A MECHANISTIC INVESTIGATION OF FCγR SIGNALING DURING ANTIBODY-ENHANCED DENGUE INFECTION

Abstract

Viruses must evade the host innate defenses for replication and dengue is no exception. During secondary infection with a heterologous dengue virus (DENV) serotype, DENV is opsonized with sub- or non-neutralizing antibodies that enhance infection of monocytes and dendritic cells through Fc-gamma receptors, a process termed antibody-dependent enhancement (ADE). However, cross-linking of activating Fc-gamma receptors signals an early antiviral response by inducing the type-I interferon-stimulated genes (ISGs). To escape this antiviral response, we demonstrate that antibody-opsonized DENV co-ligates leukocyte immunoglobulin-like receptor-B1 (LILRB1), which recruits Src homology phosphatase-1 (SHP-1) to dephosphorylate spleen tyrosine kinase (Syk) and reduce ISG induction. As Syk also regulates phagosomal maturation, it is possible that compartmentalization of DENV-containing phagosomes could be altered by differential Syk phosphorylation, thereby influencing the outcome of ADE. Indeed, we observed that LILRB1 co-ligation reduced levels of phagosomal acidification, which could be reversed by inhibiting SHP-1. Collectively, we have shown that DENV co-ligates LILRB1 to both attenuate the expression of ISGs and the rapid acidification in the phagolysosomal pathway, ensuring intracellular survival during antibody-enhanced dengue infection.