IDENTIFICATION OF A 24-KDA PROTEIN EXPRESSED BY CHICKEN ANEMIA VIRUS

Antisera raised against oriented peptide conjugates were used to ident ify and partially characterize a 24 kDa protein product expressed by c hicken anaemia virus (CAV). The peptides derived from the N and C term ini of the protein were shown to react against the native protein, exp ressed within virus-infected cells, by immunofluorescence, immunoperox idase and immunogold thin section electron microscopy techniques. The protein product was located by immunogold single labelling in intranuc lear inclusions similar to those described previously for the 13 kDa C AV protein, which causes apoptosis. The 24 kDa protein was co-localize d to the nuclear inclusions with the CAV 13 kDa protein by simultaneou s dual labelling immunogold electron microscopy. Following isolation o f the CAV proteins by nuclei isolation and SDS-PAGE, the antisera were used to probe for the protein by immunoblotting. The antisera recogni zed an expressed protein product of apparent molecular mass 30 kDa. An immunofluorescence time course study of CAV protein expression was ca rried out and the peptide antisera reacted against the protein at 12 h post-infection. Antisera against the 13 kDa protein reacted at simila r times post-infection. This was in contrast to antisera raised agains t the 52 kDa capsid protein which is detectable by immunofluorescence only after 24 h. The 13 kDa and 24 kDa proteins thus appear to be earl y antigens produced by CAV during infection.