Innate defense mechanisms against HSV-1 infection in the target tissues, skin and brain

Interference of pseudorabies virus infection on functions of porcine granulosa cells via apoptosis modulated by MAPK signaling pathways

BACKGROUND

Pseudorabies virus (PRV) is one of the major viral pathogens leading to reproductive disorders in swine. However, little is known about the effects of PRV infection on porcine reproductive system. Ovarian granulosa cells are somatic cells surrounding oocytes in ovary and required for folliculogenesis. The present study aimed to investigate the interference of PRV on functions of porcine ovarian granulosa cells in vitro.

METHODS

Primary granulosa cells were isolated from porcine ovaries. To investigate the PRV infectivity, transmission electron microscopy (TEM) was used to check the presence of viral particles, and the expression of viral gE gene was detected by quantitative real-time PCR (qPCR) in PRV-inoculated cells. After PRV infection, cell viability was detected by MTS assay, Ki67 for proliferative status was determined by immunofluorescence assay (IFA), cell cycle and apoptosis were detected by flow cytometry, and progesterone (P4) and estradiol (E2) were determined by radioimmunoassay. The checkpoint genes of cell cycle and apoptosis-related proteins were studied by qPCR and western blotting.

RESULTS

Virus particles were observed in the nucleus and cytoplasm of PRV-infected granulosa cells by TEM imaging, and the expression of viral gE gene increased in a time-dependent manner post infection. PRV infection inhibited cell viability and blocked cell cycle at S phase in porcine granulosa cells, accompanied by decreases in expression of Ki67 protein and checkpoint genes related to S phase. Radioimmunoassay revealed decreased levels in P4 and E2, and the expressions of key steroidogenic enzymes were also down-regulated post PRV-infection. In addition, PRV induced apoptosis with an increase in Bax expression and activation of caspase 9, and the phosphorylation of JNK, ERK and p38 MAPKs were significantly up-regulated in porcine ovarian granulosa cells post PRV infection.

CONCLUSIONS

The data indicate that PRV causes infection on porcine ovarian granulosa cells and interferes the cell functions through apoptosis, and the MAPK signaling pathway is involved in the viral pathogenesis.

Human Nasal and Lung Tissues Infected Ex Vivo with SARS-CoV-2 Provide Insights into Differential Tissue-Specific and Virus-Specific Innate Immune Responses in the Upper and Lower Respiratory Tract

The nasal mucosa constitutes the primary entry site for respiratory viruses, including severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). While the imbalanced innate immune response of end-stage coronavirus disease 2019 (COVID-19) has been extensively studied, the earliest stages of SARS-CoV-2 infection at the mucosal entry site have remained unexplored. Here, we employed SARS-CoV-2 and influenza virus infection in native multi-cell-type human nasal turbinate and lung tissues ex vivo, coupled with genome-wide transcriptional analysis, to investigate viral susceptibility and early patterns of local mucosal innate immune response in the authentic milieu of the human respiratory tract. SARS-CoV-2 productively infected the nasal turbinate tissues, predominantly targeting respiratory epithelial cells, with a rapid increase in tissue-associated viral subgenomic mRNA and secretion of infectious viral progeny. Importantly, SARS-CoV-2 infection triggered robust antiviral and inflammatory innate immune responses in the nasal mucosa. The upregulation of interferon-stimulated genes, cytokines, and chemokines, related to interferon signaling and immune-cell activation pathways, was broader than that triggered by influenza virus infection. Conversely, lung tissues exhibited a restricted innate immune response to SARS-CoV-2, with a conspicuous lack of type I and III interferon upregulation, contrasting with their vigorous innate immune response to influenza virus. Our findings reveal differential tissue-specific innate immune responses in the upper and lower respiratory tracts that are specific to SARS-CoV-2. The studies shed light on the role of the nasal mucosa in active viral transmission and immune defense, implying a window of opportunity for early interventions, whereas the restricted innate immune response in early-SARS-CoV-2-infected lung tissues could underlie the unique uncontrolled late-phase lung damage of advanced COVID-19. IMPORTANCE In order to reduce the late-phase morbidity and mortality of COVID-19, there is a need to better understand and target the earliest stages of SARS-CoV-2 infection in the human respiratory tract. Here, we have studied the initial steps of SARS-CoV-2 infection and the consequent innate immune responses within the natural multicellular complexity of human nasal mucosal and lung tissues. Comparing the global innate response patterns of nasal and lung tissues infected in parallel with SARS-CoV-2 and influenza virus, we found distinct virus-host interactions in the upper and lower respiratory tract, which could determine the outcome and unique pathogenesis of SARS-CoV-2 infection. Studies in the nasal mucosal infection model can be employed to assess the impact of viral evolutionary changes and evaluate new therapeutic and preventive measures against SARS-CoV-2 and other human respiratory pathogens.

