Abstract
Since
the first report from Cherry Valley ducks on a commercial duck farm in
China (2008), duck astrovirus type 1(DAstV-1) -associated duck viral
hepatitis (DVH) have been detected in several commercial duck flocks. In
the literature, no outbreak of DAstV-1 have been report in China since
2012. Here, the isolation, cultivation and characterization of DAstV-1
isolate are described. One DAstV-1 strain, designated as DAstV-SDZZ, was
isolated from a diseased duckling. The isolated astrovirus grew well in
the LMH cell line. To determine the entire genomic of the DAstV-SDZZ
isolate, next-generation sequencing (NGS) technique was conducted on
Illumina HiSeq platform. Complete
genome sequence analysis revealed that DAstV-SDZZ isolate was
91.6%-98.7% homology with others DAstV-1 deposited in Genbank. Similar
clinical symptoms were successful reproduced by experimental infection
study using the DAstV-SDZZ isolate. DAstV-SDZZ is the first DAstV-1
strain whose experimental infection study has been conducted. The
present works are likely to provide new insights into the pathogenicity
and evolution of DAstV-1 in ducks.
Keywords: duck astrovirus type 1; next-generation sequencing;
complete gene sequence; phylogenetic analysis; pathogenicity
Introduction
Astroviruses are non-enveloped,
positive-sense and single-stranded RNA viruses with a diameter of
approximately 28–30 nm (Baxendale and Mebatsion, 2004; Fauquet et al.,
2005). Their single-stranded RNA genome ranges in size from 6.8 to 7.9
kb and consisting of three open reading frames (ORFs) ; ORF 1a, ORF 1b
and ORF 2 (Fu et al., 2008; De Benedictis et al., 2011). ORF1a codes for
non-structural (NS) polyprotein, which include a serine protease,
several transmembrane (TM) helical motifs and a nuclear localization
signal (NLS) (Jiang et al., 1993; Lee and Kurtz, 1994). ORF 1b encodes
the RNA-dependent RNA polymerase (Willcocks et al., 1994), while ORF2
codes for the viral capsid structural protein that is required for
virion formation (Arias and Dubois, 2017).
In poultry, astroviruses have been reported to infect several avian
species, including chickens (Kang et al., 2018), turkeys
(Pantin-Jackwood et al., 2006), gooses (Q. Zhang et al., 2018; Yang et
al., 2018) and ducks (Chen et al., 2012; Wei et al., 2020). Astroviruses
disease in most species are causative agents of enteric diseases. In
ducks, unlike other avian species, astroviruses have been associated
with a fatal hepatitis, historically known to be caused by two types of
duck hepatitis virus (DHV-2 and DHV-3) which were considered
picornaviruses (Asplin, 1965; Haider and Calnek, 1979). More recently,
DHV-2 and DHV-3 has been identified as astrovirus based on a 391 nt ORF
1b region (Todd et al., 2009). Besides the two types of formal
classification duck astrovirus (DAstV), there are a number of unassigned
duck astrovirus waiting to be classified, such as duck DHV-3-like
astroviruses (Liu, Wang, Shi et al., 2014), duck astrovirus CPH (DAstV
CPH) (Liao et al., 2015), duck astrovirus YP-like and astroviruses
detected from wild birds (Chu et al., 2012; Liu, Wang and Zhang, 2014).
In China, duck viral hepatitis is mainly caused by duck hepatitis A
virus (DHAV) (Wen et al., 2018). No outbreaks of DAstV-1 have been
published reports in China since 2012 (Chen et al., 2012). Therefore,
little is known regarding their molecular biology and viral genetic
diversity. In addition, due to the lack of effective methods for
cultivating DAstV-1, the pathogenicity of the DAstV-1 in ducklings
remains unclear. The present paper describes the molecular
characterization of this virus and phylogenetic analysis to other
astroviruses. The reproduction experiment was conducted to investigate
the pathogenicity of the virus.