PSMB4 Degrades the Porcine Reproductive and Respiratory Syndrome Virus Nsp1α Protein via the Autolysosome Pathway and Induces the Production of Type I Interferon

S146 and M148 within the mature chain domain of PSMB4 are crucial for degrading PRRSV nsp1α

Porcine reproductive and respiratory syndrome virus (PRRSV) is a single-stranded positive-sense RNA virus with an envelope. It-encoded non-structural protein 1α (nsp1α) plays a key role in evading host immune responses. Exploring the interaction between host factors and PRRSV nsp1α is crucial for understanding the mechanism of virus immune escape and virus control. Here, we constructed a cDNA library using porcine lung tissues and identified 33 potential host proteins interacting with viral nsp1α using yeast two-hybrid (Y2H) screening. These interactions were further analyzed using Gene Ontology and KEGG pathway analysis. Confocal microscopy revealed that proteasome subunit beta type-4 (PSMB4), carnosine dipeptidase 2 (CNDP2) and poly(rC) binding protein 1 (PCBP1) colocalized with viral nsp1α. The interaction between PSMB4 and nsp1α was further confirmed by Y2H and co-immunoprecipitation. PRRSV infection did not affect PSMB4 expression in both Marc-145 cells and porcine alveolar macrophages (PAMs). Overexpression of PSMB4 reduced nsp1α protein levels in a dose-dependent manner and decreased the accumulation of both viral N and nsp1α proteins in the context of PRRSV infection, while its knockdown promoted PRRSV replication. These data suggest that PSMB4 is a host restriction factor for PRRSV. Structure prediction and truncated mutant assays found that S146 and M148 within the mature chain domain of PSMB4 were crucial for binding and degrading nsp1α. These findings suggest that PRRSV nsp1α interacts with host proteins, with PSMB4 specifically binding to degrade nsp1α, thereby inhibiting PRRSV replication.

Unlocking the genetic code: a comprehensive Genome-Wide association study and gene set enrichment analysis of cell-mediated immunity in chickens

BACKGROUND

The poultry immune system is essential for protecting against infectious diseases and maintaining health and productivity. Cell-mediated immune responses (CMIs) protect organisms against intracellular pathogens. This study aimed to enrich the findings of genome-wide association studies (GWAS) by including several systematic gene set enrichment analyses (GSEA) related to cell-mediated immune responses in chickens.

METHODS

To investigate the function of the cellular immune system, phenotypic data were collected based on the differences in skin thickness before and after impregnation with dinitrochlorobenzene (DNCB) solution. Additionally, 312 hybrid birds of the F2 generation of Arian broiler chickens and Urmia native chickens were genotyped using the Illumina 60k SNP BeadChip. A general linear model (GLM) with an FDR < 5% was used for the association analysis. Functional enrichment analysis of the identified candidate genes was performed using the Enrichr database. A protein‒protein interaction (PPI) network was constructed using the STRING database. In addition, colocalization analysis was applied to identify QTLs related to the immune system.

RESULTS

GWAS revealed 147 SNPs associated with the CMI trait, which were related to 1363 genes. These genes were significantly enriched in eight KEGG pathways, 22 Reactome pathways, and 18 biological processes. PPI network analysis led to the identification of 26 hub genes. The three hub genes PSMA3, PSMC2 and PSMB4 were enriched in almost all pathways related to cellular immunity, including the proteasome, interleukin-1 signaling, and programmed cell death pathways, which makes them important candidates involved in CMI. In addition, the MAP3K8, NLRC5, UBB, CASP6, DAPK2, TNFRSF6B, TNFSF15, and PIK3CD genes were identified as key genes in several functional pathways. A total of 10 SNPs were found in interferon-gamma QTLs, and two SNPs were found in the cell-mediated immune response QTL region, leading to the identification of 12 cellular immune response-related genes that were reported as important candidates in previous studies.

CONCLUSION

The post-GWAS analysis in this study led to the identification of key genes that regulate the biological processes of cellular immunity in chickens. Therefore, selecting birds that excel in expressing such genes can improve immunity in chickens.

Antiviral mechanism of Fuzhengjiedu San against porcine reproductive and respiratory syndrome virus

Porcine reproductive and respiratory syndrome virus (PRRSV) is a viral infectious disease that can cause infection in pigs of different ages. The condition known as porcine reproductive and respiratory syndrome poses a serious risk to the world's pig business and results in significant financial losses. Fuzhengjiedu San (FZJDS) is a traditional Chinese medicine compound, the main components include:Radix Isatidis, Radix Astragali and Herba Epimedii. It has been widely used in clinical and experimental studies, showing a wide range of biological activity. However, it is not clear whether FZJDS has anti-PRRSV activity. We observed that FZJDS had significant antiviral activity in Marc-145 cells. And FZJDS could inhibit viral infection in the stages of viral internalization and replication. Furthermore, FZJDS can inhibit PRRSV replication by inhibiting the p53 signaling pathway to affect autophagy, and FZJDS can also inhibit PRRSV replication by inhibiting the PI3K/Akt pathway.We showed in this work that FZJDS inhibits PRRSV replication in vitro and offers a novel therapeutic approach for PRRSV infection.

