In vitro immunomodulatory activity of celastrol against influenza A virus infection

Context: The influenza A virus (IAV) causes severe respiratory disease that remains a leading reason for morbidity and mortality. Previous studies have indicated that influenza complications in addition to viral replication are due to overproduction of pro-inflammatory cytokines. Therefore, a new compound is needed to be used with current antiviral drugs to modulate overproduction of pro-inflammatory cytokines in IAV infection. Objective: This study investigated the effect of celastrol on mRNA expression and concentration levels of the pro-inflammatory cytokines tumor necrosis factor alpha (TNF alpha) and interleukin-6 (IL6) that are induced by influenza A/Puerto Rico/8/34 (H1N1; PR8) in Madin-Darby Canine Kidney (MDCK) cells. The effect of this compound on virus titration and viral mRNA expression was also investigated. Methods: Confluent MDCK cells were infected with influenza virus (H1N1; PR8) and treated with celastrol at different concentrations. After incubation, mRNA expression and concentrations of TNF alpha and IL6 were investigated using real-time polymerase chain reaction (PCR) and ELISA. The viral mRNA expression and virus titration were investigated using real-time PCR and 50% tissue culture infectious dose (TCID50) assay, respectively. Results: mRNA expression and concentrations of TNFor and IL6 increased significantly in control virus compared to cell control, and decreased significantly when compared with control virus after celastrol treatment. Viral mRNA expression and virus titration did not decrease after celastrol treatment. Conclusion: Due to reducing mRNA expression and concentrations of TNF alpha and IL6, celastrol can serve as a suitable choice to control cytokine-induced inflammation in IAV infection, and therefore it can be used with current antiviral drugs.