CCL3 and Viral Chemokine-Binding Protein gG Modulate Pulmonary Inflammation and Virus Replication during Equine Herpesvirus 1 Infection

Abstract

ABSTRACT CCL3 is a proinflammatory chemokine that mediates many of the cellular changes occurring in pulmonary disease. Here, CCL3 −/− mice were used to investigate the role of this chemokine during respiratory herpesvirus infection. Compared to wild-type mice, CCL3 −/− mice infected with the alphaherpesvirus equine herpesvirus 1 (EHV-1) displayed reduced body weight loss but had higher pulmonary viral loads. Lungs from infected CCL3 −/− mice suffered a milder interstitial pneumonia, and fewer immune cells were recovered from the pulmonary airways after infection. We could also demonstrate that herpesvirus-encoded chemokine-binding glycoprotein G (gG) was capable of inhibiting the chemotactic functions of CCL3. This CCL3-mediated chemotaxis, however, was restored in the presence of gG-specific antibodies, which puts into question the advertised use of gG deletion mutants as marker vaccines. In summary, we concluded that CCL3 is a major player in controlling herpesvirus replication in the target organ, the lung, and does so by evoking a strong inflammatory response. The immunomodulatory activity of CCL3 is balanced by the expression of viral gG, whose chemokine-binding activity is mitigated in secondary infections by the production of anti-gG antibodies.