Neurovirulence detection of dengue virus using rhesus and cynomolgus monkeys.

The results of a comparative study of neurovirulence of dengue type 1 virus in two species of Old World monkeys, viz. rhesus monkeys (Macaca mulatta) and cynomolgus monkeys (Macaca fascicularis) are reported. In the present study, parental dengue type 1 (16007) and its vaccine viruses were tested by intrathalamic, intramuscular and intraspinal injections in these two species of monkey. Both species of monkeys inoculated with parental dengue type 1 virus developed neurovirulence-type lesions which were graded as minimal (V-1) and occasionally mild (V-2, in cynomolgus monkeys) in severity. The antibody response to either parental or vaccine virus was slightly less in rhesus monkeys than in cynomolgus inoculated with these strains. This comparative study possibly establishes the cynomolgus monkey as a suitable test model to replace the rhesus monkey for neurovirulence testing of dengue-1 vaccine intended for use in humans.