Infectious Bronchitis Virus Challenge Research Articles

The combination of infectious bronchitis virus BR1 and Mass vaccines provides broad protection

ABSTRACT Two vaccination-challenge trials were performed using a commercial infectious bronchitis virus (IBV) BR1 vaccine, given alone or combined with a commercial IBV Mass vaccine against challenges with IBV M41, 793B, D388 (QX), Q1, Brasil-1 or Variant 2 challenge viruses, which includes the IB viruses that are dominant in South America. The efficacy of the vaccines against the challenge viruses was investigated by determination of the ciliary activity of the tracheal epithelium after challenge. The level of protection induced by the IBV BR1 vaccine alone against the six IBV challenge strains, of which five were of heterologous genotypes, varied from 50% to 100% with an average of 80%. The level of protection induced by the combination of the IBV BR1 and IBV Mass vaccines against the six IBV challenge strains, of which four were of heterologous genotypes, varied from 80% to 100% with an average of 92%. Vaccination with IBV BR1 alone provided a high level of protection against most tested challenge viruses, though the combination of IBV BR1 and IBV Mass was more consistent, showing less variation and compliance with the criterium mentioned in the European Pharmacopoeia 10th edition (at least 80% protection) for all tested challenge viruses. These trials show that vaccination with a combination of IBV BR1 and IBV Mass vaccines provides high levels of protection against the circulating IBV strains in South America.

Protection of laying chickens against the Canadian DMV/1639 infectious bronchitis virus infection through priming with heterologous live vaccine and boosting with heterologous or homologous inactivated vaccine

The emergence of the Canadian Delmarva (DMV)/1639 infectious bronchitis virus (IBV) type strains was associated with egg production disorders in Eastern Canadian layer operations. While developing vaccines for novel IBV variants is not typically a reasonable approach, the consideration of an autogenous vaccine becomes more appealing, particularly when the new variant presents significant economic challenges. The current study aimed to compare the efficacies of two vaccination programs that included heterologous live priming by Massachusetts (Mass) and Connecticut (Conn) type vaccines followed by either a commercial inactivated Mass type vaccine or a locally prepared autogenous inactivated DMV/1639 type vaccine against DMV/1639 IBV challenge. The protection parameters evaluated were egg production, viral shedding, dissemination of the virus in tissues, gross and microscopic lesions, and immunological responses. The challenge with the DMV/1639 caused severe consequences in the non-vaccinated laying hens including significant drop in egg production, production of low-quality eggs, serious damage to the reproductive organs, and yolk peritonitis. The two vaccination programs protected the layers from the poor egg-laying performance and the pathology. The vaccination program incorporating the autogenous inactivated DMV/1639 type vaccine was more effective in reducing vial loads in renal and reproductive tissues. This was associated with a higher virus neutralization titer compared to the group that received the commercial inactivated Mass type vaccine. Additionally, the autogenous vaccine boost led to a significant reduction in the viral shedding compared to the non-vaccinated laying hens. However, both vaccination programs induced significant level of protection considering all parameters examined. Overall, the findings from this study underscore the significance of IBV vaccination for protecting laying hens.

Evaluation of protective immunity in chickens vaccinated with combined IB H120/D274 and IB H120 against IS/1494/06 in Iran

