Elucidating mechanisms leading to the natural control of HIV-1 infection is of great importance for vaccine design and for understanding viral pathogenesis. Rare HIV-1-infected individuals, termed HIV-1 controllers, have plasma HIV-1 RNA levels below the limit of detection by standard clinical assays (<50 to 75 copies/ml) without antiretroviral therapy. Although several recent studies have documented persistent low-grade viremia in HIV-1 controllers at a level not significantly different from that in HIV-1-infected individuals undergoing treatment with combination antiretroviral therapy (cART), it is unclear if plasma viruses are undergoing full cycles of replication in vivo or if the infection of new cells is completely blocked by host immune mechanisms. We studied a cohort of 21 HIV-1 controllers with a median level of viremia below 1 copy/ml, followed for a median of 11 years. Less than half of the cohort carried known protective HLA types (B*57/27). By isolating HIV-1 RNA from large volumes of plasma, we amplified single genome sequences of both pro-rt and env longitudinally. This study is the first to document that HIV-1 pro-rt and env evolve in this patient group, albeit at rates somewhat lower than in HIV-1 noncontrollers, in HLA B*57/27-positive, as well as HLA B*57/27-negative, individuals. Viral diversity and adaptive events associated with immune escape were found to be restricted in HIV-1 controllers, suggesting that replication occurs in the face of less overall immune selection.

With constantly changing environmental selection pressures, retroviruses rely upon recombination to reassort polymorphisms in their genomes and increase genetic diversity, which improves the chances for the survival of their population. Recombination occurs during DNA synthesis, whereby reverse transcriptase undergoes template switching events between the two copackaged RNAs, resulting in a viral recombinant with portions of the genetic information from each parental RNA. This review summarizes our current understanding of the factors and mechanisms influencing retroviral recombination, fidelity of the recombination process, and evaluates the subsequent viral diversity and fitness of the progeny recombinant. Specifically, the high mutation rates and high recombination frequencies of HIV-1 will be analyzed for their roles in influencing HIV-1 global diversity, as well as HIV-1 diagnosis, drug treatment, and vaccine development.

To estimate the extent of drug resistance accumulation in patients kept on a virologically failing regimen and its determinants in the clinical setting. The study focused on 110 patients of EuroSIDA on an unchanged regimen who had two genotypic tests performed at two time points (t0 and t1) when viral load was > 400 copies/ml. Accumulation of resistance between t0 and t1 was measured using genotypic susceptibility scores (GSS) obtained by counting the total number of active drugs (according to the Rega system v6.4.1) among all licensed antiretrovirals as of 1 January 2006. Patients were grouped according to the number of active drugs in the failing regimen at t0 (GSS_f-t0). At t0, patients had been on the failing combination antiretroviral therapy (cART) for a median of 11 months (range, 6-50 months). Even patients with extensive resistance to the failing regimen were still receiving benefit from treatment. An overall 6-monthly increase of 1.96 (SD, 2.23) International Aids Society-mutations and an average loss of 1.25 (SD, 1.81) active drugs were estimated. In comparison with patients with GSS_f-t0 = 0, the number of active drugs lost was -1.08 [95% confidence interval (CI), -2.13 to -0.03; P = 0.04] in those with GSS_f-t0 of 0.5-1.5 and -1.24 (95% CI, -2.44 to -0.04; P = 0.04) in those with GSS_f-t0 >or= 2. In patients kept on the same virologically failing cART regimen for a median of 6 months, there was considerable accumulation of drug resistance mutations, particularly in patients with initial low level of resistance to the failing regimen. Randomized comparisons of maintenance treatment strategies while awaiting a new suppressive therapy to become available are warranted.

A subgroup of HIV-1-infected individuals, elite controllers, have spontaneous viral control and offer an exceptional opportunity to study virological and immunolocigal factors of possible involvement in control of HIV-1 infection. The frequencies of Tregs and TH17 cells was evaluated and correlated to markers of disease progression in peripheral blood mononuclear cells from 3 different groups of individuals infected with HIV-1: treatment-naive viremic individuals, individuals on successful highly active antiretroviral therapy, and elite controllers. In addition, a group of HIV-1-negative individuals were included. We demonstrate that elite controllers have lower levels of Tregs compared with HIV-1-infected viremic individuals, but that the low Treg level does not differ between individuals with HIV-1 control, whether natural or therapy induced. We also show that T-cell activation and proliferation both correlate to the level of Tregs. Finally, the TH17/Treg ratio was similar in Elite Controllers and uninfected controls, whereas in viremic and treated HIV-1-infected individuals, the TH17/Treg ratio was lower compared with uninfected controls. We show that one feature of spontaneous HIV-1 control is a maintained balance between regulatory T cells and TH17 cells.

Ribavirin (RBV) is a broad-spectrum antiviral active against a wide range of RNA viruses. Despite having been used for decades in the treatment of chronic hepatitis C virus (HCV) infection, the precise mechanism of action of RBV is unknown. In other viruses, it inhibits propagation by increasing the rate of G-to-A and C-to-U transitions. Here, we utilized the J6/JFH1 HCV cell-culture system to investigate whether RBV inhibits HCV through the same mechanism. Infected Huh7.5 cells were treated with increasing concentrations of RBV or its phosphorylated forms. A fragment of the HCV NS5B-polymerase gene was amplified, cloned, and sequenced to estimate genetic distances. We confirm that the antiviral effect of all three RBV-drug forms on HCV relies on induction of specific transitions (G-to-A and C-to-U). These mutations lead to generation of non-infectious virions, reflected by decreased spread of HCV in cell culture despite relatively limited effect on virus genome titers. Moreover, treatment experiments conducted on a novel Huh7.5 cell line stably overexpressing adenosine kinase, a key enzyme for RBV activation, yielded comparable results. This study indicates that RBV action on HCV in hepatoma cell-culture is exerted through increase in mutagenesis, mediated by RBV triphosphate, and leading to production of non-infectious viruses.

Background: Changes in virologic response to initial combination antiretroviral therapy (cART) over calendar time may indicate improvements in cART or emergence of primary resistance. Regional variations may identify differences in available antiretroviral drugs or patient management. Methods: Virologic response (viral load < 500 copies/mL) 6 to 12 months after starting cART was analyzed in antiretroviral-naive EuroSIDA patients. Analyses were stratified by region (south, central west, north, east) or time started cART (early, 1996-1997; mid, 1998-1999; late, 2000-1904). Results: Virologic suppression was achieved by 60% of 2102 patients: 57% south (n = 560), 61% central west (n = 466), 63% north (n = 606), 58% east (n = 470) (P = 0.091). An increase was observed over time: 52% early cART, 56% mid cART, 69% late cART (P < 0.001). Overall, there were significant effects of region (P = 0.026) and time (P < 0.001) on virologic response after adjustment for confounders. Stratified by period, regional differences were less evident (early cART, P = 0.967; mid cART, P = 0.291; late cART, P = 0.163). Stratified by region, temporal changes were observed (south, P = 0.061; central west, P < 0.001; north: P = 0.070; east, P = 0.001). Conclusions: There was some evidence of regional differences in initial virologic response to cART. Improvements over time were observed, suggesting that so far, the effect of primary resistance has not been of sufficient magnitude to prevent increasing suppression rates.