Antiviral activity of corticosteroids against human parainfluenza virus type 3 infection

Z. Cholisoh, K.J. Broadley, W.R. Ford, E.J. Kidd. Cardiff University, Cardiff, UK.

Respiratory viruses, including human parainfluenza virus type 3 (HPIV-3) are the most common cause of lower respiratory tract infection in children, and are an important trigger of asthma exacerbation at all ages (Glezen et al., 1984). Many recent studies document viral stimulation of epithelial cytokine production and release by human respiratory epithelial cells in vitro (Message et al., 2001). Corticosteroids are among the most effective agents for prevention and treatment of asthma exacerbation, presumably due to their anti-inflammatory action. However, there are limited data on any antiviral effect of these agents and it remains uncertain whether corticosteroids inhibit HPIV-3 infection of the epithelium, a primary target for respiratory viruses. The aim of the study was therefore to quantify any antiviral effects of the corticosteroids; dexamethasone, fluticasone propionate, budesonide, and prednisolone on HPIV-3 infection.

HPIV-3 was grown on primary cultures of green monkey kidney epithelial cells (BSC-1).To determine the time course of viral growth and release, the culture supernatants were collected at either 1, 2, 3, or 7 days after HPIV-3 infection. The supernatants were stored at 80°C for the determination of viral content, by RT-qPCR or quantitative cell culture (plaque assay). The effects of corticosteroids; dexamethasone (10-4-10-10M), fluticasone propionate (10-4-10-10M), budesonide (10-4-10-10M), and prednisolone (10-3-10-9M), on HPIV-3 infection were examined by infecting BSC-1 cells with HPIV-3, 24 hours after corticosteroid incubation. Viral infection and replication were confirmed by RT-qPCR and plaque assay which demonstrated the presence of viral RNA in infected cells. The MTS (3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium) assay measured cell viability to ensure that any antiviral effects were not due to cytotoxicity by corticosteroids.

Viral infection and replication confirmed by RT-qPCR and the plaque assay showed that viral titres of lysates from infected cells increased with time, viral content progressively increasing between 1 and 7 days after infection. There was a high correlation of viral load (r2 = 0.944; n = 15, P<0.0001) measured by RT-qPCR and viral titre measured by plaque assay. The inhibitory effect of corticosteroids on HPIV-3 infection by plaque reduction assays showed that dexamethasone possessed antiviral activity against HPIV-3 with inhibitory concentration (IC50 ± SEM) (2.6 ± 0.3)x 10-6M compared to (4.6 ± 0.1)x10-5M of ribavirin, a guanosine analogue antiviral agent. The MTS assay showed no toxicity of dexamethasone and ribavirin which confirmed that their antiviral effect was not due to cytotoxicity. In contrast, fluticasone propionate, budesonide, and prednisolone have failed to reach a 50% inhibition in the non toxic range of concentrations. In conclusion, dexamethasone was found to have antiviral activity, while fluticasone propionate, budesonide, and prednisolone had no significant antiviral activity.

Glezen W. P., et al. J. Infect. Dis, 1984; 150: 851-857

Message, S. D. et al. Eur Respir J 2001; 18(6): 1013-1025.