Herpesvirus chemokine binding protein gG efficiently inhibits neutrophil chemotaxis in vitro and in vivo

Glycoprotein G (gG) of alphaherpesviruses has been described to function as a viral chemokine binding protein (vCKBP). More recently, mutant viruses devoid of gG have been shown to result in increased virulence, but it remained unclear if gG's potential to serve as a vCKBP is responsible for this observation. We here used equine herpesvirus type 1 (EHV-1) as a model to study the pathophysiological importance of vCKBP activity. First, in vitro chemotaxis assays studying migration of immune cells, an important function of chemokines, were established. In such assays, supernatants of EHV-1-infected cells could significantly inhibit IL-8-induced chemotaxis of equine neutrophils. Identifying gG as the responsible vCKBP was achieved by repeating similar experiments with supernatants from cells infected with a gG-negative mutant. These supernatants were unable to alter IL-8-induced equine neutrophil migration. Furthermore, recombinant EHV-1 gG was able to significantly reduce neutrophil migration, establishing gG as a bona fide vCKBP. Secondly, and importantly, in vivo analyses in a murine EHV-1 infection model showed that neutrophil migration in the target organ lung was significantly reduced in the presence of gG. In summary, we demonstrate for the first time that EHV-1 gG not only binds to chemokines but is also capable of inhibiting their chemotactic function both in vitro and in vivo, thereby contributing to viral pathogenesis and virulence.