Hide and seek... Can we eradicate HIV by treatment intensification?

Paediatric HIV infection: the potential for cure

Recent anecdotal reports of HIV-infected children who received early antiretroviral therapy (ART) and showed sustained control of viral replication even after ART discontinuation have raised the question of whether there is greater intrinsic potential for HIV remission, or even eradication ('cure'), in paediatric infection than in adult infection. This Review describes the influence of early initiation of ART, of immune ontogeny and of maternal factors on the potential for HIV cure in children and discusses the unique immunotherapeutic opportunities and obstacles that paediatric infection may present.

Towards an HIV cure based on targeted killing of infected cells: different approaches against acute versus chronic infection

PURPOSE OF REVIEW

Current regimens of combination antiretroviral therapy (cART) offer effective control of HIV infection, with maintenance of immune health and near-normal life expectancy. What will it take to progress beyond the status quo, whereby infectious virus can be eradicated (a 'sterilizing cure') or fully controlled without the need for ongoing cART (a 'functional cure')?

RECENT FINDINGS

On the basis of therapeutic advances in the cancer field, we propose that targeted cytotoxic therapy to kill HIV-infected cells represents a logical complement to cART for achieving an HIV cure. This concept is based on the fact that cART effectively blocks replication of the virus, but does not eliminate cells that are already infected; targeted cytotoxic therapy would contribute precisely this missing component. We suggest that different modalities are suited for curing primary acute versus established chronic infection. For acute infection, relatively short-acting potent agents such as recombinant immunotoxins might prove sufficient for HIV eradication, whereas for chronic infection, a long-lasting (lifelong?) modality is required to maintain full virus control, as might be achieved with genetically modified autologous T cells.

SUMMARY

We present perspectives for complementing cART with targeted cytotoxic therapy, whereby HIV infection is either eradicated or fully controlled, thereby eliminating the need for lifelong cART.

Feasibility and potential role of ferumoxytol-enhanced neuroimaging in HIV-associated neurocognitive disorder

We assessed ferumoxytol-enhanced brain MRI to identify monocyte/macrophage accumulation in HIV-associated neurocognitive disorder (HAND). Four HIV-infected subjects with undetectable HIV RNA levels on antiretroviral therapy, HIV DNA level in CD14+ cells ≥10 copies/10(6) cells, and cognitive impairment underwent ferumoxytol-enhanced brain MRI. On post-ferumoxytol susceptibility-weighted images, all HIV-infected subjects demonstrated a diffuse "tram track" appearance in the perivascular regions of cortical and deep white matter vessels suggesting ferumoxytol uptake in monocytes/macrophages. This finding was not present in an HIV-seronegative control. While ferumoxytol may have potential as an imaging biomarker for monocyte/macrophage accumulation in patients with HAND, future study is needed.

Highly significant antiviral activity of HIV-1 LTR-specific tre-recombinase in humanized mice

Stable integration of HIV proviral DNA into host cell chromosomes, a hallmark and essential feature of the retroviral life cycle, establishes the infection permanently. Current antiretroviral combination drug therapy cannot cure HIV infection. However, expressing an engineered HIV-1 long terminal repeat (LTR) site-specific recombinase (Tre), shown to excise integrated proviral DNA in vitro, may provide a novel and highly promising antiviral strategy. We report here the conditional expression of Tre-recombinase from an advanced lentiviral self-inactivation (SIN) vector in HIV-infected cells. We demonstrate faithful transgene expression, resulting in accurate provirus excision in the absence of cytopathic effects. Moreover, pronounced Tre-mediated antiviral effects are demonstrated in vivo, particularly in humanized Rag2^−/−γc^−/− mice engrafted with either Tre-transduced primary CD4⁺ T cells, or Tre-transduced CD34⁺ hematopoietic stem and progenitor cells (HSC). Taken together, our data support the use of Tre-recombinase in novel therapy strategies aiming to provide a cure for HIV.

Current antiretroviral combination therapy can efficiently suppress virus replication, but cannot eliminate HIV. Therefore, no cure for HIV exists. A main hurdle for virus eradication is seen in the existence of resting cells that contain integrated replication-competent, but temporarily silenced, HIV genomes. Therefore, the most direct approach to eliminating virus reservoirs is to remove HIV genomes from infected cells. As previous studies suggested, this may be achievable by Tre-recombinase, an engineered enzyme that can excise integrated HIV from host cell chromosomes. The present work analyzes the expression of Tre-recombinase in human cells and demonstrates highly accurate Tre activity in complete absence of Tre-related cytopathic effects. Furthermore, in vivo analysis of Tre-recombinase demonstrates highly significant antiviral effects of Tre in HIV-infected humanized mice. The presented data suggest that Tre-recombinase might become a valuable component of a future therapy that aims at virus eradication.

Factors associated with a strictly undetectable viral load in HIV-1-infected patients

OBJECTIVES

The aim of the study was to identify factors associated with a strictly undetectable viral load (VL) using a routine sensitive real-time polymerase chain reaction (RT-PCR) technology.

METHODS

From a large prospective cohort, 1392 patients with a VL<50 HIV-1 RNA copies/mL while receiving a three-drug suppressive regimen for at least 1 year were included in a cross-sectional analysis. Patients were classified into three groups and compared by univariate and multivariate analysis: 479 patients with a strictly undetectable VL (group 1; 34%), 617 patients with detectable VL below the threshold of 20 copies/mL (group 2; 44%), and 296 patients with a VL of 20-50 copies/mL (group 3; 12%).

RESULTS

Comparing groups 1 and 2, VL zenith<5 log(10) copies/mL [odds ratio (OR) 1.51; 95% confidence interval (CI) 1.15-1.99; P=0.003], current CD4 T-cell count<500 cells/μL (OR 1.44; 95% CI 1.08-1.92; P=0.01), and duration of viral suppression<50 copies/mL longer than 2 years (OR 2.32; 95% CI 1.20-4.54; P=0.01) were associated with undetectable VL. Comparing groups 1 and 3, VL zenith<5 log(10) copies/mL (OR 2.48; 95% CI 1.75-3.50; P<0.001), duration of viral suppression<50 copies/mL longer than 1 year (OR 3.33; 95% CI 1.66-6.66; P=0.0006), and nonnucleoside reverse transcriptase inhibitor (NNRTI)-based regimens (OR 1.45; 95% CI 1.03-2.04; P=0.03) were associated with undetectable VL. No individual drug effect was found within NNRTI molecules.

CONCLUSIONS

Longer duration of viral suppression<50 copies/mL, lower viral load zenith and NNRTI-based regimen were independently associated with a strictly undetectable viral load. This routinely used RT-PCR assay may prove to be a valuable tool in further large-scale studies.

Failure to clear intra-monocyte HIV infection linked to persistent neuropsychological testing impairment after first-line combined antiretroviral therapy

HIV-associated neurocognitive disorders (HAND) persist despite plasma HIV RNA suppression with antiretrovirals (ARV). Sequestered reservoirs in the central nervous system and circulating monocytes are theorized to contribute to persistent brain injury. We previously demonstrated that elevated intracellular HIV DNA from circulating cells was associated with HAND in ARV-treated and ARV-naive subjects. We now report that failure to suppress intra-monocyte HIV DNA 3.5 years after initiating ARV is linked to persistent HAND and subjects with dementia are least likely to suppress intra-monocyte HIV DNA at 3.5 years. These findings suggest that antiviral strategies may need to target intra-monocyte HIV DNA.