Virologic Determinants of Success After Structured Treatment Interruptions of Antiretrovirals in Acute HIV-1 Infection
Latently infected resting memory CD4 T cells are thought to be the major reservoir that contributes to rebound viremia after cessation of antiretrovirals (ARVs). Commencing ARVs during primary HIV-1 infection (PHI) may limit the size of the latent pool and lead to improved control of viral replication during structured treatment interruption (STI).
Individuals with PHI (n = 59) were randomized to receive ARVs with or without hydroxyurea. After STI, a good response was defined as maintenance of HIV-1 RNA <5000 copies/mL for 24 weeks off therapy. In a detailed prospective virologic substudy (n = 19), integrated HIV-1 DNA, total HIV-1 DNA, and cell-associated HIV-1 unspliced (US) RNA were quantified using a real-time polymerase chain reaction assay.
The plasma HIV-1 RNA 12 weeks after the initiation of ARVs was significantly lower in good responders (n = 7) compared with poor responders (n = 12) (P = 0.005). There were no significant differences between good and poor responders in integrated HIV-1 DNA, HIV-1 DNA, and HIV-1 US RNA. Integrated HIV-1 DNA before initiation of ARVs was strongly correlated with plasma HIV-1 RNA at week 12 (P = 0.006, r = 0.81).
HIV-1 RNA measured 12 weeks after initiation of ARV was the only virologic variable associated with viral rebound after treatment interruption in PHI.
Available from: John Zaunders
- "However, in another prospective study of PHI, eight EC were identified amongst 211 untreated PHI subjects (out of a total of 964 subjects enrolled), and there was no significant difference in symptomatic PHI (Goujard et al., 2009), but there was a clearly significant difference in HIV RNA viral load. Similarly, we found that patients who exhibited better control of HIV RNA, during treatment interruption after 6–12 months cART commenced during PHI, had a significantly lower HIV RNA level at baseline, by multivariate analysis (Bloch et al., 2006), and this correlated with lower levels of integrated HIV DNA prior to cART (Lewin et al., 2008). Another large natural history study showed that viral control was established in the majority of EC within 1 year of seroconversion , but characteristics of PHI were not reported for this cohort (Okulicz et al., 2009). "
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ABSTRACT: Long-term non-progressors (LTNP) were identified after 10-15 years of the epidemic, and have been the subject of intense investigation ever since. In a small minority of cases, infection with nef/3'LTR deleted attenuated viral strains allowed control over viral replication. A common feature of LTNP is the readily detected proliferation of CD4 T cells in vitro, in response to p24. In some cases, the responding CD4 T cells have cytotoxic effector function and may target conserved p24 epitopes, similar to the CD8 T cells described below. LTNP may also carry much lower HIV DNA burden in key CD4 subsets, presumably resulting from lower viral replication during primary infection. Some studies, but not others, suggest that LTNP have CD4 T cells that are relatively resistant to HIV infection in vitro. One possible mechanism may involve up-regulation of the cell cycle regulator p21/waf in CD4 T cells from LTNP. Delayed progression in Caucasian LTNP is also partly associated with heterozygosity of the ∆32 CCR5 allele, probably through decreased expression of CCR5 co-receptor on CD4 T cells. However, in approximately half of Caucasian LTNP, two host genotypes, namely HLA-B57 and HLA-B27, are associated with viral control. Immunodominant CD8 T cells from these individuals target epitopes in p24 that are highly conserved, and escape mutations have significant fitness costs to the virus. Furthermore, recent studies have suggested that these CD8 T cells from LTNP, but not from HLA-B27 or HLA-B57 progressors, can cross-react with intermediate escape mutations, preventing full escape via compensatory mutations. Humoral immunity appears to play little part in LTNP subjects, since broadly neutralizing antibodies are rare, even amongst slow progressors. Recent genome wide comparisons between LTNP and progressors have confirmed the HLA-B57, HLA-B27 and delta32 CCR5 allelic associations, plus indicated a role for HLA-C/KIR interactions, but have not revealed any new genotypes so far.
