Strategies of Classical Swine Fever Immune Evasion

Classical swine fever (CSF) is a highly contagious and lethal disease caused by classical swine fever virus (CSFV), and it is also a notifiable disease according to the World Organization for Animal Health. Owing to the continuous growth of the international trade in pigs and pig products, pig farming has become the pillar industry of the global livestock industry and is the most important source of animal protein for mankind. As a single-stranded RNA virus, CSFV can avoid being recognized and cleared by the host immune system through a variety of immune evasion strategies so that it persists in the host body and causes multisystemic pathology. CSF has also become one of the most serious infectious diseases affecting the pig industry, resulting in considerable economic losses to the pig industry. Therefore, understanding the main immune evasion mechanism of CSFV is very important for the prevention and control of CSF infection. This article reviews the main immune evasion mechanisms of CSFV, including the suppression of nonspecific immune responses; evasion of adaptive immune responses; and the regulation of host cell apoptosis and cell autophagy. CSFV affects type I interferon regulatory signals; the JAK-STAT signaling pathway; the RIG-I and NF-κB signaling pathways; immune cell function; the mitochondrial apoptosis pathway; and the endoplasmic reticulum stress apoptosis pathway; the PI3K-Akt signaling mediated AMPK-mTOR macroautophagy pathway through its structural proteins E^rns and E1 and E2; and the nonstructural proteins N^pro, NS4B, and NS5A to achieve immune evasion. As our understanding of CSFV immune strategies continues to deepen, we believe that this understanding will provide new strategies for the development of new vaccines and novel diagnostic methods in the future.