IFN-γ as a Major Antiviral Therapeutic for Viral Epidemics, Including Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2): A Clinically Forgotten but Potential Antiviral Cytokine and Non-Virus-Specific Antiviral as a New Antiviral Strategy

Abstract

IFN-γ is a type II IFN known as immune IFN that differs from virus-induced type I and III IFNs. IFN-γ has been clinically used to treat a wide variety of diseases. The original function of IFN-γ is its natural antiviral activity, and this molecule may be effective in viral infection and consequent disseminated multi-organ invasion. Despite its role as an inflammatory cytokine, IFN-γ induces regulatory T cells and antigen-specific regulatory B cells, which play a counter-regulatory role in the immune reaction, possibly preventing or controlling excessive immune responses such as cytokine storms that can result in death. The advantages of IFN-γ are as follows: 1) IFN-γ is a non-virus-specific antiviral therapeutic and can be used in new virus infections and epidemics; 2) IFN-γ is strongly predicted to be effective in viral infection; 3) adequate clinical data for the clinical protocols of IFN-γ including dosage and period of use, are available; 4) IFN-γ is a relatively safe drug with few side effects and no rare severe side effects; 5) IFN-γ is available immediately; and 6) IFN-γ is not expensive. New viruses have appeared every several years, causing serious epidemics to pandemic circumstances. Researchers must develop antiviral strategies against viral diseases, especially for critically serious viral epidemics. Among the IFNs, IFN-γ is regarded as suitable and strongly recommended as a major antiviral agent, at least in high-risk patients who are infected by viruses, including severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), when no vaccines or virus-specific antiviral therapeutics are available.