Insight into the Mechanisms of Adenovirus Capsid Disassembly from Studies of Defensin Neutralization

PLoS Pathogens

Glen R. Nemerow¹  Jason G. Smith¹  Steffen Lindert²  Mariena Silvestry²  Phoebe L. Stewart²  Wuyuan Lu³ 

[1] Department of Immunology and Microbial Science, The Scripps Research Institute, La Jolla, California, United States of America;Department of Molecular Physiology and Biophysics, Vanderbilt University Medical Center, Nashville, Tennessee, United States of America;Institute of Human Virology, University of Maryland School of Medicine, Baltimore, Maryland, United States of America

关键词: Defensins;    Viral packaging;    Crystal structure;    Cell binding;    Adenoviruses;    Sequence motif analysis;    Adeno-associated viruses;    Respiratory infections;   

DOI  :  10.1371/journal.ppat.1000959

学科分类：生物科学（综合）

来源: Public Library of Science

【 摘 要 】

Defensins are effectors of the innate immune response with potent antibacterial activity. Their role in antiviral immunity, particularly for non-enveloped viruses, is poorly understood. We recently found that human alpha-defensins inhibit human adenovirus (HAdV) by preventing virus uncoating and release of the endosomalytic protein VI during cell entry. Consequently, AdV remains trapped in the endosomal/lysosomal pathway rather than trafficking to the nucleus. To gain insight into the mechanism of defensin-mediated neutralization, we analyzed the specificity of the AdV-defensin interaction. Sensitivity to alpha-defensin neutralization is a common feature of HAdV species A, B1, B2, C, and E, whereas species D and F are resistant. Thousands of defensin molecules bind with low micromolar affinity to a sensitive serotype, but only a low level of binding is observed to resistant serotypes. Neutralization is dependent upon a correctly folded defensin molecule, suggesting that specific molecular interactions occur with the virion. CryoEM structural studies and protein sequence analysis led to a hypothesis that neutralization determinants are located in a region spanning the fiber and penton base proteins. This model was supported by infectivity studies using virus chimeras comprised of capsid proteins from sensitive and resistant serotypes. These findings suggest a mechanism in which defensin binding to critical sites on the AdV capsid prevents vertex removal and thereby blocks subsequent steps in uncoating that are required for release of protein VI and endosomalysis during infection. In addition to informing the mechanism of defensin-mediated neutralization of a non-enveloped virus, these studies provide insight into the mechanism of AdV uncoating and suggest new strategies to disrupt this process and inhibit infection.

【 授权许可】

CC BY