Autor(es): Fong Rachel H, Banik Soma S R, Mattia Kimberly, Barnes Trevor, Tucker David, Liss Nathan, Lu Kai, Selvarajah Suganya, Srinivasan Surabhi, Mabila Manu, Miller Adam, Muench Marcus O, Michault Alain, Rucker Joseph B, Paes Cheryl, Simmons Graham, Kahle Kristen M, Doranz Benjamin J

Resumo: Chikungunya virus (CHIKV) is a reemerging alphavirus that causes a debilitating arthritic disease - infects millions of people - for which no specific treatment is available. Like many alphaviruses, the structural targets on CHIKV that elicit a protective humoral immune response in humans are poorly defined. Here we used phage display against virus-like particles (VLPs) to isolate seven human monoclonal antibodies (MAbs) against the CHIKV envelope glycoproteins E2 - E1. One MAb, IM-CKV063, was highly neutralizing (50% inhibitory concentration, 7.4 ng/ml), demonstrated high-affinity binding (320 pM), - was capable of therapeutic - prophylactic protection in multiple animal models up to 24 h postexposure. Epitope mapping using a comprehensive shotgun mutagenesis library of 910 mutants with E2/E1 alanine mutations demonstrated that IM-CKV063 binds to an intersubunit conformational epitope on domain A, a functionally important region of E2. MAbs against the highly conserved fusion loop have not previously been reported but were also isolated in our studies. Fusion loop MAbs were broadly cross-reactive against diverse alphaviruses but were nonneutralizing. Fusion loop MAb reactivity was affected by temperature - reactivity conditions, suggesting that the fusion loop is hidden in infectious virions. Visualization of the binding sites of 15 different MAbs on the structure of E2/E1 revealed that all epitopes are located at the membrane-distal region of the E2/E1 spike. Interestingly, epitopes on the exposed topmost - outer surfaces of the E2/E1 trimer structure were neutralizing, whereas epitopes facing the interior of the trimer were not, providing a rationale for vaccine design - therapeutic MAb development using the intact CHIKV E2/E1 trimer. CHIKV is the most important alphavirus affecting humans, resulting in a chronic arthritic condition that can persist for months or years. In recent years, millions of people have been infected globally, - the spread of CHIKV to the Americas is now beginning, with over 100,000 cases occurring in the Caribbean within 6 months of its arrival. Our study reports on seven human MAbs against the CHIKV envelope, including a highly protective MAb - rarely isolated fusion loop MAbs. Epitope mapping of these MAbs demonstrates how some E2/E1 epitopes are exposed or hidden from the human immune system - suggests a structural mechanism by which these MAbs protect (or fail to protect) against CHIKV infection. Our results suggest that the membrane-distal end of CHIKV E2/E1 is the primary target for the humoral immune response to CHIKV, - antibodies targeting the exposed topmost - outer surfaces of the E2/E1 trimer determine the neutralizing efficacy of this response.

Imprenta: Journal of Virology, v. 88, n. 24, p. 14364-14379, 2014

Identificador do objeto digital: 10.1128/JVI.01943-14

Descritores: Chikungunya virus - Cell ; Chikungunya virus - Immune response ; Chikungunya virus - Molecular structure ; Chikungunya virus - Pathogenesis ; Chikungunya virus - Proteins ; Chikungunya virus - Antibodies ; Chikungunya virus - Immune response ; Chikungunya virus - Viral infections ; Chikungunya Virus - Virus ; Chikungunya virus - Vaccine ; Chikungunya virus - Chikungunya fever ; Chikungunya virus - Immunology ; Chikungunya virus - Public health

Data de publicação: 2014

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