SIMIAN IMMUNODEFICIENCY VIRUS OF AFRICAN-GREEN MONKEYS IS APATHOGENICIN THE NEWBORN NATURAL HOST

Several studies have demonstrated that newborn animals are more suscep tible to disease development following infection with retroviruses tha n adults. Adult African green monkeys (AGMs) infected with SIVagm do n ot develop AIDS-like disease and the objective of the study was to det ermine whether experimental infection of newborn AGMs with SIVagm woul d result in pathogenesis. Neonatal AGMs were found to have a higher pe rcentage of circulating CD4(+) lymphocytes than adults (62% versus 14% ) and therefore a higher potential pool of target cells for SIVagm inf ection. However, no differences in the in vitro replication kinetics o f SIVagm in peripheral blood mononuclear cells of adult or neonatal AG Ms could be observed. In vivo, the neonatal AGMs became viremic at the earliest two months after inoculation whereas the adult AGMs had evid ence of virus replication already 2 to 6 weeks after infection. None o f the animals developed AIDS-like symptoms upon infection. In the hete rologous cynomolgus macaque host, a newborn infected with SIVagm devel oped early high virus loads and died two months after birth with AIDS- like histopathologic features. It would therefore appear that in contr ast to the situation with many other retroviruses, newborn AGMs are no more permissive to SIVagm than are adults.