Pathogenic, antigenic, and phylogenetic evaluation of chicken infectious anemia virus isolates

Chicken Infectious Anemia Virus (CIAV) is a potentially immunosuppressive virus, typically affecting young chicks, that is widespread in commercial chicken flocks worldwide.; The purpose of these studies was directed at characterizing different CIAV isolates (recent field isolates, older isolates from sentinel birds and clinical accessions and from broiler chickens originating from CIAV-vaccinated or non-vaccinated broiler-breeder flocks) by pathogenic, antigenic, and phylogenetic analysis to better understand the molecular basis of relative pathogenicity observed among CIAV isolates.; A panel of eight monoclonal antibodies (Mabs) was used for antigenic characterization of twenty three different CIAV isolates. Cluster analysis of Mab neutralization data, represented as a tree structure, revealed two main divisions of isolates with two major groups, or clusters, within each division that accounted for ∼70% of the variability in the data. Analysis of virus neutralization by the Mabs revealed a clustering of isolates that may have biologically relevance.; The results from a comparative pathogenesis study of CIAV isolates indicated a graded pathogenicity among field isolates following live virus challenge using similar challenge titers. These results also suggest a classification of those isolates into three groups based on disease outcome; including anemia, histological changes in thymus, bone marrow, and spleen, and the detection of CIAV-induced apoptosis and phosphatase activity in thymus homogenates from infected chicks.; One of the CIAV isolates used in the comparative pathogenicity study, isolate 19, showed a reduced pathogenicity in one-day-old chicks by comparison to CIAV-1 and other field isolates. DNA sequence analysis revealed that a unique change from thymine to cytosine occurred at nucleotide position 672 in isolate 19. Owing to the overlapping coding regions of VP2 and VP3 in CIAV this single nucleotide change translates into a substitution of Ser105 for Phe105 in VP2 and Leu70 for Phe70 in VP3. Analyses of the sequences of the attenuated Vaccine and VN viruses showed that both these viruses contain numerous changes at both the nucleotide and predicted amino acid level. However, the nucleotide and predicated amino acid changes observed for isolate 19 were not among the changes observed in either the Vaccine or the VN virus. Therefore, the change in the DNA sequence of isolate 19 appears to be sufficient, but not necessary for reduced pathogenicity. (Abstract shortened by UMI.)...