Infectious bronchitis virus (IBV) has a variety of serotypes that cause many problems in the poultry industry. Two H120 and H120-D274 live vaccines were evaluated against strain IS/1494/06 (variant 2) infectious bronchitis virus challenge. The study aimed to determine whether it is possible to achieve success in controlling disease symptoms and pathological lesions and reducing virus shedding by combining two types of vaccines against different severities of the Poultry Infectious Bronchitis Virus. After random selection of 100 SPF chickens, four 25 chicks/group experimental groups were arranged in the H120 (IB-H120, Intervet®; Serial No: **** at 1st day + Booster 14th day + Challenged with IS/1494/06- 14 DPV), H120-D274 (Poulvac® IB Primer at 1st day + Booster 14th day + Challenged with IS/1494/06- 14 DPV), Control (No vaccine and No Challenge), and Challenged (No vaccine + Challenge). After euthanasia of the animals on the 42nd day of the research, serum neutralization (days 14, 28, and 42), ELISA (14 days after the booster vaccine and before challenged), Ciliostasis (7 days after the booster vaccine and seven days after challenged) and pathological lesion scores were evaluated on day 14 after being infected with IS/1494/06 type 2 strain (day 42). Also, the virus shedding was monitored by real-time RT-PCR. Infection with the IS/1494/06 variant2 strain showed high to moderate ciliostasis and pathologic scores. All groups that received the IB-H120-D274 vaccine had fewer lesions relatively. The IB-H120-D274 vaccinated groups showed the highest protection rates and high protection scores (70.3) compared to the IB-H120 vaccine groups (24.4). The virus shedding was significantly reduced in groups that received the H120-D274 vaccine compared to those that received the IB-H120 vaccine. In conclusion, the homologous IB-H120-D274 vaccine showed superior results compared to the IB-H120 vaccine.

Efficacy of Two Vaccination Strategies against Infectious Bronchitis in Laying Hens.

Vaccination remains the leading control method against infectious bronchitis (IB) in poultry despite the frequently observed IB outbreaks in vaccinated flocks. Here, two vaccination regimes were evaluated against challenge with the Massachusetts (Mass) infectious bronchitis virus (IBV) strain that was linked to egg production defects in Western Canada. One vaccination strategy included live attenuated IB vaccines only, and the other used both inactivated and live attenuated IB vaccines. The two immunization programs involved priming with a monovalent live attenuated IB vaccine (Mass serotype) at day-old, followed by intervals of bivalent live attenuated IB vaccines containing the Mass and Connecticut (Conn) serotypes given to the pullets at 2-, 5-, 9-, and 14-week-old. Inactivated IB vaccine (Mass serotype) was administrated to only one group of the vaccinated birds at 14-week-old. At the peak of lay, the hens were challenged with the Mass IBV isolate (15AB-01) via the oculo-nasal route. The efficacy of the vaccines was assessed following the challenge by observing clinical signs, egg production, egg quality parameters, seroconversion, and systemic T-cell subsets (CD4+ and CD8+ cells). Moreover, the viral genome loads in the oropharyngeal (OP) and cloacal (CL) swabs were quantified at predetermined time points. At 14 days post-infection (dpi), all the hens were euthanized, and different tissues were collected for genome load quantification and histopathological examination. Post-challenge, both vaccination regimes showed protection against clinical signs and exhibited significantly higher albumen parameters, higher anti-IBV serum antibodies, and significantly lower levels of IBV genome loads in OP swabs (at 3 and 7 dpi) and trachea and cecal tonsils compared to the mock-vaccinated challenged group. However, only the birds that received live attenuated plus inactivated IB vaccines had significantly lower IBV genome loads in CL swabs at 7 dpi, as well as decreased histopathological lesion scores and IBV genome loads in magnum compared to the mock-vaccinated challenged group, suggesting a slightly better performance for using live attenuated and inactivated IB vaccines in combination. Overall, the present findings show no significant difference in protection between the two vaccination regimes against the Mass IBV challenge in laying hens.

Ameliorative effects of 25-hydroxycholecalciferol levels on broiler chickens challenged with infectious bronchitis coronavirus: A novel approach

