Porcine reproductive and respiratory syndrome, a highly contagious disease, poses a severe threat to the global swine industry. Its causative agent, PRRSV, induces reproductive disorders (abortion, stillbirth) in pregnant sows and respiratory disease in piglets. The host immune system is disrupted by PRRSV, and no specific antiviral drugs are currently available. Thus, vaccination is regarded as the primary strategy for PRRS prevention and control. GP4, a key minor structural protein of PRRSV with an estimated molecular weight of 32 kDa, contains four conserved N-glycosylation sites at residues 37, 84, 120 and 130. Critical neutralizing epitopes are harbored in its extracellular domain (amino acids 40–79). PRRSV binding to the host CD163 receptor is mediated by GP4, which also regulates viral assembly and release, and induces protective immune responses. Hence, GP4 is identified as a central target for PRRS vaccine development. In this review, GP4’s structural characteristics, genetic evolution and interaction mechanisms are summarized. Its roles in viral life cycle, virulence, immune evasion and potential applications are discussed, providing a theoretical reference for PRRSV control.

As a highly contagious infectious disease in the swine industry, porcine reproductive and respiratory syndrome (PRRS) can cause reproductive disorders in sows and respiratory diseases in piglets, resulting in sustained economic losses. Nonstructural protein 10 (NSP 10), as one of the core components of the replication and transcription complex of PRRS virus (PRRSV), has both helicase and adenosine triphosphatase activities, and has the potential as a diagnostic marker. In this study, NSP10 recombinant protein was used as coating antigen, and an indirect ELISA method for PRRSV NSP10 detection was established by square matrix titration. After optimizing the assay parameters, high specificity (no reactions with other pig viruses), high sensitivity (able to detect antibodies even when the positive blood sample was diluted 1280 times), and excellent reproducibility (less than 10% variation) were shown. Therefore, the NSP10 indirect enzyme-linked immunosorbent assay (ELISA) developed in this study provides an effective technical means for enhancing PRRSV surveillance in swine herds, thereby establishing a solid foundation for the clinical diagnosis and comprehensive prevention and control of PRRSV.

Porcine reproductive and respiratory syndrome (PRRS), caused by PRRSV, remains a major threat to the global swine industry, and current control relies mainly on vaccination. GP5a, encoded by ORF5a, is a newly identified non-glycosylated envelope structural protein of PRRSV. This review summarizes published studies on the discovery, molecular characteristics, genetic evolution, biological functions, and applications of GP5a, with emphasis on its sequence variation, interactions with host and viral proteins, roles in replication and virulence, and co-evolution with GP5. GP5a is approximately 5–6 kDa and is the smallest PRRSV structural protein. Although relatively conserved, it shows amino acid variations mainly in transmembrane and intramembrane domains. GP5a interacts with host proteins and viral nonstructural proteins, participates in replication and transcription, regulates virulence, and influences immune responses. Silencing GP5a markedly reduces viral titers, and GP5a mutations are associated with attenuation and virulence reversion. GP5a co-evolves with GP5 through overlapping ORF5a/ORF5 and codon usage balance. Its immunogenicity and conserved epitopes make it a potential target for vaccines, diagnostics, and antiviral drugs, although neutralizing antibodies induced by GP5a are limited. Its structure, interactome, and precise molecular mechanisms should be clarified in further studies.

Porcine reproductive and respiratory syndrome (PRRS) has been prevalent in Germany for over 30 years, posing a significant threat to the local swine industry. There are limited analyses to offer German PRRSV ORF5 genetic and evolutionary characteristics and GP5 structural and functional features. In this study, a total of 518 sequences of the PRRSV GP5 gene were obtained from the GenBank database, encompassing 102 sequences from Germany to investigate the genetic relationships and GP5 structural and functional features. Similarly, phylogenetic and recombination analyses were used to identify genetic relationships. Two German PRRSV-1 lineage 1 strains exhibited more than 98.0% nucleotide similarity with vaccine strains. Eighteen German PRRSV-2 lineage 5 strains exhibited more than 98.0% nucleotide similarity with a prototype vaccine strain. German PRRSV-1 lineage 1 was predominant. GP5 structural and functional features were determined by N-glycosylation sites, B-cell epitopes, and transmembrane domain predictions. The main N-glycosylation patterns and transmembrane domains of German PRRSV-1 lineage 1 were time-dependent. Mutations of German PRRSV-1 lineage 3 in the primary neutralizing epitope were detected. In conclusion, these findings reveal lineage-specific molecular variation and improve the understanding of the molecular evolution of German PRRSV.