Neutralization characteristics of dengue viruses isolated in mosquito cell culture and suckling mouse brain from a case of laboratory dengue infection.

One of the authors (Y.O.) of this paper was accidentally infected in the laboratory with dengue type 4 virus, isolated in Thailand in 1978 using the C6/36 clone of Singh's Aedes albopictus cells (SA). Two strains of the virus were isolated from Y.O.'s serum on the first day of illness using SA and suckling mouse brain (SMB). The SA-isolate and the infecting virus were neutralized with high efficiency by Y.O.'s convalescent sera, but the SMB-isolate was neutralized much less efficiently by the same sera. When the hosts of the isolates were exchanged (SA to SMB, and vice versa), the neutralization efficiencies were reversed. For analysis of this phenomenon, prototype dengue type 4 virus exclusively passed in SMB and the same type of virus passaged 10 times in SA were compared with the initial SA- and SMB-isolates in neutralization tests with sera from patients with dengue hemorrhagic fever (DHF) obtained in Thailand. The two strains of the prototype virus and the SA-isolate had similar high reactivities, but the SMB-isolate had low reactivity with sera of the DHF patients.