Human antibodies as broad alphavirus immunotherapeutics

SUMMARY Chikungunya virus (CHIKV) is a mosquito-transmitted alphavirus that has caused large-scale epidemics on multiple continents over the past decade. CHIKV infections can result in persistent and debilitating arthritis that can last for years after infection. Related members of the alphavirus genus, including Mayaro virus (MAYV) and Ross River virus, also are associated with severe musculoskeletal disease, whereas other more distant family members, such as Western, Venezuelan, and Eastern Equine Encephalitis viruses cause central nervous system disease and death. At present, there are no licensed therapeutics for alphaviruses. Moreover, these viruses are significant global health threats due to the broad distribution of their mosquito vectors. Human monoclonal antibodies (mAbs) are an attractive platform for virus immunotherapy because they are well tolerated, highly specific, and can be engineered to have long half-life in vivo. We previously used single B cell sorting to isolate a large panel of human mAbs from CHIKV patients during their convalescent phase or from patients receiving a virus-like particle vaccine. These studies have led to: (i) the discovery of broadly neutralizing mAbs that target the B domain of the E2 glycoprotein and protect mice from musculoskeletal disease induced by CHIKV and MAYV; and (ii) the identification of pan-alphavirus mAbs that protect mice against both arthritogenic and encephalitic alphaviruses by targeting a conserved epitope on E1. We will build on these discoveries to develop new broadly inhibitory alphavirus antibody therapies. In Aim 1, we will engineer Fc mutations into broadly protective antibodies to augment their in vitro and in vivo properties even further. In Aim 2, we will perform viral escape studies to define mechanisms of neutralization and protection, and determine if mAb cocktails are less susceptible to viral escape than single mAb therapies. In addition, we will titrate pairwise ratios of mAbs in a cocktail, one neutralizing (E2-B-targeting) and one non-neutralizing yet protective (E1-targeting) component, to explore synergistic relationships for in vitro and in vivo antiviral activities. The most potent two-component mAb cocktail will be down-selected from studies in mice and then tested for pharmacokinetic and efficacy profiles in non-human primate models of disease for both CHIKV and MAYV (Aim 3). At the end of the funding period, we anticipate having proof-of-concept large animal data on a broadly inhibitory alphavirus therapeutic mAb cocktail.