Abstract
Equine herpesviruses (EHV) infect horses early during life and the persistence of these viruses through establishment of latency represents a real risk. 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 to characterise the cytokine gene expression profile of peripheral blood mononuclear cells (PBMC) after in vitro EHV-1, EHV-4, and EHV-2 infection and to determine the efficacy of inactivated Parapoxvirus ovis (iPPVO) against these 3 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, and iPPVO induced a significant increase of IFN-α, IFN-β, and IFN-γ gene expression. EHV-4 also triggered a significant increase of IL-6 and TNF-α mRNA. EHV-2 triggered a significant increase of IFN-α, IFN-β, IFN-γ, 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 mRNA during EHV infection and reduced the inflammatory response induced by EHV-2. In conclusion, this study suggests that the presence of iPPVO potentiates the development of the immune response to in vitro EHV infection.
Highlights
Equine herpesviruses (EHV) are endemic viruses responsible for many clinical signs and have considerable economic impact on the horse industry
EHV-1 infection of peripheral blood mononuclear cells (PBMC) induced an increase of IFN-γ and type I IFN mRNA expression and a moderate elevation of TNF-α when measured at 18 and 24 hpi
Our results demonstrated that inactivated Parapoxvirus ovis (iPPVO) treatment induced a high and transient mRNA expression of type I interferon (IFN-α and IFN-β) and a moderate expression of IFN-γ and TNF-α as previously described in equine PBMC [21]
Summary
Equine herpesviruses (EHV) are endemic viruses responsible for many clinical signs and have considerable economic impact on the horse industry. The Herpesviridae is divided into three subfamilies: alphaherpesvirinae (EHV-1, EHV-4, and EHV-3), gammaherpesvirinae (EHV-2, EHV-5), and betaherpesvirinae [1]. EHV-4 is the main α-herpesvirus responsible for acute respiratory diseases in horses. EHV-1 induces respiratory diseases as well as abortion, neonatal death, and neurological disease [2,3]. The γ-herpesvirus EHV-2 is associated with respiratory diseases and is highly prevalent in horses [4]. A characteristic of EHV is their ability to establish latency after a period of viraemia, when viruses persist subclinically in the host. Latency in the trigeminal ganglia for EHV-1 and EHV-4 [5]
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