Neutralization mechanisms of human anti-alphavirus monoclonal antibodies
MICROBE-HOST INTERACTIONS Neutralization Mechanisms of Human Anti-alphavirus Monoclonal Antibodies Lauren Elizabeth Williamson Dissertation under the direction of Professor James E. Crowe, Jr. Alphaviruses cause a debilitating arthritogenic or encephalitic disease in humans and can result in millions of cases worldwide. Additionally, the encephalitic alphaviruses have potential for use as bioterrorism agents. There are no licensed vaccines or antiviral drugs to combat these viruses. To design therapeutic candidates against alphaviruses, an understanding of the human humoral response is key. Through characterization of human anti-alphavirus monoclonal antibodies (mAbs) from two survivors of natural Eastern equine encephalitis virus (EEEV), two main mechanisms of neutralization were identified. Neutralizing E2-specific mAbs potently neutralize EEEV through stabilization of virus particles to inhibit virus entry into host cells. In contrast, neutralizing E1-specific mAbs inhibit virus egress through recognition of cryptic epitopes on intact virus particles that become exposed during virus maturation on the surface of infected cells. Both mechanisms of neutralization can protect against subcutaneous or stringent aerosol EEEV challenge. Given the cryptic nature of these epitopes, regions of the E1 glycoprotein are highly conserved (i.e., fusion loop), which can be targeted by mAbs for cross-reactivity, cross-neutralization, and cross-protection. In addition to neutralization, other mAb-mediated mechanisms appear to be involved, such as interaction with macrophages through Fc and complement receptors, to aid in in vivo efficacy against alphavirus infection. Altogether, a landscape of the human humoral response against alphaviruses, with a special focus on EEEV, was characterized during these studies to help inform rationale vaccine design and identify therapeutic candidates against alphaviruses.