Demonstration of equine herpesvirus-1 gene expression in the placental trophoblasts of naturally aborted equine fetuses.

This study details the first in-vivo demonstration of the EHV-1 gene in the placental cells of naturally aborted horse fetuses, suggesting that the EHV-1 infection may directly spread from uterine lining cells to placental cells.

Study Objective and Methodology

• The primary objective of this research was to examine the presence and impact of Equine herpesvirus-1 (EHV-1) infection in aborted horse fetuses. EHV-1 is a virus known to cause various diseases in horses, including abortions in pregnant mares.
• The researchers conducted an in-depth study on seven aborted fetuses and their placentas, which were infected with EHV-1. The infection was established through techniques like immunohistochemical labelling and polymerase chain reaction, especially focussing on lung tissues.
• In addition, the scientists also analysed the placentas by non-isotopic in-situ hybridization – a method used to detect specific DNA or RNA sequences – specifically focusing on the EHV-1 glycoprotein B (gB) gene.

Research Findings

• The research results indicated that positive hybridization signals – those showing evidence of the EHV-1 gene – were observed in the cytoplasm of placental cells, specifically in the microcotyledons, of all seven placentas examined.
• The presence of the EHV-1 RNA was also noted in the epithelium – or skin tissue – of the allantochorion (outermost membrane around the fetus) in six out of seven placentas. This means the EHV-1 gene was extensively present in the infected placentas.
• Despite the substantial presence of EHV-1 RNA, there was no EHV-1 antigen detected in the placentas through immunohistochemical examination. Antigens are substances that induce an immune response, and their absence implies the lack of an immune response against EHV-1 in the placenta.

Research Implications

• This study successfully demonstrates the presence of the EHV-1 gene in the placental cells of aborted horse fetuses, leading to a groundbreaking discovery in the veterinary field.
• The findings suggest a possible direct cell-to-cell transmission route of EHV-1, spreading from the endometrial cells (cells lining the uterus) to the placental cells (trophoblasts). This could provide valuable insights into how the virus operates and spreads, potentially offering new ways to prevent or treat the infection.