Equine abortion (herpes) virus: evaluation of markers in a field vaccination trial.

The study investigates the effectiveness of a vaccine for equine abortion virus (EAV), finding that three vaccinated mares may have had a natural infection concurrent with vaccination. The research also explores strains of the virus found in vaccinated and non-vaccinated mares, as well as in a fetus, while attempting to distinguish between the vaccine strain and wild-type strains.

Study Set-Up

• The research involved twelve mares which were given a vaccine derived from an attenuated (weakened) EAV strain labelled RAC-H. Two mares that did not receive the vaccination were used as control subjects for comparison.
• The scientists suspected that a natural infection was present in at least three of the vaccinated mares, possibly happening around the time of vaccination.

Virus Isolation and Characterization

• Part of the research included isolating and characterizing the EAV from nasal secretions of six vaccinated mares, one non-vaccinated mare, and from various organs of a fetus aborted by a vaccinated mare.
• The scientists made distinctions between the RAC-H strain (used in the vaccine) and the wild-type virus by assessing how sensitive isolated EAV was to a chemical named dithiothreitol.

Findings

• Among the ten EAV isolates, the scientists determined four to be the vaccine strain, while the remaining six were identified as wild-type strains.
• Three of the wild-type strains came from two vaccinated mares and a non-vaccinated control, while the other three were obtained from the aborted fetus.

L Cell Plaque Formation

• The research paper also mentioned an attempt to use the ability of the EAV strains to form plaques (visible patches of viral infection) in a cloned line of “L cells” (a type of laboratory cell culture) as a marker for the study.
• However, this method was deemed unsuitable for use in this research.

Overall, the study indicates that natural infection may influence the effectiveness of the EAV vaccine, and further research is needed to understand these interactions and to develop more reliable markers for study.