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Effects of atorvastatin and pravastatin on immune activation and T-cell function in antiretroviral therapy-suppressed HIV-1-infected patients

Overton, Edgar Turnera; Sterrett, Saraha; Westfall, Andrew O.a; Kahan, Shannon M.b; Burkholder, Greera; Zajac, Allan J.b; Goepfert, Paul A.a,b; Bansal, Anjua

doi: 10.1097/QAD.0000000000000475
Research Letters
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This retrospective study was designed to assess statin effects on T-cell activation from HIV-infected individuals. Peripheral blood mononuclear cells from antiretroviral therapy suppressed HIV-infected individuals receiving atorvastatin or pravastatin were evaluated for T-cell activation, exhaustion and function. Atorvastatin was associated with a significant reduction in CD8 T-cell activation (HLA-DR, CD38/HLA-DR) and exhaustion (TIM-3, TIM-3/PD-1) whereas pravastatin had no effect. In contrast, pravastatin increased antigen specific interferon γ production. These results suggest a differential effect of statins on immune activation and function.

aDepartments of Medicine

bDepartment of Microbiology, University of Alabama at Birmingham, Birmingham, Alabama, USA.

Correspondence to Dr Anju Bansal, Department of Medicine, University of Alabama at Birmingham, 845, 19th Street South, BBRB 557, Birmingham, AL 35294, USA. Tel: +1 205 996 2214; fax: +1 205 975 6027; e-mail: abansal@uab.edu

Received 25 March, 2014

Revised 28 August, 2014

Accepted 29 August, 2014

Immune activation contributes to HIV pathogenesis [1–10]. Even with suppressive antiretroviral therapy (ART), immune activation persists and remains elevated compared with HIV-uninfected individuals [11–15]. Although statins primarily serve as lipid-lowering therapy [16,17], they also reduce T-cell surface signaling molecules and decrease T-cell activation [18–21]. Recent studies demonstrate that statins reduce T-cell activation and are associated with decreased morbidity and mortality among HIV-infected persons [22–24]. Specifically, atorvastatin significantly reduced T-cell activation in viremic HIV-infected individuals [25]. Here, we evaluated the effects of pravastatin and atorvastatin on T-cell activation and exhaustion in ART-suppressed individuals.

We used cryopreserved samples from 21 HIV-infected persons who were virologically suppressed (<50 copies/ml) with ART for more than 12 months (range, 20–137) and remained suppressed throughout follow-up [26]. Seventeen received adjunctive statin therapy for more than 6 months (range, 3–32): seven individuals received 10 mg atorvastatin; 10 received pravastatin (five with 20 mg; five with 40 mg). A median viability of 97% and recovery at 87% was observed for peripheral blood mononuclear cell (PBMC) samples used in this study. As a control group, we identified four ART-suppressed individuals (median CD4+ T-cell count: 498 cells/mm3; median duration of ART: 119 weeks) not receiving statins. The study was approved by the Institutional Review Board at University of Alabama at Birmingham, Alabama, USA.

To assess statin effects on T-cell proliferation, we performed in-vitro assays as previously described [27] using cryopreserved PBMC from four statin-naive individuals. We compared in-vitro effects of three statins on T-cell proliferation in response to Staphylococcal enterotoxin B (SEB) using cells from four ART-suppressed controls (no statin). Compared with pravastatin, both atorvastatin and rosuvastatin significantly suppressed SEB-mediated CD4+ and CD8+ T-cell proliferation which was partially restored with exogenous mevalonate (Fig. 1a,b).

Fig. 1

Fig. 1

Ex-vivo analyses of expression levels of activation (CD38, HLA-DR), exhaustion (PD-1, TIM-3), and memory (CD27, CD45RO) markers were performed on cryopreserved PBMC from the 17 individuals receiving adjuvant statins before and during statin therapy and the four controls using surface staining with fluorochrome conjugated antibodies for specific cell surface markers [27]. Clinical and demographic features were not significantly different between groups (data not shown). Hyperlipidemia was the indication for statin use in all individuals; none were diabetic patients. In addition, baseline levels of immune activation and exhaustion were similar between the two groups. CD8+ T-cell activation (HLA-DR and HLA-DR/CD38) and exhaustion (TIM-3) markers were significantly reduced following atorvastatin but not pravastatin treatment (Fig. 1c,d). A significant reduction of CD4+ T-cell exhaustion markers (TIM-3 and PD-1) was also observed with atorvastatin (P < 0.05). We did not identify any sex-specific differences in activation or exhaustion marker expression. To evaluate whether ART alone explained these changes, we measured changes in expression levels on PBMC from four virologically suppressed and statin naive individuals. We identified no changes in activation (CD38, HLA-DR) or exhaustion markers (TIM-3, PD-1), suggesting that ART therapy alone did not dictate our findings.

