Newcastle disease (ND) is an acute and highly contagious disease caused by the Newcastle disease virus (NDV) infecting poultry, which has caused great harm to the poultry industry around the world. Rapid diagnosis of NDV is important to early treatment and early institution of control measures. In this review, we comprehensively summarize the most recent research into NDV, including historical overview, molecular structure, and infection mechanism. We then focus on detection strategies for NDV, including virus isolation, serological assays (such as hemagglutination and hemagglutination-inhibition tests, enzyme linked immunosorbent assay, reporter virus neutralization test, Immunofluorescence assay, and Immune colloidal gold technique), molecular assays (such as reverse transcription polymerase chain reaction, real-time quantitative PCR, and loop-mediated isothermal amplification) and other assays. The performance of the different serological and molecular biology assays currently available was also analyzed. To conclude, we examine the limitations of currently available strategies for the detection of NDV to lay the groundwork for new detection assays.

Porcine reproductive and respiratory syndrome virus (PRRSV) is a severe disease with substantial economic consequences for the swine industry. The DEAD-box helicase 3 (DDX3X) is an RNA helicase that plays a crucial role in regulating RNA metabolism, immunological response, and even RNA virus infection. However, it is unclear whether it contributes to PRRSV infection. Recent studies have found that the expression of DDX3X considerably increases in Marc-145 cells when infected with live PRRSV strains Ch-1R and SD16; however, it was observed that inactivated viruses did not lead to any changes. By using the RK-33 inhibitor or DDX3X-specific siRNAs to reduce DDX3X expression, there was a significant decrease in the production of PRRSV progenies. In contrast, the overexpression of DDX3X in host cells substantially increased the proliferation of PRRSV. A combination of transcriptomics and metabolomics investigations revealed that in PRRSV-infected cells, DDX3X gene silencing severely affected biological processes such as ferroptosis, the FoxO signalling pathway, and glutathione metabolism. The subsequent transmission electron microscopy (TEM) imaging displayed the typical ferroptosis features in PRRSV-infected cells, such as mitochondrial shrinkage, reduction or disappearance of mitochondrial cristae, and cytoplasmic membrane rupture. Conversely, the mitochondrial morphology was unchanged in DDX3X-inhibited cells. Furthermore, silencing of the DDX3X gene changed the expression of ferroptosis-related genes and inhibited the virus proliferation, while the drug-induced ferroptosis inversely promoted PRRSV replication. In summary, these results present an updated perspective of how PRRSV infection uses DDX3X for self-replication, potentially leading to ferroptosis via various mechanisms that promote PRRSV replication.

Background: Porcine epidemic diarrhea virus (PEDV), an enteric coronavirus, has become the major causative agent of acute gastroenteritis in piglets since 2010 in China.Results: In the current study, 91 complete spike (S) gene sequences were obtained from PEDV positive samples collected from 17 provinces in China from March 2020 to March 2021. A phylogenetic analysis showed that 92.3% (84 out of 91) of the identified strains belonged to GII subtype, while 7.7% (7 out of 91) were categorized as S-INDEL like strains and grouped within GI-c clade. Based on a recombination analysis, six of S-INDEL like strains were recombinant strains originated from S-INDEL strain FR/001/2014 and virulent strain AJ1102. In addition, PEDV variant strains (CH/GDMM/202012, CH/GXDX/202010 et al) carrying novel insertions (360QGRKS364 and 1278VDVF1281) in the S protein were observed. Furthermore, the deduced amino acid sequences for the S protein showed that multiple amino acid substitutions in the antigenic epitopes in comparison with the vaccine strains.Conclusions: In conclusion, these data provide novel molecular evidence on the epidemiology and molecular diversity of PEDV in 2020–2021. This information may help design a strategy for controlling and preventing the prevalence of PEDV variant strains in China.

The current vaccines for porcine reproductive and respiratory syndrome virus (PRRSV) have failed to provide broad protection against infection by various strains of PRRSV. Porcine Interleukin-4 (pIL-4) plays an important role in the regulation of the immune response and has been used previously as an immunological adjuvant. The objective of this study was to construct a recombinant PRRSV expressing pIL-4 and to evaluate the immune response of the recombinant virus in piglets. The pIL-4 gene was inserted in the PRRSV (CH-1R strain) infectious clone by overlap PCR. Indirect immunofluorescence assay (IFA) and Western blotting were used to confirm the recombinant virus. The stability of the recombinant virus was assessed by DNA sequencing and IFA after 15 passages in vitro. Recombinant virus was injected into pigs and efficacy of immune protection was evaluated in comparison with the parental virus. The recombinant virus (CH-1R/pIL-4) was successfully rescued and shown to have similar growth kinetics as the parental virus. The recombinant virus was stable for 15 passages in cell culture. Pigs vaccinated with CH-1R/pIL-4 produced a similar humoral response to the response elicited by parental virus, but IL-4 level in the supernatant of PBMCs from pigs vaccinated with CH-1R/pIL-4 was significantly higher than the parent virus at 28 days post-immunization (DPI). Flow cytometric (FCM) analysis showed that the percentage of CD4+CD8+ double positive T (DPT) cells in the CH-1R/pIL-4 vaccinated group was significantly higher than the parental virus at 3 and 7 Days Post-Challenge (DPC), and the IL-4 level in the blood significantly increased at 7 DPC. However, the viral load and histopathology did not show significant difference between the two groups. A recombinant PRRSV expressing porcine IL-4 was rescued and it remained genetically stable in vitro. The recombinant virus induced higher DPT ratios and IL-4 levels in the blood after HP-PRRSV challenge compared to the parental virus in piglets. However, it did not significantly improve protection efficacy of PRRSV vaccine.

The host cell membrane-associated RING-CH 8 protein (MARCH8), a member of the E3 ubiquitin ligase family, regulates intracellular turnover of many transmembrane proteins and shows potent antiviral activities. Generally, 2 antiviral modes are performed by MARCH8. On the one hand, MARCH8 catalyzes viral envelope glycoproteins (VEGs) ubiquitination and thus leads to their intracellular degradation, which is the cytoplasmic tail (CT)-dependent (CTD) mode. On the other hand, MARCH8 traps VEGs at some intracellular compartments (such as thetrans-Golgi network, TGN) but without inducing their degradation, which is the cytoplasmic tail-independent (CTI) mode, by which MARCH8 hijacks furin, a cellular proprotein convertase, to block VEGs cleavage. In addition, the MARCH8 C-terminal tyrosine-based motif (TBM)²²²YxxL²²⁵also plays a key role in its CTI antiviral effects. In contrast to its antiviral potency, MARCH8 is occasionally hijacked by some viruses and bacteria to enhance their invasion, indicating a duplex role of MARCH8 in host pathogenic infections. This review summarizes MARCH8’s antiviral roles and how viruses evade its restriction, shedding light on novel antiviral therapeutic avenues.