This study aimed to see how 25-hydroxyvitamin D 3 [25(OH)D] supplementation affected the performance, immunity, and vitamin D status of broilers, with and without infectious bronchitis virus challenge. Day-old chicks (n = 1000) were divided into four dietary treatments. All experimental treatments were containing 5000 IU of D3 and supplemented with 0, 100, 300, or 500 g/tonne of Bio D® containing 0, 13.94, 41.82 or 69.70 mg 25(OH)D, respectively. In unchallenged birds, the inclusion of 25(OH)D significantly improved survival rates and EPEF values, and no significant difference in LBW, BWG, FC, or FCR was observed. In infectious bronchitis virus (IBV)-challenged birds, the 25(OH)D treatment showed less deterioration in BWG, and FC compared with the control, especially 25(OH)D500 group. The lowest mortality was observed in the 25(OH)D500 group. The health status of chicks fed diets supplemented with 25(OH)D post-challenge had significantly better CD4, CD8, and immunoglobulin (IgG, IgM) levels, H/L ratio, total leucocytic count (TLC) in peripheral blood and IBV titers, cytokine (including interleukin (IL) 10) and (IFN)-γ expression, and reduced IBV shedding. After IBV challenge, all 25(OH)D groups recorded higher levels of plasma vitamin D than the control. Furthermore, 25(OH)D groups showed significantly higher antibody titers than the control group. In general, dietary supplementation with different levels of 25(OH)D had a positive effect on inflammatory reaction and stimulated the systemic innate immune responses of chickens during IBV challenge. In turn, recovery in the challenged birds with 25(OH)D rapidly occurred compared with that in the control group.

Infectious Bronchitis Coronavirus: Genome Evolution in Vaccinated and Non-Vaccinated SPF Chickens.

Infectious Bronchitis virus (IBV) continues to cause significant economic losses for the chicken industry despite the use of many live IBV vaccines around the world. Several authors have suggested that vaccine-induced partial protection may contribute to the emergence of new IBV strains. In order to study this hypothesis, three passages of a challenge IBV were made in SPF chickens sham inoculated or vaccinated at day of age using a live vaccine heterologous to the challenge virus. All birds that were challenged with vaccine heterologous virus were positive for viral RNA. NGS analysis of viral RNA in the unvaccinated group showed a rapid selection of seven genetic variants, finally modifying the consensus genome of the viral population. Among them, five were non-synonymous, modifying one position in NSP 8, one in NSP 13, and three in the Spike protein. In the vaccinated group, one genetic variant was selected over the three passages. This synonymous modification was absent from the unvaccinated group. Under these conditions, the genome population of an IBV challenge virus evolved rapidly in both heterologous vaccinated and non-vaccinated birds, while the genetic changes that were selected and the locations of these were very different between the two groups.

Development of a Nanoparticle Multiepitope DNA Vaccine against Virulent Infectious Bronchitis Virus Challenge.

To develop a safe and effective nanoparticle (NP) multiepitope DNA vaccine for controlling infectious bronchitis virus (IBV) infection, we inserted the multiepitope gene expression box SBNT into a eukaryotic expression vector pcDNA3.1(+) to construct a recombinant plasmid pcDNA/SBNT. The NP multiepitope DNA vaccine pcDNA/SBNT-NPs were prepared using chitosan to encapsulate the recombinant plasmid pcDNA/SBNT, with a high encapsulation efficiency of 94.90 ± 1.35%. These spherical pcDNA/SBNT-NPs were 140.9 ± 73.2 nm in diameter, with a mean ζ potential of +16.8 ± 4.3 mV. Our results showed that the chitosan NPs not only protected the plasmid DNA from DNase degradation but also mediated gene transfection in a slow-release manner. Immunization with pcDNA/SBNT-NPs induced a significant IBV-specific immune response and partially protected chickens against homologous IBV challenge. Therefore, the chitosan NPs could be a useful gene delivery system, and NP multiepitope DNA vaccines may be a potential alternative for use in the development of a novel, safe, and effective IBV vaccine.

Protection against avian coronavirus conferred by oral vaccination with live bacteria secreting LTB-fused viral proteins

