Pathomorphologic characterization of CNS damage in monkeys infected with persistent variant of measles virus vaccine strain L-16.

The lesions of CNS were examined in monkeys infected intracerebrally (i.c.) with a variant of measles virus vaccine strain L-16 isolated after prolonged persistence in human cell culture NEr-2. The persisting virus variant appeared pathogenic for monkeys. The changes which had developed in their CNS within 30 to 60 days post-infection (p.i.) were alike to acute measles encephalitis which was evidenced by giant cell formation at the injection site. Twenty-two months p.i. the chronic character of lesions was evident from the appearance of foci of neuron destruction. Based on morphologic findings it was suggested that strain L-16-H has acquired some properties characteristic of nonattenuated virus.