Protective Efficacy of Different Live Attenuated Infectious Bronchitis Virus Vaccination Regimes Against Challenge With IBV Variant-2 Circulating in the Middle East.

Hesham A Sultan,Abdel Hamid I Bazid,Wael K El Feil,Mohamed A Zain El-Abideen,Ahmed Ali,Walid H Kilany

doi:10.3389/fvets.2019.00341

Hesham A Sultan, Abdel Hamid I Bazid + Show 4 more

Open Access

https://doi.org/10.3389/fvets.2019.00341

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Abstract

Six vaccination regimes using classical (Mass-type) and variant (IB-VAR2 and IB-793B) live vaccines were evaluated against Middle Eastern variant-2 infectious bronchitis virus challenge. Six groups of SPF chicks (30 birds/group) were vaccinated using prime-boost regimes at day-1 and day-14 using; IB-M41:IB-VAR2, IB-VAR2:IB-VAR2, IB-VAR2:IB-M41, IB-Ma5:IB-793B, IB-793B:IB-793B, and IB-793B:IB-Ma5, respectively. Ciliostasis and lesion scores were evaluated at day-5 after each vaccination. Birds were challenged intranasally at 14-day post 2nd vaccination using 105EID50/0.1 ml/bird of wild-type IBV (Eg/1212B/2012). At 3, 5, and 7-day post challenge (DPC) virus shedding was monitored by real-time RT-PCR. Five chicks/group were euthanized at 7DPC for ciliostasis and lesion scoring and histopathology was conducted on 3 chicks/group. Seroconversion was evaluated at 14 DPC. All groups primed with the 793B vaccine showed relatively higher ciliostasis scores compared to other groups. The IB-VAR2 vaccinated groups showed the highest protection rates (80–100%) and high protection score (67.6–73.2%) compared to the 793B vaccine groups (50–60%). The virus shedding was significantly reduced at 3 and 5DPC in groups received the IBV-VAR2 (prime or booster) compared to those received the 793B vaccine. In conclusion, the homologous IBV-VAR2 vaccine showed superior results compared to 793B or Mass-type vaccines confirming the importance of IBV vaccine seed homology to the circulating IBV strains.

Highlights

Avian Infectious bronchitis (IB) is a highly contagious and economically important worldwide viral disease of chickens
Infectious bronchitis virus (IBV) mainly causes respiratory disease and nephritis in chickens but Vaccination Regimes Against IBV VAR2 can result in poor weight gain and lost feed efficiency in broilers and reduced numbers and quality of eggs in layers [5]
This study aimed to evaluate the protective efficacy of 3 different vaccination regimes using combinations of an attenuated Egyptian IBV variant-2 vaccine combined with Egyptian Mass type vaccine in comparison to their corresponding variant 793B and Mass-type live attenuated vaccines against the Middle Eastern IBV variant-2 virus

Summary

Introduction

Avian Infectious bronchitis (IB) is a highly contagious and economically important worldwide viral disease of chickens. Several IBV serotypes or antigenic variant strains emerged due to changes in the IBV genome through point mutations, deletions, insertions or RNA recombination and these variants are often responsible for IB outbreaks in vaccinated chicken flocks [8,9,10]. Pathogenic variants such as D274 and D1466, 793B, Israel variant 1, and 2 [11, 12] have evolved over the last decades

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