Porcine Reproductive and Respiratory Syndrome Virus Antagonizes PCSK9's Antiviral Effect via Nsp11 Endoribonuclease Activity

Innate Immune Evasion of PRRSV nsp11 through Degradation of the HDAC2 by Its Endoribonuclease Activity

Porcine reproductive and respiratory syndrome virus (PRRSV), a member of the Arteriviridae family, represents a persistent menace to the global pig industry, causing reproductive failure and respiratory disease in pigs. In this study, we delved into the role of histone deacetylases (HDAC2) during PRRSV infection. Our findings revealed that HDAC2 expression is downregulated upon PRRSV infection. Notably, suppressing HDAC2 activity through specific small interfering RNA led to an increase in virus production, whereas overexpressing HDAC2 effectively inhibited PRRSV replication by boosting the expression of IFN-regulated antiviral molecules. Furthermore, we identified the virus's nonstructural protein 11 (nsp11) as a key player in reducing HDAC2 levels. Mutagenic analyses of PRRSV nsp11 revealed that its antagonistic effect on the antiviral activity of HDAC2 is dependent on its endonuclease activity. In summary, our research uncovered a novel immune evasion mechanism employed by PRRSV, providing crucial insights into the pathogenesis of this virus and guiding the development of innovative prevention strategies against PRRSV infection.

Nanobodies against porcine CD163 as PRRSV broad inhibitor

PRRSV (Porcine Reproductive and Respiratory Syndrome Virus) is a major swine pathogen causing economic losses. To the date, effective broad PRRSV inhibitory strategies have not been available in practice yet. Targeting the key viral receptor CD163 to block PRRSV entry has emerged as an alternative approach beside vaccines for PRRSV inhibition. As an effective therapeutic tool, nanoantibodies (Nbs) have been widely used in antiviral research. In this study, a phage display VHH library was constructed for the selection of Nbs against porcine CD163 scavenger receptor cysteine-rich 5-9 domain (SRCR5-9). After five rounds of bio-panning and indirect ELISA, seven CD163-specific Nbs (Nb1-Nb7) were identified. All obtained Nbs displayed strong affinity to CD163 receptor and excellent antiviral activity. In particular, Nb2 exhibited significant broad inhibitory effects on variable PRRSV lineages and downregulated virus-related NF-κB signaling. Further studies suggested that Nbs mainly exerted antiviral functions by interfering with virus attachment stage, and also decreased the transcription of CD163. The conformational epitopes recognized by Nbs were localized in the SRCR5 domain of CD163, a crucial region in PRRSV infection. Overall, our findings provide a novel insight into the biofunction of CD163 in antiviral infection and the development of broad-spectrum strategies against PRRSV.

BST2 negatively regulates porcine reproductive and respiratory syndrome virus replication by restricting the expression of viral proteins

Porcine reproductive and respiratory syndrome virus (PRRSV) has seriously affected the viability of swine industries worldwide, and effective measures to control PRRSV are urgently required. Understanding the mechanisms of action of antiviral proteins is crucial for developing antiviral strategies. Interferon-induced bone marrow stromal cell antigen 2 (BST2) can inhibit the replication of various viruses via different pathways. However, little is known about the effects of BST2 on PRRSV. Therefore, this study aimed to evaluate whether the interferon-induced BST2 can inhibit PRRSV replication. We used western blotting and RT-qPCR techniques to analyze the effect of BST2 overexpression and knockdown on PRRSV replication. Overexpression of BST2 inhibited the replication of PRRSV, whereas knockdown of BST2 by small interfering RNA promoted PRRSV replication. Additionally, the expression of BST2 was upregulated during the early phase of PRRSV infection in porcine alveolar macrophages. Analysis of PRRSV proteins showed that BST2 restricted the expression of several non-structural viral proteins. BST2 downregulated the expression of Nsp12 through a proteasome-dependent pathway and downregulated the expression and transcription of E protein. These findings demonstrate the potential of BST2 as a critical regulator of PRRSV replication.

