Structural and functional study of picornaviruses

Thesis

Picornaviruses are responsible for a variety of human and animal diseases, ranging from hepatitis A, foot and mouth disease, through polio to hand-foot-and-mouth disease and the common cold. In addition to their importance in causing diseases, they also serve as models for understanding the basic mechanisms of host-pathogen interactions, virus entry and viral genome release.

Although the structure of a number of picornaviruses from the Entero, Cardio, Aphtho and Senecavirus genera have been determined at close to atomic resolution with X-ray crystallography, structural and functional studies on Parecho, Kobu and Hepatovirus are very limited. I have thus studied members of these genera: Ljungan virus, Aichi virus and hepatitis A virus to further understanding of the molecular basis of pathogenesis, viral entry, assembly and stability for these viruses in particular and for picornaviruses in general. In addition I have studied the VLPs of CVA16 as potential vaccine candidates.

The atomic structure of Ljungan virus determined by cryo-EM, shows remarkable features, including an extended VP1 C-terminus, forming a major protuberance on the outer surface of the virus, and a basic motif at the N-terminus of VP3, which orders some 12% of the viral genome. This charge-driven RNA attachment suggests that this branch of the picornaviruses use a different mechanism of genome encapsidation.

The cryo-EM structure of Aichi virus at 3.7 Å resolution is intermediate between the enteroviruses and cardioviruses. On the outer surface a polyproline helix structure, not seen previously in picornaviruses is present at the C-terminus of VP1, corresponding to the position where integrin binding motifs are found in some other picornaviruses. A peptide corresponding to this polyproline motif somewhat attenuates virus infectivity suggesting a role in attachment to a cellular receptor.

The cryo-EM structure of a complex between hepatitis A virus and a potent neutralizing antibody, together with other data suggest that this antibody mimics receptor binding.

2A proteins from Ljungan virus, Sebokele virus and human parechovirus play a different role in these viruses compared to other members of the picornavirus family and the X-ray structures of these proteins reveal incredible plasticity and an H-box motif that may not be catalytically active.

In summary, this thesis provides an insight into some important aspects of host-virus interactions especially the events occurring during viral assembly and receptor recognition.

Authors: Zhu, L

• DOI: 10.5287/ora-mvypdeazw
• Type of award: DPhil
• Level of award: Doctoral
• Awarding institution: University of Oxford