Virulence,immunogenicitiy and antigenic relation of avian paramyxovirus type I strains from different avians

Three avian paramyxovirus type Ⅰ (APMV Ⅰ) strains, named CPMV, GPMV and PPMV, were isolated from chickens, geese and pigeons, respectively. The results of virulence tests showed that the virulences of CPMV and GPMV were similar to that of F48E9, which is the type strain of virulent Newcastle disease virus(NDV). However, PPMV was avirulent to chickens, and showed similar pathogenicity to LaSota strain. The results of sequence analysis indicated that the cleavage site of the fusion protein of CPMV and GPMV was 112K-R-Q-K-R-F117, which is the representive motif of virulent NDV. While, the hydrolyze site of PPMV was 112G-R-Q-G-R-L117, which is typical motif of avirulent type. After inactivated, the three isolates were inoculated into chicken and high levels of HI antibody against three isolates were detected. The immunized chickens were challenged by CPMV and GPMV, and showed that all of the chickens could be protected. Crossing test of HI showed that there were no obvious differences in antigenicity between GPMV and LaSota. While, little difference in antigenicity was found among the other two isolates and LaSota. These data are helpful to study the new-type vaccine and pathogenesis of APMV Ⅰ.