Isolation of equine herpesvirus-1 lacking glycoprotein C from a dead neonatal foal in Japan.

The research focuses on a variant strain of Equine Herpesvirus-1 (EHV-1), strain 5089, that was found in a dead newborn horse in Japan. This variant is notable as it mainly spreads via cell-to-cell infection and lacks the Glycoprotein C component that is characteristic of the typical EHV-1 strain.

Virus Characteristics and Spread

• The researchers isolated and studied the EHV-1 variant, strain 5089, from the lung of a deceased neonatal foal. Its uniqueness lies in its mode of transmission, which is primarily cell-to-cell. This is different from the wild-type EHV-1 virus that spreads effectively as a cell-free virus.
• The virus titer, or concentration, of the 5089 strain found in culture supernatants and within infected cells was lower than that of the typical EHV-1 strain.
• The group found that treating the 5089 virus strain with heparin had no impact on the virus’s ability to infect cultured cells. This differs from many viruses, where heparin treatment often hinders their infectivity.

Glycoprotein C Analysis

• Glycoprotein C (gC) was not detected in 5089 virions (virus particles) or in cells infected with the 5089 strain. Detection was done through Western blotting and fluorescent antibody tests, methods often used for identifying specific proteins in a sample.
• Further analysis using Reverse Transcriptase-Polymerase Chain Reaction (RT-PCR) showed that the expression level of gC mRNA in the 5089 strain was significantly lower compared to the wild-type EHV-1 strain.
• An exploration of the gC coding region in the 5089 virus exhibited a point mutation in the promoter region of the gC gene. However, this mutation did not impact the promoter activity, suggesting other factors besides the mutation could be influencing gC expression in the 5089 strain.

Conclusions

• Findings from the study suggest that the absence of gC in the 5089 strain might be one of the reasons why it spreads via cell-to-cell infection.
• There’s also an implication that gC mRNA expression may not be effectively activated due to factors other than the mutation in the gC promoter region. This area warrants further exploration to better understand why this EHV-1 variant lacks gC unlike the wild-type strain.