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The capacity for oral infection, dissemination, and transmission of the dengue-2 candidate vaccine virus DEN-2 PDK53 and an isolate from a vaccinate individual, DEN-2 Ia8, were compared with the parent strain DEN-2 16681. Capacity for oral infection and dissemination to the brain and salivary gland tissues were significantly lower in the first two than in the parent strain (P < 0.001). Replication was more than 100 times higher for the parent strain when compared with the dengue-2 candidate vaccine virus. Transmission was not demonstrated in the mosquitoes orally infected with DEN-2 PDK53 and DEN-2 Ia8, whereas transmission was achieved in 57% (8 of 14) of mosquitoes infected with the parent virus strain. Using immunofluorescence, viral antigen was detected in the mosquitoes infected with DEN-2 PDK53 and DEN-2 Ia8. It was seen mainly in the form of specks scattered in some parts of the tissues, and was strikingly different from that seen in the parent strain, in which major parts of the tissues contained viral antigen in the form of rings and specks. The biological markers of DEN-2 PDK53 and DEN-2 Ia8 retained the biological characteristic of the vaccine after a mosquito passage and a human and mosquito passage, respectively.
Khin et al. (Thu,) studied this question.