is an evolution that needs to be closely monitored.

HIV-1 co-receptor tropism and disease progression in children and young adults with perinatally acquired HIV-1 infection. The HICCUP Study

ObjectivesRetrospective analysis of evolution of HIV tropism and association with disease progression in perinatal HIV-1 infection (PaHIV). MethodologyEligible patients with PaHIV were grouped as slow, rapid or long-term non-progressors (LTNP). The V3 region of gp120 was sequenced from stored plasma samples and tropism determined by geno2pheno algorithm (FPR 5.75%). Logistic regression with generalised estimating equations assessed factors associated with R5 virus. Time to tropism change was assessed using standard survival methods. ResultsAt baseline (n=48) median age was 12 years (IQR 9.3–14.8), 52% were female, 79% were Black African, 96% were non-B subtypes and 81% (39/48) had R5-using virus. Median follow-up was 7.7 years (308.6 person-years), with a median of five (range 1–14) samples per subject (total 252). Analysing all samples, R5 virus was associated with higher current CD4 cell count (median 520 cells/mm3 R5 vs 202 for X4, P=0.0005), LTNP (35% vs 11%, P=0.05), non-Black ethnicity (74% vs 89%, P=0.05) and female gender (55% vs 28%, P=0.005). Twelve of 38 (31%) with R5 virus at baseline switched to X4/dual-using virus, with an estimated 5-year risk of switch of 24.4% (95% CI 9.7–39.2%) predicted by lower current CD4 cell count (unadjusted HR 0.62/50 cells higher, 95% CI 0.47–0.81, P=0.0006). Eleven of 19 (58%) with X4/dual-using virus subsequently had R5 virus at one or more time points. ConclusionMaraviroc was a treatment option for 81% at 12 years, falling to 56% at 18 years, with lower CD4 cell count predictive of co-receptor switching. Paediatric studies of CCR5 antagonists should be expedited to ensure they are an early treatment option before tropism switching occurs.

HIV co-receptor tropism prediction remains stable over time in treatment-naïve patients.

HIV co-receptor tropism determination is essential before prescribing the CCR5 antagonist maraviroc. British HIV Association guidelines suggest tropism testing may remain valid for only 90 days in antiretroviral-naïve patients. We aimed to determine the accuracy of this figure. Tropism was assessed in 26 antiretroviral-naïve patients with ongoing viral replication, sampled yearly from first clinic visit. The V3 region of HIV-1 was sequenced in triplicate, then tropism predicted using the Geno2Pheno system. Baseline tropism prediction remained valid for a median of 52 months (range 7-81). For 19/26 individuals baseline tropism remained unchanged throughout a median of 54 months follow-up; 18 R5 tropic and 1 X4 tropic. In seven patients (27%) baseline tropism switched at least once (range 1-4 switches) during follow-up; however, their baseline tropism prediction remained valid for a median of 45 months. Co-receptor tropism in treatment-naïve patients with ongoing viral replication appears highly stable over time, suggesting that baseline genotypic tropism prediction may be valid for a longer duration in patients delaying ART initiation. In this study, baseline tropism prediction remained valid for a median of 52 months, suggesting current guidelines recommending repeat testing after 90 days may be excessively conservative in their assessment of tropism stability.

Frequency of coreceptor tropism in PBMC samples from HIV-1 recently infected blood donors by massively parallel sequencing: the REDS II study

