Statins are inhibitors of cholesterol synthesis that may have direct inhibitory effects on HIV replication [1,2]. All statins block the prenylation of the small GTPase Rho necessary for the processes of viral entry and budding , and some statins block HIV attachment to target cells mediated by LFA-1 . Conversely, statins may perturb the activation of immune cells and increase HIV transcription . The ambiguity in the antiviral mechanism of statins and the lack of clinical studies specifically designed to evaluate their effects on HIV-infected patients impedes a correct evaluation of the potential benefits of this treatment.
We designed an open-label randomized pilot study to evaluate whether different doses of atorvastatin inhibit HIV replication after antiretroviral discontinuation. Eligible subjects were chronically HIV-1-infected patients with viral loads of less than 50 copies/ml and CD4 cell counts of 500 cells/μl or greater during the past 6 months of HAART. The background of AIDS-defining pathologies, intercurrent infections, creatinine phosphokinase of 500 U/l or greater, transaminase levels (alanine aminoaspartate or alanine aminotransferase) threefold higher than normal, and concomitant treatment with other statins or fibrates were exclusion criteria.
The study was approved by the ethics committee of the hospital. Forty-one patients agreed to participate in the study. All patients interrupted HAART and were randomly assigned to an untreated control group (n = 15) or to begin atorvastatin 40 or 80 mg/day, Ator40 (n = 13) and Ator80 (n = 13) groups, respectively. The main baseline epidemiological, virological, immunological and biochemical parameters were well-balanced among the groups (not shown). After the randomization day (baseline visit), participants were visited weekly until week 4 and monthly until week 12. Whole blood, plasma and peripheral blood mononuclear cells were obtained at baseline and at weeks 4 and 12 as described .
Reasons for withdrawal from the study were: CD4 cell count less than 350 cells/μl, viral load 100 000 copies/ml or greater (confirmed), opportunistic infection, acute retroviral symptoms and an increase in creatinine phosphokinase or transaminases of grade 3 or above. A total of 16 participants discontinued the study (five, seven and four patients from the control, Ator40 and Ator80 groups, respectively). Overall, five patients discontinued atorvastatin because of toxicity or intolerance: four subjects from the Ator40 group and one from the Ator80 group. A further 10 subjects (four patients in the control group and three patients from either atorvastatin group) discontinued the study as a result of safety reasons and restarted HAART. One participant from the control group was lost to follow-up.
The plasma HIV-1-RNA level (Nuclisens EasyQ method, limit of detection 50 copies/ml) at weeks 4 and 12 was the main endpoint of the study. The median viral load (median log) increased from the baseline less than 50 (1.70) to 20 000 (4.30), to 130 000 (5.11) and to 12 000 copies/ml (4.08) in the control, Ator40 and Ator80 groups, respectively, at week 4. Increases were significantly different when the Ator80 and Ator40 groups were compared (P < 0.05), but none of them was significantly different from the control group. At week 12, the median viraemia was 16 500 (4.21), 8600 (3.89) and 18 000 copies/ml (4.26) for the control, Ator40 and Ator80 groups, respectively (P = ns; Fig. 1a). Changes in immunological parameters were measured as described . The absolute counts of CD4 T cells significantly and similarly decreased at weeks 4 and 12 in all groups (Fig. 1b). In parallel, an increase in the CD8 T-cell number and activation (CD38 expression) was observed, without differences between groups (not shown).
Atorvastatin induced decreases in total serum cholesterol that were similar for both doses of statins (Ator40 group: from 213 at baseline to 109 mg/dl at week 12; Ator 80 group: from 217 to 128 mg/dl), and significantly greater (P < 0.05, Mann–Whitney test) than in the control group (from 201 to 168 mg/dl). An analysis of the relationship between serum cholesterol and different parameters revealed a significantly different viral rebound at week 4 (P < 0.05) when patients were classified according to baseline total serum cholesterol (higher or lower than 200 mg/dl; Fig. 1c). To assess the independent contribution of atorvastatin treatment and baseline cholesterol to this difference, we performed a multivariate analysis using the linear regression model (forward manner with the significance entry level at 0.05). Surprisingly, this analysis showed that the viral load at week 4 was not influenced by atorvastatin treatment but correlated with baseline total cholesterol (Pearson coefficient 0.376, P < 0.05).
To explain this paradoxical relationship, we evaluated the effects of atorvastatin on HIV production by cultured peripheral blood mononuclear cells (obtained from untreated HIV-infected individuals). Control cultures produced detectable levels of p24 after 5 days of culture (median 166 pg/ml) that were slightly but significantly (28 ± 20%, P < 0.05) increased by subtoxic atrovastatin concentrations (1 μg/ml; Fig. 1d).
Several groups have reported preliminary data on the failure of statins to control HIV replication in vivo[4–6]. Our study extends this observation to a different clinical setting (HAART interruption). This failure may be explained by the multiple potential effects of statins in vivo that are not always in an inhibitory direction. The antiviral effects of statins could be compensated by the activation of HIV transcription or the inhibition of immune control . Our data support this hypothesis (Fig. 1d) and point to a potential role of serum cholesterol in HIV replication in vivo, which is consistent with the impact of membrane cholesterol and lipid rafts on HIV replication in vitro. Nonetheless, this relationship is unclear in vivo, and only scant data with animal models support this relationship for other viruses [9,10].
Considering this possible direct correlation, we may suspect a benefit of atorvastatin only when it is taken before the interruption of HAART, with a tight control of drug interactions and the added toxicity. In addition, our data show that low doses of statins were paradoxically associated with an elevated rate of toxicity, although some of these effects are unlikely to be related to statin treatment (nephrolythiasis). Atorvastatin toxicity may act synergistically with HIV replication, causing a high number of dropouts throughout the current study.
In conclusion, despite anti-HIV activity described in vitro, atorvastatin failed to reduce viral rebound and CD4 cell loss in patients with viral suppression after the interruption of HAART. Nonetheless, the association of baseline serum cholesterol with viral rebound suggests that atorvastatin, when given before HAART interruption, could have a positive impact on HIV-1 replication by lowering serum cholesterol. Further studies should be designed to investigate these mechanisms in more detail and the value of serum and membrane cholesterol as a target to control HIV replication in vivo.
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