Antibody-dependent enhancement of dengue virus infection inhibits RLR-mediated Type-I IFN-independent signalling through upregulation of cellular autophagy

Scientific Reports, Feb 2016

Antibody dependent enhancement (ADE) of dengue virus (DENV) infection is identified as the main risk factor of severe Dengue diseases. Through opsonization by subneutralizing or non-neutralizing antibodies, DENV infection suppresses innate cell immunity to facilitate viral replication. However, it is largely unknown whether suppression of type-I IFN is necessary for a successful ADE infection. Here, we report that both DENV and DENV-ADE infection induce an early ISG (NOS2) expression through RLR-MAVS signalling axis independent of the IFNs signaling. Besides, DENV-ADE suppress this early antiviral response through increased autophagy formation rather than induction of IL-10 secretion. The early induced autophagic proteins ATG5-ATG12 participate in suppression of MAVS mediated ISGs induction. Our findings suggest a mechanism for DENV to evade the early antiviral response before IFN signalling activation. Altogether, these results add knowledge about the complexity of ADE infection and contribute further to research on therapeutic strategies.

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Antibody-dependent enhancement of dengue virus infection inhibits RLR-mediated Type-I IFN-independent signalling through upregulation of cellular autophagy

Abstract Antibody dependent enhancement (ADE) of dengue virus (DENV) infection is identified as the main risk factor of severe Dengue diseases. Through opsonization by subneutralizing or non-neutralizing antibodies, DENV infection suppresses innate cell immunity to facilitate viral replication. However, it is largely unknown whether suppression of type-I IFN is necessary for a successful ADE infection. Here, we report that both DENV and DENV-ADE infection induce an early ISG (NOS2) expression through RLR-MAVS signalling axis independent of the IFNs signaling. Besides, DENV-ADE suppress this early antiviral response through increased autophagy formation rather than induction of IL-10 secretion. The early induced autophagic proteins ATG5-ATG12 participate in suppression of MAVS mediated ISGs induction. Our findings suggest a mechanism for DENV to evade the early antiviral response before IFN signalling activation. Altogether, these results add knowledge about the complexity of ADE infection and contribute further to research on therapeutic strategies. Introduction Dengue virus (DENV) is a mosquito-borne virus that causes dramatic public health issues in more than 100 countries, particularly in Asia and Latin America. It is estimated that more than 50 million people are infected by DENV annually1. The geographic expansion of the vector, the Aedes aegypti mosquito, contributes to a continuous increase in the incidence and severity of the disease2. There are four serotypes of DENV (DEVN 1–4), and each of them could cause a spectrum of outcomes from subclinical to death3. Moreover, secondary heterotypic infection or waning immunity of infants born to mothers infected by DENV has been observed to significantly increase the likelihood of acquiring severe disease4. Moreover, antibody (Ab)-dependent enhancement (ADE) has been thought to be involved in the immunopathogenesis of severe dengue forms, including dengue haemorrhagic fever (DHF) and dengue shock syndrome (DSS). It has been hypothesized that the preexisting heterotypic antibodies form a complex with the virus, via Fc receptors in the target cells, to facilitate the infection of target cells, including monocytes, macrophages and mature DCs5,6. Many earlier in vitro studies have reproduced an enhanced infection of Fc-receptor bearing cells resembling that of DHF/DSS patients7,8. In addition, passively transferring DENV-specific monoclonal antibodies into an animal model resulted in a notable clinical manifestation and viraemia9,10. These findings suggest that subneutralizing antibodies are sufficient to induce DHF/DSS in spite of aberrant cellular immunity, which allows exploration of the pathogenesis of severe dengue disease in a culture system. Given that elevated viraemia is normally accompanied by a high concentration of proinflammatory and immunomodulatory cytokines11, it is therefore necessary to understand the connections between the DENV-Ab complex and those cytokines. A previous study using the THP-1 cell line found that DENV-ADE infection could suppress the expression of IL-12, IFN-γ and TNF-α, while stimulating the expression of the anti-inflammatory cytokines IL-6 and IL-1012. It was then proposed that DENV-ADE specifically modulated IL-10 production to suppress type I IFN signalling, as well as upregulating dihydroxyacetone kinase (DAK) and autophagy-related 5 (ATG5) to restrain IFN-α/β production13. Another study using human macrophages also revealed a similar function of IL-6, but not IL-10, that was regulated by ADE14. All these results suggest the importance of anti-inflammatory cytokines in the IFN antiviral pathway, especially IL-1015. However, it is so far unclear whether the induction of IL-10 or IL-6 could directly increase cellular viral replication or whether they are only the byproducts of DENV-ADE infection. In addition, the phenomenon that DENV-ADE infection suppresses the secretion of type I IFN was not found in any other in vitro studies using human primary monocytes7,16. Therefore, it is reasonable to postulate a more pervasive mechanism in DENV-ADE infection, which does not rely on the suppression of IFNα/β or increased IL-10/IL-6. In this study, we used the IFN-deficient monocytic cell line K562 to show that ADE effects are independent of the suppression of type I IFN. Meanwhile, both DENV and DENV-ADE infection induced direct expression of NOS2 through activation of the RIG-I/MDA-5-MAVS signalling axis. We further report that DENV-ADE induced higher expression of autophagy-related proteins (ATG5-ATG12) and elevated autophagosome formation to facilitate viral replication. This supplies a new strategy for DENV-ADE to contend with innate cell immunity in the context of extensive IFN antagonism. Results The enhancement activity of DENV-ADE infection is dependent on the final concentration of anti-PrM antibody Distinct types of monocytes such as THP-1, U937 and K562 have been extensively used to explore the mechanisms o (...truncated)


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Xinwei Huang, Yaofei Yue, Duo Li, Yujiao Zhao, Lijuan Qiu, Junying Chen, Yue Pan, Juemin Xi, Xiaodan Wang, Qiangming Sun, Qihan Li. Antibody-dependent enhancement of dengue virus infection inhibits RLR-mediated Type-I IFN-independent signalling through upregulation of cellular autophagy, Scientific Reports, 2016, Issue: 6, DOI: 10.1038/srep22303