Groups of one-day-old broiler chicks were vaccinated via the oculo-nasal route with different live infectious bronchitis virus (IBV) vaccines: Massachusetts (Mass), 793B, D274 or Arkansas (Ark). Clinical signs and gross lesions were evaluated. Five chicks from each group were humanely killed at intervals and their tracheas collected for ciliary activity assessment and for the detection of CD4+, CD8+ and IgA-bearing B cells by immunohistochemistry (IHC). Blood samples were collected at intervals for the detection of anti-IBV antibodies. At 21 days post-vaccination (dpv), protection conferred by different vaccination regimes against virulent M41, QX and 793B was assessed. All vaccination programmes were able to induce high levels of CD4+, CD8+ and IgA-bearing B cells in the trachea. Significantly higher levels of CD4+ and CD8+ expression were observed in the Mass2 + 793B2-vaccinated group compared to the other groups (subscripts indicate different manufacturers). Protection studies showed that the group of chicks vaccinated with Mass2 + 793B2 produced 92% ciliary protection against QX challenge; compared to 53%, 68% and 73% ciliary protection against the same challenge virus by Mass1 + D274, Mass1 + 793B1 and Mass3 + Ark, respectively. All vaccination programmes produced more than 85% ciliary protection against M41 and 793B challenges. It appears that the variable levels of protection provided by different heterologous live IBV vaccinations are dependent on the levels of local tracheal immunity induced by the respective vaccine combination. The Mass2 + 793B2 group showed the worst clinical signs, higher mortality and severe lesions following vaccination, but had the highest tracheal immune responses and demonstrated the best protection against all three challenge viruses.
Infectious bronchitis virus (IBV) is one of the foremost causes of economic loss within the poultry industry. IBV is a commonly occurring, economically significant pathogen of commercial chicken. Economic consequences to the poultry industry comprise mortality, growth retardation and high condemnation rates in meat-type birds. In addition, decreased egg production, reduced internal and external egg quality, and reduced hatchability have been documented in layers and breeders affecting the performance of both meat-type and egg-laying birds. Apart from this some nephro-pathogenic strains cause kidney damage. Secondary pathogens can complicate the disease resulting in increased morbidity and mortality. Being a single stranded RNA virus, IBV has an enormous capacity to change both by spontaneous mutation and by genetic recombination resulting into the emergence of new variants. Since the first isolation of virus in 1937, it has been found almost all over the world. In addition, most countries are now known to have their own indigenous IBV variants. Despite the use of currently available live and inactivated vaccines, one of the most important difficulties to control IB is related to emergence of variant strains. The following paper reviews the current status of research into IBV.
The objectives of the present study were to assess the mucosal, cellular, and humoral immune responses induced by two different infectious bronchitis virus (IBV) vaccination regimes and their efficacy against challenge by a variant IBV Q1. One-day-old broiler chicks were vaccinated with live H120 alone (group I) or in combination with CR88 (group II). The two groups were again vaccinated with CR88 at 14 days of age (doa). One group was kept as the control (group III). A significant increase in lachrymal IgA levels was observed at 4 doa and then peaked at 14 doa in the vaccinated groups. The IgA levels in group II were significantly higher than those in group I from 14 doa. Using immunohistochemistry to examine changes in the number of CD4 ؉ and CD8؉ cells in the trachea, it was found that overall patterns of CD8 ؉ cells were dominant compared to those of CD4 ؉ cells in the two vaccinated groups. CD8؉ cells were significantly higher in group II than those in group I at 21 and 28 doa. All groups were challenged oculonasally with a virulent Q1 strain at 28 doa, and their protection was assessed. The two vaccinated groups gave excellent ciliary protection against Q1, although group II's histopathology lesion scores and viral RNA loads in the trachea and kidney showed greater levels of protection than those in group I. These results suggest that greater protection is achieved from the combined vaccination of H120 and CR88 of 1-day-old chicks, followed by CR88 at 14 doa. T he prevention of infectious bronchitis (IB) in chickens isachieved through the use of live and inactivated vaccines, which provide protection against virulent field IB viruses (IBVs) in the event of an exposure. Despite these preventative measures, outbreaks of IB frequently occur in many poultry producing countries (1-3). This is probably due to the emergence of new variants of infectious bronchitis virus (1-5). For the successful protection of chickens against infection, it is essential to identify the prevalent genotypes in the region, determine the cross-protective potential of available vaccines, and optimize strategic vaccination programs.IB was first described in the United States during the 1930s and was identified in the United Kingdom in 1948. Thereafter, many IBV variants were isolated from Europe, significantly a variant called 793B that emerged in the 1990s (6). Later, IBV QX was first identified in China (7) before spreading to Europe (8). Another IBV genotype, Q1, genetically and serologically distinct from the classical IBVs, was also reported in China (9), the Middle East (10), and Europe (11). To contain this strain, an effective vaccination program is needed. However, very little is known about the cross protection induced by the commercially available vaccines or vaccination regimes against this variant Q1.An effective and long-lasting protection against IBV infection requires the activation of effector, memory cell-mediated, and humoral immune responses (HIRs) against the virus (12). A number of studies have reported the systemi...
A number of broiler flocks with respiratory disease and high mortality in five broiler farms in Libya were sampled for detection of infectious bronchitis virus (IBV). Twelve IBV strains from these farms were detected by reverse transcription polymerase chain reaction (RT-PCR) and differentiated by nucleotide sequencing of the hypervariable region of the S1 gene. A pair-wise comparison of the sequences showed two distinctive patterns. Those from farms 1, 2, 4 and 5, formed a separate cluster with 94-99% relatedness to the Egyptian IBV strains CK/Eg/BSU-2/2011, CK/Eg/BSU-3/2011 and Eg/1212B. Sequences from the farm 3 formed another cluster with 100% relatedness to Eg/CLEVB-2/IBV/012 and IS/1494/06. This appears to be the first report on the co-circulation of variant IBVs in Eastern part of Liby
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