The devastating impact of infectious bronchitis (IB) triggered by the IB virus (IBV), on poultry farms is generally curbed by livestock vaccination with live attenuated or inactivated vaccines. Yet, this approach is challenged by continuously emerging variants and by time limitations of vaccine preparation techniques. This work describes the design and evaluation of an anti-IBV vaccine comprised of E. coli expressing and secreting viral spike 1 subunit (S1) and nucleocapsid N-terminus and C-terminus polypeptides fused to heat-labile enterotoxin B (LTB) (LS1, LNN, LNC, respectively). Following chicken oral vaccination, anti-IBV IgY levels and cellular-mediated immunity as well as protection against virulent IBV challenge, were evaluated 14 days following the booster dose. Oral vaccination induced IgY levels that exceeded those measured following vaccination with each component separately. Following exposure to inactivated IBV, splenocytes isolated from chicks orally vaccinated with LNN or LNC -expressing bacteria, showed a higher percentage of CD8+ cells as compared to splenocytes isolated from chicks vaccinated with wild type or LTB-secreting E. coli and to chicks subcutaneously vaccinated. Significant reduction in viral load and percent of shedders in the vaccinated chicks was evident starting 3 days following challenge with 107.5 EID50/ml virulent IBV. Taken together, orally delivered LTB-fused IBV polypeptide-expressing bacteria induced virus-specific IgY antibody production and was associated with significantly shorter viral shedding on challenge with a live IBV. The proposed vaccine design and delivery route promise an effective and rapidly adaptable means of protecting poultry farms from devastating IB outbreaks.

Infectious Bronchitis Virus Infection of Chicken: The Essential Role of Mucosal Immunity.

Infection with either virulent or vaccine strains of infectious bronchitis virus (IBV) elicits a complex interaction of nonspecific, innate, mucosal, cellular, and humoral immunity, thereby mounting an optimal defensive response in chickens. Through this process, mucosal immunity plays an essential role in preventing infection and clearing the virus. It also assists in the development of longer lasting local immunity against IBV, mainly in the respiratory tract but also in the oviduct and gastrointestinal mucosal linings. The head-associated lymphoid tissues, particularly the Harderian gland, have an important role in the synthesis of immunoglobulin A (IgA). Levels of this immunoglobulin in lachrymal fluid often reflect the degree of protection against IBV challenge. Beyond the head, the importance of mucosal immunity has predominantly been studied in the trachea. Though IgA has been the major focus of IBV mucosal immunity investigations, the role of mucosa-associated nonspecific, innate, and cellular immune responses may also be significant. Ciliary movements and nonspecific substances in the mucosa, such as mucins and peptides, assist in the entrapment and removal of living and nonliving antigens. Mucosa-associated innate immune responses determine cascades of downstream cellular and humoral immunity against IBV. Cellular immunity, particularly involving CD4+, CD8+, and other T-cell subsets, have been studied in mucosa-associated sites, especially the trachea. The strength of cellular immunity at mucosal sites has been associated with protection against IBV. Recently, the evaluation of mucosal immunity has shifted from traditional methods to quantitative assays of mRNA transcription of immune genes. This and other molecular-based approaches will likely boost our understanding of chicken mucosal immunity against virulent and vaccine strains of IBV. It has been well accepted that mucosal immunity plays an important role in pathogenicity, vaccinal immunity, and protection conferred against virulent IBV.

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

Infectious bronchitis virus (IBV) poses significant financial and biosecurity challenges to the commercial poultry farming industry. IBV is the causative agent of multi-systemic infection in the respiratory, reproductive and renal systems, which is similar to the symptoms of various viral and bacterial diseases reported in chickens. The avian immune system manifests the ability to respond to subsequent exposure with an antigen by stimulating mucosal, humoral and cell-mediated immunity. However, the immune response against IBV presents a dilemma due to the similarities between the different serotypes that infect poultry. Currently, the live attenuated and killed vaccines are applied for the control of IBV infection; however, the continual emergence of IB variants with rapidly evolving genetic variants increases the risk of outbreaks in intensive poultry farms. This review aims to focus on IBV challenge–infection, route and delivery of vaccines and vaccine-induced immune responses to IBV. Various commercial vaccines currently have been developed against IBV protection for accurate evaluation depending on the local situation. This review also highlights and updates the limitations in controlling IBV infection in poultry with issues pertaining to antiviral therapy and good biosecurity practices, which may aid in establishing good biorisk management protocols for its control and which will, in turn, result in a reduction in economic losses attributed to IBV infection.