BackgroundThe interaction of HIV-1 and target cells involves sequential binding of the viral gp120 Env protein to the CD4 receptor and a chemokine co-receptor (either CCR5 or CXCR4). CCR5 antagonists have proved to be an effective salvage therapy in patients with CCR5 using variants (R5) but not with variants capable of using CXCR4 (×4) phenotype. Thus, it is critically important to determine cellular tropism of a country’s circulating HIV strains to guide a management decision to improve treatment outcome. In this study, we report the prevalence of R5 and ×4 HIV strains in 45 proviral DNA massively parallel sequencing “MPS” data from recently infected Brazilian blood donors.MethodsThe MPS data encompassing the tropism-related V3 loop region of the HIV‐1 env gene was extracted from our recently published HIV-1 genomes sequenced by a paired-end protocol (Illumina). HIV‐1 tropism was inferred using Geno2pheno[coreceptor] algorithm (3.5 % false-positive rate). V3 net charge and 11/25 rules were also used for coreceptor prediction.ResultsAmong the 45 samples for which tropism were determined, 39 were exclusively R5 variants, 5 ×4 variants, and one dual-tropic or mixed (D/M) populations of R5 and ×4 viruses, corresponding to 86.7, 11.1 and 2.2 %, respectively. Thus, the proportion of all blood donors that harbor CXCR4-using virus was 13.3 % including individuals with D/M-tropic viruses.ConclusionsThe presence of CCR5-tropic variants in more than 85 % of our cohort of antiretroviral-naïve blood donors with recent HIV-1 infection indicates a potential benefit of CCR5 antagonists as a therapeutic option in Brazil. Therefore, determination of viral co-receptor tropism is an important diagnostic prerequisite.

685. Efficient Targeted Gene Modification in Primary Human Hematopoietic Cells Using Co-Delivery of Nuclease mRNA and AAV Donors

Current clinical HIV treatment strategies applying gene-editing technologies to disrupt the HIV co-receptor CCR5 via nuclease delivery are limited by inefficient bi-allelic disruption and the lack of a combinatorial approach to control HIV infection. The ability to target additional factors conferring HIV resistance to the CCR5 locus with efficient bi-allelic disruption has the potential to translate to improved clinical outcomes. Here we demonstrate a novel method in which RNA-based nuclease expression is paired with AAV-mediated delivery of a homologous gene-targeting donor template to achieve highly efficient targeted recombination in primary human T-cells. This method consistently achieves an average of 60% rates of homology directed recombination into the CCR5 locus in T-cells (>20 experiments with multiple donors); with up to 90% of the gene-modified population exhibiting bi-allelic modification. T-cells modified with this protocol maintain a diverse repertoire and engraft in immune deficient, NOD/SCID/gc-/- (NSG) mice as efficiently as unmodified control T-cells. Using this method, we have integrated chimeric antigen receptors (CARs) into the CCR5 locus; and show that the resulting “targeted CAR” or tCAR T-cells exhibit anti-tumor activities indistinguishable from those generated using lentiviral random integration. Alternatively, we introduced the C46 HIV fusion inhibitor by targeted recombination generating T cell populations with very high-rates of bi-allelic CCR5 disruption paired with protection from HIV with CXCR4 co-receptor tropism. Next, as proof of principle, we utilized the CCR5 site as a ‘safe harbor’ locus for targeted gene addition of the human Wiskott-Aldrich syndrome (WAS) gene. Finally, this novel protocol was also successfully applied to adult human mobilized CD34+ cells, resulting in 10-20% homologous gene targeting, the first such report in adult human CD34+ cells at the CCR5 locus. Our results demonstrate that high-efficiency targeted integration is feasible in primary human cells, and highlight the potential of gene editing technologies to engineer CAR T-cells or other T cell products with myriad novel functional properties.

Determination of HIV-1 coreceptor tropism using proviral DNA in women before and after viral suppression.

