Pathogenicity of antigenic variants of Newcastle disease virus Italian strain selected with monoclonal antibodies.

Antigenic variants of the Italian strain of NDV were selected using monoclonal antibodies directed against the HN and F proteins of Italian virus. Antigenic mapping of the HN and F proteins using variant viruses in cross neutralization tests revealed the presence of at least two different epitopes on HN and four epitopes on F protein. Immunoselected variant viruses were demonstrated to have different intravenous pathogenicity index than the parental Italian virus.