Phytochemical-Based Immunomodulation: A Promising Therapeutic Approach for Viral Infections

Viral diseases, whether pandemic, endemic, or epidemic, are a leading cause of global mortality and disability. Consequently, developing effective viral inhibitors is a critical public health priority. Beyond antiviral drugs, a promising therapeutic strategy involves using immunomodulators, which are antiviral agents that enhance the host's immune system against infection. Phytochemicals (PCHs) derived from plants exhibit diverse bioactive properties, including significant antioxidant and immunomodulatory effects. Notably, PCHs have attracted considerable attention due to their broad-spectrum inhibitory actions against numerous viruses, including SARS-CoV-2, dengue virus, hepatitis viruses, and herpes viruses. Recent research has shown how PCHs may target specific signaling pathways implicated in a cytokine storm, a potentially fatal clinical syndrome characterized by an excessive production of pro-inflammatory cytokines and immune cell activation. Numerous studies have investigated the immunomodulatory effects of PCHs on immune function, specifically their ability to regulate key cellular and molecular interactions within the immune system. Additionally, by modulating host immunity, PCHs can enhance the antiviral response. Furthermore, these substances interfere with complex cellular signaling networks, emphasizing their efficacy in preventing viral infections. This review examines the significant and advanced mechanisms PCHs influence immune function during viral illnesses. We subsequently evaluate the potential applications of PCHs as immunomodulatory agents for treating viral infections and discuss their current clinical limitations.