Research progress on the molecular mechanism of immune escape of porcine reproductive and respiratory syndrome virus

Porcine reproductive and respiratory syndrome (PRRS), caused by the porcine reproductive and respiratory syndrome virus (PRRSV), is a severe and highly contagious disease that results in significant economic losses for the pig industry. Currently, vaccination is one of the most effective methods for controlling PRRS; however, due to the extensive genetic variation of PRRSV and the generation of homologous immunity, vaccines provide protective effects only against homologous strains and lack effective cross-protection against heterologous strains. Furthermore, PRRSV encodes a variety of proteins with immune escape functions, and the mechanisms underlying these functions are complex and not yet fully understood. This complexity presents substantial challenges to the prevention, control, and eradication of the disease. Therefore, this article reviews the various escape mechanisms of PRRSV identified in recent years, with the aim of providing insights into the pathogenic mechanisms of PRRSV and facilitating the development of safer and more effective vaccines and therapeutics.

Understanding Post-Translational Modifications in Porcine Reproductive and Respiratory Syndrome Virus Infection

Porcine reproductive and respiratory syndrome virus (PRRSV) is a highly contagious virus affecting pigs with significant impacts to the swine industry worldwide. This review provides a comprehensive understanding of post-translational modifications (PTMs) associated with PRRSV infection. We discuss the various types of PTMs, including phosphorylation, ubiquitination, SUMoylation, acetylation, glycosylation, palmitoylation, and lactylation, that occur during PRRSV infection. We emphasize how these modifications affect the function and activity of viral proteins, thereby influencing virus replication, assembly, and egress. Additionally, we delve into the host cellular responses triggered by PRRSV, particularly the PTMs that regulate host signaling pathways and immune responses. Furthermore, we summarize the current understandings of how PTMs facilitate the ability of virus to evade the host immune system, enabling it to establish persistent infections. Finally, we address the implications of these modifications in the development of novel antiviral strategies and the potential for exploiting PTMs as therapeutic targets. This review highlights the significance of PTMs in shaping viral pathogenicity and host antiviral mechanisms and provides valuable insights for future research aimed at developing effective interventions against PRRSV infections.

The dual role of autophagy during porcine reproductive and respiratory syndrome virus infection: A review

Autophagy is a highly conserved catabolic process that transports cellular components to lysosomes for degradation and reuse. It impacts various cellular functions, including innate and adaptive immunity. It can exhibit a dual role in viral infections, either promoting or inhibiting viral replication depending on the virus and the stage of the infection cycle. Porcine reproductive and respiratory syndrome virus (PRRSV) is a significant pathogen impacting the sustainable development of the global pork industry. Recent research has shown that PRRSV has evolved specific mechanisms to facilitate or impede autophagosome maturation, thereby evading innate and adaptive immune responses. These primary mechanisms involve viral proteins that target multiple regulators of autophagosome formation, including autophagy receptors, tethering proteins, autophagy-related (ATG) genes, as well as the functional proteins of autophagosomes and late endosomes/lysosomes. Additionally, these mechanisms are related to the post-translational modification of key components, viral antigens for presentation to T lymphocytes, interferon production, and the biogenesis and function of lysosomes. This review discusses the specific mechanisms by which PRRSV targets autophagy in host defence and virus survival, summarizes the role of viral proteins in subverting the autophagic process, and examines how the host utilizes the antiviral functions of autophagy to prevent PRRSV infection.

Molecular mechanism of autophagy in porcine reproductive and respiratory syndrome virus infection

Porcine reproductive and respiratory syndrome virus (PRRSV), a significant pathogen affecting the swine industry globally, has been shown to manipulate host cell processes, including autophagy, to facilitate its replication and survival within the host. Autophagy, an intracellular degradation process crucial for maintaining cellular homeostasis, can be hijacked by viruses for their own benefit. During PRRSV infection, autophagy plays a complex role, both as a defense mechanism of the host and as a tool exploited by the virus. This review explores the current understanding of the molecular mechanisms underlying autophagy induction under PRRSV infection, its impact on virus replication, and the potential implications for viral pathogenesis and antiviral strategies. By synthesizing the latest research findings, this article aims to enhance our understanding of the intricate relationship between autophagy and PRRSV, paving the way for novel therapeutic approaches against this swine pathogen.

