Structural studies of antibody-mediated neutralization of human rhinovirus 14

Zhiwei Che, Purdue University

Abstract

Human rhinovirus is a major cause of common cold. It is a member of Picornaviruses, one of the largest animal virus families, which also includes poliovirus, foot-and-mouth disease virus, Coxsackie virus, and hepatitis A virus. While the antibody-mediated neutralization of Picornaviruses has been studied extensively, the mechanism is still not clear. Using a combination of X-ray crystallography, electron microscopy and molecular biology in this study, the molecular basis of the neutralization of HRV14 by several different monoclonal antibodies was investigated. Structures of HRV14 complexed with mAb17-IA, Fab17-IA, Fab12-IA, and Fab1-IA have been determined using cryo-electron microscopy (cryo-EM) and image reconstruction techniques. The comparison between these structures shows that strongly neutralizing antibodies (mAb12-IA and mAb17-IA) bind bivalently to the virion surface, whereas weakly neutralizing antibodies (mAb1-IA) bind monovalently. This result provides evidence to support the hypothesis that neutralizing efficacy of an antibody is dependent upon how tight it binds to the virus, because bivalent binding mode can increase the binding avidity by 100-1000 fold. No conformational changes on the viral capsid were observed in any of the complex structures. The sequences of the variable domains of mAb17-IA, mAb12-IA, and mAb1-IA all show conservation of the charged residues suggesting that such residues are crucial for the antibody binding. Modeling studies of cryo-EM image reconstructions of HRV14:Fab1-IA and HRV14:Fab12-IA complex structures confirmed that coulombic interactions dominate the paratope/epitope interface. In addition, it is shown that these coulombic interactions dictate the orientation of the bound Fab. These findings, along with the crystallographic structure of HRV14-Fab17-IA, strongly support a simple scheme of antibody neutralization where neutralization is not dependent upon antibody-mediated conformational changes in the virion surface. Instead, neutralization seems to be more dependent upon processes that simply require antibody binding such as abrogation of cell attachment, aggregation, and opsonization.

Degree

Ph.D.

Advisors

Smith, Purdue University.

Subject Area

Biophysics|Molecular biology|Microbiology|Immunology

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