The characterization of the spike protein and a comparison of two pathotypes of avian infectious bronchitis virus

Abstract

Eleven monoclonal antibodies (MAb) were produced to the Gray stain of IBV. Six MAbs neutralized for the Gray strain, and three of these MAbs were IgGl[ak], conformation-dependent and serotype specific. The other three neutralizing MAbs were IgG2[ak], conformation-independent and bound to six strains of IBV. An additional five MAbs were nonneutralizing, IgG1, conformation-dependent and bound only the Gray strain of IBV. In the neutralizing assays with at least two of the nonneutralizing MAbs, 5C5C9 and 9B1B6, the embryos showed no gross kidney lesions. Nine MAbs were topographically mapped to define a series of overlapping epitopes. The embryonating chicken egg (ECE) system was used to examine the pathology and viral replication of two pathotypes of IBV. Gross pathology in the lungs was demonstrated with the Ark strain, and gross pathology in the kidneys was demonstrated with the Gray strain. The study confirmed that gross pathologies associated with the respective pathotypes could consistently be reproduced in the ECE model, and that viral replication was present in the lungs and kidneys of both pathotypes. An in vivo time course study examined both the kidneys and the lungs of chicks infected with either pathotype for viral replication and gross pathology. Although viral replication in the lungs and kidneys was present on each day examined, there were distinct differences in the amount of viral RNA. A difference in the initial presentation and distribution of viral antigen was detected in the lungs and kidneys of the pathotypes. Two MAbs that defined epitopes on the spike protein and were shared by the strains tested, were examined in neutralizing assays with the Gray, Arkansas, Mass41, Conn46, and a field strain, PP14. One MAb neutralized the Gray, Mass41, and PP14, and the other MAb neutralized the Conn46 and PP14...