Statins inhibit cytomegalovirus replication by interfering with the isoprenoid arm of the mevalonate pathway

Abstract

Summary Primary infection of human cytomegalovirus (HCMV) is rarely recognized in the immune competent host, and seroprevalence reaches 80% in the older population. Life-long persistence is the hallmark of HCMV. In immunocompromised patients such as in transplant recipients and HIV-infected patients, infections are a major concern and are associated with severe morbidity and mortality. Both reactivation and primary infection can occur. In the absence of vaccines against HCMV, the management and prevention of infection relies on the three systemic drugs approved for CMV treatment, ganciclovir, foscarnet and cidofovir. Considering the extended treatment period required for the treatment in immunocompromised patients, several drawbacks are limiting the use of these drugs: severe acute and long-term toxicities, and a shared viral target with the risk of emergence of drug cross-resistance. There is an urgent need for new therapeutic approaches with a good safety profile and an alternative mechanism of action that would ideally interfere earlier in the HCMV replication cycle. Statins are a well-tolerated and extensively studied group of cholesterol-lowering drugs, exhibiting strong anti-inflammatory and immune-modulatory activities. Antiviral effects of statins have been reported on different viruses alone or in combination with selective antiviral inhibitors and have been associated with cholesterol-lowering or cholesterol- independent mechanisms. So far, despite a large number of statins currently used in clinics, little is known about the potential of statins against HCMV. The goal of this study was to investigate the in vitro anti-CMV activity of four statins (atorva-, fluva-, prava- and simvastatin) in human aortic endothelial cells (HAEC) and fibroblasts. Our findings demonstrate that all statins dose-dependently reduce HCMV titers in both cell types. Atorva-, fluva- and simvastatin showed comparable EC50 and EC90, within a low micromolar range in HAEC, whereas pravastatin exhibited only limited effects. The same hierarchy was observed in fibroblasts, although all statins exhibited slightly less anti-CMV potency. The reduction of HCMV titers did not result from an inhibition of HCMV entry or an activation of the type I IFN response, but from the alteration of the expression of several viral antigens. Interestingly, statins treatment not only blocked the accumulation of immediate early antigens, but also interferes independently with early and late antigen expression. Despite our attempts, the key mediator of the anti-CMV activity of statins was not identified. However, metabolite rescue experiments suggested an involvement of the non-sterol isoprenoid arm of the mevalonate pathway as the mode-of-action. Anti-CMV activity of all statins was almost completely abrogated by mevalonate and partially reversed by geranylgeranyl-pyrophosphate, an isoprenoid intermediate, whereas cholesterol failed to counteract the effects of statins. In an attempt to evaluate potential clinical benefits, we demonstrate an additive anti-CMV activity of statins at therapeutically relevant concentrations. While, the antiviral activity of statins was comparable to ganciclovir, statins enhanced the anti-CMV activity of low doses of ganciclovir suggesting a potential benefit for combination therapy. Finally, statins anti- CMV activity was retained in a ganciclovir-resistant HCMV strain. In conclusions, these findings provide new insight into the beneficial effects of statins, adding antiviral activity against HCMV to their list of pleiotropic properties. Although the in vivo anti-CMV activity of statins might be limited to the lipophilic compounds, this supports further clinical investigation of the beneficial use of statins, as part as a cholesterol-lowering or anti-inflammatory therapy, against HCMV infection. Special attention should be taken to evaluate statins in combined therapy for the management of active HCMV disease and against cross-resistant HCMV strain. Finally, we believe this work may reveal potential targets for alternative anti-viral therapies.