Attenuated, replication-competent herpes simplex virus type 1 mutant G207:Safety evaluation of intracerebral injection in nonhuman primates

This study examined the safety of intracerebral inoculation of G207, an att enuated, replication-competent herpes simplex virus type 1 (HSV-1) recombin ant, in nonhuman primates. Sixteen New World owl monkeys (Aotus nancymae [k aryotype 1, formerly believed to be A. trivirgatus]), known for their exqui site susceptibility to HSV-1 infection, were evaluated. Thirteen underwent intracerebral inoculation with G207 at doses of 10(7) or 10(9) PFU, two wer e vehicle inoculated, and one served as an infected wild-type control and r eceived 10(3) PFU of HSV-1 strain F. HSV-1 strain F caused rapid mortality and symptoms consistent with HSV encephalitis, including fever, hemiparesis , meningitis, and hemorrhage in the basal ganglia. One year after G207 inoc ulation, seven of the animals were alive and exhibited no evidence of clini cal complications. Three deaths resulted from nonneurologic causes unrelate d to HSV infection, and three animals were sacrificed for histopathologic e xamination. Two animals were reinoculated with G207 (10(7) PFU) at the same stereotactic coordinates 1 year after the initial G207 inoculation. These animals were alive and healthy 2 years after the second inoculation. Cerebr al magnetic resonance imaging studies performed both before and after G207 inoculation failed to reveal radiographic evidence of HSV-related sequelae. Despite the lack of outwardly observable HSV pathology, measurable increas es in serum anti-HSV titers were detected. Histopathological examination of multiple organ tissues found no evidence of HSV-induced histopathology or dissemination. We conclude that intracerebral inoculation of up to 109 PFU of G207, well above the efficacious dose in mouse tumor studies, is safe an d therefore appropriate for human clinical trials.