Porcine hemagglutinating encephalomyelitis virus induces apoptosis in a porcine kidney cell line via caspase-dependent pathways

Abstract

Porcine hemagglutinating encephalomyelitis is an acute, highly contagious disease in piglets that is caused by the porcine hemagglutinating encephalomyelitis virus (PHEV). However, the pathogenesis of PHEV and the relationship between PHEV and the host cells are not fully understood. In this study, we investigated whether the PHEV-induced cytopathic effect (CPE) was caused by apoptosis. Replication of PHEV in a porcine kidney-derived cell line (PK-15 cells) caused an extensive CPE, leading to the destruction of the entire monolayer and the death of the infected cells. Staining with Hoechst 33,342 revealed morphological changes in the nuclei and chromatin fragmentation. In addition, PHEV caused DNA fragmentation detectable by agarose gel electrophoresis 48h post-infection, increasing with the incubation time. The percentage of apoptotic cells increased with the incubation time and reached a maximum at 96h post-infection, as determined using flow cytometry and fluorescence microscopy of cells that were stained with annexin V-FITC and propidium iodide (PI). Moreover, as is commonly observed for coronavirus infections of other animals, the activities of the effecter caspase, caspase-3, and the initiator caspases, caspase-8 and caspase-9, which are representative factors in the death receptor-mediated apoptotic pathway and the mitochondrial apoptotic pathway, respectively, were increased in PHEV-infected PK-15 cells. Moreover, the tripeptide pan-ICE (caspase) inhibitor Z-VAD-FMK blocked PHEV-induced apoptosis but did not have an effect on virus production by 96h post-infection. These results suggested that PHEV induces apoptosis in PK-15 cells via a caspase-dependent pathway. Apoptotic death of infected cells is detrimental to animals because it causes cell and tissue destruction. Although the pathological characteristics of PHEV are largely unknown, apoptosis may be the pathological basis of the lesions resulting from PHEV infection.

Porcine deltacoronavirus induces caspase-dependent apoptosis through activation of the cytochrome c-mediated intrinsic mitochondrial pathway

“…However, several viruses promote apoptosis to facilitate the release and dissemination of the viral progeny for further invasion of the neighboring cells. This irreversible death event is characterized with cytolytic features after viral infections, including CPE in vitro or/and important biological processes promoting cell damage, tissue injury, and disease severity in vivo ( 2012; Kim and Lee, 2014;Lan et al, 2013;Lee and Kleiboeker, 2007;St-Louis and Archambault, 2007;Sarmento et al, 2006;Suzuki et al, 2008;Zhang et al, 2015). The present study demonstrated that PDCoV triggers apoptosis in ST cells, as evident from apoptotic parameters including oligonucleosomal DNA fragmentation and PS exposure.…”

Antiviral effect of lithium chloride on porcine epidemic diarrhea virus in vitro

“…Apoptosis is considered to be a host innate defense mechanism that eliminates virus-infected cells. However, some viruses possess the ability to actively induce apoptosis to facilitate the release and dissemination of viral progeny to neighboring cells for further invasion, which are important biological parts in viral pathogenesis and disease processes that promote cell death and tissue injury (DeDiego et al, 2011;Favreau et al, 2012;Lan et al, 2013). PEDV induced caspaseindependent apoptosis through activation of mitochondrial apoptosisinducing factor has been demonstrated (Kim and Lee, 2014).…”

Porcine epidemic diarrhea virus induces caspase-independent apoptosis through activation of mitochondrial apoptosis-inducing factor

“…However, many viruses have the ability to actively induce apoptosis as a response to viral replication, thereby facilitating the release and dissemination of viral progeny to neighboring cells. This pro-apoptotic event is one of the cytolytic properties of viral infections causing CPE in vitro or/and plays a pathogenic role contributing to cell damage, tissue injury, and disease severity in vivo DeDiego et al, 2011;Eleouet et al, 1998;Favreau et al, 2012;Lan et al, 2013;Lee and Kleiboeker, 2007;St-Louis and Archambault, 2007;Sarmento et al, 2006;Suzuki et al, 2008). At present, it is unknown whether PEDV triggers apoptotic cell death, and if so, whether virusinduced apoptosis aids or worsens viral replication and pathogenicity.…”