Antiviral activity of aspirin against RNA viruses of the respiratory tract-an in vitro study

Abstract

Aim: Aspirin (acetylsalicylic acid) has been used for more than 115 years in medicine. Research exists to show that aspirin has antiviral effects in vitro, for example, by blocking influenza virus propagation via NF-κB inhibition when used at high concentrations and short-term incubation steps. The aim of this study was to confirm the antiviral activity of aspirin against influenza virus and further elucidate the activity of aspirin against other respiratory viruses.

Methods: Tests to detect antiviral activity were performed using plaque-reduction assays. Aspirin was administered to the virus-infected cell cultures one hour after infection. Prior to these assays, the non-cytotoxic concentrations of aspirin on cells used for propagation of the respective viruses were determined.

Results: Aspirin was found to be highly effective against influenza A H1N1 virus. The antiviral activity against further respiratory RNA viruses was less distinct. Respiratory syncytial virus was minimally inhibited. However, the activity of aspirin against rhinoviruses was more pronounced. Aspirin demonstrated antiviral activity against all human rhinoviruses (HRV), but the effect on members of the "major group" viruses, namely HRV14 and HRV39, was greater than on those of the "minor group," HRV1A and HRV2.

Conclusions: These data demonstrate a specific antiviral activity of aspirin against influenza A virus and HRV. The mode of action against rhinoviruses is still unknown and requires further investigation, as does the possibility of aspirin being effective in vivo to treat the common cold.

Keywords: acetylsalicylic acid; antiviral activity; aspirin; influenza; plaque-reduction assay; rhinoviruses.

Figure 1

In vitro cytotoxicity of aspirin. In vitro cytotoxicity of aspirin was tested on physiologically active cells used for the propagation of viruses: MDCK (A), HEp‐2 (B), BGM (C) and HeLa (D) over a period of several days. The titration curves show the dose‐dependent cytotoxicity determined using six replicates for each serial dilution for day 1 (blue), day 3 (red) and day 5 (green) for each of the cell lines. The standard deviations in all assays ranged between approximately 2% and 10%. IC50 values were determined graphically and are presented in Table 1

Figure 2

Determination of a dose‐dependent antiviral activity of aspirin against RNA viruses (FluA A; RSV, C; CA9, D) and DNA viruses (HSV‐1, E; Adeno 5, F). A semi‐quantification step was performed using plaque‐reduction assays (for FluA, RSV, CA9, HSV‐1) or with analyses of cytopathogenic effect and the quantification of viral proteins (Adeno 5). X‐axes show the titration of aspirin. Virus controls (without test substance) as well as positive controls are included in the figure: Ribavirin^® (5–20 μg/mL) against FluA (A, B), RSV (C), CA9 (D) and Acyclovir^® for HSV‐1 (E) and Sinupret^® 30 (7.5 μg/mL, laboratory standard, l‐Std) against Adeno 5 (F). The figures present the percentage inhibition of the infectivity of the aspirin‐treated cell cultures (MDCK/FluA; HEp‐2/RSV; HEp‐2/HSV‐1; HEp‐2/Adeno 5; BGM/CA9) in comparison with the non‐treated virus control (100% infection). Data are derived from four replicates of one representative study of two or three different experiments. The standard deviations in all assays ranged between 5% and 15%. The virus doses used for the respective infection experiments (multiplicities of infection, M.O.I.) differed finally between an M.O.I. of 0.0004 (RSV, CA9, HSV‐1) and 10³ TCID ₅₀/mL (Adeno 5)

Figure 3

Determination of the antiviral activity of aspirin against human rhinoviruses: Plaque‐forming units per mL (PFU/mL) were determined for quantification of the antiviral activity against HRV1A (A), HRV2 (B), HRV14 (C) and HRV39 (D). The figures present the percentage inhibition of the infectivity of the aspirin‐treated cell cultures (HeLa cells) in comparison with the non‐treated virus control (100% infection). Ribavirin^® (10–20 μg/mL) served as internal positive control. Data derived from four replicates of one representative study of three different experiments. The standard deviations in all assays ranged between 7% and 18%. All viruses were used with an M.O.I. of 0.0004