A New Vaccine For Equine Herpesvirus On The Horizon

Equine herpesvirus-1 (EHV-1) is the major cause worldwide of epidemic abortion in mares, along with neonatal deaths in foals, and also cause respiratory illness and nervous system disease. This virus, along with the closely related equine herpesvirus-4 (EHV-4) which causes respiratory illness in horses, has a considerable and adverse impact on the economics of all sectors of the equine industry. The currently available vaccines for EHV-1 are based on whole virus and have been generally ineffective in affording complete protection against the disease.

An alternative to using whole virus vaccines is to use recombinant DNA techniques to identify and synthesis individual virus components which either alone, or in combination, provide significant immunity. Australian researchers have recently completed a RIRDC-funded study which has paved the way towards a successful vaccine to control EHV-1. Progress towards production of the new subunit vaccine can be summarized as follows:

  1. Two EHV-1 glycoproteins were identified which gave protective immune responses in an animal model of EHV-1 disease. The immune responses also act against EHV-4.
  2. An adjuvant was selected which enhanced the immune response of the EHV-1 antigens.
  3. Methods were developed for quantification, medium scale up and high level production of the two vaccine antigens.
  4. The safety of the formulation was demonstrated in horses.
  5. The vaccine preparation and formulation satisfies the requirements of the regulatory bodies Australian Quarantine Inspection Service (AQIS) and the Genetic Manipulation Advisory Committee (GMAC), as necessary for such a vaccine. Protocols can now be developed for the National Registration Authority for registration of a vaccine.
  6. A sufficient quantity of antigen was prepared for formulation and is available for dose responses and additional safety trials in horses. The principal researchers Millar Whalley and Daria Love have received funding from RIRDC to continue this work through to 2001. This new work aims to obtain data on the effectiveness of vaccine strategies for EHV-1 and -4 and to update epidemiological information on the incidence of EHV -1 in horse populations in the current vaccination environment. The researchers also aim to make recommendations for management of horses to decrease the incidence of equine herpesvirus and this includes vaccination strategies.

These outcomes will have an important impact on the management of disease caused by EHV-1 and –4. This is only possible through the dedication of the equine researchers and the commitment of RIRDC to fund such projects which aim to improve the health and well being of horses.

—Rural Industries Research and Development Corporation www.rirdc.gov.au/home.html.

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