Dengue virus serotype-2 impairs proliferation of healthy donors' T lymphocytes.

OBJECTIVES: T lymphocytes are not infected by dengue virus (DENV), nevertheless it is possible that exposure to DENV may affect their function. T lymphocytes from DENV-infected individuals are impaired in their proliferative capacity, although this effect has been attributed to altered function of antigen-presenting cells rather than to an intrinsic defect on T lymphocytes. Here we analyzed whether T lymphocytes from healthy donors became impaired in their proliferative capacity following in vitro exposure to DENV serotype-2 (DENV-2), as well as the possible mechanisms for this. METHODS: Isolated CD4+ and CD8+ T lymphocytes from healthy donors were in vitro exposed to DENV-2, before polyclonal activation, cell proliferation, IL-2 synthesis. IL-2Rα expression, nuclear translocation of NF-AT and NF-κB, and intracellular calcium flux were assessed. RESULTS: In vitro exposure of both CD4+ and CD8+ T lymphocytes from healthy donors to DENV-2 impairs cell proliferation, IL-2 synthesis, and IL-2Rα (CD25) cell membrane expression. Signalling wise, exposure to DENV-2 impairs the nuclear translocation of NF-AT, downstream of intracellular calcium mobilization, as well as that of NF-κB. CONCLUSION: In the course of a dengue infection, direct exposure of T lymphocytes to DENV could affect cell-mediated immune responses.

Improving dengue virus diagnosis in rural areas of Mexico.

Evaluation of an “in-house system” for the diagnosis of dengue infection by detection of specific IgM and IgG antibodies showed that 25 out of 34 (73.53%) serum samples were positive for IgM antibodies; 6 (17.64%) were positive for IgG and 3 (8.8%) were negative for both IgM and IgG anti-DENV antibodies. Ten samples from “non-symptomatic” people were all negative. In order to evaluate the anti-DENV ELISA, 20 serum samples obtained from healthy individuals from a non-endemic region (Mexico City) and 20 serum samples previously classified as positive were tested. All 20 samples from healthy individuals proved to be negative for both IgM and IgG anti-DENV antibodies, whereas not all positive samples resulted as positive in our assay.

Gene expression in human macrophages infected with dengue virus serotype-2.

Infection by any of the four serotypes of dengue viruses (DEN-1, -2, -3 and -4) may result in either a relatively benign fever, called dengue fever (DF), a fatal disease, such as dengue haemorrhagic fever (DHF) or dengue shock syndrome (DSS). Several lines of evidence suggest that soluble immune response mediators may be involved in the severity of dengue infections. For instance, elevated seric levels of IL-8 are a common feature in DHF patients. Because other chemokines, cytokines, adhesion molecules, chemokine and cytokine receptors, as well as cytokine-related molecules may also be involved in dengue virus pathogenesis, we aimed at analysing the gene expression of such molecules in the course of an in vitro DEN-2 infection of human peripheral blood monocyte-derived macrophages, a cell type regarded as a primary target for DEN. Nylon membrane gene arrays containing 375 different human cytokine-related genes were used as a first step to search for differentially expressed genes upon infection. Transcripts for IL-8, IL-1beta, osteopontin, GRO-alpha, -beta and -gamma, I-309, and some other molecules showed to be upregulated upon infection, whereas others such as MIC-1, CD27L and CD30L, were downregulated. Four genes were selected for reverse transcriptase-polymerase chain reaction based gene-expression analysis as a way to partially confirm microarray results. This approach pointed out 25 macrophage-expressed cytokine-related genes that could be relevant in DEN-2 pathogenesis.