Suppression of lytic replication of Kaposi’s sarcoma-associated herpesvirus by autophagy during initial infection in NIH 3T3 fibroblasts

Abstract

Kaposi's sarcoma-associated herpesvirus (KSHV) is the infectious cause of the angioproliferative neoplasm Kaposi's sarcoma (KS). We first confirmed the susceptibility of NIH 3T3 fibroblasts to KSHV by infecting them with BCP-1-derived KSHV. Lytic replication of KSHV was confirmed by PCR amplification of viral DNA isolated from culture supernatants of KSHV-infected cells. The template from KSHV-infected NIH 3T3 cells resulted in an intense viral DNA PCR product. A time course experiment revealed the disappearance of KSHV-specific DNA in culture supernatant of NIH 3T3 cells during a period between 48 h and 72 h postinfection. Furthermore, 3 days postinfection, infected NIH 3T3 cells showed no evidence of latent or lytic transcripts, including LANA, vFLIP, vCyclin, and vIL-6. These results imply that KSHV infection in NIH 3T3 cells is unstable and is rapidly lost on subsequent culturing. Additionally, we detected an enhancement of autophagy early in infection with KSHV. More interestingly, inhibition of autophagy by Beclin 1 siRNA or 3-methyladenine significantly increased the amount of KSHV-specific DNA in the culture supernatant of NIH 3T3 cells when compared to the group treated with KSHV infection alone, implying that autophagy prevents lytic replication of KSHV. Taken together, our data suggest that autophagy could be one of the cellular mechanisms utilized by host cells to promote viral clearance.

Oncogenic KSHV-encoded interferon regulatory factor upregulates HMGB2 and CMPK1 expression to promote cell invasion by disrupting a complex lncRNA-OIP5-AS1/miR-218-5p network

“…Moreover, these homologous proteins are also in favor of KSHV-induced tumorigenesis. For examples viral interferon regulatory factors (vIRFs) [6], viral interleukin-6 (vIL-6) [7], viral G protein-coupled receptor (vGPCR) [8], viral Bcl-2 (vBcl-2) [9], viral FLICE inhibitory protein (vFLIP) [10] and viral cyclin (vCyclin) [11] have been shown to be pro-oncogenic or promote tumorigenesis.…”

Kaposi’s sarcoma-associated herpesvirus (KSHV) utilizes the NDP52/CALCOCO2 selective autophagy receptor to disassemble processing bodies

“…Autophagy is initially tumour suppressive, promoting degradation of damaged organelles, preserving genomic stability, and removing pathogens. In cancers of viral origin, like KS, viral inhibition of autophagic flux can help control xenophagy of new viral particles and aid in the establishment of latent infection (Jang et al , 2016). However, once cancer is established, autophagic flux promotes progression of established tumours by a variety of approaches, including promoting a pro-tumourigenic and proinflammatory environment (Vescovo et al , 2020; Liu & Debnath, 2016).…”

Redefining De Novo Gammaherpesvirus Infection Through High-Dimensional, Single-Cell Analysis of Virus and Host

“…MHV68 infection of endothelial cells results in a significant cell fraction of cells undergoing persistent infection (Suarez and van Dyk, 2008). KSHV infection of fibroblasts results in variable lytic or latent infection (Jang et al, 2016; Krishnan et al, 2004; Matthews et al, 2011), and EBV infection in gastric epithelial cells includes both lytic and latent outcomes (Hill et al, 2013; Ma et al, 2011; Nawandar et al, 2015). Despite the restricted gene expression of Virus low cells, expression of multiple viral genes strongly suggests that these cells have the potential to impact biological outcomes and immune regulation.…”