EXPERIMENTAL MEASLES .1. PATHOGENESIS IN THE NORMAL AND THE IMMUNIZEDHOST

An animal model to study measles pathogenesis and the correlates of pr otective immunity was established using rhesus monkeys. A measles isol ate, obtained during an epidemic of measles in the primate colony at t he University of California, Davis, was passaged through rhesus monkey s and amplified in rhesus mononuclear cells to create a pathogenic vir us stock. Sequence analysis of the nucleoprotein and hemagglutinin gen es of this isolate revealed strong homology with the Chicago 89 strain of measles virus. Conjunctival/intranasal inoculation of juvenile rhe sus monkeys with this virus resulted in skin rash, pneumonia, and syst emic infection with dissemination to other mucosal sites and to the ly mphoid tissues. inflammation and necrosis occurred in the lungs and ly mphoid tissues and many cell types were infected with measles virus on Day 7 postinoculation (p.i.). The most commonly infected cell type wa s the a lymphocyte in lymphoid follicles. Measles antigen was found in follicular dendritic cells on Day 14 p.i. In contrast to naive monkey s infected with measles virus, animals vaccinated with the attenuated Moraten strain did not develop clinical or pathologic signs of measles after challenge. However, moderate to marked hyperplasia occurred in the lymph nodes and spleen of a vaccinated animal on Day 7 after patho genic virus challenge, suggesting that an effective measles vaccine li mits but does not prevent infection with wild-type measles virus. (C) 1997 Academic Press.