The biological functions of PRRSV nonstructural protein NSP2 in viral infection and replication and its role in host regulatory mechanisms.

Porcine reproductive and respiratory syndrome virus (PRRSV) is a single-stranded, positive-sense arterivirus that causes reproductive and respiratory disorders in sows. It is one of the most important pathogens affecting the global swine industry and is widespread worldwide. To date, PRRSV continues to undergo mutation and evolution. NSP2, as the largest non-structural protein generated via proteolytic cleavage of viral polyproteins, has the highest sequence variability among all PRRSV proteins. It cooperates with other non-structural proteins to orchestrate viral replication and modulate host immune responses. This review systematically summarizes the multifaceted functions of NSP2 in the viral life cycle, including its structural and functional characteristics, relationship with viral virulence, mechanisms in viral replication and assembly, role in host immune regulation, and interaction network with both viral and host proteins. These findings provide a theoretical framework for elucidating PRRSV pathogenesis and immune evasion strategies.