The Mutation Tendency of the gp85 Gene of Chinese Field Strains of ALV-J from 1999 to 2003

Fourteen field strains of J Avian leukosis virus Subgroup(ALV-J)was isolated from farms with suspected diseased chickens and identified by inoculating the samples into embryo fibroblast, indirect immunofluorescence assay (IFA) and PCR amplification To observe the antigenic variants of the GP85 protein, the env gene of 14 field strains were cloned and sequenced. The induced amino acid sequences of the GP85 protein of the isolated field strains were compared with HPRS-103. The results indicated that the GP85 protein of ALV-J had multiple changes,and those changes clustered in the regions of hr1, hr2 and vr3 .The identity of the amino acid of the GP85 protein among different ALV-J strains differs from 86.6% to 100%. The ratio of NS/S in Gp85 and its variable regions indicated that these variable regions may be the most likely targets for immune selective pressure.