Xu Zhendong (1937- ) is a native of Fengrun, Hebei Province. He graduated from Department of Veterinary Medicine, Beijing Agriculture University. He is now working as vice director of Harbin Institute of Veterinary Science, Chinese Academy of Agriculture. He had focused on research on immunity of equine infectious anemia. He had also been the director in research in enzootic leukosis and Newcastle disease. His development of Donkey leucocyte attenuated vaccine of Equine Infectious Anemia together with Shen Rongxian made him the winner of Technological Advancement Award, First Class, awarded by Agriculture Ministry and National Invention Award, First Class. In 1984, he was conferred the title of National Young and Middle-aged Expert with Outstanding Contributions. In 1985, he finished study on "Diagnosing bovine leucosis by applying PPAELISA", which made him win the Second-class Prize of Technological Advancement, awarded by Chinese Academy of Agricultural Science in 1986. In 1990, he finished study on application of monoclonal antibody probe in diagnosing enzootic bovine leukosis, which made him the winner of the Technological Advancement Award, Second Class, awarded by Chinese Academy of Agriculture in 1991.

STUDY ON IMMUNITY OF EQUINE INFECTIOUS ANEMIA

Shen Rongxian and Xu Zhendong

(Harbin Institute of Veterinary Science, Chinese Academy of Agriculture)

Abstract

Development and Application of Equine Infectious Anemia Donkey Leucocyte Attenuated Virus Vaccine are discussed.

Equine Infectious Anemia (EIA), caused by a member of retroviridiae, is characterized by high fever, anemia and petechia in various organs, etc. A large number of horses died during an acute outbreak, while the animal tolerating the disease will become chronic or symptomless. The infection source is the horses with virus persistence. The disease costs a huge economic loss in the horse raising countries.

As EIA is caused by a lentivirus, within which antigenic shift occurs, many scholars in the world had tried to develop effective vaccines, but failed. In our laboratory, an attenuated vaccine with good immunogenicity was obtained by changing the viral growth conditions through the passages and adaptation of a virulent EIA virus strain in donkey leucocyte for ten years. In prolonged observation (from 6 to 39 months), the vaccinated horses did not reveal any side effects. Reversion tests in horses showed that there was no occurrence of reversion. The horses inoculated with the attenuated virus could not induce infection in the healthy horses through cohabitant test-Foals born from vaccinated mares were tested biologically and proved to be free of the virus.

Obvious humoral and cellular immune responses were detected in the vaccinated horses. In the challenge tests with virulent EIA virus, the vaccination could offer over 85% protection for horses. The vaccine could not only protect the challenge of the Chinese homologous EIA strain, but also the American heterogeneous Wyoming virus strain. The immunity persisted for over three years.

Since 1975, the vaccine has been applied in the field and more than one million of Equidae were vaccinated in China. The morbidities were markedly decreased with vaccine application, at present, there was hardly any disease occurring and EIA has been effectively controlled and prevented in China.

In 1983, an international symposium on immunity to EIA was held in Harbin, and the vaccine was well received and affirmed by the experts from America, France and Japan. And then many countries, especially Latin American Countries which were affected by EIA, wished to introduce the vaccine for the prevention of this disease. In 1987 and 1989, the safety tests and field trial were carried out in Cuba and Argentina.

The success of EIA attenuated vaccine made not only a huge economic benefit in the control of EIA, but also a break-through in the immunological theory of lentivirus. Soon after the discovery of AIDS virus, the scholars in the United States and France proved that both AIDS and EIA viruses belong to Lentivirus. The EIA virus is very similar to AIDS virus in the following aspects: mode of transmission; monocytes as virus reservoir; morphological and genetic structure; pathogenesis with T cells as target and persistent infection; cross serological reaction between p26 of EIAV and p24 of AIDS virus.

Therefore, disclosing the immunological secrets of EIA, and especially setting EIA as an animal model will open a new way to the immunological study and vaccine development for lentivirus diseases of men and animals.