Agnoprotein 1a and agnoprotein 1b of avian polyomavirus are apoptotic inducers

Avian polyomavirus (APV) causes an acute fatal disease in a variety of avia n species. DNA laddering indicating apoptosis was demonstrated in APV-infec ted chicken embryo (CE) cells. DNA laddering, however, was not observed in Vero cells infected with mammalian polyomavirus simian virus 40. Expression of APV agnoprotein la and agnoprotein Ib induced apoptosis in insect cells and CE cells. An APV full-length plasmid transfected in CE cells induced a poptosis, and infectious virus was produced. After transfection of CE cells with a plasmid containing a mutated initiation codon for agnoprotein la an d agnoprotein 1 b, however, a considerably lower number of apoptotic cells was observed, and no infectious progeny was produced.