CHARACTERIZATION OF POST-TRANSLATIONAL MODIFICATIONS DURING HUMAN CYTOMEGALOVIRUS INFECTION: IMPLICATIONS FOR NOVEL ANTIVIRALS

Human Cytomegalovirus (HCMV), a widespread β-Herpesvirus, establishes a lifelong latency in the myeloid lineage, with reactivation often driven by inflammation. Autoimmune diseases (AD) are characterized by chronic inflammation due to an abnormal immune response against the body’s own tissues. In genetically predisposed patients, HCMV has been associated with AD, but whether it initiates or supports the development of AD is still not known. Citrullination is a post-translational modification (PTM) catalyzed by peptidylarginine deaminases (PAD) that convert peptidylarginine into peptidylcitrulline, whose dysregulation has been linked to a spectrum of ADs, cancer, and neurodegenerative disorders. Against this background, the goal of this project is to characterize citrullination during infection with HCMV, that may be relevant In the etiopathogenesis of AD. Here, we demonstrate that HCMV infection upregulates the overall pattern of citrullination in HFF (Human Foreskin Fibroblasts) using two different approaches: a specific antibody recognizing citrullinated residues and a citrulline-specific rhodamine phenylglyoxal (RhPG)-based probe. Consistently, PAD2 expression increased both at the mRNA and protein levels, suggesting a predominant role for this isoform in HCMV-induced citrullination. Surprisingly, viral replication rate of the HCMV is strongly impaired in the presence of a specific pan PAD-inhibitor, indicating that citrullination is required for HCMV replication. By mass- spectrometry based-analysis, we observed antiviral proteins of the IFIT and Mx1 family to be significantly citrullinated at 48 hpi, suggesting that HCMV has evolved a strategy to evade the host’s immune system by their citrullination-mediated inactivation. Based on our preliminary results, we hypothesize that altering HCMV-induced viral and /or cellular protein PTMs, which we show for the first time to be essential for HCMV replication, might represent an alternative