•This is the first report of the anti-DHAV abilities of APS and its sulfate.•The different anti-DHAV abilities between APS and BSRPS were firstly compared.•The anti-DHAV abilities of APS and sAPS were significant in vitro while not in vivo.•Treatment theory based on syndrome differentiation was used to explain the results.•The treatment of combination of sAPS and other drugs would be effective on DVH.This paper studied the anti-duck hepatitis A virus (DHAV) activities of Astragalus polysaccharide (APS) and its sulfate (sAPS) compared with those of Bush Sophora Root polysaccharide (BSRPS) and its sulfate (sBSRPS). The antiviral activities of APS and sAPS were measured by MTT and real-time PCR methods, in vitro. In vivo experiment, the mortality rate and the evaluation indexes of hepatic injury, peroxidative injury and immune level were measured. Just like the condition of BSRPS and sBSRPS, the anti-DHAV activities of sAPS were stronger than those of APS, both in vitro and in vivo. It indicated sulfated modification could enhance the antiviral ability of polysaccharide. But unlike the antiviral effects of BSPRS and sBSRPS in vivo, APS and sAPS did not reduce the mortality rates as their abilities of scavenging free radicals and alleviating the hepatic injuries were weaker than those of BSRPS and sBSRPS. And they even did not enhance the immune levels.

•This is the first report that BSRPS and sBSRPS can anti-DHAV in vitro and vivo.•This is the first report that sBSRPS has higher anti-DHAV activity than BSRPS.•This is the first report of the anti-DHAV mechanism of BSRPS and sBSRPS in vitro.•Only can BSRPS inhibit replication, sBSRPS depress both replication and release of DHAV.•Anti-DHAV activity of BSRPS and sBSRPS might not be associated with the adsorption.In order to research the sulfating modification in enhancing the anti-duck hepatitis A virus (DHAV) activity of Bush Sophora Root polysaccharide (BSRPS), sulfated Bush Sophora Root polysaccharide (sBSRPS) was prepared by chlorosulfonic acid–pyridine method. KBr pellets method was applied to analyze their different structures. Anti-DHAV activity was studied by duck embryonic hepatocytes culture in vitro and artificial inoculation method in vivo. Direct immunofluorescence method and Real-time PCR were applied to study the antiviral mechanism of adsorption, replication and release in vitro and the dynamic change of virus content of blood in vivo. The results showed at the most effective content, sBSRPS (7.813 μg/mL) could inhibit both replication and release of DHAV in vitro, BSRPS (500 μg/mL) only inhibit replication. The relative expression of DHAV gene at the 8th h and the mortality rate of sBSRPS group were significantly reduced. These results indicated sBSRPS performed more effectively in anti-DHAV activity than BSRPS.

•This is the first description of the replication cycle of DHAV-1.•Firstly find that DHAV-1 adsorption saturated at 90 min post-infection.•The replication lasted around 13 h after early protein synthesis for about 5 h.•The release of DHAV-1 was in steady state after 32 h.Duck hepatitis A virus type 1 (DHAV-1) is an important agent of duck viral hepatitis. Until recently, the replication cycle of DHAV-1 is still unknown. Here duck embryonic hepatocytes infected with DHAV-1 were collected at different time points, and dynamic changes of the relative DHAV-1 gene expression during replication were detected by real-time PCR. And the morphology of hepatocytes infected with DHAV was evaluated by electron microscope. The result suggested that the adsorption of DHAV-1 saturated at 90 min post-infection, and the virus particles with size of about 50 nm including more than 20 nm of vacuum drying gold were observed on the infected cells surface. What׳s more, the replication lasted around 13 h after the early protein synthesis for about 5 h, and the release of DHAV-1 was in steady state after 32 h. The replication cycle will enrich the data for DVH control and provide the foundation for future studies.