Viruses

Cancer cells often have defects in antiviral pathways, making them susceptible to oncolytic viruses like vesicular stomatitis virus (VSV). However, some cancer cells resist viral infection through the constitutive expression of interferon-stimulated genes. This study examined whether NF-κB activation and NF-κB-dependent antiviral signaling contribute to resistance to VSV infection in the PC3 cell line, derived from an aggressive metastatic prostate cancer (PrCa) tumor. We found that NF-κB localized to the nucleus in VSV-infected PC3 cells, but not in the VSV-susceptible LNCaP PrCa cell line. Analysis of the upstream NF-κB inhibitor IκB-α revealed higher levels of both total and phosphorylated IκB-α in PC3 cells compared to LNCaP cells, indicating constitutive activation of the NF-κB pathway via an IκB-α-dependent mechanism. Notably, VSV infection did not alter IκB-α phosphorylation in PC3 cells, suggesting that VSV may amplify NF-κB signaling through an IκB-α–independent pathway. Furthermore, PC3 cells displayed elevated levels of the NF-κB p65 protein subunit compared to LNCaP cells, with its phosphorylated form significantly increased upon VSV infection. These results from phosphorylation assays confirm that multiple steps in the NF-κB pathway are differentially activated in PC3 and LNCaP cells. Finally, the expression of several NF-κB-dependent cytokines and proinflammatory genes, including IL12 and IL6, was upregulated following VSV infection in PC3 cells, as compared to LNCaP cells. Collectively, these findings suggest that enhanced NF-κB signaling may underlie the resistance of PC3 cells to VSV oncolysis, potentially offering new insights into therapeutic strategies targeting NF-κB in resistant prostate cancers.

Foot-and-mouth disease virus (FMDV) infection elicits sustained, high-level interleukin-10 (IL-10) secretion in cattle and pigs, which correlates with lymphopenia and immunosuppression. We previously showed that macrophages are the principal source of IL-10 during FMDV infection in mice, but the viral trigger and host pathways remained unknown. In the present study, we examined whether the FMDV structural protein VP3 regulates IL-10 expression. To this end, a eukaryotic VP3 expression vector was transfected into porcine alveolar macrophages (3D4/21 cells), and IL-10 expression together with related signaling pathways was interrogated by qRT-PCR, ELISA, Western blot, co-immunoprecipitation (Co-IP), confocal microscopy, and luciferase reporter assays. The results showed that VP3 significantly increased IL-10 mRNA and protein levels (p < 0.001) in a time-dependent manner. Mechanistically, VP3 promoted phosphorylation of PI3K, AKT, and mTOR; this effect was abolished by the PI3K inhibitor LY294002, which also abrogated VP3-induced IL-10 secretion (p < 0.05). Furthermore, VP3 upregulated mRNA expression of STAT3, ATF1, and CREB (p < 0.05) and enhanced IL-10 promoter activity. The STAT3 inhibitor Stattic reduced IL-10 secretion by 22% (p < 0.05). Co-IP and confocal microscopy confirmed direct binding of VP3 to PI3K in the cytoplasm. In conclusion, FMDV VP3 induces IL-10 overexpression by directly activating the PI3K/AKT-mTOR signaling pathway, thereby elucidating a key mechanism of FMDV-induced immunosuppression.

Bovine gammaherpesvirus 4 (BoGHV-4) is an opportunistic uterine pathogen whose reactivation is associated with postpartum inflammation and bacterial lipopolysaccharide (LPS). Platelet-rich plasma (PRP) is a regenerative biotherapeutic capable of modulating inflammatory responses, although its effects may vary depending on BoGHV4 genotype. In this study, primary bovine endometrial cells (BECs) were cultured in medium containing 10% PRP instead of fetal bovine serum, infected with two genetically divergent BoGHV-4 isolates (07-435, genotype 3; 10-154, genotype 2), and subsequently stimulated with bacterial lipopolysaccharide (LPS, 100 ng/mL). Expression of the viral immediate-early gene IE-2 and host immune genes (TLR4, TNF-α, CXCL8, and IFN-γ) were quantified by RT-qPCR from 4 to 48 h after stimulation. Isolate 07-435 induced a sustained activation of IE-2 and gradual cytokine upregulation, while isolate 10-154 elicited an early but transient inflammatory response followed by gene downregulation. PRP did not modify the strain-specific patterns of viral and inflammatory gene expression but established a common inflammatory baseline, whereas the magnitude and temporal profile of the response continued to be dictated by the viral genotype. These findings indicate that BoGHV-4 genotypic diversity remained the main determinant of response intensity and duration, supporting PRP as a context-dependent rather than a universal antiviral modulator.