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1.  Epigenetic analysis of HIV-1 proviral genomes from infected individuals: Predominance of unmethylated CpG’s 
Virology  2013;449:181-189.
Efforts to cure HIV-1 infections aim at eliminating proviral DNA. Integrated DNA from various viruses often becomes methylated de novo and transcriptionally inactivated. We therefore investigated CpG methylation profiles of 55 of 94 CpG’s (58.5%) in HIV-1 proviral genomes including ten CpG’s in each LTR and additional CpG’s in portions of gag, env, nef, rev, and tat genes. We analyzed 33 DNA samples from PBMC’s of 23 subjects representing a broad spectrum of HIV-1 disease. In 22 of 23 HIV-1-infected individuals, there were only unmethylated CpG’s regardless of infection status. In one long term nonprogressor, however, methylation of proviral DNA varied between 0 and 75% over an 11-year period although the CD4+ counts remained stable. Hence levels of proviral DNA methylation can fluctuate. The preponderance of unmethylated CpG’s suggests that proviral methylation is not a major factor in regulating HIV-1 proviral activity in PBMC’s. Unmethylated CpG’s may play a role in HIV-1 immunopathogenesis.
doi:10.1016/j.virol.2013.11.013
PMCID: PMC4060985  PMID: 24418551
Epigenetics of HIV-1 proviral DNA; Integrated HIV-1 DNA in PBMC’s from infected individuals; Wide spectrum of infection outcome; Bisulfite sequencing; Methylation analysis of integrated HIV-1 genomes; Predominance of unmethylated CpG’s in PBMC’s; Escape from proviral DNA methylation; Fluctuation of CpG methylation in one LTNP individual
2.  Molecular Epidemiology of HIV Type 1 Subtypes in Rwanda 
Abstract
HIV-1 infection is characterized by genetic diversity, with multiple subtypes and recombinant variants circulating, particularly in sub-Saharan Africa. During the Rwandan genocide, many women experienced multiple rapes and some became HIV-1 infected. We studied plasma and peripheral blood mononuclear cells (PBMCs) from 30 infected women comprising two exposure groups: those with numerous contacts, raped multiple times, and women with one lifetime sexual partner and no history of rape. Population-based sequences from gag, pol, and env genes were analyzed to determine HIV-1 subtypes and intersubtype recombination. Individual plasma-derived variants from 12 women were also analyzed. Subtype A was found in 24/30 (80%), intersubtype recombination (AC and AD) in 4/30 (13%), and subtypes C and D in 1/30 each. In two subjects, the pattern of HIV-1 recombination differed between plasma and PBMC-derived sequences. Intersubtype recombination was common, although there were no significant differences in subtype or recombination rates between exposure groups.
doi:10.1089/aid.2012.0095
PMCID: PMC3653399  PMID: 23458210
3.  Recombination Between Variants from Genital Tract and Plasma: Evolution of Multidrug-Resistant HIV Type 1 
AIDS Research and Human Retroviruses  2012;28(12):1766-1774.
Abstract
Multidrug-resistant (MDR) HIV-1 presents a challenge to the efficacy of antiretroviral therapy (ART). To examine mechanisms leading to MDR variants in infected individuals, we studied recombination between single viral genomes from the genital tract and plasma of a woman initiating ART. We determined HIV-1 RNA sequences and drug resistance profiles of 159 unique viral variants obtained before ART and semiannually for 4 years thereafter. Soon after initiating zidovudine, lamivudine, and nevirapine, resistant variants and intrapatient HIV-1 recombinants were detected in both compartments; the recombinants had inherited genetic material from both genital and plasma-derived viruses. Twenty-three unique recombinants were documented during 4 years of therapy, comprising ∼22% of variants. Most recombinant genomes displayed similar breakpoints and clustered phylogenetically, suggesting evolution from common ancestors. Longitudinal analysis demonstrated that MDR recombinants were common and persistent, demonstrating that recombination, in addition to point mutation, can contribute to the evolution of MDR HIV-1 in viremic individuals.
doi:10.1089/aid.2011.0383
PMCID: PMC3505048  PMID: 22364185
4.  The S40 residue in HIV-1 Gag p6 impacts local and distal budding determinants, revealing additional late domain activities 
Retrovirology  2013;10:143.
Background
HIV-1 budding is directed primarily by two motifs in Gag p6 designated as late domain-1 and −2 that recruit ESCRT machinery by binding Tsg101 and Alix, respectively, and by poorly characterized determinants in the capsid (CA) domain. Here, we report that a conserved Gag p6 residue, S40, impacts budding mediated by all of these determinants.