Enhanced Protection by Recombinant Newcastle Disease Virus Expressing Infectious Bronchitis Virus Spike Ectodomain and Chicken Granulocyte-Macrophage Colony-Stimulating Factor.

We previously reported that recombinant Newcastle disease virus LaSota (rLS) expressing infectious bronchitis virus (IBV) Arkansas (Ark)-type trimeric spike (S) ectodomain (Se; rLS/ArkSe) provides suboptimal protection against IBV challenge. We have now developed rLS expressing chicken granulocyte-macrophage colony-stimulating factor (GMCSF) and IBV Ark Se in an attempt to enhance vaccine effectiveness. In the current study, we first compared protection conferred by vaccination with rLS/ArkSe and rLS/ArkSe.GMCSF. Vaccinated chickens were challenged with virulent Ark, and protection was determined by clinical signs, viral load, and tracheal histomorphometry. Results showed that coexpression of GMCSF and the Se from rLS significantly reduced tracheal viral load and tracheal lesions compared with chickens vaccinated with rLS/ArkSe. In a second experiment, we evaluated enhancement of cross-protection of a Massachusetts (Mass) attenuated vaccine by priming or boosting with rLS/ArkSe.GMCSF. Vaccinated chickens were challenged with Ark, and protection was evaluated. Results show that priming or boosting with the recombinant virus significantly increased cross-protection conferred by Mass against Ark virulent challenge. Greater reductions of viral loads in both trachea and lachrymal fluids were observed in chickens primed with rLS/ArkSe.GMCSF and boosted with Mass. Consistently, Ark Se antibody levels measured with recombinant Ark Se protein-coated ELISA plates 14 days after boost were significantly higher in these chickens. Unexpectedly, the inverse vaccination scheme, that is, priming with Mass and boosting with the recombinant vaccine, proved somewhat less effective. We concluded that a prime and boost strategy by using rLS/ArkSe.GMCSF and the worldwide ubiquitous Mass attenuated vaccine provides enhanced cross-protection. Thus, rLS/GMCSF coexpressing the Se of regionally relevant IBV serotypes could be used in combination with live Mass to protect against regionally circulating IBV variant strains.

Effects of a combination of Mass and Dutch variant as an inactivated vaccine against variant 2 avian infectious bronchitis virus challenge

The present study aimed to evaluate the effects of inactivated vaccines combining Mass and Dutch variants as vaccine boosters after H120 priming on inhibiting variant 2 viral load in the kidneys (as the target organ) and reducing fecal shedding. Ciliostasis score and antibody response were investigated as well. A total of 150 specific-pathogen-free (SPF) chicken were divided into six groups. All groups were vaccinated with a single dose of attenuated H120 vaccine except for two (no vaccine groups). Then, three groups received booster vaccines with inactivated polyvalent vaccines. At the 42 day of age, all groups were challenged with variant 2 viruses except for one (no vaccine group). Next, antibody response and infectious bronchitis virus viral load in kidneys and fecal shedding were evaluated by the enzyme-linked immunosorbent assay and quantitative real-time polymerase chain reaction. Then the ciliostasis score was investigated. In general, a vaccination program including a mass serotype attenuated vaccine (H120) as priming and polyvalent vaccines can significantly protect chickens against variant 2 infection through reducing viral load in kidneys and fecal shedding. Furthermore, the vaccination program can decrease ciliostasis in the epithelial ciliary tissue.

Virulence Properties of GI-23 Infectious Bronchitis Virus Isolated in Poland and Efficacy of Different Vaccination strategies.

