Imunopatologia da dengue: receptores de quimiocinas CC e células iNKT

O Dengue virus (DENV), um flavivirus transmitido por mosquitos, é um sério problema de saude publica em paises tropicais. Mecanismos da resposta imune na infeccao ainda nao estao bem elucidados. Dados clinicos tem mostrado uma associacao entre niveis de quimiocinas CC no plasma e a severidade da doenca. Neste contexto, avaliamos o papel de receptores de quimiocinas CC, CCR1, CCR2 e CCR4, na infeccao pelo dengue utilizando animais KO para estes receptores. Alemdisso, avaliamos in vivo a contribuicao de celulas NKT invariantes (iNKT), linfocitos T ¿À nao convencionais, na resposta do hospedeiro utili zando uma amostra de DENV-2 adaptada em camundongos que leva a uma infeccao que se assemelha ao quadro de FHD/SCD. Camundongos C57/Bl6 (WT) apresentam sinais clinicos e danotecidual, incluindo trombocitopenia, hemoconcentracao, niveis elevados de transaminases e citocinas pro-inflamatorias, alem de mortalidade. Quimiocinas CC, como CCL2, CCL3 e CCL5, sao produzidas no baco e figado de animais WT. Animais CCR1-/- possuem fenotipo moderado, com doenca e mortalidade similares a animais WT. Em animais CCR2-/- a mortalidade, dano hepatico, niveis de IL-6 e IFN-Á, e ativacao de leucocitos foram atenuadas. Entretanto, trombocitopenia,hemoconcentracao e niveis sistemicos de TNF- ¿ foram similares aos de animais WT. CCL17, um ligante de CCR4, e produzido durante a infeccao. Em animais CCR4-/- a mortalidade, lesao tecidual e inflamacao sistemi ca estao fortemente reduzidas. Mesmo com diferencas no perfil de doencaem animais KO, nao houve alteracoes na carga viral. Celulas iNKT esplenicas e hepaticas sao ativadas e produzem IFN-Á na infeccao. Animais deficientes em iNKT (J¿18-/-) sao bastante resistentes a infeccao, comparados a animais WT. Este fenotipo e parcialmente revertido pela transferencia de celulas iNKT purifi cadas para animais J¿18-/-. Estes animais apresentam resposta inflamatoria reduzida, com baixos niveis de IL-6, IFN-Á e CXCL1, reduzida lesao hepatica e menor ativacao d e celulas NK eneutrofilos. A carga viral no baco e figado tambem foi reduzida. Tratamento com ¿GalCer e a delecao de CD1d nao alteram o fenotipo observado em animais WT. Em resumo, receptores de quimiocinas CC tem papeis diferentes na infeccao pelo DENV-2 e a ativacao endogena de celulas iNKT durante a infeccao contribui de forma importante para a resposta sistemica e local associada a sindr ome do choque pelo dengue em camundongos.Dengue virus (DENV), a mosquito-borne flavivirus, is a serious public health problem in many tropical countries. Immune mechanisms involved in the pathogenesis of DENV infection are not fully elucidated. Recent clinical data showed an association between levels of different CC chemokines in plasma and severity of dengue. In this regard, we evaluated the role of CC chemokine receptors CCR1, CCR2 and CCR4 in dengue infection using KO mice for these receptors. Furthermore, we assessed the in vivo contribution of invariant Natural Killer T (iNKT)cells, non-conventional áâ T lymphocytes, to the host response using a mouseadapted DENV-2 strain that causes a disease resembling severe dengue infection. Infected C57/Bl6 mice (WT) presented clinical disease and tissue damage, including thrombocytopenia, hemoconcentration, increased levels of transaminases and proinflammatory cytokines, and lethality. CC chemokines, such as CCL2, CCL3 and CCL5, are strongly produced in spleen and liver of WT mice. CCR1-/- mice had a mildphenotype with disease presentation and lethality similar to those of WT mice. In CCR2-/- mice, lethality, liver damage, levels of IL-6 and IFN-ã, and leukocyte activation were attenuated. However, thrombocytopenia, hemoconcentration and systemic TNF-á levels were similar to infected WT mice. CCL17, a CCR4 ligand, is produced upon infection. In CCR4-/- mice, lethality, tissue injury and systemic inflammation were markedly decreased. Despite differences in disease presentation in CCR-deficient mice, there were no significant differences in viral load. Splenic andhepatic iNKT cells became activated and produce IFN-ã upon infection. Mice deficient in iNKT cells (Já18-/-) are highly resistant to the infection when compared to WT animals. The phenotype was partially recovered by adoptive transfer of iNKT cells to Já18-/-animals. Já18-/- mice presented decreased systemic and local inflammatory responses, with lower levels of IL-6, IFN-ã and CXCL1, reduced liver injury and diminished activation of NK cells and neutrophils. Viral load in spleen and liver was also lower in Já18-/- mice relative to WT mice. áGalCer treatment and CD1dablation had no effects in disease progression. In conclusion, CC chemokine receptors have discrete roles in DENV-2 and endogenous iNKT cell activation during DV infection contributes to the systemic and local inflammatory responses that lead to shock and death, suggesting that CC chemokine receptors and iNKT cells may be associated to the inflammatory response involved in dengue shock syndrome in mice