Results
Whereas budding normally results in formation of single spherical particles ~100 nm in diameter and containing a characteristic electron-dense conical core, the substitution of Phe for S40, a change that does not alter the amino acids encoded in the overlapping pol reading frame, resulted in defective CA-SP1 cleavage, formation of strings of tethered particles or filopodia-like membrane protrusions containing Gag, and diminished infectious particle formation. The S40F-mediated release defects were exacerbated when the viral-encoded protease (PR) was inactivated or when L domain-1 function was disrupted or when budding was almost completely obliterated by the disruption of both L domain-1 and −2. S40F mutation also resulted in stronger Gag-Alix interaction, as detected by yeast 2-hybrid assay. Reducing Alix binding by mutational disruption of contact residues restored single particle release, implicating the perturbed Gag-Alix interaction in the aberrant budding events. Interestingly, introduction of S40F partially rescued the negative effects on budding of CA NTD mutations EE75,76AA and P99A, which both prevent membrane curvature and therefore block budding at an early stage.
Conclusions
The results indicate that the S40 residue is a novel determinant of HIV-1 egress that is most likely involved in regulation of a critical assembly event required for budding in the Tsg101-, Alix-, Nedd4- and CA N-terminal domain affected pathways.
doi:10.1186/1742-4690-10-143
PMCID: PMC3907034  PMID: 24257210
HIV-1; Alix; Tsg101; Nedd4; CA NTD; Viral particle maturation; Protease; Viral budding
5.  A novel denaturing heteroduplex tracking assay for genotypic prediction of HIV-1 tropism 
Journal of virological methods  2012;185(1):108-117.
Human immunodeficiency virus type 1 (HIV-1) is characterized by sequence variability. The third variable region (V3) of the HIV-1 envelope glycoprotein gp120 plays a key role in determination of viral coreceptor usage (tropism) and pathogenesis. This report describes a novel denaturing heteroduplex tracking assay (HTA) to analyze the genetic variation of HIV-1 V3 DNA. It improved upon previous non-denaturing HTA approaches to distinguish HIV-1 CCR5 and CXCR4 tropic viruses in mixed populations. The modifications included the use of a single-stranded fluorescent probe based on the consensus V3 sequence of HIV-1 CCR5 tropic viruses, Locked Nucleic Acid (LNA) “clamps” at both ends of heteroduplex DNA, and denaturing gel electrophoresis using Mutation Detection Enhancement (MDE®) as matrix. The analysis demonstrated that the LNA “clamps” increased its melting temperature (Tm) and the thermal stability of heteroduplex DNA. The partially denaturing gel used a defined concentration of formamide, and significantly induced mobility shifts of heteroduplex DNA that was dependent on the number and patterns of DNA mismatches and insertions/deletions. This new technique successfully detected tropisms of 53 HIV-1 V3 clones of known tropism, and was able to separate and detect multiple V3 DNA variants encoding tropisms for CCR5 or CXCR4 in a mixture. The assay had the sensitivity to detect 0.5% minority species. This method may be useful as a research tool for analysis of viral quasispecies and for genotypic prediction of HIV-1 tropism in clinical specimens.
doi:10.1016/j.jviromet.2012.06.013
PMCID: PMC3417067  PMID: 22728273
HIV-1 gp120 V3; denaturing heteroduplex tracking assay; Locked Nucleic Acid clamps; viral tropism
6.  Evolution and Recombination of Genes Encoding HIV-1 Drug Resistance and Tropism during Antiretroviral Therapy 
Virology  2010;404(1):5-20.
Characterization of residual plasma virus during antiretroviral therapy (ART) is a high priority to improve understanding of HIV-1 pathogenesis and therapy. To understand the evolution of HIV-1 pol and env genes in viremic patients under selective pressure of ART, we performed longitudinal analyses of plasma-derived pol and env sequences from single HIV-1 genomes. We tested the hypotheses that drug resistance in pol was unrelated to changes in coreceptor usage (tropism), and that recombination played a role in evolution of viral strains. Recombinants were identified by using Bayesian and other computational methods. High-level genotypic resistance was seen in ~70% of X4 and R5 strains during ART. There was no significant association between resistance and tropism. Each patient displayed at least one recombinant encompassing env and representing a change in predicted tropism. These data suggest that, in addition to mutation, recombination can play a significant role in shaping HIV-1 evolution.
doi:10.1016/j.virol.2010.04.008
PMCID: PMC3186207  PMID: 20451945
HIV-1 drug resistance; HIV-1 recombination; HIV-1 tropism

Results 1-6 (6)