Infectious bronchitis virus (IBV) is one of the most important poultry pathogens, leading significant economic losses worldwide. IBV is characterised by highly genetic, serotype, and pathotypic variability. Despite extensive immunoprophylaxis strategies, the emergence of new genetic lineages is frequently observed in the field, causing disease control to be more complicated. In the last decade, the spread of variants assigned to the GI-23 lineage of IBV (formerly known as Var2) started from Middle-Eastern countries and reached Europe in the last few years. Recently, the introduction and fast spread of Var2-like IBVs in Poland was reported. In this study, the virulence properties and efficacy of different vaccination programmes were evaluated against infection with the IBV GI-23 strain gammaCoV/Ck/Poland/G052/2016. The pathogenicity of the Var2 isolate was conducted in one-day-old and three-week-old SPF chickens and showed that the course of the disease is age dependent. Seven vaccination programmes using Mass, 793B, QX alone or in combination, and Var2 live vaccines were tested against the GI-23 infectious bronchitis virus challenge. All groups were scored according to the ciliostasis test at 5 days post challenge. Two immunoprophylaxis strategies generated full protection against gammaCoV/Ck/Poland/G052/2016 infection—Var2 and Mass used in one-day-old chickens boosted by a combination of the QX and 793B vaccine (both with a ciliostasis score of 0 and 100% protection).

Effects of Amino Acid-Bound Zinc and Manganese Feed Additives on MHC Haplotype Chickens Challenged with Infectious Bronchitis Coronavirus.

Major histocompatibility complex (MHC) congenic chicken lines have been used as a model to study infectious bronchitis virus (IBV) immune responses in chickens. Zinc (Zn) and manganese (Mn) are trace minerals that act as enzyme cofactors in cellular reactions. In addition, Zn is an important modulator of immune responses, especially in the respiratory tract. Zinc and Zn + Mn amino acid complex supplements were tested to alleviate the effects of an IBV challenge using relatively resistant and susceptible MHC congenic chicken lines. Prior to the challenge with IBV, the amino acid-bound supplements induced better weight gain in the IBV-resistant chicken line (331/B2) compared to the birds fed with the sulfate-delivered supplements. No body weight differences were detected between IBV-challenged and unchallenged 331/B2 birds supplemented with Zn in amino acid complex. A reduction of respiratory signs was observed in 335/B19 birds fed with the diet supplemented with Zn in amino acid complexes at 4 dpi. Compared to the sulfate-bound trace minerals, 331/B2 chickens fed with the amino acid-bound supplements presented milder clinical sign trends at 6 dpi and less severe airsacculitis at 14 dpi. The total antibody response in serum in 331/B2 birds fed with the amino acid-bound Zn ration was the highest among all groups tested. Both amino acid-delivered trace mineral supplements induced a slightly higher antibody response than the sulfate-bound ration in both chicken lines. This experiment provides insights into the effect of Zn and Mn on the immunity of chickens with known different susceptibilities to IBV.

Regulation of Immunity-Related Genes by Infectious Bronchitis Virus Challenge in Spleen of Laying Chickens.

Understanding of host pathogen interactions is important in planning strategies for effective control of the pathogen. The present study investigated the regulation of genes involved in the activation of splenic immune system in mature laying chickens challenged with T strain of infectious bronchitis virus (IBV). Among all the genes studied, the relative expression levels of Fas cell surface death receptor (FAS), interleukin 7 (IL7), IL18, proteasome subunit alpha 3 (PSMA3), major histocompatibility complex, class II (MHCII), interferon alpha (IFNα), immunoglobulin A (IgA), and nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB) were significantly (p < 0.05) upregulated, while Toll-like receptor 7 (TLR7) and TLR5 were significantly downregulated in the challenge compared with the control group. Genes such as vascular cell adhesion molecule 1 (VCAM1), FK506-binding protein 1B (FKBP1B), transforming growth factor-beta 3 (TGFB3), NLR family pyrin domain containing 3 (NLRP3), TYRO3 protein tyrosine kinase (TYRO3), TNF receptor-associated factor 3 (TRAF3), C-X-C motif chemokine receptor 4 (CXCR4), macrophage inflammatory protein-3 (MIP3A), TLR2-1, TLR3, and TLR21 were not altered in mRNA expression levels between the challenge and control groups. In conclusion, the splenic immune response to IBV infection involved the regulation of cytokines, TLRs and NF-κB.

Cytokine Responses in Tracheas from Major Histocompatibility Complex Congenic Chicken Lines with Distinct Susceptibilities to Infectious Bronchitis Virus.

