MORE THAN ONE-COMPONENT OF THE NEWCASTLE-DISEASE VIRUS PARTICLE IS CAPABLE OF INTERFERON INDUCTION

The interferon (IFN)-inducing capacities of intact NDV virions, beta-p ropiolactone-inactivated particles and several structural components w ere compared, using human PBML as the IFN producing cells. Intact and inactivated virions as well as the nucleocapsid fraction did not diffe r significantly in their IFN-inducing capacity. In contrast, genomic R NA as well as M protein fraction and envelopes induced IFN titres to a level of about 10% of those achieved with virions. NDV-induced IFN pr oduction could be blocked specifically by incubation with polyclonal a nti-NDV-monoclonal antibodies (mAbs) and with two of three anti-HN-mAb s, but not with anti-NDV-mAbs directed against the F, M or NP protein. In addition, IFN induction by fixed MDBK cells, expressing NDV surfac e proteins after infection with NDV Ulster, was inhibited by one of tw o anti-F-mAbs. The results suggest that the induction of IFN synthesis in human PBML is a complex process involving not only the HN protein but also the uncleaved F protein precursor, a component of the M prote in fraction and- once having entered the cell - the genomic RNA.