Porcine reproductive and respiratory syndrome virus triggers Golgi apparatus fragmentation-mediated autophagy to facilitate viral self-replication.

Macroautophagy/autophagy is a cellular degradation and recycling process that maintains the homeostasis of organisms. A growing number of studies have reported that autophagy participates in infection by a variety of viruses. Porcine reproductive and respiratory syndrome virus (PRRSV) causes severe financial losses to the global swine industry. Although much research has shown that PRRSV triggers autophagy for its own benefits, the exact molecular mechanisms involved in PRRSV-triggered autophagy remain to be fully elucidated. In the current study, we demonstrated that PRRSV infection significantly induced Golgi apparatus (GA) fragmentation, which promoted autophagy to facilitate viral self-replication. Mechanistically, PRRSV nonstructural protein 2 was identified to interact with and degrade the Golgi reassembly and stacking protein 65 dependent on its papain-like cysteine protease 2 activity, resulting in GA fragmentation. Upon GA fragmentation, GA-resident Ras-like protein in brain 2 was disassociated from Golgi matrix protein 130 and subsequently bound to unc-51 like autophagy activating kinase 1 (ULK1), which enhanced phosphorylation of ULK1 and promoted autophagy. Taken together, all these results expand the knowledge of PRRSV-triggered autophagy as well as PRRSV pathogenesis to support novel potential avenues for prevention and control of the virus. More importantly, these results provide the detailed mechanism of GA fragmentation-mediated autophagy, deepening the understanding of autophagic processes.IMPORTANCEPorcine reproductive and respiratory syndrome virus (PRRSV) infection results in a serious swine disease affecting pig farming worldwide. Despite that numerous studies have shown that PRRSV triggers autophagy for its self-replication, how PRRSV induces autophagy is incompletely understood. Here, we identify that PRRSV Nsp2 degrades GRASP65 to induce GA fragmentation, which dissociates RAB2 from GM130 and activates RAB2-ULK1-mediated autophagy to enhance viral replication. This work expands our understanding of PRRSV-induced autophagy and PRRSV replication, which is beneficial for anti-viral drug development.

Development of an enzyme-linked immunosorbent assay based on viral antigen capture by anti-spike glycoprotein monoclonal antibody for detecting immunoglobulin A antibodies against porcine epidemic diarrhea virus in milk.

BACKGROUND: Porcine epidemic diarrhea (PED), caused by PED virus (PEDV), is a severe enteric disease burdening the global swine industry in recent years. Especially, the mortality of PED in neonatal piglets approaches 100%. Maternal antibodies in milk, particularly immunoglobulin A (IgA) antibodies, are of great importance for protection neonatal suckling piglets against PEDV infection as passive lactogenic immunity. Therefore, appropriate detection methods are required for detecting PEDV IgA antibodies in milk. In the current study, we prepared monoclonal antibodies (mAbs) against PEDV spike (S) glycoprotein. An enzyme-linked immunosorbent assay (ELISA) was subsequently developed based on PEDV antigen capture by a specific anti-S mAb. RESULTS: The developed ELISA showed high sensitivity (the maximum dilution of milk samples up to 1:1280) and repeatability (coefficient of variation values < 10%) in detecting PEDV IgA antibody positive and negative milk samples. More importantly, the developed ELISA showed a high coincidence rate with a commercial ELISA kit for PEDV IgA antibody detection in clinical milk samples. CONCLUSIONS: The developed ELISA in the current study is applicable for PEDV IgA antibody detection in milk samples, which is beneficial for evaluating vaccination efficacies and neonate immune status against the virus.

Molecular epidemiology and genetic variation analyses of porcine circovirus type 2 isolated from Yunnan Province in China from 2016-2019.

BACKGROUND: Porcine circovirus type 2 (PCV2) is the causative agent of porcine circovirus-associated disease (PCVAD). Its prevalence in swine herds was first reported in China in 2000. PCV2 infection causes immunosuppression that leads to multiple diseases, causing serious economic problems for the swine industry in China. Since information on the genetic variation of PCV2 in Yunnan province is limited, this study aims to investigate the molecular epidemiological and evolutionary characteristics of PCV2 from 2016 to 2019. METHODS: A total of 279 clinical samples were collected from different regions of Yunnan between 2016 to 2019, and PCV2 was detected by PCR. We then amplified full genomes from the positive samples, and the sequences were analysed for homology and genetic evolution. RESULTS: Overall, 60.93% (170/279) of the screened swine herd samples were positive for PCV2. We sequenced 15 Yunnan province PCV2 strains from positive samples. Analyses of the complete genomes and Cap genes led to the classification of the 15 Yunnan PCV2 strains into PCV2a (2 of 15), PCV2b (1of 15) and PCV2d (12 of 15). All strains shared 94.3-99.9% of their identities with the nucleotide sequences of complete genomes in this study and shared 94.2-99.9% identity with the reference sequences. All strains share 89.4-100% and 86.8-100% of their identities with the nucleotide and amino acid (aa) sequences of Cap, respectively. CONCLUSIONS: The results of this study provide evidence that PCV2a, PCV2b and PCV2d genotypes coexisted in Yunnan Province from 2016 to 2019, and the priority prevalence genotype was PCV2d. The data provide evidence for the increased genetic diversity and insights into the molecular epidemiology of PCV2. This study also provides basic data for the Yunnan province PCV2 molecular epidemiological survey and accumulates effective materials for the development of PCV2 vaccines.