The chicken major histocompatibility complex (MHC) B locus has been linked to resistance to infectious diseases. We have previously provided evidence that the MHC congenic chicken lines 331/B2 and 335/B19 differ in susceptibility to infectious bronchitis virus (IBV) strains M41 and ArkDPI in in vivo challenge experiments. Innate immune responses can be difficult to measure in vivo because they are nonspecific and can be triggered by environmental factors. In an attempt to address this issue, we used tracheal organ cultures derived from 331/B2 and 335/B19 birds to study local cytokine production after in vitro challenge with IBV M41. Interferon (IFN)-β, interleukin (IL)-1β, IL-6, and IL-10 gene expression and production were assessed. Tracheal organ cultures derived from 335/B19 birds presented an increased inflammatory response compared to 331/B2. However, it was not possible to discriminate between cytokine responses in IBV-infected and phosphate-buffered saline-treated tracheal organ cultures. Because tracheal processing entails physical damage to the trachea, it is possible that the tracheal organ cultures presented high levels of inflammation regardless of the IBV challenge. To demonstrate the effects of IBV on innate immune responses in the MHC congenic chicken lines, we performed an additional in vivo experiment that focused on cytokine gene expression and production in tracheas up to 60 hr after a challenge with IBV M41. Our results corroborate previous in vivo observations that suggest that detrimental local inflammatory responses in 335/B19 birds might be associated with their susceptibility to IBV and that inflammation does not necessarily lead to the assembly of an appropriate adaptive immune response. This work provides further insight into the increased susceptibility of 335/B19 birds to infectious bronchitis.

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

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.

Limited Protection Conferred by Recombinant Newcastle Disease Virus Expressing Infectious Bronchitis Spike Protein.

Recombinant Newcastle disease virus (NDV) LaSota (LS) expressing secreted trimeric spike (S)-ectodomain (Se) of infectious bronchitis virus (IBV) (rLS/IBV.Se) was developed and evaluated for protection conferred against IBV challenge. The IBV S-ectodomain protein, which is S excluding the transmembrane anchor and short cytoplasmic domain of S2, expressed from recombinant LS corresponds to an Arkansas (Ark)-type IBV. In a first experiment, chickens were primed at 1 day of age or primed at 1 day of age and boosted at 14 days of age with 104 50% embryo infectious doses (EID50)/bird of rLS/IBV.Se and challenged with a virulent Ark strain. A single vaccination proved completely ineffective at protecting chickens against challenge, whereas priming and boosting reduced clinical signs and tracheal lesions but did not reduce viral load in lachrymal fluids. In experiment 2, the vaccine dose was increased to 107 EID50/bird and a different virulent Ark strain was used for challenge. In addition, chickens were singly immunized on either day 1 or day 10 after hatch. NDV antibody levels detected in vaccinated chickens were moderate, with hemagglutination inhibition titers varying between 4 and 5 log2. Slightly higher antibody levels to NDV were observed in chickens vaccinated on day 10 versus day 1 but without the difference achieving statistical significance. In contrast, antibody responses measured using recombinant IBV S1 protein-coated ELISA plates were significantly greater in chickens vaccinated on day 10 than on day 1. The use of a higher rLS/IBV.Se dose substantially enhanced the success of a single vaccination compared to experiment 1. Signs and tracheal lesions were reduced more effectively in chickens vaccinated at day 10 after hatch. However, as in experiment 1, vaccination did not reduce the viral loads in tear fluids of challenged chickens. Similar results, in which no reduction in viral load in the trachea was apparent from rLS/IBV.S vaccination, have been obtained by others. Further work is needed to understand the immune responses induced by this recombinant virus that seems to provide some protection against the disease but does not reduce viral loads in the upper respiratory tract.

