Kidney Cell–Adapted Infectious Bronchitis Virus Arkansas Delmarva Poultry Industry Vaccine Confers Effective Protection Against Challenge

Abstract

We previously demonstrated that adaptation of an embryo-attenuated infectious bronchitis virus (IBV) Arkansas Delmarva Poultry Industry (ArkDPI)-derived vaccine to chicken embryo kidney (CEK) cells shifted the virus population towards homogeneity in spike (S) and nonstructural protein genes. Moreover, the typical Ark vaccine subpopulations emerging in chickens vaccinated with commercial Ark vaccines were not detected in chickens vaccinated with the CEK-adapted virus. In this study, chickens vaccinated with a low dose (1.6 × 10(3) EID50/bird, where EID50 is 50% embryo infectious dose) of CEK-adapted Ark vaccine at 5 days of age showed a significant reduction of IBV RNA in lachrymal fluids and decreased incidence of IBV RNA detection in tracheal swabs 5 days after challenge compared to unvaccinated challenged chickens. In a second experiment, 5-day-old chickens were vaccinated with 10(4) or 10(5) EID50/chicken of CEK-adapted Ark vaccine, and protection was compared to chickens vaccinated with 10(5) EID50/chicken of the commercial ArkDPI-derived vaccine from which the CEK-adapted virus originated. All vaccinated chicken groups showed a significant reduction of respiratory signs and viral load 5 days after Ark virulent challenge compared to unvaccinated challenged controls. No viral subpopulations different from the challenge virus were detected in chickens vaccinated with CEK-Ark after challenge. In contrast, IBV S1 sequences differing from the predominant population in the challenge virus were detected in several chickens vaccinated with the commercial Ark attenuated vaccine. From an applied perspective, the CEK-adapted IBV ArkDPI-derived vaccine is an improved and effective vaccine candidate with which to protect chickens against virulent Ark-type strains.

Kidney Cell–Adapted Infectious Bronchitis ArkDPI Vaccine is Stable and Protective

“…Besides the fact that typical ArkDPI vaccine subpopulations do not emerge after vaccination with the more homogeneous CEKp7 as previously demonstrated, the most promising result confirmed in this study was that CEKp7Ep2 vaccination drastically reduces the emergence of subpopulations from the Ark challenge strain (8). Although sequences slightly differing from the challenge virus were detected in only 7%-8% (1/15 and 1/13) of chickens that had been vaccinated with either 10 4.0 or 10 5.0 EID 50 of CEKp7e2, sequences differing from the challenge strain were detected in 77% (10/13) of chickens vaccinated with the commercial attenuated ArkDPI vaccine.…”

“…Corroborating previous results (8), CEKp7e2 conferred effective protection against Ark virulent challenge as determined both by clinical signs and viral load in two animal trials. Furthermore, a strong secondary B lymphocyte specific immune response in the Harderian gland was successfully elicited by the experimental vaccine.…”

“…JN861120) previously described (3) was used for challenge purposes. Viruses were titered in ECE as generally accepted (5,23) including slight modifications previously described (8). In brief, in addition to macroscopic embryo changes, the embryo weight and IBV RNA detection by quantitative reverse transcriptase polymerase chain reaction (qRT-PCR) (2) in embryo allantoic fluids (AF) were used to determine the virus titers.…”

“…Vaccine virus subpopulations, which quickly become predominant in chickens after vaccination (4,12,22), likely provide a source for the emergence of novel vaccine-like viruses commonly isolated from broiler respiratory disease. In addition to subpopulations originating from vaccine virus, accumulating evidence shows that subpopulations emerge from wild Ark challenge virus in chickens that had been vaccinated with attenuated ArkDPI vaccines (8,18). Thus, C Senior and corresponding author: E-mail: torohar@auburn.edu AVIAN DISEASES 61:221-228, 2017 current ArkDPI-derived vaccines contribute to emergence of novel Ark-like variants in the industry.…”

Analysis of Immune Response of Chicken Primary Cells by Infection With Korean IBV Strain

“…As the rst line of defense, innate immunity is activated within two days after antigenic stimulation. At this initial stage of IBV infection, cytokines and chemokines are produced and co-stimulatory pathways are activated [3,16,17]. Then we speculated the transcriptome analysis of infected kidney tissue by an IBV strain with renal tropism might be helpful to understand the pathogenesis of IB.…”