Genetic mutations in live infectious bronchitis vaccine viruses following single or dual in vitro infection of tracheal organ cultures

Abstract

Despite regular co-vaccination of two different strains of live infectious bronchitis vaccine viruses, little is known about possible mutations in these viruses following vaccination. As an alternative to chicks, this study used an in vitro infection model to identify single-nucleotide polymorphisms (SNPs) within the part-S1 gene of two live infectious bronchitis virus vaccine strains (793B and Massachusetts) following single or dual inoculation onto tracheal organ cultures. Results indicate that viral titres reduced over the duration of the study; conversely, the amount of detected infectious bronchitis virus genome increased. Results demonstrate a greater number of nonsynonymous SNPs in both vaccine strains when they are co-inoculated, compared with the single inoculations. The influence of the increased SNP and hydrophobic properties of the translated proteins on the vaccine viruses' virulence is unknown.

Comparative protective immunity provided by live vaccines of Newcastle disease virus or avian metapneumovirus when co-administered alongside classical and variant strains of infectious bronchitis virus in day-old broiler chicks

“…With both experiments, Sanger sequencing showed that the genotype of strains recovered using OP swabs altered from Mass to 793B after 14 dpv. As reported previously [26,27], while the Mass genotype made up the majority of detections during early sampling days (3-14 dpv), the 793B strain became the dominant strain by 21 dpv. The reason for the shifting of genotypes from Mass to 793B is not known, however, previous work has highlighted that different IBV strains can differentially induce host expression pathways, in particular TLR7 [65] and IFN-b [66].…”

“…Recent work has shown that IBV vaccines can undergo genetic mutations following inoculation into the chicken host [26,27]. As persistent mutations can alter strain characteristics [28], it is preferable to monitor potential changes.…”

Infectious Bronchitis Virus (Gammacoronavirus) in Poultry Farming: Vaccination, Immune Response and Measures for Mitigation

“…Currently, IBV vaccination programs have gained more attention with respect to the use of low-virulent, live or inactivated killed vaccines with the aim of booster shots at certain times to increase immunity and reduce the antagonistic response of epithelial cells in the respiratory region [89]. However, there is a significant limitation in applying live IBV vaccines because the attenuation of the vaccine is naturally deficient with respect to its capability in stimulating a mucosal immune response [90,91], which is a critical part of controlling IBV infection since killed vaccine can be an option [92,93]. Nonetheless, it was possible that inactivated killed vaccines can be applied to stimulate t mucosal immune responses once combined with several nanoparticles [92].…”

Infectious Bronchitis Coronavirus Infection in Chickens: Multiple System Disease with Immune Suppression

“…In addition, attenuated IBV strains used for vaccination can spread among individual birds within flocks [ 121 ], and changes in virulence during bird-to-bird passage can lead to production problems [ 120 , 122 ]. Coinfection of host cells with live attenuated IB vaccines and wild type IBV can also result in genomic recombination contributing to the virus evolution [ 11 , 123 ] as well as mutations that can occur under the effect of immune pressure [ 124 , 125 , 126 ]. Although the global poultry industry practices hatchery vaccination against IB, Day 1 may not be the optimum time for vaccination in terms of inducing systemic and mucosal immune responses against IB [ 106 ] because of the developing immune system [ 127 ].…”

“…Given the available scientific evidence against IB vaccination at the hatchery [ 106 , 110 ], it may also be appropriate to postpone the first IB vaccination to a barn vaccination done at seven days of age relying on maternal antibody response to protect the chickens during the first week of life [ 110 ]. There are numerous issues surrounding the use of live attenuated IB vaccines [ 11 , 99 , 119 , 120 , 121 , 122 , 123 , 124 , 125 , 126 ], and relying on inactivated vaccines can be an option, but they inherently lack the ability to induce mucosal immune response, which is critical for the control of IB [ 131 , 132 , 133 ]. It is possible that inactivated vaccines can be used for the induction of mucosal immune response when combined with various nanoparticles [ 132 ].…”