Abstract
Astroviruses are enterically transmitted viruses that cause infections in mammalian and avian species. Astroviruses are nonenveloped, icosahedral viruses comprised of a capsid protein shell and a positive-sense, single-stranded RNA genome. The capsid protein undergoes dramatic proteolytic processing both inside and outside of the host cell, resulting in a coordinated maturation process that affects cellular localization, virus structure, and infectivity. After maturation, the capsid protein controls the initial phases of virus infection, including virus attachment, endocytosis, and genome release into the host cell. The astrovirus capsid is the target of host antibodies including virus-neutralizing antibodies. The capsid protein also mediates the binding of host complement proteins and inhibits complement activation. Here, we will review our knowledge on the astrovirus capsid protein (CP), with particular attention to the recent structural, biochemical, and virological studies that have advanced our understanding of the astrovirus life cycle.
Highlights
The family Astroviridae is divided into two genera: genus Mamastrovirus including viruses that infect mammals, and genus Avastrovirus including viruses that infect avian species
We focus on the astrovirus capsid protein (CP): its assembly into virus particles, its processing, its structure, its interactions with host antibodies and complement, and its entry into cells
The astrovirus CP is synthesized from the viral subgenomic RNA and is 72–90 kDa [3,4,5,6]
Summary
The family Astroviridae is divided into two genera: genus Mamastrovirus including viruses that infect mammals, and genus Avastrovirus including viruses that infect avian species. Astrovirus infections in birds cause diverse pathologies including enteritis, hepatitis, and nephritis. Astrovirus infections in mammals typically cause gastroenteritis and in rare cases cause neurological syndromes and encephalitis. Human astroviruses (HAstV) are recognized as a leading cause of childhood viral gastroenteritis, with eight canonical serotypes (HAstV-1 to HAstV-8) and several noncanonical human genogroups. RNA genome of 6–8 kb (reviewed in [1,2]). The two ORFs at the 50 -end of the genome, ORF1a and ORF1b, encode nonstructural polyproteins nsp1a and nsp1ab, which are proteolytically processed into smaller proteins including an RNA-dependent RNA polymerase, a serine protease, a viral genome-linked protein (VPg), and several other proteins with unknown functions. The third ORF at the 30 -end of the genome, ORF2, encodes the astrovirus capsid protein (CP). We focus on the astrovirus CP: its assembly into virus particles, its processing, its structure, its interactions with host antibodies and complement, and its entry into cells
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