APOPTOSIS IN THE MOUSE CENTRAL-NERVOUS-SYSTEM IN RESPONSE TO INFECTION WITH MOUSE-NEUROVIRULENT DENGUE VIRUSES

Apoptosis has been suggested as a mechanism by which dengue (DEN) viru s infection may cause neuronal cell death (P. Despris, M. Flamand, P.- E. Ceccaldi, and V. Deubel, J. Virol. 70:4090-4096, 1996). In this stu dy, me investigated whether apoptotic cell death occurred in the centr al nervous system (CNS) of neonatal mice inoculated intracerebrally wi th DEN virus, We showed that serial passage of a wild-type human isola te of DEN virus in mouse brains selected highly neurovirulent variants which replicated more efficiently in the CNS. Infection of newborn mi ce with these neurovirulent variants produced fatal encephalitis withi n 10 days after inoculation. Virus-induced cell death and oligonucleos omal DNA fragmentation were observed in mouse brain tissue by day 9. I nfected mouse brain tissue was assayed for apoptosis by in situ termin al deoxynucleotidyl transferase-mediated dUTP nick end labeling and fo r virus replication by immunostaining of viral antigens and in situ hy bridization. Apoptotic cell death and DEN virus replication were restr icted to the neurons of the cortical and hippocampal regions. Thus, DE N virus-induced apoptosis in the CNS was a direct result of virus infe ction. In the murine neuronal cell line Neuro 2a, neuroadapted DEN vir us variants showed infection patterns similar to those of the parental strain. However, DEN virus-induced apoptosis in these cells was more pronounced after infection,vith the neurovirulent variants than after infection with the parental strain.