J Am Chem Soc. 2018 Dec 11. doi: 10.1021/jacs.8b10131. [Epub ahead of print]
Competition between Normative and Drug-Induced Virus Self-Assembly Observed with Single-Particle Methods.
Kondylis P, Schlicksup CJ, Brunk NE, Zhou J, Zlotnick A, Jacobson SC.
Abstract
Disruption of virus capsid assembly has compelling antiviral potential that has been applied to Hepatitis B Virus (HBV). HBV core protein assembly can be modulated by heteroaryldihydropyrimidines (HAPs), such molecules are collectively termed core protein allosteric modulators (CpAMs). Though the antiviral effects of CpAMs are acknowledged, the mechanism of action remains an open question. Challenging aspects of characterizing misdirected assembly are the large size and non-uniform nature of the final particles. In this study of HBV assembly, we observed a competition between normative and CpAM-induced aberrant assembly with electron microscopy and single particle nanofluidic techniques. This competition was a function of the strength of the association energy between individual core proteins, which is proportional to ionic strength. With strong association energy, assembly reactions primarily yielded morphologically normal HBV capsids, despite the presence of HAP. At weak association energy, HAPs led to increased assembly product size and disrupted morphology. The smallest particles were T = 4 icosahedra, whereas the larger particles were defective spheres, ellipsoids, and bacilliform cylinders, with regions of T = 4 geometry interspersed with flat regions. Deviation from the spherical T = 4 geometry progressively increased with particle size, which is consistent with the interpretation of a competition between two alternative assembly pathways.