Bornavirus Antigens in Psittaciformes Infected with Psittaciform Bornavirus and their Use in Diagnostic Procedures

Author(s): Josephine M McHugh, Siwo R de Kloet

This study describes the occurrence of psittaciform bornavirus antigens and antibodies in tissues of birds persistently infected with psittaciform bornavirus. Analysis of serum of infected birds shows that antibodies against the P40 nucleoprotein occur most commonly, whereas antibodies to the glycoprotein are virtually completely absent. Classical Western blotting using rabbit antibodies showed that the P40 nucleoprotein is the only antigen which can be reliably detected in tissues as diverse as brain, liver, feather calami and material such as cloacal swabs. The sensitivity of the latter approach is about 1 µg. Using automated Western blotting (ProteinSimple, WES) improved this sensitivity to about 200 pg. Rabbit antibodies against the P24 phosphoprotein detect a cross-reacting protein of the same molecular size in a classical Western blot of tissue homogenates of uninfected birds. Rabbit antibodies against the P16 matrix protein do not detect the protein in a Western blot, classical or automated, possibly through shielding by other components in the tissue homogenates or prevention of the transfer of the protein from the gel to the PDVF membrane during the blotting, although such antibodies can be used as detection antibodies in a sandwich ELISA analysis where the capture antibodies are of avian origin. The latter approach allows the detection of the P24 phosphoprotein and the P16 matrix protein in feather calami and cloacal swabs at a sensitivity of approximately 200 pg.

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