Available from: Barbara S Slusher
- "Although cART has been successful, it has not eradicated the disease as the virus can persist in resting memory CD4+ T cells as well as macrophages and astrocytes (Coiras et al. 2009). These latent reservoirs of HIV are easily and quickly activated if cessation of cART treatment occurs (Lewin et al. 2008). Elimination of these reservoirs is a major goal of current research in the HIV field. "
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ABSTRACT: The accumulation of excess glutamate in the extracellular space as a consequence of CNS trauma, neurodegenerative diseases, infection, or deregulation of glutamate clearance results in neuronal damage by excessive excitatory neurotransmission. Glutamate excitotoxicity is thought to be one of several mechanisms by which HIV exerts neurotoxicity that culminates in HIV-associated neurocognitive disorders (HAND). Excess glutamate is released upon HIV infection of macrophage/microglial cells and has been associated with neurotoxicity mediated by gp120, transactivator of transcription (Tat) and other HIV proteins. Several strategies have been used over the years to try to prevent glutamate excitotoxicity. Since the main toxic effects of excess glutamate are thought to be due to excitotoxicity from over activation of glutamate receptors, antagonists of these receptors have been popular therapeutic targets. Early work to ameliorate the effects of excess extracellular glutamate focused on NMDA receptor antagonism, but unfortunately, potent blockade of this receptor has been fraught with side effects. One alternative to direct receptor blockade has been the inhibition of enzymes responsible for the production of glutamate such as glutaminase and glutamate carboxypeptidase II. Another approach has been to regulate the transporters responsible for modulation of extracellular glutamate such as excitatory amino acid transporters and the glutamate-cystine antiporter. There is preliminary experimental evidence that these approaches have potential therapeutic utility for the treatment of HAND. These efforts however, are at an early stage where the next steps are dependent on the identification of drug-like inhibitors as well as the development of predictive neuroAIDS animal models.
Available from: Marina Alexander
- "Production of HIV was quantified by measuring the Reverse Transcriptase activity in cell culture supernatant at days 4, 7, and 10 post-infection as previously described  as well as by measuring integrated HIV DNA and RNA at day 4 post-infection using real-time PCR (iCycler, Bio-Rad, Hercules, CA). Integrated HIV DNA was quantified using a nested Alu-long terminal repeat (LTR) PCR as previously described [49,50]. In brief, we used standards that contained random integration sites as previously described ; all samples were run in triplicate and we used an additional control reaction that included the LTR primer alone [49,50]. "
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ABSTRACT: We recently described that HIV latent infection can be established in vitro following incubation of resting CD4+ T-cells with chemokines that bind to CCR7. The main aim of this study was to fully define the post-integration blocks to virus replication in this model of CCL19-induced HIV latency.
High levels of integrated HIV DNA but low production of reverse transcriptase (RT) was found in CCL19-treated CD4+ T-cells infected with either wild type (WT) NL4.3 or single round envelope deleted NL4.3 pseudotyped virus (NL4.3- Δenv). Supernatants from CCL19-treated cells infected with either WT NL4.3 or NL4.3- Δenv did not induce luciferase expression in TZM-bl cells, and there was no expression of intracellular p24. Following infection of CCL19-treated CD4+ T-cells with NL4.3 with enhanced green fluorescent protein (EGFP) inserted into the nef open reading frame (NL4.3- Δnef-EGFP), there was no EGFP expression detected. These data are consistent with non-productive latent infection of CCL19-treated infected CD4+ T-cells. Treatment of cells with phytohemagluttinin (PHA)/IL-2 or CCL19, prior to infection with WT NL4.3, resulted in a mean fold change in unspliced (US) RNA at day 4 compared to day 0 of 21.2 and 1.1 respectively (p = 0.01; n = 5), and the mean expression of multiply spliced (MS) RNA was 56,000, and 5,000 copies/million cells respectively (p = 0.01; n = 5). In CCL19-treated infected CD4+ T-cells, MS-RNA was detected in the nucleus and not in the cytoplasm; in contrast to PHA/IL-2 activated infected cells where MS RNA was detected in both. Virus could be recovered from CCL19-treated infected CD4+ T-cells following mitogen stimulation (with PHA and phorbyl myristate acetate (PMA)) as well as TNFα, IL-7, prostratin and vorinostat.
In this model of CCL19-induced HIV latency, we demonstrate HIV integration without spontaneous production of infectious virus, detection of MS RNA in the nucleus only, and the induction of virus production with multiple activating stimuli. These data are consistent with ex vivo findings from latently infected CD4+ T-cells from patients on combination antiretroviral therapy, and therefore provide further support of this model as an excellent in vitro model of HIV latency.
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