Increase in the sensitivity of dengue diagnosis by combination of reverse transcriptase-polymerase chain reaction and passage on cell cultures.

We passaged 52 serum samples from dengue patients on C6/36 cells for 7 days and checked the culture fluids by RT-PCR. Two serum samples, which were negative by direct RT-PCR, became positive. One sample was collected on fever day 1 and the other on fever day 2. Results indicate that combination of reverse transcriptase-polymerase chain reaction (RT-PCR) with passage of serum samples on C6/36 cells increases the sensitivity of dengue diagnosis.

Human immune responses to dengue viruses.

Dengue fever (DF) and dengue hemorrhagic fever (DHF)/dengue shock syndrome (DSS) are major public health problems in many areas of the world. We are analyzing the human immune responses to dengue viruses, in order to understand the mechanism of recovery from dengue virus infections and the pathogenesis of DHF/DSS. Human natural killer (NK) cells lyse dengue virus-infected cells to a greater degree than uninfected cells. Antibodies to dengue viruses augment the lysis of dengue virus-infected cells by NK cells. Dengue virus-infected monocytes produce high levels of interferon alpha (IFN alpha). DR+ lymphocytes also produce high levels of IFN alpha after contact with dengue virus-infected monocytes. The IFN alpha produced protects uninfected monocytes from dengue virus infection. These results suggest that NK cells and IFN alpha may play an important role in controlling primary dengue virus infection. Dengue virus-specific CD4+CD8(-)T lymphocytes and CD4(-)CD8+T lymphocytes are present in the peripheral blood mononuclear cell population from donors who were infected with dengue virus. Most of CD4+T lymphocytes are dengue serotype-crossreactive. They lyse dengue virus-infected autologous cells in an HLA class II-restricted fashion, and produce interferon gamma (IFN gamma). IFN gamma augments dengue virus infection of monocytic cells in the presence of antidengue virus antibodies by increasing the number of Fc gamma receptors. Dengue virus-specific CD8+T lymphocytes lyse dengue virus-infected autologous cells in an HLA class I-restricted fashion. These CD8+T lymphocytes are also dengue serotype-crossreactive.(ABSTRACT TRUNCATED AT 250 WORDS)