Abstract
The duck hepatitis A virus (DHAV), a member of the family Picornaviridae, is the major cause of outbreaks with high mortality rates in young ducklings. It has three distinctive serotypes and among them, serotypes 1 (DHAV-1) and 3 (DHAV-3) were recognized in China. To investigate evolutionary and antigenic properties of the major capsid protein VP1 of these two serotypes, a primary target of neutralizing antibodies, we determined the VP1 coding sequences of 19 DHAV-1 (spanning 2000-2012) and 11 DHAV-3 isolates (spanning 2008-2014) associated with disease outbreaks. By bioinformatics analysis of VP1 sequences of these isolates and other DHAV strains reported previously, we demonstrated that DHAV-1 viruses evolved into two genetic lineages, while DHAV-3 viruses exhibited three distinct lineages. The rate of nucleotide substitution for DHAV-1 VP1 genes was estimated to be 5.57 x 10-4 per site per year, which was about one-third times slower than that for DHAV-3 VP1 genes. The population dynamics analysis showed an upward trend for infection of DHAV-1 viruses over time with little change observed for DHAV-3 viruses. Antigenic study of representative DHAV-1 and DHAV-3 strains covering all observed major lineages revealed no detectable changes in viral neutralization properties within the serotype, despite the lack of cross-neutralization between serotypes 1 and 3 strains. Structural analysis identified VP1 mutations in DHAV-1 and DHAV-3 viruses that underpin the observed antigenic phenotypes. Results of our experiments described here shall give novel insights into evolution and antigenicity of duck picornaviruses.
Highlights
Duck hepatitis A virus (DHAV) belongs to the genus Avihepatovirus in the Picornaviridae family
To study molecular evolution and genetic variation of the major capsid protein VP1 of DHAV1 and DHAV-3 viruses circulated in China over the past decade, we isolated 19 DHAV-1 strains and 11 DHAV-3 strains, each from individual farms where disease outbreaks were documented
These poultry farms that derived DHAV-1 isolates are located in four different provinces (Shandong, Jiangsu, Henan, and Guangdong) with most farms residing in Shandong (Table 1)
Summary
Duck hepatitis A virus (DHAV) belongs to the genus Avihepatovirus in the Picornaviridae family. DHAV-1 is the most widespread and virulent serotype that has the most significant impact on the worldwide poultry industry, while DHAV-2 and DHAV-3 have only been reported in the Taiwan and the USA and the southeastern Asia [3,4]. These two serotypes have recently become prevalent in China, Taiwan, and Korea [5,6,7,8,9]. There is little information about genetic and antigenic variations associated with DHAV-1 since its first recognition in 1980
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