Equid herpesvirus 1: platelets and alveolar macrophages are potential sources of activated TGF-B1 in the horse.

The research investigates the cellular response of horses to the Equid herpesvirus 1 (EHV-1) infection, exploring platelets and alveolar macrophages as possible sources of activated Transforming Growth Factor Beta 1 (TGF-B1), a protein that impedes certain immune responses thus highlighting potential cellular sources for virus-induced immune suppression.

Study Objectives and Methods

• The researchers studied the short-lived cell responses to EHV-1 in vivo (within the living organism) and in vitro (in a controlled laboratory setting). The focus was primarily on the action of Transforming Growth Factor Beta 1 (TGF-B1), a protein known to hinder T cell responses—an integral part of the body’s immune response.
• This study also sought to investigate potential sources of activated TGF-B1 within the horse which could contribute to the suppression of the immune response during EHV-1 infection. The researchers looked with specific interest at circulating platelets, lymph nodes, bronchial epithelium, and alveolar macrophages.

Observations and Findings

• The experiment confirmed the presence of latent (present but not active or visible) TGF-B1 in circulating platelets, lymph nodes, bronchial epithelium, and alveolar macrophages in the horse.
• The researchers discovered that in vitro activation of the platelets resulted in the release of latent TGF-B1; however, the virus alone did not activate TGF-B1.
• Interestingly, following exposure to EHV-1 in vitro or in vivo, circulating leucocytes did not show increased levels of active TGF-B1 which could suggest that the virus does not directly activate TGF-B1 in these cells.
• On the contrary, alveolar macrophages acquired post-mortem showed both latent and active TGF-B1. This hints that these cells could be a source of activated TGF-B1 during EHV-1 infection.
• The activation of TGF-B1 in the bronchial epithelium and mesenteric lymph node leucocytes varied from horse to horse, suggesting that the mechanism of TGF- B1 activation during EHV-1 infection may be dependent on individual specificities.

Research Significance

• This research gives new insights into how EHV-1 could be suppressing the immune response in horses, highlighting the role of TGF-B1 and locating potential sources of its activation—the alveolar macrophages and, possibly, the bronchial epithelium and mesenteric lymph node leucocytes.
• The findings could catalyze more targeted studies on TGF-B1 and its role in viral infections, and also lay ground for the development of therapeutic interventions to combat EHV-1 and similar diseases.