Replication Cycle of Astroviruses

Abstract

Astrovirus infections cause gastroenteritis in mammals and have been identi fi ed as causative agents of diverse pathologies in birds such as hepatitis in ducks and poult enteritis mortality syndrome (PEMS), which causes enteritis and thymic and bursal atrophy in turkeys. Human astroviruses are recognized as the second leading cause of childhood viral gastroenteritis worldwide. Eight traditional astrovirus serotypes have been identi fi ed in humans, but recently novel astrovirus strains isolated from humans have been associated with diseases other than gastroenteritis. Herein we summarize our current knowledge of the astrovirus life cycle. Though there are gaps in our understanding of astrovirus replication, similarities can be drawn from Picornaviridae and Caliciviridae virus families. There are, however, unique characteristics of the astrovirus life cycle, including intracellular proteolytic processing of viral particles by cellular caspases, which has been shown to be required for the maturation and exit of viral progeny.

Detection of a mammalian-like astrovirus in bird, European roller (Coracias garrulus)

“…59 At present, the family Astroviridae consists of two genera 60 Mamastrovirus (MAstV) and Avastrovirus (AAstV) with 19 and 3 offi-61 cially ratified species (Guix et al, 2013;Bosch et al, 2014;http:// 62 www.iah-virus.org/astroviridae/). The number of newly discovered 63 astroviruses is rapidly increasing and many are still waiting for 64 classification (Guix et al, 2013; Knowles et al, 2012;Méndez et al, 2013;Bosch et al, 70 2014). The genome is arranged in three open reading frames 71 (ORFs), although an alternative ORF X was described in human 72 and some mammalian astroviruses (Firth and Atkins, 2010 localization signals (NLS).…”

“…The genome is arranged in three open reading frames 71 (ORFs), although an alternative ORF X was described in human 72 and some mammalian astroviruses (Firth and Atkins, 2010 localization signals (NLS). The ORF1a also encodes a serine pro-80 tease enzyme (Knowles et al, 2012;Méndez et al, 2013) and a 81 viral protein genome-linked (VPg) (Fuentes et al, 2012). The puta-82 tive VPg protein is depicted as bound to both the 5 0 end of the 83 genomic-and subgenomic RNA (sgRNAs) (Fuentes et al, 2012;84 Méndez et al, 2013), respectively.…”

“…The ORF1a also encodes a serine pro-80 tease enzyme (Knowles et al, 2012;Méndez et al, 2013) and a 81 viral protein genome-linked (VPg) (Fuentes et al, 2012). The puta-82 tive VPg protein is depicted as bound to both the 5 0 end of the 83 genomic-and subgenomic RNA (sgRNAs) (Fuentes et al, 2012;84 Méndez et al, 2013), respectively. ORF1b encodes an 85 RNA-dependent RNA polymerase (RdRp) with conserved amino 86 acid motifs (Koonin, 1991).…”

“…ORF1b encodes an 85 RNA-dependent RNA polymerase (RdRp) with conserved amino 86 acid motifs (Koonin, 1991). Between the ORF1a and ORF1b there 87 is a conserved heptameric ribosomal frameshift signal 88 (AAAAAAC) forming a downstream stem-loop (SL) structure 89 (Jiang et al, 1993;Méndez et al, 2013). The third coding region 90 (ORF2) is overlapped with ORF1b and encodes the viral capsid pro-91 tein.…”

“…The third coding region 90 (ORF2) is overlapped with ORF1b and encodes the viral capsid pro-91 tein. During the RNA replication ORF2 is expressed from a sgRNA 92 (Méndez et al, 2013). The sgRNA promoter sequence has a highly 93 conserved nucleotide sequence motif and is present upstream the 94 ORF2 start codon (Méndez et al, 2013).…”