HGF and coinfection: One of the mechanisms for other viral co-infection to trigger KSHV reactivation is the secretion of inflammatory cytokines, such as oncostatin M (OSM), hepatocyte growth factor (HGF), interferon-γ (IFN-γ), and Toll-like receptors 7 and 8 (TLR7/8) (Mercader et al., 2000; Gregory et al., 2009) triggered by co-infected viruses.