Classical swine fever virus infection suppresses claudin-1 expression to facilitate its replication in PK-15 cells

Long non-coding RNA LOC103222771 promotes infection of porcine reproductive and respiratory syndrome virus in Marc-145 cells by downregulating Claudin-4

Porcine reproductive and respiratory syndrome (PRRS) is an important swine disease caused by infection of porcine reproductive and respiratory syndrome virus (PRRSV), which leads to huge loss in swine industry. How to effectively control PRRS is challenging. Long non-coding RNA (lncRNA) are key regulator of viral infections and anti-virus immunological responses, therefore, further understanding of lncRNAs will aid to identification of novel regulators of viral infections and better design of prevention and control strategies to viral infection related diseases and immune disorders. We demonstrated that PRRSV infection upregulated the expression of lncRNA LOC103222771 in Marc-145 cells and porcine alveolar macrophage cells (PAMs) and that LOC103222771 is mainly located in cytoplasm. Knockdown of LOC103222771 could inhibit the PRRSV infection in Marc-145 cells. RNA-seq analysis and subsequent validation revealed increased expression of Claudin-4 (CLDN4) in Marc-145 when LOC103222771 was specifically downregulated，suggesting that LOC103222771 might be an upstream regulator of CLDN4, an important component of tight junctions for establishment of the paracellular barrier that controls the flow of molecules in the intercellular space between epithelial cells. We and others showed that Downregulation of CLDN4 could boost the infection of PRRSV. Collectively, LOC103222771/CLDN4 signal axis might be a novel mechanism of PRRSV pathogenesis, implying a potential therapeutic target against PRRSV infection.

Hazara orthonairovirus nucleoprotein facilitates viral cell-to-cell spread by modulating tight junction protein, claudin-1

Background

Tight junctions act as a barrier that prevents invasion of pathogens through epithelial cells. This study aims to elucidate the correlation between tight junctions and nairoviruses using Hazara orthonairovirus (HAZV) as a surrogate model for Crimean-Congo hemorrhagic fever virus.

Methods

mRNA, total protein, and cell surface protein levels of tight junction proteins were examined by quantitative real-time reverse transcription polymerase chain reaction, immunoblot and flow cytometry, respectively. HAZV growth was measured by plaque assay. Immunofluorescence assay was used to examine viral cell-to-cell spread. The interaction between HAZV nucleoprotein and claudin-1 was analyzed by immunoprecipitation.

Results

HAZV infection induced mRNA of several tight junction proteins, especially claudin-1. HAZV infection also induced cell surface expression of claudin-1 protein. Claudin-1 overexpression inhibited the growth of HAZV by blocking its cell-to-cell spread. In contrast, HAZV nucleoprotein completely inhibited HAZV-induced cell surface expression of claudin-1, and this inhibition required interaction between HAZV nucleoprotein and claudin-1.

Conclusion

HAZV nucleoprotein was shown to bind to claudin-1 to negatively regulate its cell surface expression, and so can promote cell-to-cell spread of HAZV. This is the first presentation of a possible mechanism behind how nairoviruses counteract tight junction barrier function.

Zika Virus Requires the Expression of Claudin-7 for Optimal Replication in Human Endothelial Cells

Zika virus (ZIKV) infection has been associated with a series of neurological pathologies. In patients with ZIKV-induced neurological disorders, the virus is detectable in the central nervous system. Thus, ZIKV is capable of neuroinvasion, presumably through infection of the endothelial cells that constitute the blood-brain barrier (BBB). We demonstrate that susceptibility of BBB endothelial cells to ZIKV infection is modulated by the expression of tight-junction protein claudin-7 (CLDN7). Downregulation of CLDN7 reduced viral RNA yield, viral protein production, and release of infectious viral particles in several endothelial cell types, but not in epithelial cells, indicating that CLDN7 implication in viral infection is cell-type specific. The proviral activity of CLDN7 in endothelial cells is ZIKV-specific since related flaviviruses were not affected by CLDN7 downregulation. Together, our data suggest that CLDN7 facilitates ZIKV infection in endothelial cells at a post-internalization stage and prior to RNA production. Our work contributes to a better understanding of the mechanisms exploited by ZIKV to efficiently infect and replicate in endothelial cells and thus of its ability to cross the BBB.