IDENTIFICATION AND GROUPING OF NEWCASTLE-DISEASE VIRUS-STRAINS BY RESTRICTION SITE ANALYSIS OF A REGION FROM THE F-GENE

A 75% region of the F gene (between nucleotides 334 and 1682) of Newca stle disease virus (NDV) RNA was amplified by reverse transcription-po lymerase chain reaction (RT-PCR). PCR products were cleaved by three r estriction endonucleases and the positions of thirty cleavage sites we re mapped in more than 200 NDV strains. Restriction site analysis esta blished six major groups of NDV isolates and unique fingerprints of va ccine strains. Group I comprised lentogenic strains isolated mainly fr om waterfowl with some from chickens. ''Old'' (prior to 1960s) North A merican isolates of varying virulence including lentogenic and mesogen ic vaccine strains belonged to group II. Group III included two early isolates from the Far East. Early European strains (Herts 33 and Itali en) of the first panzootic (starting in the late 1920s) and their desc endants with some modifications were placed into group IV. NDV strains isolated during the second panzootic of chickens (starting in the ear ly 1960s) were classified into two groups. Group V included strains or iginating in imported psittacines and in epizootics of chickens at the early 1970s. Group VI comprised strains from the Middle East in the l ate 1960s and later isolates from Asia and Europe. Pigeon paramyxoviru s-l strains that were responsible for the third panzootic formed a dis tinct subgroup in group VI. Our grouping of NDV strains has confirmed group differences established by monoclonal antibodies. It is conclude d that restriction site analysis off gene PCR amplicons is a relativel y fast, simple and reliable method for the differentiation and identif ication of NDV strains.