DEFINING THE ROLE OF ANTIBODY FCR REGIONS IN DENGUE VIRUS NEUTRALIZATION, CLEARANCE AND POST INFECTION IMMUNITY

Abstract

Dengue disease is the most common arboviral (viral-arthropod borne) disease in humans, with over 40% of the human population in 100 countries at risk of infection. Dengue virus causes an estimated 50–100 million infections each year. It has been observed endemically in tropical and subtropical regions and recently the records of dengue cases have extended geographically to Europe and the United States of America. The latest World Health Organization reports show the increasing numbers of dengue cases globally; and it is suggested that due to limited access to Dengue diagnostics, the actual infection number is more than three times the dengue burden estimate of the WHO (World Health Organization) (Nature 2013; 496: 504-7). The spectrum of clinical symptoms ranges from an acute debilitating, self-limited febrile illness called Dengue Fever (DF) to a life-threatening vascular leakage syndrome, referred to as Dengue Hemorrhagic Fever/Shock Syndrome (DHF/DSS) (Guzman, Halstead et al. 2010). An increased risk of severe disease manifestation has been associated with sequential infection by different viral serotypes and this is hypothesized to be an effect of antibody dependent enhancement (ADE) (Sabin 1952, Halstead, Nimmannitya et al. 1967, Balsitis, Williams et al. 2010). To date, there is no virus-specific treatment available and the economic costs of dengue disease are estimated to be very high. Previously our laboratory has generated a fully human antibody based on the natural immune response of dengue patients termed 14C10. The 14C10 antibody has remarkable protective activity at low concentrations in vitro and in vivo. Thus, it is a good therapeutic candidate for dengue virus serotype 1 (DENV1) infection (Teoh, Kukkaro et al. 2012). ADE in dengue infection is proposed to occur when antibodies at low concentrations create immune complexes with the virus and facilitate virus entry into Fc (Fragment crystallizable) receptor bearing cells. In my project, I employ molecular engineering methodologies to dissect the role of Fc-receptor binding through the Fc-region of an anti-Dengue antibody in DENV neutralization and clearance. Specifically we use modifications to the genetic template of the 14C10 antibody to investigate how changes in subclass, glycosylation and Fc-receptor binding activity impacts in vitro and in vivo on neutralizing activity. We also aim to establish the role of the Fc domain of the 14C10 antibody in DENV1 infectivity versus neutralization. Furthermore, we test human and mouse-human variants of the 14C10 and their different subclasses on their ability to trigger heterotypic and homotypic ADE. Finally, my project aims to investigate the impact of 14C10-based antibody therapy upon the ability of the treated hosts to generate their own protective immune response where the virus has been rapidly neutralized and cleared from circulation. The data presented herein represents a thorough mechanistic dissection of a therapeutic candidate antibody for DENV1 with important implications for how this may be employed in a clinical context.