BackgroundAn HIV-1 tropism test is recommended prior to CCR5 antagonist administration to exclude patients harboring non-R5 virus from treatment with this class of antiretrovirals. HIV-1 tropism determination based on proviral DNA (pvDNA) may be useful in individuals with plasma viral RNA suppression. We developed a genotypic tropism assay for pvDNA and assessed its performance in a retrospective analysis of samples collected longitudinally.ResultsWe randomly selected paired plasma/PBMC samples from the Women’s Interagency HIV Study with plasma viral load ≥5,000 cp/mL at time 1 (T1), undetectable viral load maintained for ≥1 year and CD4+ >200 cells/μL at time 2 (T2). pvDNA was isolated from cryopreserved PBMCs. Sequences were analyzed in triplicate from 49/50 women, with tropism assigned using the geno2pheno (g2p) algorithm. The median time between T1 and T2 was 4.1 years. CXCR4-using virus was detected in 24% of the RNA samples and 33% of the pvDNA samples at T1, compared to 37% of the pvDNA samples at T2. Concordance between plasma RNA and pvDNA tropism was 88% at T1 and 80% at T2. The g2p scores for RNA (T1) vs DNA (T1, T2) were strongly correlated (Spearman rho: 0.85 (T1); 0.78 (T2)). In women with evidence of tropism switch at T2 (either R5 to non-R5 or non-R5 to R5), there was a correlation between change in tropism and time. Mean pvDNA viral load decreased by 0.4 log10 copies/106 cells between T1 and T2 (p < 0.0001), but this decrease was not significantly associated with tropism status.ConclusionsWe demonstrated that pvDNA tropism in women with HIV-1 suppression is concordant with prior RNA tropism results, even after a median time of >4 years. pvDNA tropism testing may be useful to determine eligibility of patients with viral suppression to switch to a CCR5-antagonist based regimen as well as for research purposes.Electronic supplementary materialThe online version of this article (doi:10.1186/s12981-015-0055-x) contains supplementary material, which is available to authorized users.

Chemokine co-receptor usage in HIV-1-infected treatment-naïve voluntary counselling and testing clients in Southern Taiwan

ObjectiveThe goal of this present study was to determine the proportion of CCR5-tropic and CXCR4-tropic viruses and impact of tropism test on clinical presentation, CD4 cell counts, viral load and...

Thymic HIV-2 infection uncovers posttranscriptional control of viral replication in human thymocytes.

A unique HIV-host equilibrium exists in untreated HIV-2-infected individuals. This equilibrium is characterized by low to undetectable levels of viremia throughout the disease course, despite the establishment of disseminated HIV-2 reservoirs at levels comparable to those observed in untreated HIV-1 infection. Although the clinical spectrum is similar in the two infections, HIV-2 infection is associated with a much lower rate of CD4 T-cell decline and has a limited impact on the mortality of infected adults. Here we investigated HIV-2 infection of the human thymus, the primary organ for T-cell production. Human thymic tissue and suspensions of total or purified CD4 single-positive thymocytes were infected with HIV-2 or HIV-1 primary isolates using either CCR5 or CXCR4 coreceptors. We found that HIV-2 infected both thymic organ cultures and thymocyte suspensions, as attested to by the total HIV DNA and cell-associated viral mRNA levels. Nevertheless, thymocytes featured reduced levels of intracellular Gag viral protein, irrespective of HIV-2 coreceptor tropism and cell differentiation stage, in agreement with the low viral load in culture supernatants. Our data show that HIV-2 is able to infect the human thymus, but the HIV-2 replication cycle in thymocytes is impaired, providing a new model to identify therapeutic targets for viral replication control. HIV-1 infects the thymus, leading to a decrease in CD4 T-cell production that contributes to the characteristic CD4 T-cell loss. HIV-2 infection is associated with a very low rate of progression to AIDS and is therefore considered a unique naturally occurring model of attenuated HIV disease. HIV-2-infected individuals feature low to undetectable plasma viral loads, in spite of the numbers of circulating infected T cells being similar to those found in patients infected with HIV-1. We assessed, for the first time, the direct impact of HIV-2 infection on the human thymus. We show that HIV-2 is able to infect the thymus but that the HIV-2 replication cycle in thymocytes is impaired. We propose that this system will be important to devise immunotherapies that target viral production, aiding the design of future therapeutic strategies for HIV control.

