BiP/GRP78 is a pro-viral factor for diverse dsDNA viruses that promotes the survival and proliferation of cells upon KSHV infection

The Endoplasmic Reticulum (ER)-resident HSP70 chaperone BiP (HSPA5) plays a crucial role in maintaining and restoring protein folding homeostasis in the ER. BiP's function is often dysregulated in cancer and virus-infected cells, conferring pro-oncogenic and pro-viral advantages. We explored BiP's functions during infection by the Kaposi's sarcoma-associated herpesvirus (KSHV), an oncogenic gamma-herpesvirus associated with cancers of immunocompromised patients. Our findings reveal that BiP protein levels are upregulated in infected epithelial cells during the lytic phase of KSHV infection. This upregulation occurs independently of the unfolded protein response (UPR), a major signaling pathway that regulates BiP availability. Genetic and pharmacological inhibition of BiP halts KSHV viral replication and reduces the proliferation and survival of KSHV-infected cells. Notably, inhibition of BiP limits the spread of other alpha- and beta-herpesviruses and poxviruses with minimal toxicity for normal cells. Our work suggests that BiP is a potential target for developing broad-spectrum antiviral therapies against double-stranded DNA viruses and a promising candidate for therapeutic intervention in KSHV-related malignancies. Overall design: Exogenous RTA expression was induced in iSLK.219 cells by treatment with 1 µg/mL of doxycycline (Fisher Scientific, Waltham, MA, USA). To prevent viral DNA replication, these cells were induced with Dox in the presence of phosphonoformate (PFA) 100µM (Sigma Aldrich P6801). Viral reactivation was evaluated by microscopy detection of the PAN-RFP reporter and immunoblot for viral proteins. Total cellular and viral RNA was isolated from iSLK.219 cells at 72h post reactivation in the presence or absence of 10µM HA15 (Selleckchem S8299), using the RNAeasy Plus Mini kit (QIAGEN 74134) following manufacturers' recommendations, including a DNAse treatment step. RNA sequencing libraries were generated using the NEBNext Ultra II RNA Library Prep Kit (New England BioLabs E7760) and sequenced using a 150bp paired-end protocol on an Illumina NextSeq550 instrument. Following demultiplexing, the sequenced reads were aligned to the human genome GRcHg38 version 41 and the KSHV genome GQ994935.1. Read abundance and differential gene expression were determined using the DESeq2 package.