Equine PBMC cytokines profile and efficacy of a Parapoxvirus ovis based-immunomodulator after in vitro α- and γ-EHV infection

Horses are usually infected during the first months of life by several equine herpesviruses, such as EHV-1, EHV-4 or EHV-2. The persistence of these respiratory viruses through establishment of latency, often characterised by an absence of clinical signs, represents a real risk to the horse population. Reactivation of latent EHV could cause disease in both carriers and naive animals in contact. A better understanding of the immune response to EHV infection is necessary to improve our methods of prevention and decrease the risk of transmission. The objectives of this study were 1/ to characterise the cytokine gene expression profile of PBMC after in vitro EHV infection (EHV-1, EHV-4 and EHV-2) and 2/ To determine the efficacy of the inactivated Parapoxvirus ovis (iPPVO), a known immunomodulator in horses , against these same viruses. PBMC were isolated from 3 horses and infected in vitro with EHV-1, EHV-4 or EHV-2, in the presence or absence of iPPVO. In vitro culture of PBMC with EHV-1, EHV-4, EHV-2 and iPPVO induced a significant increase of IFN-α, IFN-β and IFN-γ gene expression. Moreover, EHV-2 induced a significant increase of IL-1β, IL-6 and TNF-α mRNA. The presence of iPPVO induced an earlier and stronger expression of IFN-α, IFN-β and IFN-γ during EHV infection. The presence of iPPVO reduced also the inflammatory response induced by EHV-2. In conclusion, this study suggests that the presence of iPPVO potentiates the development of the immune response during infection EHV in vitro.