Research Progress on NSP11 of Porcine Reproductive and Respiratory Syndrome Virus

Porcine reproductive and respiratory syndrome (PRRS) is a virulent infectious disease caused by the PRRS virus (PRRSV). The non-structural protein 11 (NSP11) of PRRSV is a nidovirus-specific endonuclease (NendoU), which displays uridine specificity and catalytic functions conserved throughout the entire NendoU family and exerts a wide range of biological effects. This review discusses the genetic evolution of NSP11, its effects on PRRSV replication and virulence, its interaction with other PRRSV and host proteins, its regulation of host immunity, the conserved characteristics of its enzyme activity (NendoU), and its diagnosis, providing an essential theoretical basis for in-depth studies of PRRSV pathogenesis and vaccine design.

Recent advances in inhibition of porcine reproductive and respiratory syndrome virus through targeting CD163

Porcine reproductive and respiratory syndrome virus (PRRSV) has plagued the pig industry for more than 30 years and causes great economic losses. At present different commercial vaccines are available but limited tools. Until now at least six potential host factors are identified as the key receptors for PRRSV infection. Among them, CD163 molecule is the most important and critical in PRRSV life cycle responsible for mediating virus uncoating and genome release. It determines the susceptibility of target cells to the virus. Several PRRSV non-permissive cells (such as PK-15, 3D4/21, and BHK-21) are demonstrated to become completely susceptible to PRRSV infection in the presence of expression of porcine CD163 protein. Therefore, CD163 has become the target for the design of novel antiviral molecules disrupting the interaction between CD163 and viral glycoproteins, or the breeding of gene-modified animals against PRRSV infection. In this review, we comprehensively summarize the recent progress in inhibition of PRRSV replication via targeting CD163 receptor. In addition, whether there are other potential molecules interacting with CD163 in the process of uncoating of virus life cycle is also discussed.

Evasion of Antiviral Innate Immunity by Porcine Reproductive and Respiratory Syndrome Virus

Innate immunity is the front line for antiviral immune responses and bridges adaptive immunity against viral infections. However, various viruses have evolved many strategies to evade host innate immunity. A typical virus is the porcine reproductive and respiratory syndrome virus (PRRSV), one of the most globally devastating viruses threatening the swine industry worldwide. PRRSV engages several strategies to evade the porcine innate immune responses. This review focus on the underlying mechanisms employed by PRRSV to evade pattern recognition receptors signaling pathways, type I interferon (IFN-α/β) receptor (IFNAR)-JAK-STAT signaling pathway, and interferon-stimulated genes. Deciphering the antiviral immune evasion mechanisms by PRRSV will enhance our understanding of PRRSV’s pathogenesis and help us to develop more effective methods to control and eliminate PRRSV.

The role of PCSK9 in infectious diseases

BACKGROUND

In recent years, many aspects of the physiological role of PCSK9 have been elucidated, particularly regarding its role in lipid metabolism, cardiovascular risk, and its role in innate immunity. Increasing evidence is available about the involvement of PCSK9 in the pathogenesis of viral infections, mainly HCV, and the regulation of host response to bacterial infections, primarily sepsis and septic shock. Moreover, the action of PCSK9 has been investigated as a crucial step in the pathogenesis of malaria infection and disease severity.

OBJECTIVE

This paper aims to review the available published literature on the role of PCSK9 in a wide array of infectious diseases.

CONCLUSION

Besides the ongoing investigation on PCSK9 inhibition among HIV-infected patients to treat HIV- and ART-related hyperlipidemia, preclinical studies indicate how PCSK9 is involved in reducing the replication of HCV. Interestingly, high plasmatic PCSK9 levels have been described in patients with sepsis. Moreover, a protective role of PCSK9 inhibition has also been proposed against dengue and SARS-CoV-2 viral infections. Finally, a loss of function in the PCSK9-encoding gene has been reported to reduce malaria infection mortality.