Arkansas Delmarva Poultry Industry Research Articles

Infectious Bronchitis Virus Immune Responses in the Harderian Gland upon Initial Vaccination.

In recent years, Arkansas Delmarva Poultry Industry (ArkDPI)-derived infectious bronchitis (IB) virus (IBV) vaccines have been used to characterize the immune responses of chickens subsequent to vaccination on day of hatch or beyond. Perhaps because ArkDPI vaccines display increased heterogeneity, the results on cell immune responses have shown ambiguity. In the current study, we investigated the effects of vaccination with a highly stable and homogeneous Massachusetts (Mass)-type vaccine on days 1 or 7 of age on Harderian gland (HG) responses. Confirming previous studies, both IBV serum antibodies and lachrymal IgA levels were greater upon vaccination on day 7 compared with vaccination on day 1 of age. Unlike results with ArkDPI viruses, a clear trend was detected for both B and T cells in the HG after Mass-type vaccination. Consistent with antibody responses, B- and T-helper (CD3+CD4+) cell frequencies were higher in birds vaccinated on day 7 of age. Cytotoxic T cells (CD3+CD8+) were also increased compared with chickens vaccinated on day 1 of age. Depending on the most likely age of IB outbreaks to occur in a particular region, postponing the first IBV vaccination may optimize immune responses.

Effects of Chicken MHC Haplotype on Resistance to Distantly Related Infectious Bronchitis Viruses

The major histocompatibility complex (MHC) B locus of chickens has been associated with resistance to different viral diseases. We previously provided evidence that chicken lines expressing MHC haplotypes B2 and B19 exhibit different resistance to a challenge with infectious bronchitis virus (IBV) Massachusetts 41 (M41). In the current study, we attempted to determine if those differences were true for genetically diverse IB viruses, i.e., IBV M41 and Arkansas-Delmarva poultry industry (ArkDPI). Clinical, pathologic, molecular, and immunologic outcomes were compared. Our results showed subtle clinical and pathologic differences between the two MHC chicken lines tested. Clinical differences were observed in respiratory signs at 2 days postinfection (dpi) in M41-infected birds. Pathologic differences were detected in viral load at 2 dpi in M41-infected birds and in tracheal epithelial thickness at 6 dpi in ArkDPI-infected birds. Substantial differences were observed in antibody responses at 14 dpi. The transcriptome analysis showed that B19 chickens highly expressed genes related to inflammatory and innate immune responses. This increased immune gene expression detected in B19 birds at 6 dpi did not lead to enhanced antibody production at 14 dpi. On the other hand, B2-haplotype chickens highly expressed genes related to cell responses, suggesting that B2 is able to diligently control the infection. Although not identical, genes triggered by M41 and ArkDPI are part of communal pathways and suggest similar immune and cell responses to both IBV genotypes. This work provides modest evidence for differential resistance to IBV by chickens displaying different MHC haplotypes as well as insights into the expression of a variety of genes after IBV replication in the host.

Kidney Cell-Adapted Infectious Bronchitis Virus Arkansas Delmarva Poultry Industry Vaccine Confers Effective Protection Against Challenge.

We previously demonstrated that adaptation of an embryo-attenuated infectious bronchitis virus (IBV) Arkansas Delmarva Poultry Industry (ArkDPI)-derived vaccine to chicken embryo kidney (CEK) cells shifted the virus population towards homogeneity in spike (S) and nonstructural protein genes. Moreover, the typical Ark vaccine subpopulations emerging in chickens vaccinated with commercial Ark vaccines were not detected in chickens vaccinated with the CEK-adapted virus. In this study, chickens vaccinated with a low dose (1.6 × 10(3) EID50/bird, where EID50 is 50% embryo infectious dose) of CEK-adapted Ark vaccine at 5 days of age showed a significant reduction of IBV RNA in lachrymal fluids and decreased incidence of IBV RNA detection in tracheal swabs 5 days after challenge compared to unvaccinated challenged chickens. In a second experiment, 5-day-old chickens were vaccinated with 10(4) or 10(5) EID50/chicken of CEK-adapted Ark vaccine, and protection was compared to chickens vaccinated with 10(5) EID50/chicken of the commercial ArkDPI-derived vaccine from which the CEK-adapted virus originated. All vaccinated chicken groups showed a significant reduction of respiratory signs and viral load 5 days after Ark virulent challenge compared to unvaccinated challenged controls. No viral subpopulations different from the challenge virus were detected in chickens vaccinated with CEK-Ark after challenge. In contrast, IBV S1 sequences differing from the predominant population in the challenge virus were detected in several chickens vaccinated with the commercial Ark attenuated vaccine. From an applied perspective, the CEK-adapted IBV ArkDPI-derived vaccine is an improved and effective vaccine candidate with which to protect chickens against virulent Ark-type strains.

