Anti-Viral Effects of Paracetamol during Human Cytomegalovirus Infection

Stephen Clark, Rhiannon Wilkinson, Valerie O’Donnell, Gavin Wilkinson, Peter Tomasec. Cardiff University, Cardiff, UK.

Human cytomegalovirus (HCMV) is an important pathogen that establishes life-long persistent infections in the majority of the population1. This is the major viral cause of congenital malformation and is associated with substantial morbidity and mortality in immunocompromised individuals, most notably patients with HIV AIDS and transplant recipients1. There is an urgent need for novel therapeutics for HCMV, particularly where these can be combined with existing anti-viral drugs. Inhibitors of cyclooxygenase 2 (COX2, also known as prostaglandin H synthase 2) have been shown to suppress HCMV replication in vitro2,3. We expand these observations to show that HCMV replication in primary human fibroblasts could be inhibited by the well-tolerated COX inhibitor paracetamol (acetaminophen).

Infection of human foetal foreskin-fibroblasts (HFFFs) with the low-passage clinical HCMV strain Toledo (at a MOI of 10) stimulated cellular COX activity within 24 hours, as measured by the concentration of PGE2 in the media by HPLC-tandem mass spectrometry (0.46 ± 0.12 to 0.89 ± 0.10 ng/ml, mean ± SEM in triplicate). Basal and virus-stimulated levels of PGE2 were greatly reduced with COX inhibitors paracetamol (acetaminophen, 1mM) or aspirin (acetylsalicylic acid, 1mM) applied directly after exposure to the virus (typically 0.05 ± 0.01 ng/ml). Under similar conditions, these drugs impaired replication of HCMV. The IC50 concentrations were calculated as 0.4 mM paracetamol or 1.3 mM aspirin.

HCMV strains Toledo/GFP and Merlin/GFP were used at a MOI of 2 × 10-4 PFU/cell to measure the spread of the virus in HFFF over two weeks. Incubation with 1 mM paracetamol dramatically reduced virus replication and spread, with 47 % of cells treated with Toledo alone infected at 14 days, compared to 5 % of cells treated with Toledo and 1 mM paracetamol (determined by flow cytometry). Furthermore, the HCMV strain Merlin was similarly impaired in it’s ability to spread in HFFF (38 % with virus alone compared to 5 % with virus and 1 mM paracetamol). Our HCMV strain Merlin was derived from a bacterial artificial chromosome; a genetically-defined source of HCMV is important as adaptations occur even during the early stages of passage in cell culture4.

To our knowledge, this is the first description of an anti-viral effect of paracetamol in HCMV infection in vitro. In addition, this is the fist time that the role of COX and PGE2 has been investigated with the prototype HCMV strain Merlin. This work could have important implications for the future clinical management of HCMV.

1. Mocarski ES. (2006) Cytomegaloviruses. In: Fields BN et al, (eds). Fields Virology. Lippincott-Raven, pp 2447–2492

2. Tanaka J et al. (1988) Virology 163 (1): 205-8

3. Schröer J and Shenk TE. (2008) PNAS 105 (49): 19468-73

4. Stanton RJ et al. (2010) JCI 120 (9) 3191-208

This work was supported by the Wellcome Trust.