Equine herpesvirus type 1 infects dendritic cells in vitro: stimulation of T lymphocyte proliferation and cytotoxicity by infected dendritic cells.

Equine herpesvirus type 1 (EHV-1) appears to infect dendritic cells (cells that activate the immune system), leading to respiratory disease and other health problems in horses. This research study reveals that although these cells can boost the immune response, they do not prevent short-term immunity after the infection.

EHV-1 and its Impact on Horses

• The research focuses on the Equine herpesvirus type 1 (EHV-1), which causes respiratory diseases, abortion, and myeloencephalopathy (a neurological disorder) in horses.
• Like other herpesviruses, cell-mediated immunity, a type of immune response, is vital for recovery and protection.
• There is not enough information on the role of antigen-presenting cells like dendritic cells (DCs) in relation to the immunity response to this virus.

Infection Process and Effect on Dendritic Cells

• The peripheral blood DCs, which are responsible for triggering the immune response, were exposed to EHV-1. The result displayed the expression of viral glycoprotein gB in the cells, indicating virus replication within them.
• A susceptible cell line (RK13) was exposed to infected DCs or their supernatants, confirming that the EHV-1 infection process was productive, meaning the virus was able to reproduce successfully.
• However, DCs showed signs of damage as infected DCs lost their viability and started forming multinucleated cells (syncytial formation).

Stimulation of Immune Response

• Despite the negative effects, the DCs were found to be much more effective at boosting peripheral blood T-cell proliferation (increase in the number of T-cells, a type of immune cell) and cytotoxicity (the ability to kill infected cells).
• Intranasal infection with EHV-1 led to a T-cell proliferation response in ponies, but it began to decline 15 weeks post-infection and ceased at 22 weeks.
• No cytotoxic responses were detected 35 weeks after the initial infection, but they emerged 7 weeks after a second infection.

Significance of Findings

• This study is essential as it shows how equine DCs can stimulate the immune response when infected with EHV-1, even though they don’t prevent short-lasting immunity after the infection.
• These findings broaden our understanding of EHV-1 and its interaction with the immune system. Further research may possibly lead to improved vaccine development and treatment for EHV-1.