The Induction of Infectivity in Human Astrovirus in Response to Capsid Proteolysis
Tao, Yizhi Jane
Master of Arts
Astrovirus is a non-enveloped, T=3, positive-sense RNA virus that presents with self-limiting gastroenteritis; however, it has been additionally associated with serious presentations such as nephritis, hepatitis, and encephalitis, which is compounded by its propensity to engage in cross-species penetrations. Astrovirus undergoes a complex capsid maturation process mediated by host proteases in which an inert, immature capsid composed of VP90 is sequentially cleaved to yield a highly infectious particle composed of VP34 and VP27/VP25, which form the capsid shell and spikes, respectively. By overexpressing a VP9070-418 truncate in insect cells, we have demonstrated that the shell domain alone cannot support particle assembly, implying a crucial role for the dimeric contacts within the spike. Various monomeric, shell domain truncates (i.e. VP9071-252, VP9071-283, VP9071-313, and VP9071-415) have been successfully expressed and purified, but none yielded useful crystals, suggesting the structural context of the capsid lattice may be needed to stabilize their conformational flexibility.