Infectious bronchitis virus and brown shell colour: Australian strains of infectious bronchitis virus affect brown eggshell colour in commercial laying hens differently

Comparison of Immune-Related Gene Expression in Two Chicken Breeds Following Infectious Bronchitis Virus Vaccination

This study aims to identify the immune-related genes and the corresponding biological pathways following infectious bronchitis virus vaccination in Taiwan Country and White Leghorn chicken breeds. Transcriptomic analyses of the spleen of these two breeds were conducted by next-generation sequencing. Compared to White Leghorn chicken, Taiwan Country chicken showed a significantly higher level of anti-infectious bronchitis virus (IBV) antibodies at 14 and 21 days pos vaccination. At 7 days post vaccination, in the Taiwan Country chicken, higher expression of mitogen-activated protein kinase 10, Major histocompatibility complex class 1, and V-set pre-B cell surrogate light chain 3 were found. In contrast, the White Leghorn chicken had a high expression of interleukin 4 induced 1, interleukin 6, and interleukin 22 receptor subunit alpha 2. These findings have highlighted the variations in immune induction between chickens with distinct genetic background and provided biological pathways and specific genes involved in immune responses against live attenuated IBV vaccine.

Infectious bronchitis virus in Australia: a model of coronavirus evolution - a review

Infectious bronchitis virus (IBV) was first isolated in Australia in 1962. Ongoing surveillance and characterization of Australian IBVs have shown that they have evolved separately from strains found throughout the rest of the world, resulting in the evolution of a range of unique strains and changes in the dominant wild-type strains, affecting tissue tropism, pathogenicity, antigenicity, and gene arrangement. Between 1961 and 1976 highly nephropathogenic genotype GI-5 and GI-6 strains, causing mortalities of 40% to 100%, predominated, while strains causing mainly respiratory disease, with lower mortality rates, have predominated since then. Since 1988, viruses belonging to two distinct and novel genotypes, GIII and GV, have been detected. The genome organization of the GIII strains has not been seen in any other gammacoronavirus. Mutations that emerged soon after the introduction of vaccination, incursion of strains with a novel lineage from unknown sources, recombination between IBVs from different genetic lineages, and gene translocations and deletions have contributed to an increasingly complex IBV population. These processes and the consequences of this variation for the biology of these viruses provide an insight into the evolution of endemic coronaviruses during their control by vaccination and may provide a better understanding of the potential for evolution of other coronaviruses, including SARS-CoV-2. Furthermore, the continuing capacity of attenuated IBV vaccines developed over 40 years ago to provide protection against viruses in the same genetic lineage provides some assurance that coronavirus vaccines developed to control other coronaviruses may continue to be effective for an extended period.

Avian Viruses that Impact Table Egg Production

Eggs are a common source of protein and other nutrient components for people worldwide. Commercial egg-laying birds encounter several challenges during the long production cycle. An efficient egg production process requires a healthy bird with a competent reproductive system. Several viral pathogens that can impact the bird's health or induce reversible or irreversible lesions in the female reproductive organs adversely interfere with the egg industry. The negative effects exerted by viral diseases create a temporary or permanent decrease in egg production, in addition to the production of low-quality eggs. Several factors including, but not limited to, the age of the bird, and the infecting viral strain and part of reproductive system involved contribute to the form of reproductive disease encountered. Advanced methodologies have successfully elucidated some of the virus-host interactions relevant to the hen's reproductive performance, however, this branch needs further research. This review discusses the major avian viral infections that have been reported to adversely affect egg productivity and quality and aims to summarize the current understanding of the mechanisms that underlie the observed negative effects.

Characterization of S1 gene sequence variations of attenuated QX-like and variant infectious bronchitis virus strains and the pathogenicity of the viruses in specific-pathogen-free chickens

Besides the vaccine strains, the Malaysian variant (MV) and QX-like are the predominant IBVs detected on commercial poultry farms. These two virus strains are distinct based on genomic and pathogenicity studies. In this study, we determined the sequence of the S1 gene and compared the pathogenicity of serial passage 70 (P70) of Malaysian QX-like (QX/P70) and MV (MV/P70) strains with that of their respective wild-type viruses. The nucleotide and amino acid sequences of the complete S1 genes of QX/P70 and MV/P70 showed 1.4 to 1.6% and 3.0 to 3.3% variation, respectively, when compared to the wild-type virus. Most of the mutations were insertions and substitutions in the hypervariable regions (HVRs), primarily in HVR 3. Furthermore, selection pressure analysis showed that both viruses are under purifying selection. A pathogenicity study in specific-pathogen-free (SPF) chickens showed a reduction in respiratory and kidney lesions in chickens inoculated with MV/P70, but not with QX/P70, when compared to the respective wild-type viruses. However, MV/P70 is still pathogenic and can cause ciliary damage. In conclusion, the MV IBV strain is more responsive than the QX-like IBV strain following the attenuation process used for the development of a live attenuated IBV vaccine.