Derivation and characterisation of a live equid herpes virus-1 (EHV-1) vaccine to protect against abortion and respiratory disease due to EHV-1.

The research article focuses on the development and testing of a live vaccine for equid herpes virus-1 (EHV-1), a condition that often results in abortion and respiratory diseases in horses. The experiment involves the use of a specific EHV-1 strain (M8). The aim is to create a vaccine using this strain that can provide efficient protection against the harmful effects of EHV-1, notably abortion in pregnant mares and respiratory diseases.

Methodology

• The researchers used the German abortion strain M8 of EHV-1 and cultivated it in equine dermal (ED) cells. This was done with a low multiplicity of infection in the presence of 5-bromo-2-deoxy uridine.
• The resultant stock was dialysed, titrated, and cloned through terminal dilution. This process was carried out in ED cells grown in 96-well microtitration plates.
• 192 different clones were generated, each originating from a single focus. Among these, clone 147 (C147) was found to be limited in its growth at and above temperatures of 38.5 degrees C, and it was also limited in growth at 37 degrees C in rabbit kidney (RK-13) cells. Due to these growth restrictions in EHV-1 isolation and titration cells, clone 147 was classified as EHV-4-like.

Testing the Vaccine

• The C147 clone was then used as a potential vaccine and tested on a group of pregnant Welsh Mountain pony mares. Its efficacy was evaluated based on its ability to protect against abortions due to EHV-1.
• Results of the testing showed that a single, intranasal (IN) vaccination was able to protect five out of six (83.3%), and a second group of four out of five (80%) of the mares from EHV-1-induced abortion, occurring 4-6 months post-immunisation.
• In contrast, all six mares in the unvaccinated group aborted between 9 and 19 days following the IN EHV-1 challenge.
• Besides protection from abortions, vaccinated groups of mares were also significantly protected against clinical reactions such as fever, nasal shedding, and viraemia following the challenge infection.

Conclusion

• These results suggest that the derived EHV-1 vaccine using the C147 clone of the M8 strain could be an effective preventive measure against EHV-1 induced abortions in mares and potentially against related respiratory diseases.
• Additional research would be needed to assess long-term effects, potential side effects of this vaccine, and to further validate its efficacy in a larger population.