Three (MoCAV/F2, MoCAV/F8 and MoCAV/F11) of four mouse mAbs established against the A2/76 strain of chicken anemia virus (CAV) showed neutralization activity. Immunoprecipitation showed a band at~50 kDa in A2/76-infected cell lysates by neutralizing mAbs, corresponding to the 50 kDa capsid protein (VP1) of CAV, and the mAbs reacted with recombinant VP1 proteins expressed in Cos7 cells. MoCAV/F2 and MoCAV/F8 neutralized the 14 CAV strains tested, whereas MoCAV/F11 did not neutralize five of the strains, indicating distinct antigenic variation amongst the strains. In blocking immunofluorescence tests with the A2/76-infected cells, binding of MoCAV/F11 was not inhibited by the other mAbs. MoCAV/F2 inhibited the binding of MoCAV/ F8 to the antigens and vice versa, suggesting that the two mAbs recognized the same epitope. However, mutations were found in different parts of VP1 of the escape mutants of each mAb: EsCAV/F2 (deletion of T89+A90), EsCAV/F8 (I261T) and EsCAV/F11 (E144G). Thus, the epitopes recognized by MoCAV/F2 and MoCAV/F8 seemed to be topographically close in the VP1 structure, suggesting that VP1 has at least two different neutralizing epitopes. However, MoCAV/F8 did not react with EsCAV/F2 or EsCAV/F8, suggesting that binding of MoCAV/F8 to the epitope requires coexistence of the epitope recognized by MoCAV/F2. In addition, MoCAV/ F2, with a titre of 1 : 12 800 to the parent strain, neutralized EsCAV/F2 and EsCAV/F8 with low titres of 32 and 152, respectively. The similarity of the reactivity of MoCAV/F2 and MoCAV/F8 to VP1 may also suggest the existence of a single epitope recognized by these mAbs.
An H5N1 highly pathogenic avian influenza virus was isolated from conjunctiva of a whooper swan with neurological signs, which was captured during the latest H5N1 HPAI outbreak in Japan. The conjunctival swab contained a larger amount of the virus in comparison with the tracheal swab. This is the first report on H5N1 virus isolation from the conjunctiva of a wild bird, and the result may suggest the conjunctival swab to be a critical sample for H5N1 HPAIV detection in waterfowl. Phylogenetic analysis of the HA gene indicated that the virus falls into H5N1 clade 2.3.2.1.
Viral neuraminidase inhibitors are widely used as synthetic anti-influenza drugs for the
prevention and treatment of influenza. However, drug-resistant influenza A virus variants,
including H5N1 highly pathogenic avian influenza viruses (HPAIVs), have been reported.
Therefore, the discovery of novel and effective antiviral agents is warranted. We screened
the antiviral effects of 11 herbal tea extracts (hibiscus, black tea, tencha, rosehip tea,
burdock tea, green tea, jasmine tea, ginger tea, lavender tea, rose tea and oak tea)
against the H5N1 HPAIV in vitro. Among the tested extracts, only the
hibiscus extract and its fractionated extract (frHibis) highly and rapidly reduced the
titers of all H5 HPAIVs and low pathogenic AIVs (LPAIVs) used in the pre-treatment tests
of Madin–Darby canine kidney (MDCK) cells that were inoculated with a mixture of the virus
and the extract. Immunogold electron microscopy showed that anti-H5 monoclonal antibodies
could not bind to the deformed H5 virus particles pretreated with frHibis. In
post-treatment tests of MDCK cells cultured in the presence of frHibis after infection
with H5N1 HPAIV, the frHibis inhibited viral replication and the expression of viral
antigens and genes. Among the plants tested, hibiscus showed the most prominent antiviral
effects against both H5 HPAIV and LPAIV.
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