No abstract

Antibodies against dengue virus type 2 and 4 proteins in acute-phase sera of 10 primary and 10 secondary dengue fever and dengue hemorrhagic fever patients were studied by Western blotting. In the first group the immune response was barely detectable, while in the second group more proteins were detected, with a very strong reaction. Anti-NS1 and -NS3 antibodies were detected mainly in secondary cases. Anti-E, -NS3, and -NS5 antibodies were detected in a high number of cases. The possibility of implementing early diagnostic assays for antigen detection is suggested.

A recombinant vaccine that expresses the envelope (E) gene of dengue virus type 4 was tested for immunogenicity and protection in Macaca fascicularis. One hundred micrograms of semipurified recombinant E protein (E4rec) expressed in Pichia pastoris was used to immunize three animals. Neutralizing antibodies to dengue 4 virus with a titer of 1:30 were detected in all immunized monkeys prior to challenge. Animals were challenged with 10 5 plaqueforming units of dengue 4 virus. One vaccine-immunized monkey was protected from viremia, while the other two were partially protected. Monkeys immunized with E4rec elicited the highest neutralizing antibody titers (P < 0.05) ranging from 1:85 to 1:640 at day 30. In both immunized and control animals, the longest duration of viremia correlated with earliest and highest level of IgM antibody to dengue virus. The vaccinated animals showed anamnestic antibody responses upon virus challenge, indicating successful priming by the recombinant vaccine. Our results suggest that E4rec expressed in P. pastoris can provide partial protection against viremia. However, the results were not effective enough to use it as a vaccine candidate. Further work is required to improve the quality of the immunogen.

Summaryobjective Differential diagnosis of infections that cause similar diseases and may be active simultaneously in the same geographical areas is greatly needed. Dengue and yellow fever viruses (DENV and YFV) are transmitted by the same species of mosquito and both can cause haemorrhagic fever symptoms. These viruses are active mainly in regions where expensive and sophisticated technologies are not available. Our objective was to develop a simple, reliable and easy-to-perform method to detect and identify these viruses.methods We slightly modified a generic RT-PCR able to detect the mentioned viruses and other members of this genus: specific primers for each one of these viruses were designed and included in the nested reaction instead of one of the generic ones. The reaction was optimized and viruses are amplified giving rise to bands of different sizes distinguishable in agarose gels.results This test is able to detect and identify the four DENVs and YFV to a high level of sensitivity and specificity and can be used with clinical samples. This simple, reliable and easy-to-perform method able to detect and identify dengue 1-4 and YFV can be used in poor endemic countries.keywords dengue, yellow fever, diagnostic, PCR