Traditional Chinese Medicine-Derived Extract and Bioactive Compounds Against Porcine Reproductive and Respiratory Syndrome Virus (PRRSV): Pharmacological Mechanisms, Therapeutic Evidence, and Translational Prospects

Porcine reproductive and respiratory syndrome (PRRS) is one of the most economically important viral diseases affecting the global swine industry, causing substantial production losses through reproductive failure, respiratory disease, increased mortality and impaired growth. Although vaccines against PRRS are available, their effectiveness can be limited by the considerable genetic diversity of porcine reproductive and respiratory syndrome virus (PRRSV), and they do not guarantee complete protection against infection or viral transmission. In contrast, Traditional Chinese Medicines (TCMs), which have been used for centuries, are receiving increasing attention because of their diverse antiviral and immunomodulatory properties. TCMs include individual herbs and complex formulations containing a wide range of bioactive compounds that can act at multiple molecular targets to interfere with viral infection and modulate host responses. This review highlights the potential of TCMs and their bioactive constituents as alternative or complementary strategies for controlling PRRSV infection. It describes the structure and replication cycle of PRRSV to provide a basis for understanding viral replication in target cells, as well as the mechanisms by which viral non-structural proteins interfere with host immune responses. Evidence from in vitro and in vivo studies is summarized to evaluate the anti-PRRSV activity of TCMs and to elucidate the molecular mechanisms underlying the antiviral effects of their bioactive constituents. Furthermore, this review discusses synergistic approaches, nanotechnology-based strategies for improving TCM-compounds bioavailability/vaccine performance and the interplay between PRRSV infection and the gut microbiota. Finally, translational prospects of TCM-based interventions have been discussed, highlighting toxicity concerns and the need for strict quality control to prevent plant substitution and minimize batch-to-batch variability. The discussion also addressed the limited translation of in vitro findings to in vivo efficacy, inconsistent outcomes in animal studies and the need to comply with relevant regulatory requirements before clinical or commercial application.