Interactome analysis of Crimean-Congo hemorrhagic fever virus glycoproteins reveals HAX1 as a host restriction factor against the virion packaging

Abstract Crimean-Congo hemorrhagic fever virus (CCHFV) is a biosafety level-4 and World Health Organization-recognized priority pathogen requiring urgent Research & Development attention. The glycoproteins of CCHFV, Gn and Gc, are considered to play multiple roles in the viral life cycle by interactions with host cells; however, these interactions remain largely unclear to date. Here, we analyzed the cellular interactomes of CCHFV glycoproteins by affinity purification-quantitative mass spectrometry and identified 45 host proteins as high-confidence Gn/Gc interactors. These host molecules are involved in transmembrane transport, metabolism, oxidative stress, protein folding and glycosylation, etc., in line with the potential physiological actions of the viral glycoproteins. As a proof of principle, we detailedly elucidated the role of an identified cellular protein, HAX1, and therefore uncovered an interesting host antiviral strategy. HAX1 interacts with Gn by its C-terminus, while its N-terminal region leads to mitochondrial localization. By the strong interaction, HAX1 sequestrates Gn to mitochondria, thus depriving Gn of its normal Golgi localization that is indispensable for functional glycoprotein-mediated progeny virion packaging. Consistently, the notable inhibitory activity of HAX1 against viral packaging and hence propagation was further elucidated in the contexts of pseudotyped and authentic CCHFV infections by series of loss/gain-of-function assays in cellular and animal infection models. Together, the findings not only provide a systematic CCHFV Gn/Gc-host protein-protein interaction map, but also unravel a novel cellular antiviral mechanism, which may facilitate further studies on CCHFV biology and therapeutic approaches.