Hatchery Spray Cabinet Administration Does Not Damage Avian Coronavirus Infectious Bronchitis Virus Vaccine Based on Analysis by Electron Microscopy and Virus Titration.

studies in our laboratory showed that the Arkansas-Delmarva Poultry Industry (Ark-DPI) vaccine given to 1-day-old chickens by hatchery spray cabinet replicated poorly and failed to adequately protect broilers against homologous virus challenge, whereas the same vaccine given by eye-drop did replicate and the birds were protected following homologous virus challenge. To determine if mechanical damage following spray application plays a role in failure of the Ark-DPI vaccine, we examined the morphology of three Ark-DPI vaccines from different manufacturers using an electron microscope and included a Massachusetts (Mass) vaccine as control. One of the Ark-DPI vaccines (vaccine A) and the Mass vaccine had significantly (P < 0.005) fewer spikes than the other two Ark-DPI vaccines. We also found that the Ark-DPI and Mass vaccines had significantly (P < 0.005) fewer spike proteins per virus particle when compared to their respective challenge viruses. This observation is interesting and may provide some insight into the mechanism behind infectious bronchitis virus attenuation. No obvious differences were observed in virus morphology and no consistent trend in the number of spikes per virion was found in before- and after-spray samples. We also determined the vaccine titer before and after spray in embryonated eggs and found that both Ark-DPI and Mass vaccines had a similar drop in titer, 0.40 logi and 0.310 logi, respec10ively. Based on these data, it appears that mechanical damage to the Ark-DPI vaccine is not occurring when delivered by a hatchery spray cabinet, suggesting that some other factor is contributing to the failure of that vaccine when given by that method.

Comparison of vaccine subpopulation selection, viral loads, vaccine virus persistence in trachea and cloaca, and mucosal antibody responses after vaccination with two different Arkansas Delmarva Poultry Industry -derived infectious bronchitis virus vaccines.

Factors responsible for the persistence of Arkansas Delmarva Poultry Industry (ArkDPI)-derived infectious bronchitis vaccines in commercial flocks and the high frequency of isolation of ArkDPI-type infectious bronchitis viruses in respiratory cases are still unclear. We compared dynamics of vaccine viral subpopulations, viral loads, persistence in trachea and cloaca, and the magnitude of infectious bronchitis virus (1BV)-specific antibody induction after vaccination with two commercial ArkDPI-derived Arkansas (Ark) serotype vaccines. One of the vaccines (coded vaccine B) produced significantly higher vaccine virus heterogeneity in vaccinated chickens than the other vaccine (coded A). Chickens vaccinated with vaccine B had significantly higher viral loads in tears at 5 days postvaccination (DPV) than those vaccinated with vaccine A. Vaccine B also induced a significantly higher lachrymal immunoglobulin M response at 11 DPV, an earlier peak of IBV-specific lachrymal immunoglobulin A, and higher serum antibodies than vaccine A. In addition, a significantly higher proportion of birds vaccinated with vaccine B had vaccine virus detected in the trachea at 20 DPV than those vaccinated with vaccine A. Furthermore, the virus detected at 20 DPV in most of the chickens vaccinated with vaccine B was a single specific subpopulation (subpopulation 4) selected from multiple vaccine subpopulations detected earlier at 5 and 7 DPV in the same chickens. On the other hand, a higher proportion of chickens vaccinated with vaccine A had virus detected in cloacal swabs at 20 DPV. Thus we found differences in mucosal antibody induction and selection and persistence of vaccine viruses between two ArkDPI-derived vaccines from different manufacturers. The higher vaccine virus heterogeneity observed in chickens vaccinated with vaccine B compared with those vaccinated with vaccine A may be responsible for these differences. Thus the high frequency of Ark IBV viruses in the field may be due to the inherent ability of some ArkDPI-derived vaccine viruses to be selected and persist in vaccinated chickens. Vaccine virus persistence may offer genetic material for recombination or may undergo mutations with the potential to result in increased virulence.

The Proportion of Specific Viral Subpopulations in Attenuated Arkansas Delmarva Poultry Industry Infectious Bronchitis Vaccines Influences Vaccination Outcome

We investigated the significance of differing proportions of specific subpopulations among commercial Arkansas (Ark) Delmarva poultry industry (DPI) vaccines with regard to vaccination outcome. Two ArkDPI-derived vaccines that contain a higher proportion of viruses with S1 genes that become selected during replication in chickens exhibited more rapid establishment of those selected subpopulations in chickens, produced significantly higher viral loads in tears, and induced higher antibody responses compared with two other ArkDPI vaccines with lower proportions of viruses that become selected in chickens. The presence of higher proportions of selected subpopulations was also associated with a significantly higher incidence of respiratory signs early after vaccination and in some cases more severe tracheal lesions. However, one of the ArkDPI-derived vaccines with a lower proportion of selected subpopulations, despite producing a lower viral load in tears, also induced a higher incidence of respiratory signs later after vaccination and more severe tracheal lesions. Furthermore, one of the ArkDPI-derived vaccines with a higher proportion of selected subpopulations, despite producing a higher viral loads in tears, resulted in less severe tracheal damage. These discrepancies suggest that infectious bronchitis virus (IBV) load in tears may not always predict degree of tracheal damage and that phenotypic characteristics other than S1 may also be involved in severity of vaccine reactions following ArkDPI vaccine administration. We observed lower antibody responses to the vaccines that produced lower viral loads, which might contribute to the persistence of Ark serotype IBV vaccines observed in commercial flocks.

The Proportion of Specific Viral Subpopulations in Attenuated Arkansas Delmarva Poultry Industry Infectious Bronchitis Vaccines Influences Vaccination Outcome

The Proportion of Specific Viral Subpopulations in Attenuated Arkansas Delmarva Poultry Industry Infectious Bronchitis Vaccines Influences Vaccination Outcome