The Proteome and Secretome of Cortical Brain Cells Infected With Herpes Simplex Virus

Infections of the brain with herpes simplex virus type 1 (HSV-1) cause life-threatening Herpes simplex encephalitis (HSE) characterized by viral replication in neurons and neuro-inflammation including an infiltration of peripheral immune cells. HSV-1 reprograms host cells to foster its own replication and for immune evasion, but eventually the immune responses clear the infection in most patients. However, many survivors suffer from long-term neuronal damage and cannot regenerate all brain functions. HSV-1 influences the physiology of neurons, astrocytes, oligodendrocytes and microglia, and significantly changes their protein expression and secretion pattern. To characterize temporal changes upon HSV-1 infection in detail, we inoculated mixed primary cultures of the murine brain cortex, and performed quantitative mass spectrometry analyses of the cell-associated proteome and the secretome. We identified 28 differentially regulated host proteins influencing inflammasome formation and intracellular vesicle trafficking during endocytosis and secretion. The NIMA-related kinase 7 (NEK7), a critical component of the inflammasome, and ArfGap1, a regulator of endocytosis, were significantly up-regulated upon HSV-1 infection. In the secretome, we identified 71 proteins including guidance cues regulating axonal regeneration, such as semaphorin6D, which were enriched in the conditioned media of HSV-1 infected cells. Modulation of inflammasome activity and intracellular membrane traffic are critical for HSV-1 cell entry, virus assembly, and intracellular spread. Our proteome analysis provides first clues on host factors that might dampen the inflammasome response and modulate intracellular vesicle transport to promote HSV infection of the brain. Furthermore, our secretome analysis revealed a set of proteins involved in neuroregeneration that might foster neuronal repair processes to restore brain functions after clearance of an HSV-1 infection.

Duck Plague Virus Promotes DEF Cell Apoptosis by Activating Caspases, Increasing Intracellular ROS Levels and Inducing Cell Cycle S-Phase Arrest

Background: Duck plague virus (DPV) can induce apoptosis in duck embryo fibroblasts (DEFs) and in infected ducks, but the molecular mechanism of DPV-induced apoptosis remains unknown. Methods: We first used qRT-PCR and a Caspase-Glo assay to determine whether the caspase protein family plays an important role in DPV-induced apoptosis. Then, we used an intracellular ROS detection kit and the mitochondrial probe JC-1 to respectively detect ROS levels and mitochondrial membrane potential (MMP). Finally, flow cytometry was used to detect apoptosis and cell cycle progression. Results: In this study, the mRNA levels and enzymatic activities of caspase-3, caspase-7, caspase-8, and caspase-9 were significantly increased during DPV-induced apoptosis. The caspase inhibitors Z-DEVD-FMK, Z-LEHD-FMK, and Q-VD-Oph could inhibit DPV-induced apoptosis and promote viral replication. Subsequently, a significant decrease in MMP and an increase in the intracellular ROS levels were observed. Further study showed that pretreating infected cells with NAC (a ROS scavenger) decreased the intracellular ROS levels, increased the MMP, inhibited apoptosis, and promoted viral replication. Finally, we showed that DPV infection can cause cell cycle S-phase arrest. Conclusions: This study shows that DPV causes cell cycle S-phase arrest and leads to apoptosis through caspase activation and increased intracellular ROS levels. These findings may be useful for gaining an understanding of the pathogenesis of DPV and the apoptotic pathways induced by α-herpesviruses.

Innate Immune Mechanisms and Herpes Simplex Virus Infection and Disease

Innate immune responses play a major role in the control of herpes simplex virus (HSV) infections, and a multiplicity of mechanisms have emerged as a result of human evolution to sense and respond to HSV infections. HSV in turn has evolved a number of ways to evade immune detection and to blunt human innate immune responses. In this review, we summarize the major host innate immune mechanisms and the HSV evasion mechanisms that have evolved. We further discuss how disease can result if this equilibrium between virus and host response is disrupted.

Different effects of the immunostimulatory drug Stimforte on infections of hepatitis C virus and herpes simplex virus type 1

Stimforte, an immune response-stimulating preparation, is active with respect to hepatitis C virus (HCV) and herpes simplex virus type I (HSV-1). The effects of Stimforte in animals infected with either HCV or HSV-1 are fundamentally different. In mice with acute herpes virus infection, Stimforte administration leads to a higher activity of natural killer cells and cytotoxic lymphocytes, and the amount of interferon (IFN) λ grows. In mice infected with HCV, Stimforte administration results in a significant increase in IFN-β but not IFN-λ in blood and affected organs. Stimforte has been found to affect directly HCV reproduction that causes the infected cell death, but it does not affect HSV-1 reproduction in the Vero cells (V).