Dengue Virus Induces Increased Activity of the Complement Alternative Pathway in Infected Cells

Abstract

Severe dengue virus (DENV) infection is associated with overactivity of the complement alternative pathway (AP) in patient studies. Here, the molecular changes in components of the AP during DENV infection were investigated. mRNA for factor H (FH), a major negative regulator of the AP, was significantly increased in DENV-infected endothelial cells (EC) and macrophages, but, in contrast, production of extracellular FH protein was not. This discord was not seen for the AP activator factor B (FB), with DENV induction of both FB mRNA and protein, nor was it seen with Toll-like receptor 3 or 4 stimulation of EC and macrophages, which induces both FH and FB mRNA and protein. Surface-bound and intracellular FH protein was, however, induced by DENV, but only in DENV antigen-positive cells, while in two other DENV-susceptible immortalized cell lines (ARPE-19 and human retinal endothelial cells), FH protein was induced both intracellularly and extracellularly by DENV infection. Regardless of the cell type, there was an imbalance in AP components and an increase in markers of complement AP activity associated with DENV-infected cells, with lower FH relative to FB protein, an increased ability to promote AP-mediated lytic activity, and increased deposition of complement component C3b on the surface of DENV-infected cells. For EC in particular, these changes are predicted to result in higher complement activity in the local cellular microenvironment, with the potential to induce functional changes that may result in increased vascular permeability, a hallmark of dengue disease. Dengue virus (DENV) is a significant human viral pathogen with a global medical and economic impact. DENV may cause serious and life-threatening disease, with increased vascular permeability and plasma leakage. The pathogenic mechanisms underlying these features remain unclear; however, overactivity of the complement alternative pathway has been suggested to play a role. In this study, we investigate the molecular events that may be responsible for this observed alternative pathway overactivity and provide novel findings of changes in the complement system in response to DENV infection in primary cell types that are a major target for DENV infection (macrophages) and pathogenesis (endothelial cells) Our results suggest a new dimension of cellular events that may influence endothelial cell barrier function during DENV infection that could expand strategies for developing therapeutics to prevent or control DENV-mediated vascular disease.

Transcriptome of the Aedes aegypti Mosquito in Response to Human Complement Proteins

“…Interestingly, the vast majority of human infections by DENV are asymptomatic (~70%) [48], and these individuals are associated with lower systemic complement activation [49]. In contrast, higher activation of the complement system and an excess of production of hC5a have been observed in severe dengue [50][51][52].…”

High-resolution proteomics identifies potential new markers of Zika and dengue infections

“…The complement system has an ambivalent role in Flavivirus infection: it can be protective by limiting viral replication, or contribute to disease severity when excessively activated and causing an exacerbated inflammatory response 27 . Its occurrence amongst the differentially expressed proteins might link to the increased activity of the complement systems in DENV infections 28,29 .…”

Humanized Mice in Dengue Research: A Comparison with Other Mouse Models

“…Its double-stranded RNA (dsRNA) activates endosomal toll-like receptor 3 (TLR3), and its single-stranded RNA (ssRNA) activates TLR7 and TLR8 [33]. DENV also activates the complement system and TLR9/cGAS [34][35][36]. The activation of these PRRs initiates the antiviral response with a strong and early production of interferon-β (IFN-β), a weak production of interferon-γ (IFN-γ), and antimicrobial peptides (AMP) in cells such as keratinocytes [37].…”