Immunochemical Behavior and Isolation of Equine Hemagglutinins Found in Normal and Hyperimmune Serum

In studying Equine Infectious Anemia (EIA), a specific viral disease of
Equidae, characterized by intermittent fever, anemia and progressive weakness,
questions have arisen as to the existence of a viral hemagglutinin. Raised
hemagglutinin levels are present in the infected sera, but this is further complicated
by the fact that some horse serums contain relatively high levels of
hemagglutinins which are believed to be non-specific natural agglutinins. This
investigation, which parallels research currently in progress on the EIA virus
proper, is designed to characterize those agglutinins found in non-infected sera.
Two principal types of equine hemagglutinins were studied; (1) the natural
occurring non-specific blood agglutinin, and (2) hyperimmune isoagglutinins produced
in a primary immune response following injection of heterogenic equine
erythrocytes. Both species of agglutinins were obtained from whole serum.
Standard immunological techniques such as reduction and alkylation, heat
inactivation, ion-exchange chromotography, density gradient ultracentrifugation,
and electrophoresis were employed in the investigation of structural and biological
characteristics of the hemagglutinins.
The results have shown that natural equine hemagglutinins are heterospecific.
They are sensitive to heat (56°C) and reducing agents such as mercaptoethanol.
Natural agglutinins have a sedimentation coefficient of 18.65 and electrophoretically
migrate as alpha2 globulins. The hyperimmune isohemagglutinin is a specific antibody reactive with a
well defined antigen. It is relatively heat stabile and hemagglutinating activity
is reduced with mercaptoethanol. Similarly, the isoagglutinin has the some
sedimentation coefficient and electrophoretic mobility as the natural antibody.
The isoagglutinin is unique in that it represents a new class of antibody not previously
reported.