Viral decay dynamics in HIV-infected patients receiving ritonavir-boosted saquinavir and efavirenz with or without enfuvirtide: a randomized, controlled trial (HIV-NAT 012)

The efficiency of the human CD8+ T cell response: how should we quantify it, what determines it, and does it matter?

Multidisciplinary techniques, in particular the combination of theoretical and experimental immunology, can address questions about human immunity that cannot be answered by other means. From the turnover of virus-infected cells in vivo, to rates of thymic production and HLA class I epitope prediction, theoretical techniques provide a unique insight to supplement experimental approaches. Here we present our opinion, with examples, of some of the ways in which mathematics has contributed in our field of interest: the efficiency of the human CD8+ T cell response to persistent viruses.

Differential effects of efavirenz, lopinavir/r, and atazanavir/r on the initial viral decay rate in treatment naïve HIV-1-infected patients

Initial viral decay rate may be useful when comparing the relative potency of antiretroviral regimens. Two hundred twenty-seven ART-naïve patients were randomized to receive efavirenz (EFV) (n = 74), lopinavir/ritonavir (LPV/r) (n = 77), or atazanavir/ritonavir (ATV/r) (n = 79) in combination with two NRTIs. The most frequently used NRTI combinations in the EFV and ATV/r groups were the nonthymidine analogues tenofovir and emtricitabine or lamivudine (70% and 68%, respectively) and, in the LPV/r group, lamivudine and the thymidine analogue zidovudine (89%). HIV-1 RNA was monitored during the first 28 days after treatment initiation. Phase 1 and 2 decay rate was estimated in a subset of 157 patients by RNA decrease from days 0 to 7, and days 14 to 28. One-way ANOVA and subsequent Tukey's post hoc tests were used for groupwise comparisons. Mean (95% CI) HIV-1 RNA reductions from days 0 to 28 were 2.59 (2.45-2.73), 2.42 (2.27-2.57), and 2.13 (2.01-2.25) log(10) copies/ml for the EFV-, LPV/r-, and ATV/r-based treatment groups, respectively, with a significantly larger decrease in the EFV-based group at all time points compared with ATV/r (p < 0.0001), and with LPV/r at days 7-21 (p < 0.0001-0.03). LPV/r gave a greater RNA decrease compared with ATV/r from day 14 (p = 0.02). Phase 1 decay rate was significantly higher in the EFV group compared with LPV/r (p = 0.003) or ATV/r (p < 0.0001). No difference was found in phase 2 decrease. EFV-based treatment gave a more rapid decline in HIV-1 RNA than did either of the boosted protease inhibitor-based regimens. The observed differences may reflect different inherent regimen potencies.

A perspective on antiviral resistance

More than 25 years after the licensure of aciclovir and then penciclovir, followed by their respective prodrugs valaciclovir and famciclovir, cases of clinically relevant resistance to these drugs in immunocompetent individuals remain very rare. The aim of this review is to focus on the mechanism of action of these anti HSV drugs and then briefly compare this favourable outcome with that of CMV, HIV, HBV and influenza. A central theme is that resistance is an epiphenomenon of failure to suppress virus replication, so that improved potency and selectivity should be prioritised when developing new drugs rather than activity against resistant strains per se.

Italian consensus statement on management of HIV-infected individuals with advanced disease naïve to antiretroviral therapy

BACKGROUND

Individuals with advanced HIV infection naïve to antiretroviral therapy represent a special population of patients frequently encountered in clinical practice. They are at high risk of disease progression and death, and their viroimmunologic response following the initiation of highly active antiretroviral therapy may be more incomplete or slower than that of other patients. Infection management in such patients can also be complicated by underlying conditions, comorbidities, and the need for concomitant medications.

AIM

To provide practical guidelines to those clinicians providing care to HIV-infected patients in terms of diagnostic assessment, monitoring, and treatment.

CONCLUSIONS

The principals of antiretroviral treatment in asymptomatic naïve patients with advanced HIV infection are the same as those applicable to the general population with asymptomatic HIV infection. Naïve patients with advanced HIV infection and a history of AIDS-defining illnesses urgently need antiretroviral treatment, with the choice of antiretroviral regimen and timetable based on such factors as concomitant treatment and prophylaxis, drug interactions, and potential concomitant drug toxicity. Finally, an adequate counseling program - both before and after HIV-testing - that includes aspects other than treatment adherence monitoring is a crucial step in disease management.

HIV dynamics and integrase inhibitors

The integrase inhibitor (INI) raltegravir has shown promising results in clinical trials to date, reducing second phase HIV RNA levels by 70% in comparison with standard regimens. These trial results have been limited by the 50 copies/ml detection limit of the HIV RNA assay and have not investigated the effect of an INI regimen on levels of latently infected cells. Mathematical models that duplicated previous raltegravir results were extended to estimate effects of an INI regimen on HIV RNA beyond second phase and on HIV DNA levels. Depending on assumptions underlying later phase HIV RNA generation and its interaction with latently infected cells, HIV RNA in later phases can be lower or show no difference with an INI, and similarly for HIV DNA. If latent infection is maintained by differentiation of stem cells with integrated HIV DNA, then an INI regimen will eventually have no added benefit. Other hypotheses that allow ongoing replication predict continually lower HIV RNA levels with an INI regimen, but this differential effect need not translate to a reduction in latent infection. Investigation of HIV RNA and HIV DNA levels with an INI will provide better understanding of how these components are generated and maintained under antiretroviral therapy.

Plasma HIV RNA decline and emergence of drug resistance mutations among patients with multiple virologic failures receiving resistance testing-guided HAART

Early recognition of virologic failure in patients with extensive drug resistance receiving salvage-HAART is essential to avoid exposure to subinhibitory regimens. We studied plasma viral load (PVL) decline and rates of drug-resistance mutation (DRM) accumulation in such patients. A prospective, 48 week study of 38 heavily pretreated patients receiving genotypic resistance testing (GRT)-guided HAART was conducted. The rate of PVL decline was studied by weekly PVL determinations. To assess DRM accumulation, serial GRTs were performed in all nonresponders (never reaching PVL <50 or two PVLs >50 copies/ml after suppression). Over 48 weeks, 10 patients (26%) were nonresponders. Receiving less then two fully active drugs and having an elevated number of PI and NRTI mutations at baseline were strongly associated with virologic failure. There was no evidence of a difference in the change from baseline PVL to week 1 and 2 between responders and nonresponders. By contrast, PVL reductions from week 2 to week 3 and thereafter were significantly greater for responders (p < 0.01). Among nonresponders, the incidence rates per patient-month (95% CI) of emergent DRM were 0.67 (0.13-1.20), 0.40 (0.00-0.74), and 0.37 (0.00-0.75) at weeks 4, 8, and 24, respectively. Having limited baseline resistance, receiving at least two fully active drugs, and showing constant PVL reductions from week 2 to week 3 and thereafter were predictive of virologic response. In contrast, early changes in PVL levels were not. Virologic failure was associated with detection of emergent DRMs. Virologic rebound in patients on salvage-HAART should be addressed aggressively.