An in vitro model for dengue virus infection that exhibits human monocyte infection, multiple cytokine production and dexamethasone immunomodulation

An important cytokine role in dengue fever pathogenesis has been described. These molecules can be associated with haemorrhagic manifestations, coagulation disorders, hypotension and shock, all symptoms implicated in vascular permeability and disease worsening conditions. Several immunological diseases have been treated by cytokine modulation and dexamethasone is utilized clinically to treat pathologies with inflammatory and autoimmune ethiologies. We established an in vitro model with human monocytes infected by dengue virus-2 for evaluating immunomodulatory and antiviral activities of potential pharmaceutical products. Flow cytometry analysis demonstrated significant dengue antigen detection in target cells two days after infection. TNF-alpha, IFN-alpha, IL-6 and IL-10 are produced by in vitro infected monocytes and are significantly detected in cell culture supernatants by multiplex microbead immunoassay. Dexamethasone action was tested for the first time for its modulation in dengue infection, presenting optimistic results in both decreasing cell infection rates and inhibiting TNF-alpha, IFN-alpha and IL-10 production. This model is proposed for novel drug trials yet to be applyed for dengue fever.

The role of natural killer cells in the early period of infection in murine cutaneous leishmaniasis

In order to study the role of natural killer (NK) cells during the early period of Leishmania infection, BALB/c mice were selectively and permanently depleted of NK cells by injection with 90Sr and subsequently infected with Leishmania (Leishmania) amazonensis (HSJD-1 strain). 90Sr is known to selectively deplete NK cells, leaving an intact T- and B-cell compartment and preserving the ability to produce both interferon alpha and IL-2. This method of depletion has advantages when compared with depletion using anti-NK cell monoclonal antibodies because the effect is permanent and neither activates complement nor provokes massive cell death. In the present study, after one month of treatment with 90Sr, the depletion of NK cells was shown by a more than ten-fold reduction in the cytotoxic activity of these cells: 2 x 106 spleen cells from NK-depleted animals were required to reach the same specific lysis of target cells effected by 0.15 x 106 spleen cells from normal control animals. The histopathology of the skin lesion at 7 days after Leishmania infection showed more parasites in the NK cell-depleted group. This observation further strengthens a direct role of NK cells during the early period of Leishmania infection

Expression of interferons-alpha and -beta, tumor necrosis factor-alpha and transcription factors, IRF-1 and IRF-2, in leukocytes induced during interferon production

Analysis of gene expression in peripheral blood lymphocytes is of special interest because it could reflect physiological conditions. We have examined the expression and compared the relative amounts of specific mRNAs for interferons (IFN-alpha and IFN-beta), tumor necrosis factor-alpha (TNF-alpha) and interferon regulatory factors (IRF-1 and IRF-2) from interferon primed and Sendai virus induced peripheral blood leukocytes. Results obtained showed that IRF-1 was highly inducible by IFN treatment, IFN-alpha, TNF-alpha and IRF-2 were weakly induced by IFN treatment, and IFN-beta was not inducible by priming the cells with recombinant human IFN-alpha 2b. The IFN-alpha, IFN-beta, IRF-2 and TNF-alpha transcripts increased upon viral infection. The IRF-1 mRNA was rapidly induced by IFN treatment and decreased after Sendai virus infection. Our results show that, in peripheral blood lymphocytes, IFN-alpha and -beta genes have a different response to IFN induction, thus suggesting different regulatory mechanisms for IFN induction of type I IFN genes in peripheral blood lymphocytes