Infection of endothelial cells with equine herpesvirus-1 (EHV-1) occurs where there is activation of putative adhesion molecules: a mechanism for transfer of virus.

This study presents evidence that activation of certain molecules on cells facilitates the transmission of equine herpesvirus-1 (EHV-1) from infected white blood cells and confines the infection to specific tissues. The study involved comparing tissues from mares infected with EHV-1 and healthy mares, and revealed that these molecules were present in the lining of the reproductive tract and nasal area where the virus is known to infect.

Activation of Adhesion Molecules

• The research highlights a crucial step in the transmission of the EHV-1 virus from infected leucocytes, or white blood cells. The study suggests that there exists a mechanism for viral transfer where activation of certain adhesion molecules on endothelial cells (the cells that line the interior surface of blood vessels) and leucocytes occurs.
• Endothelial and leucocyte adhesion molecules are proteins located on the cell surface that enable cells to stick together or adhere. In the context of this research, the activation of such molecules suggests a means by which the virus could latch onto and infect host cells.

Experimental Investigation

• The researchers analyzed a range of tissues from two mares in late pregnancy that were intentionally infected with EHV-1 and compared these with tissues from healthy pregnant and nonpregnant mares.
• Rabbit antisera was used to identify which tissues in normal nonpregnant and pregnant mares expressed these adhesion molecules. Also, the research sought to determine if the variety of tissues expressing these molecules was different in pregnant mares due to infection.

Research Findings

• The findings indicated that the endothelium (inner lining) of the pregnant reproductive tract expressed these adhesion molecules. Also, in the two EHV-1 infected pregnant mares, endothelial cells in the nasal mucosa similarly expressed these activated molecules.
• The locations that showed expression of these molecules matched with the sites where viral infection of endothelial cells is known to occur, suggesting that the expression of these molecules is a key step in the transfer of the virus from white blood cells to endothelial cells.
• The researchers concluded that the process of the virus adhering to these specific molecules in certain tissues may explain the restricted tissue tropism, implying that the virus is selective in the tissues it infects.