Minimal capsid composition of infectious human astrovirus

Human astrovirus is an important etiological agent of acute gastroenteritis in young children. Despite advances in the characterization of the structure of the virion by cryo-electron microscopy and of capsid proteins by x-ray crystallography, the definition of the minimal polypeptide composition of infectious virus particles has been elusive. In this work we show that mature infectious particles are composed by only two proteins; VP34 that forms the core domain of the virus, and VP27 that constitutes the 30 dimeric spikes present on the virus surface. Our results also indicate that during the transition of immature (90 spikes) to mature (30 spikes) virus particles, that occur during trypsin activation, the viral protein VP25, that most likely forms the 60 spikes that are lost during maturation, detaches from the virus particle. This information is relevant to better understand the biology of virus entry and also for the efficient development of subunit vaccines. •The capsid of infectious human astrovirus 8 is formed by two proteins, VP34 and VP27.•The capsid protein VP25 is released during trypsin activation of astrovirus infectivity.•The virus can be equally infectious when carrying abundant amounts of VP25.