Analysis of the immune response and identification of antibody epitopes against the sigma C protein of avian orthoreovirus following immunization with live or inactivated vaccines

Authors: DAWE, WILLIAM - University Of Georgia; Kapczynski, Darrell; LINNEMANN, ERIC - University Of Georgia; GAUTHIERSLOAN, VANESSA - University Of Georgia; SELLERS, HOLLY - University Of Georgia

Submitted to: Avian Diseases
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/1/2022
Publication Date: 1/11/2023
Citation: Dawe, W.H., Kapczynski, D.R., Linnemann, E.G., Gauthiersloan, V., Sellers, H. 2023. Analysis of the immune response and identification of antibody epitopes against the sigma C protein of avian orthoreovirus following immunization with live or inactivated vaccines. Avian Diseases. 66(4): 465-475. https://doi.org/10.1637/aviandiseases-D-22-99992.
DOI: https://doi.org/10.1637/aviandiseases-D-22-99992

Interpretive Summary: The Reoviridae family represents the largest family of double-stranded RNA (dsRNA) viruses, and the members have been isolated from a wide range of mammals, birds, reptiles, fishes, insects, and plants. Orthoreoviruses, one of the 15 recognized genera in the Reoviridae family, can infect humans and nearly all mammals, and birds. Avian orthoreoviruses (ARV) infections cause significant disease in the poultry industry. Vaccines against ARV are available and should be matched to field viruses. This study explores the immune response of birds following vaccination against ARV contemporary and field variants.

Technical Abstract: Avian orthoeoviruses are causative agents of tenosynovitis and viral arthritis in both chickens and turkeys. Current commercial reovirus vaccines do not protect against disease caused by emerging variants. Custom made inactivated reovirus vaccines are commonly utilized to help protect commercial poultry against disease. Antibody epitopes located on the viral attachment protein, sigma C, involved in virus neutralization, have not been clearly identified. In this study, chickens were vaccinated with either a commercial S1133 vaccine (Genotype 1 (GT1)), a GT1 field isolate (117816), or a GT5 field isolate (94826), and sera were used to identify linear B-cell epitopes within the sigma C protein. SPF chickens were vaccinated twice with either: 1) live and live, 2) inactivated and inactivated, or 3) combination of live and inactivated. Epitope mapping was performed on individual serum samples from birds in each group using S1133, 117816, and 94826 sigma C sequences spotted onto microarray chips. Results indicate vaccination with a combination of live and inactivated viruses resulted in a greater number of B cell binding sites on the outer-capsid domains of sigma C for 117816, 94826, but not S1133. In contrast, the S1133 vaccinated birds demonstrated fewer epitopes and those epitopes were located in the stalk region of the protein. However, within each of the vaccinated groups, the highest virus-neutralization titers were observed in the live/inactivated groups. This study demonstrates differences in antibody binding sites within sigma C between genetically distinct reoviruses and provides an initial antigenic characterization of avian orthoreoviruses and insight into the inability of vaccine induced antibodies to provide adequate protection against variant reovirus induced disease.