Siah2- and LRSAM1-mediated K63-linked ubiquitination of snakehead vesiculovirus nucleoprotein facilitates viral replication

Nucleoprotein (N) is well known for its function in the encapsidation of the genomic RNAs of negative-strand RNA viruses, which leads to the formation of ribonucleoproteins that serve as templates for viral transcription and replication. However, the function of the N protein in other aspects during viral infection is far from clear. In this study, the N protein of snakehead vesiculovirus (SHVV), a kind of fish rhabdovirus, was proved to be ubiquitinated mainly via K63-linked ubiquitination. We identified nine host E3 ubiquitin ligases that interacted with SHVV N, among which seven E3 ubiquitin ligases facilitated ubiquitination of the N protein. Further investigation revealed that only two E3 ubiquitin ligases, Siah E3 ubiquitin protein ligase 2 (Siah2) and leucine-rich repeat and sterile alpha motif containing 1 (LRSAM1), mediated K63-linked ubiquitination of the N protein. SHVV infection upregulated the expression of Siah2 and LRSAM1, which maintained the stability of SHVV N. Besides, overexpression of Siah2 or LRSAM1 promoted SHVV replication, while knockdown of Siah2 or LRSAM1 inhibited SHVV replication. Deletion of the ligase domain of Siah2 or LRSAM1 did not affect their interactions with SHVV N but reduced the K63-linked ubiquitination of SHVV N and SHVV replication. In summary, Siah2 and LRSAM1 mediate K63-linked ubiquitination of SHVV N to facilitate SHVV replication, which provides novel insights into the role of the N proteins of negative-strand RNA viruses.

IMPORTANCE

Ubiquitination of viral protein plays an important role in viral replication. However, the ubiquitination of the nucleoprotein (N) of negative-strand RNA viruses has rarely been investigated. This study aimed at investigating the ubiquitination of the N protein of a fish rhabdovirus SHVV (snakehead vesiculovirus), identifying the related host E3 ubiquitin ligases, and determining the role of SHVV N ubiquitination and host E3 ubiquitin ligases in viral replication. We found that SHVV N was ubiquitinated mainly via K63-linked ubiquitination, which was mediated by host E3 ubiquitin ligases Siah2 (Siah E3 ubiquitin protein ligase 2) and LRSAM1 (leucine-rich repeat and sterile alpha motif containing 1). The data suggested that Siah2 and LRSAM1 were hijacked by SHVV to ubiquitinate the N protein for viral replication, which exhibited novel anti-SHVV targets for drug design.

The Identification of Host Proteins That Interact with Non-Structural Proteins-1α and -1β of Porcine Reproductive and Respiratory Syndrome Virus-1

Porcine reproductive and respiratory syndrome viruses (PRRSV-1 and -2) are the causative agents of one of the most important infectious diseases affecting the global pig industry. Previous studies, largely focused on PRRSV-2, have shown that non-structural protein-1α (NSP1α) and NSP1β modulate host cell responses; however, the underlying molecular mechanisms remain to be fully elucidated. Therefore, we aimed to identify novel PRRSV-1 NSP1-host protein interactions to improve our knowledge of NSP1-mediated immunomodulation. NSP1α and NSP1β from a representative western European PRRSV-1 subtype 1 field strain (215-06) were used to screen a cDNA library generated from porcine alveolar macrophages (PAMs), the primary target cell of PRRSV, using the yeast-2-hybrid system. This identified 60 putative binding partners for NSP1α and 115 putative binding partners for NSP1β. Of those taken forward for further investigation, 3 interactions with NSP1α and 27 with NSP1β were confirmed. These proteins are involved in the immune response, ubiquitination, nuclear transport, or protein expression. Increasing the stringency of the system revealed NSP1α interacts more strongly with PIAS1 than PIAS2, whereas NSP1β interacts more weakly with TAB3 and CPSF4. Our study has increased our knowledge of the PRRSV-1 NSP1α and NSP1β interactomes, further investigation of which could provide detailed insight into PRRSV immunomodulation and aid vaccine development.

Research Progress of Porcine Reproductive and Respiratory Syndrome Virus NSP2 Protein

Porcine reproductive and respiratory syndrome virus (PRRSV) is globally prevalent and seriously harms the economic efficiency of pig farming. Because of its immunosuppression and high incidence of mutant recombination, PRRSV poses a great challenge for disease prevention and control. Nonstructural protein 2 (NSP2) is the most variable functional protein in the PRRSV genome and can generate NSP2N and NSP2TF variants due to programmed ribosomal frameshifts. These variants are broad and complex in function and play key roles in numerous aspects of viral protein maturation, viral particle assembly, regulation of immunity, autophagy, apoptosis, cell cycle and cell morphology. In this paper, we review the structural composition, programmed ribosomal frameshift and biological properties of NSP2 to facilitate basic research on PRRSV and to provide theoretical support for disease prevention and control and therapeutic drug development.