We measured CD27 and CD45RO expression to assess changes in memory T-cell subsets: naive (CD27+CD45RO+), intermediate (CD27+CD45 RO−), late (CD27−CD45RO+) and terminally differentiated (CD27−CD45RO−) phenotypes [28]. A shift to an earlier stage of differentiation and a reduction in terminally differentiated subset was noted with atorvastatin but no change with pravastatin (Fig. 1e,f). Atorvastatin-related reduction of activation marker expression was restricted to terminally differentiated (CD27−CD45RO−) subset of CD8+ T-cells (HLA-DR [44% decline, P = 0.063] and CD38/HLA-DR [55% decline, P = 0.031]); data not shown. These differences were not explained by different proportions of terminally differentiated CD8+ T-cells between the two groups before or during statin time points (P = 0.13, Fig. 1e, f). By contrast, CD4+ T-cell activation (HLA-DR and CD38/HLA-DR) increased with pravastatin in the early differentiated subset (CD27+CD45RO+; P ≤ 0.0312), but this change was not reflected in the total CD4+ T-cell population (data not shown).

As atorvastatin was able to reduce markers associated with chronic T-cell activation and exhaustion, we next evaluated whether statin treatments improved T-cell functionality. When PBMC were antigenically stimulated with HIV (gag) or cytomegalovirus (CMV) (pp65) peptide pools, increased proliferation and interferon-γ production by CMV-specific CD4+ and CD8+ T-cell subsets was observed only for the pravastatin group (data not shown). No functional changes for HIV were observed in either statin group.

Our study demonstrates a differential effect of atorvastatin and pravastatin on T-cell activation, exhaustion and function. Atorvastatin significantly reduced markers of activation and exhaustion on T-cell populations; an effect most pronounced on terminally differentiated effector memory CD8+ T cells. Given that this T-cell subset contributes to the detrimental inflammatory state of chronic viral infections, these changes may be very important in the context of HIV infection, even in persons with suppressed viremia [29,30]. We focused on virologically suppressed individuals with persistent immune activation. Similar to data from viremic individuals, we found reduced CD8+ T-cell activation markers with atorvastatin [25]. This appears to be statin-specific, as pravastatin had no effect on these markers.

Atorvastatin, but not pravastatin, reduced markers of exhaustion (TIM-3 and TIM-3/PD-1) on CD8+ T cells. PD-1is upregulated on both CD4+ and CD8+ T cells during chronic HIV infection even after ART administration and has been correlated with functional T-cell exhaustion in chronic viral infections [31]. Reducing PD-1 and TIM-3 expression may restore T-cell function [32,33]. Whether the reduction of these inhibitory pathways by statins will yield improved immune responses needs further evaluation.

Limitations of our study include its small sample, non-randomized approach, and baseline CD4+ cell count differences. Speculatively, as the pravastatin group had higher CD4+ before and during statin CD4+ count, this group might exhibit lower levels of immune activation prior to statin initiation. However, baseline expression of markers was not different between groups (data not shown). In addition, a comparison of activation markers in patients (CD4+ < 500 cells/mm3) showed similar patterns as shown in Fig. 1c and d, which suggests that a higher CD4+ cell count in pravastatin was not responsible for a lack of detectable impact on the activation/exhaustion markers.

In conclusion, atorvastatin reduced markers of T-cell activation and exhaustion in virologically suppressed HIV-infected individuals. Given the anti-inflammatory effects of statins and the recent American College of Cardiology/American Heart Association guidelines suggesting the benefits of statins extend beyond lipid-lowering, future research will assess which statin provides the greatest benefit for HIV-infected persons.

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Acknowledgements

The authors are indebted to the participants enrolled in the Center For AIDS Research Network of Integrated Clinical Systems (CNICS) studies at UAB. The authors are also very grateful to Marion Spell and the UAB Center For AIDS Research Flow core for technical support and also to Tiffanie Mann for excellent technical assistance.

Author contributions: E.T.O., A.J.Z., P.A.G. and A.B. contributed to the conception and design of the experiments; S.S. and S.M.K. performed the experiments; A.B. and S.S. analyzed the data; A.O.W. performed the statistical analysis of the data; E.T.O., G.B. and P.A.G. provided clinical care for the patients; G.B. helped identify patients for the study. E.T.O. and A.B. wrote the manuscript. A.B. supervised the entire project. E.T.O. and S.S. contributed equally to the writing of the article.

Source of funding: This work was supported by the NIH-funded CNICS (R24 AI067039). Flow cytometry was performed, in part, in the UAB Center for AIDS Research Flow Cytometry Core, which is funded by NIH grant P30 AI027767. A.Z. was supported by AI099867 and S.K. was supported in part by training grant AI007051.

Presentation: This work was presented at the Immune Activation in HIV Infection: Basic Mechanisms and Clinical Implications meeting (poster # 1008), 3–8 April 2013, Breckenridge, Colorado.

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Conflicts of interest

There are no conflicts of interest.

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