Radial haemolysis in gel used in serological studies on Venezuelan equine encephalomyelitis virus.

Radial haemolysis in gel was successfully used for the detection of antibody in convalescents after laboratory infection with Venezuelan equine encephalomyelitis (VEE) virus at remote intervals after infection (up to 23 years). The antibodies reacted only with VEE antigen but not with Sindbis and Chikungunya alphavirus antigens. Radial haemolysis in gel was sensitive as the haemagglutination inhibition test but the antibody could be titrated by the diameter of the haemolysis zone omitting the serum dilutions. Slight deviations in the virus dose used for sensitization of erythrocytes or in pH values were not critical. For the test, the sera were heated at 56 degrees C for 30 min. Both sera stored for long periods and those collected on paper disks could be used.