Chronic inflammation in a long-term cohort of HIV-infected patients according to the normalization of the CD4:CD8 ratio.

In HIV-infected patients a low CD4:CD8 ratio can persist despite CD4 recovery with long-term antiretroviral treatment (ART). As CD4:CD8 inversion is considered a marker of immune-senescence, we aimed to assess if it was associated with the chronic inflammation state in aging patients with HIV. A total of 112 patients with a >15 year history of HIV infection and ART were included, 85 of whom were suppressed. All subjects were tested for interleukin (IL)-6, high-sensitivity (hs)-PCR, and D-dimer levels. Complete clinical, therapeutic, and hematochemical data were retrieved. Coreceptor tropism based on HIV-DNA gp120 genotyping was also available within the past 6 months. A progressive increase in the CD4:CD8 ratio over time was observed without reaching a plateau. Based on the CD4:CD8 ratio at the time of testing, patients were classified into group A (normal ratio ≥0.9) and group B (<0.9). A normal ratio was observed in 37% of patients. Variables associated with an inverted CD4:CD8 ratio were older age, nadir CD4, and detectable HIV viremia. No association between HIV subtype, coreceptor tropism, cytomegalovirus (CMV), hepatitis B virus (HBV), and hepatitis C virus (HCV) coinfections and CD4:CD8 ratio was observed. Group B patients showed a trend for a higher frequency of diabetes and hypertriglyceridemia compared to group A patients, but they did not differ in IL-6, hs-PCR, and D-dimer levels or in frequency of severe non-AIDS-associated events. In conclusion, CD4:CD8 ratio normalization occurs rarely, even after several years of ART. Chronic inflammation in patients aging with HIV does not seem to be directly dependent on the CD4:CD8 ratio. However, the persistent immune dysregulation expressed by a CD4:CD8 inversion might be linked to a higher risk of non-AIDS events, especially metabolic disorders.

HIV-2 interaction with cell coreceptors: amino acids within the V1/V2 region of viral envelope are determinant for CCR8, CCR5 and CXCR4 usage.

BackgroundHuman immunodeficiency virus 1 and 2 (HIV-1 and HIV-2) use cellular receptors in distinct ways. Besides a more promiscuous usage of coreceptors by HIV-2 and a more frequent detection of CD4-independent HIV-2 isolates, we have previously identified two HIV-2 isolates (HIV-2MIC97 and HIV-2MJC97) that do not use the two major HIV coreceptors: CCR5 and CXCR4. All these features suggest that in HIV-2 the Env glycoprotein subunits may have a different structural organization enabling distinct - although probably less efficient - interactions with cellular receptors.ResultsBy infectivity assays using GHOST cell line expressing CD4 and CCR8 and blocking experiments using CCR8-specific ligand, I-309, we show that efficient replication of HIV-2MIC97 and HIV-2MJC97 requires the presence of CCR8 at plasma cell membrane. Additionally, we disclosed the determinants of chemokine receptor usage at the molecular level, and deciphered the amino acids involved in the usage of CCR8 (R8 phenotype) and in the switch from CCR8 to CCR5 or to CCR5/CXCR4 usage (R5 or R5X4 phenotype). The data obtained from site-directed mutagenesis clearly indicates that the main genetic determinants of coreceptor tropism are located within the V1/V2 region of Env surface glycoprotein of these two viruses.ConclusionsWe conclude that a viral population able to use CCR8 and unable to infect CCR5 or CXCR4-positive cells, may exist in some HIV-2 infected individuals during an undefined time period, in the course of the asymptomatic stage of infection. This suggests that in vivo alternate molecules might contribute to HIV infection of natural target cells, at least under certain circumstances. Furthermore we provide direct and unequivocal evidence that the usage of CCR8 and the switch from R8 to R5 or R5X4 phenotype is determined by amino acids located in the base and tip of V1 and V2 loops of HIV-2 Env surface glycoprotein.