Ambient ammonia does not appear to inhibit the immune response to infectious bronchitis virus vaccination and protection from homologous challenge in broiler chickens

Commercial broilers are commonly exposed to gaseous ammonia (NH3) originating from degradation of nitrogen-containing excreta in the litter during the grow-out period. Ammonia concentrations in the air are higher in poorly ventilated houses and appear to coincide with the elevated incidence of respiratory disease occurring during the winter months. This study examined the effect of NH3 on the immune response to infectious bronchitis virus (IBV) vaccination and protection against homologous serotype challenge in commercial broiler chickens. One-day-old chicks were administered IBV vaccine and exposed to 30–60 ppm of NH3. At 28 DOA, birds were challenged oculonasally with a pathogenic homologous IBV, and protection was measured by viral detection, clinical signs, ciliostasis, and presence of airsacculitis. IBV-specific serum IgG and lacrimal fluid IgA titers, as well as Harderian gland (HG) immune cell phenotypes, were evaluated. Ammonia exposure was associated with an increased incidence of airsacculitis among non-vaccinated, challenged birds. Vaccinated, NH3-exposed birds were completely protected from IBV challenge. Ammonia had subtle effects on cilia morphology and function but did not affect vaccine or challenge virus replication and clearance, clinical signs, ciliostasis, tracheal histopathology scores, or immune responses. In the HG of vaccinated birds, the percent of leukocytes, MHC I+/MHC IIhi expression, IgM+ expression, and CD8+ expression was increased, while mucosal IgA and serum IgG titers were nominal. Non-vaccinated, IBV-challenged birds exhibited an increased percent of leukocytes, MHC I+/MHC IIhi expression, and IgM+ expression in the HG at 5 dpc, followed by increased mucosal IgA and serum IgG titers and CD8+ expression at 10–14 dpc. In contrast, vaccinated, IBV-challenged birds had a minimal increase in MHC I+/MHC IIhi expression, and serum IgG antibody titers in vaccinated birds increased rapidly. The results indicate that commercial broilers exposed to moderate levels of ambient NH3 are equally protected against IBV challenge if appropriately vaccinated, and the absence of robust immune activation in vaccinated, challenged birds suggests that the challenge virus was efficiently neutralized before establishing infection. In contrast, ambient NH3 exposure was associated with a higher incidence of airsacculitis in non-vaccinated, challenged birds, despite the apparent lack of differences in the immune response between birds in the NH3-exposed and NH3 control groups.

Genes involved in mitochondrial biogenesis and function may not show synchronised responses to mitochondria in shell gland of laying chickens under infectious bronchitis virus challenge

BackgroundEgg formation takes place in the oviduct of laying hens over a 24 h period. Infectious bronchitis virus (IBV) causes pathological lesions in the chicken oviduct. In the current study, mitochondrial counts were determined in three different segments of the oviduct during egg formation in laying chickens challenged with IBV T strain. Nuclear DNA encoded genes that are involved in mitochondrial biogenesis, fission and function were studied in the shell gland of the oviduct undergoing virus multiplication.ResultsIn the shell gland, the mitochondrial count was significantly lower (P < 0.05) in the challenged group, compared with the control group. However, it did not vary in response to IBV challenge in the isthmus and magnum regions of the oviduct. The gene succinate dehydrogenase complex, subunit A, flavoprotein variant (SDHA) was down-regulated in the shell gland by IBV challenge (P < 0.05), while other genes being studied did not show responses to the challenge (P > 0.05). Differential expression of the genes was observed at different time-points of egg-shell formation. The expression levels of citrate synthase (CS), cytochrome C, somatic (CYC, S) and sodium-potassium adenosine triphosphatase (Na+-K+ATPase) genes were significantly higher, while those of SDHA and dynamin related protein 1 (Drp1) genes were significantly lower, at 15 h compared with 5 h following oviposition of the previous egg. The expression level of peroxisome proliferator-activated receptor gamma coactivator 1-alpha (PGC-1α) did not show significant change at different time-points.ConclusionsIt was concluded that IBV T strain infection in laying hens reduced mitochondrial counts only in the shell gland region of the oviduct. The genes involved in mitochondrial biogenesis or function may not show synchronised responses to that of mitochondria in the shell gland of chickens under T strain of IBV challenge.