Tumour necrosis factor plays a deleterious role in the pathogenesis of chikungunya virus infection.

Arthralgia is a hallmark of chikungunya virus (CHIKV) infection and can be very debilitating and associated with a robust local inflammatory response. Many pathophysiological aspects associated with the disease remain to be elucidated. Here, we describe a novel model of CHIKV infection in immunocompetent mice and evaluate the role of tumour necrosis factor in the pathogenesis of the disease. C57BL/6 wild type (WT) or TNF receptor 1 deficient (TNFR1-/- ) mice were inoculated with 1 × 106 PFU of CHIKV in the paw. Alternatively, etanercept was used to inhibit TNF in infected WT mice. Hypernociception, inflammatory and virological analysis were performed. Inoculation of CHIKV into WT mice induced persistent hypernociception. There was significant viral replication in target organs and local production of inflammatory mediators in early time-points after infection. CHIKV infection was associated with specific humoral IgM and IgG responses. In TNFR1-/- mice, there was a decrease in the hypernociception threshold, which was associated with a milder local inflammatory response in the paw but delayed viral clearance. Local or systemic treatment with etanercept reduced CHIKV-induced hypernociception. This is the first study to describe hypernociception, a clinical correlation of arthralgia, in immunocompetent mice infected with CHIKV. It also demonstrates the dual role of TNF in contributing to viral clearance but driving tissue damage and hypernociception. Inhibition of TNF may have therapeutic benefits but its role in viral clearance suggests that viral levels must be monitored in CHIKV-infected patients and that TNF inhibitors should ideally be used in combination with anti-viral drugs.

Função das células dendríticas durante a infecção experimental por Trypanosoma cruzi: papel de SOCS2 / Dendritic cell function during experimental Trypanosoma cruzi infection: role of SOCS2

A infecção por Trypanosoma cruzi (T. cruzi), causador da doença de Chagas, induz uma reação inflamatória e a eficiência da resposta imune (RI) do hospedeiro é importante para que a infecção persista ou seja eliminada. A expressão de SOCS2 (Supressor de Sinalização de Citocinas)2, uma proteína intracelular, é parcialmente mediada por lipoxinas (LXA4, eicosanoide anti-inflamatório) em células dendríticas (DCs), a principal célula apresentadora de antígeno (APC). Demonstramos que SOCS2 é fundamental durante a infecção por T. cruzi modulando a geração/expansão de células Th1, Treg e de memória e no controle da função cardíaca. No presente trabalho, nós pesquisamos o papel de SOCS2 na função de DCs e na indução/manutenção da RI durante a infecção experimental por T. cruzi. Camundongos CD11cDTR transgênicos (depleção de DCs), selvagens (WT) e deficientes de SOCS2 (knockout/KO) foram infectados com a cepa Y de T. cruzi. Nossos resultados demonstraram um aumento da parasitemia nos animais depletados de DCs, ressaltando que DCs são cruciais no controle da infecção por T. cruzi. Durante a RI inata a ausência de SOCS2 resultou na redução da frequência de DCs produtoras de citocinas inflamatórias (IL-12 e TNF-α), mas não de IL-10, sem alterar a expressão dos receptores do tipo Toll (TLR2 e TLR4) e de MHC II. Em contraste, uma diminuição na expressão da molécula co-estimuladora CD80 foi observada em DCs deficientes de SOCS2. Durante a RI adaptativa a ausência de SOCS2 em DCs resultou no aumento dos níveis de expressão de TLR2 e TLR4 e na redução da frequência de DCs expressando MHCII. A transferência adotiva de DCs deficientes de SOCS2 ocasionou aumento da parasitemia e mudanças do perfil da RI frente a infecção por T. cruzi, principalmente: i) reduzindo a frequência de células NK produtoras de IFN-γ e de IL17; ii) diminuindo a frequência de células T CD8 produtoras de IFN-γ e de T CD4 produtoras de IL-17, apesar de aumentar células T CD4 produtoras de IFN-γ; ausência de SOCS2 em DCs também resultou em redução de células produtoras de IL-10, como T CD4 e CD19, além das células Treg. Nossos resultados também demonstraram que SOCS2 é importante na modulação da apoptose durante a infecção por T. cruzi, onde a deficiência de SOCS2 leva a um aumento da apoptose de neutrófilos durante a RI inata, de macrófagos nas RI inata e adaptativa e de linfócitos na RI adaptativa. Nossos resultados in vitro demonstraram um aumento de caspase 3 total e clivada em neutrófilos deficientes em SOCS2. Em conjunto, nossos resultados demonstraram que SOCS2 é crucial na modulação das funções de DCs durante a geração e regulação da RI inata e adaptativa durante a infecção por T. cruzi.

The infection by Trypanosoma cruzi (T. cruzi), which causes Chagas' disease, induces an inflammatory reaction and the efficacy of the host immune response (IR) is important to persist or eliminate the infection. SOCS2 (supressor of cytokine signaling)2 expression, an intracellular protein, is partially mediated by lipoxins (LXA4, anti-inflammatory eicosanoid) in dendritic cells (DCs), the main antigen-presenting cell (APC). We demonstrated that SOCS2 is fundamental during T. cruzi infection by modulating the generation/expansion of Th1, Treg and memory cells and in the control of heart function. In the present work, we investigated the role of SOCS2 in DCs function and induction/maintenance of IR during experimental T. cruzi infection. CD11cDTR transgenic mice (DCs depletion), wild type (WT) and SOCS2 (knockout/KO) were infected with Y strain of T. cruzi. Our results demonstrated an increased parasitemia in depleted DCs animals, emphasizing that DCs are crucial in control of T. cruzi infection. During innate IR, absence of SOCS2 resulted in decreased frequency of inflammatory cytokines (IL-12 and TNF-α), but not IL-10 by DCs, without change the Tolllike receptor expression (TLR2 and TLR4) and MHCII. In contrast, a decreased expression of CD80 costimulatory molecule was observed in SOCS2 deficient DCs. During adaptive IR, absence of SOCS2 in DCs resulted in increased levels of TLR2 and TLR4 expression and reduced frequency of DCs expressing MHCII. Adoptive transfer of SOCS2 deficient DCs caused increased parasitemia and changes in IR profile against T. cruzi infection, specifically: i) reducing the frequency of NK cells producing IFN-γ and IL-17; ii) reducing the frequency of CD8 T cells producing IFN-γ and CD4 T cells producing IL-17, despite increasing CD4 T cells producing IFN-γ; absence of SOCS2 in DCs also resulted in reduction of cells producing IL-10 such as CD4 and CD19, besides Treg cells. Our results also demonstrated that SOCS2 is important in apoptosis modulation during T. cruzi infection, where absence of SOCS2 leads to increased apoptosis in neutrophils during innate IR, macrophages in innate and adaptive IR and lymphocytes in adaptive IR. Our in vitro results demonstrated an increase in cleaved and total caspase 3 in SOCS2 deficient neutrophils. Together, our results demonstrated that SOCS2 is crucial in the modulation of DCs' function during generation/regulation of innate and adaptive IR during T. cruzi infection