Detection of equine herpesvirus-specific effector and memory cytotoxic immunity in the equine upper respiratory tract.

The research investigates how the immune system of horses responds to equine herpesvirus-1 infection, with a focus on the cellular immune effects in the upper respiratory tract.

Understanding the Research

• The study was driven by the importance of understanding the immune responses to equine herpesvirus-1(EHV-1), specifically the mucosal immunity. Mucosal immunity refers to the immune response that occurs at mucosal surfaces, like the lining of the nose and throat which are often entry points for pathogens.
• Equine Herpesvirus-1 is a common virus in horses causing respiratory disease, abortion in pregnant mares, neonatal death, and paralysis. A detailed understanding of the immune response to this virus is important for developing effective therapies and vaccines.
• The study focused on how the immune system responds on a cellular level, in various mucosal and systemic lymphoid tissues that are associated with the upper respiratory tract. Lymphoid tissues, such as the tonsils and lymph nodes, are crucial components of the immune system where immune cells are produced and subsequently deployed to fight off infections.

The Experiment

• Four young horses (age 1-2 years) were infected with the Army 183 strain of EHV-1, which is a neurovirulent strain of the virus. They were euthanized one week later for study. Another foal that was not infected served as a control.
• Tissue samples were taken from the horses’ tonsils, draining lymph nodes, and peripheral blood mononuclear cells (PBMC). This allowed the researchers to examine the virus-specific memory and effector processes and measure cytolytic or “cell-killing” activity at the cellular level.
• The researchers used a 4-hour chromium release assay to test for virus-specific cytotoxic activity. This is a classical method used in immunology to determine the cytotoxic activity of certain immune cells. When the immune cells encounter infected cells, they destroy them, releasing the radioactive chromium.

Findings

• The study found that EHV-1 specific cytotoxic activity was notably present in the mucosal lymphoid tissues of the horses’ upper respiratory tract. This activity was most prominent in the lining of the nasopharynx, suggesting an active immune response combating the viral replication.
• Such activity was also found in the bloodstream of some horses one week after infection. This implies that the cytotoxic cells were circulated with blood to reach other parts of the body – a typical response during a systemic infection.
• Virus-specific memory cytotoxic activity was elevated in the bloodstream and detectable in the lymph nodes. Memory cytotoxic activity refers to the ability of the immune system to remember previously-encountered pathogens and respond more rapidly and efficiently to subsequent infections.

In conclusion, the study provides useful insights into the cellular immune response to EHV-1 infection and could pave the way for developing effective immunotherapies or vaccines.