In vitro replication capacity of HIV-2 variants from long-term aviremic individuals

To establish whether efficient suppression of virus replication in HIV-2-infected individuals is associated with low replicative capacity of HIV-2, replication kinetics of HIV-2 variants from long-term aviremic individuals was analyzed and compared with that of the relatively slow-replicating HIV-1 variants from asymptomatics and long-term nonprogressors (AS/LTNP). On average, HIV-2 from aviremic individuals had lower replication rates than HIV-1 variants from AS/LTNP in cells of 8 donors (0.45 log10 [range 0.14-0.77] vs. 0.58 log10 [range 0.32-0.99] pg RT/ml/day, P = 0.036). The relatively low replication rate of HIV-2 compared to HIV-1 variants was not related to different sensitivities to inhibition by CD8+ T cells or different degrees of infectivity. HIV-2 replication rates increased with progressive infection and with switch from CCR5 to CXCR4 usage. The relatively low replicative capacity of HIV-2 variants from aviremic individuals likely contributes to the low viral load and benign course of infection in these individuals

Construction and characterisation of infectious recombinant HIV-1 clones containing CTL epitopes from structural proteins in Nef.

In this study the construction is described of HIV-1 molecular clones in which CTL epitopes from RT or Env late proteins were inserted into the Nef early protein. The ectopic epitopes were efficiently processed from the recombinant Nef proteins, were recognized by their cognate CTL in cytolytic assays, and did not perturb virus replication or viral protein expression in vitro. These recombinant viruses will therefore be an important tool in studying the effect of distinct epitope expression kinetics on the efficiency of CTL-mediated suppression of HIV-1 replication

Kinetics of antiviral activity by human immunodeficiency virus type 1-specific cytotoxic T lymphocytes (CTL) and rapid selection of CTL escape virus in vitro

The antiviral activity of a CD8(+) cytotoxic T-lymphocyte (CTL) clone (TCC108) directed against a newly identified HLA-B14-restricted epitope, human immunodeficiency virus type 1 (HIV-1) Rev(67-75) SAEPVPLQL, was analyzed with respect to its kinetics of target cel

Coreceptor usage of human immunodeficiency virus type 2 primary isolates and biological clones is broad and does not correlate with their syncytium-inducing capacities

Entry of human immunodeficiency virus type 1 (HIV-1) into target cells is mediated by binding of the surface envelope glycoprotein to the CD4 molecule. Interaction of the resulting CD4-glycoprotein complex with alpha- or beta-chemokine receptors, depending on the biological phenotype of the virus, then initiates the fusion process. Here, we show that primary HIV-2 isolates and biological clones, in contrast to those of HIV-1, may use a broad range of coreceptors, including CCR-1, CCR-3, CCR-5, and CXCR-4. The syncytium-inducing capacity of these viruses did not correlate with the ability to infect via CXCR-4 or any other coreceptor. One cell-free passage of the intermediate isolates in mitogen-stimulated, CD8+ cell-depleted peripheral blood mononuclear cells resulted in the outgrowth of variants with CCR-5 only, whereas the coreceptor usage of late and early isolates did not change. Since HIV-2 is less pathogenic in vivo than HIV-1, these data suggest that HIV pathogenicity in vivo is not directly related to the spectrum of coreceptors used in in vitro systems

Broadening of coreceptor usage by human immunodeficiency virus type 2 does not correlate with increased pathogenicity in an in vivo model.

The pathogenic properties of four primary human immunodeficiency virus type 2 (HIV-2) isolates and two primary HIV-2 biological clones were studied in an in vivo human-to-mouse chimeric model. The cell-associated viral load and the ability to reduce the severity of the induced graft-versus-host disease symptoms, the CD4/CD8 ratio and the level of repopulation of the mouse tissues by the graft, were determined. All HIV-2 strains, irrespective of their in vitro biological phenotype, replicated to high titres and significantly reduced graft-versus-host disease symptoms as well as the CD4/CD8 ratios. Reduction of graft repopulation caused by infection with the respective HIV-2 strains showed that the in vitro replication rate, syncytium-inducing capacity and ability to infect human macrophages did influence the in vivo pathogenic potential whereas broadening of coreceptor usage did not

Decline of simian immunodeficiency virus (SIV)-specific cytotoxic T lymphocytes in the peripheral blood of long-term nonprogressing macaques infected with SIVmac32H-J5.

The evolution of simian immunodeficiency virus (SIV)–specific cytotoxic T lymphocyte precursors (CTLps) and their relationship with virus replication were studied in SIV‐infected macaques. After primary viremia, 3 of 8 macaques l

Impact of natural sequence variation in the V2 region of the envelope protein of human immunodeficiency virus type 1 on syncytium induction: A mutational analysis.

Several studies have demonstrated a functional role for the V1-V2 region of the human immunodeficiency virus type 1 (HIV-1) envelope surface glycoprotein gp120 in the membrane fusion processes underlying viral entry and syncytium induction. In a study with chimeric primary envelope genes, we have previously demonstrated that the exchange of V2 regions was sufficient to transfer syncytium-inducing capacity to a non-syncytium-inducing envelope protein. The exchanged V2 regions, comprising a number of variable amino acids, conferred changes to both the predicted secondary structure and to the net positive charge of the V2 loops. In a syncytium-forming assay based on transient envelope protein expression in CD4+ SupT1 cells, we have extended this observation by mutating the variable positions of the V2 region to determine the relative contribution of individual amino acids to syncytium formation. It can be shown that simultaneous mutation of multiple amino acids is needed to interfere with the V2 region-determined syncytium-inducing phenotype. Single amino acid changes either influencing charge of predicted secondary structure of the V2 loop proved to be insufficient to abolish V2 region-controlled syncytium formation. This robust V2 organization may allow the virus to accumulate mutations, while retaining its biological phenotype

Antiviral resistance of biologic HIV-2 clones obtained from individuals on nucleoside reverse transcriptase inhibitor therapy

Objective: To study phenotypic and genotypic resistance of HIV-2 against nucleoside reverse transcriptase inhibitors (NRTI). Methods: Biologic HIV-2 clones were generated from 3 patients before and after initiation of antiretroviral therapy with zidovudine (AZT) in patient RH2-7, AZT and didanosine (ddI) in patient PH2-1, and after addition of lamivudine (3TC) to AZT monotherapy in patient RH2-5. The sensitivity to NRTI of the virus clones, as defined by the 50% inhibitory concentration (IC50), was determined in vitro. The predicted amino acid sequences of the reverse transcriptase proteins from these clones were determined. Results: Comparing the sensitivity of the biologic HIV-2 clones obtained after start of therapy with those from antiviral naive patients, resistance had developed to AZT (patients RH2-7 and RH2-5) and 3TC (patient PH2-1 and RH2-5). No resistance to AZT was observed in the biologic clone from PH2-1 obtained after start of therapy. The resistant clones from RH2-5 and PH2-1, but not RH2-7, contained amino acid mutations at positions where HIV-1 has been shown to mutate after AZT and 3TC treatment. Conclusions: Phenotypic resistance of HIV-2 to nucleoside analogues, which developed in HIV-2-infected patients treated with NRTIs, was associated with genotypic changes. Some of the mutations at amino acid positions in the HIV-2 reverse transcriptase gene corresponded with those involved in HIV-1 resistance, although no conventional mutations associated with resistance to AZT were observed