Genetic characteristics of clones derived from measles virus strain L-16.

The L-16 vaccine strain of measles virus produced in L-41 cell cultures of various size (0.5-0.2 mm in diameter), with clear or opaque centers, thus being genetically heterogeneous by the S and P markes. The clones derived from the L-16 strain differed from it and from each other in a number of genetic properties. Clones isolated at different temperatures, 35 degrees or 32 degrees C, differed from each other in thermostability, sensitivity to interferon, interferon-inducing activity, antigenicity and plaque size. Marked correlations were established between cytopathic activity (TC) and reproductive activity in L-41 cell cultures; thermostability at 50 degrees C (T50 character) and inactivation constant; and interferon-inducing activity and sensitivity to interferon.