Four virus clones were derived from the Edmonston strain of
measles virus by repeated plaque purification. These clones
were compared with the vaccine strains Schwarz and CAM-70 in
terms of biological activities including plaque formation,
hemagglutination, hemolysis and replication in Vero cells and
chick embryo fibroblasts (CEF).
Two clones of intermediate plaque yielded mixed plaque
populations on subcultivation whereas the other two, showing
small and large plaque sizes, showed stable plaque phenotypes.
The vaccine strains showed consistent homogeneous plaque
All the Edmonston clones showed agglutination of monkey
erythrocytes in isotonic solution while both vaccine strains
hemagglutinated only in the presence of high salt
Variation in the hemolytic activity was observed among the
four clones but no hemolytic activity was detected for the
vaccine virus strains.
Vaccine strains replicated efficiently both in Vero cells and
CEF. All four clones showed efficient replication in Vero
cells but different replication profiles in CEF. Two of them
replicated efficiently, one was of intermediate efficiency and
the other showed no replication in CEF.
Two of the clones showed characteristics similar to vaccine
strains. One in terms of size and homogeneity of plaques, the
other for a low hemolytic activity and both for the efficiency
of propagation in CEF.