Arch Virol (1997) 142: 2147±2160
Hepatitis A virus subviral particles: puri®cation, accumulation,
and relative infectivity of virions, provirions and procapsids
N. E. Bishop
and D. A. Anderson
Hepatitis Research Unit, Macfarlane Burnet Centre for Medical Research,
Fair®eld, Victoria, Australia
Accepted July 9, 1997
Summary. Virus-speci®c particles were isolated from hepatitis A virus (HAV)-
infected cells and the role of each particle type in the replicative cycle assessed.
Mature virions, provirions (immature virions) and empty capsids (procapsids)
were detected in cell lysates, and both virions and provirions were found in the
culture supernatant. Particle types were separated by isopycnic caesium
chloride gradient- or linear sucrose density gradient-ultracentrifugation, and
their capsid proteins characterised. Virions, provirions and procapsids contain-
ing both VP1 and varying levels of the VP1 precursor protein PX were found,
suggesting that trimming of PX is not essential for particle formation.
Provirions (containing VP0) and virions (containing VP2) could not be clearly
separated with these techniques, but sucrose gradients allowed greater
separation of particle pools with distinct VP0 contents and speci®c infectivities
which could be used for further studies of the biological role of VP0 cleavage.
Virions, with a higher sedimentation coef®cient and buoyant density
presumably re¯ecting a more compact structure, had a higher relative infectivity
when compared to provirions. HAV-infected cells therefore contain a hetero-
genous mixture of RNA-containing viral particles with characteristics between
those of true provirions and virions, but all such particles are released from the
cell and can participate in further rounds of infection.
Hepatitis A virus (HAV) is a non-enveloped, positive-stranded RNA virus in the
Picornavirus family. Despite sharing the same general structure and overall
replicative strategy with other picornaviruses, HAV has many unique
characteristics which have led to its classi®cation as the sole member of the
* Present address: Division of Biochemistry, School of Biological Sciences, University
of Manchester, Manchester, U.K.