Characterization of the highly immunogenic VP2 protrusion domain as a diagnostic antigen for members of Birnaviridae family.

Birnaviridae is a family of viruses (birnaviruses) which consists of four genera, members of which cause diseases in fish, birds, mollusks, and insects. The genome of birnaviruses encodes the highly immunogenic VP2 capsid protein. In order to demonstrate that the VP2 protein can be exploited as a diagnostic antigen for birnaviruses, we developed a lateral flow assay based on the surface-exposed VP2 protrusion domain of a representative birnavirus, infectious bursal disease virus (IBDV) of serotype 1 which causes the highly devastating infectious bursal disease in chickens. The biophysical characterization of the purified domain reveals that the domain predominantly consists of ß-sheets, exists in a trimeric form, and remains folded at high temperatures, making it suitable for diagnostic purposes. Owing to its highly immunogenic nature and excellent biophysical properties, we employed the VP2 protrusion domain in a gold nanoparticle-based lateral flow assay for rapid detection of anti-IBDV antibodies in serum samples of infected chickens. Our results indicate that the domain binds anti-IBDV antibodies with high specificity during laboratory testing and on-site testing. The lateral flow assay reported here yields comparable results in a qualitative manner as obtained through a commercial enzyme-linked immunosorbent assay (ELISA). As VP2 is a common capsid protein of birnaviruses, the lateral flow assay can be generalized for other birnaviruses, and members of Tetraviridae and Nodaviridae families which contain homologous VP2 capsid proteins.

Seroprevalence of infectious bursal disease virus in local chickens in Udu Local Government Area of Delta State, South East Nigeria.

Infectious Bursal Disease Virus (IBDV) poses a great global threat to the poultry industry. Knowledge of the occurrence of the disease is important in the design and implementation of a control program, therefore this study determines the seroprevalence of IBDV in local chickens in Udu Local Government Area of Delta State. 250 chickens were bled by exsanguination and sera obtained were screened using Agar Gel Immunodiffusion (AGID) test. The seropositivity was 51.6%, which is indicates endemicity of the disease. Biosecurity and good sanitary measures are recommended. Molecular characterization of the strains should be carried out for inclusion in generic vaccines.

Oral exposure of broiler breeder hens to extra thyroxine modulates early adaptive immune responses in progeny chicks.

Based on the findings of a recent study suggesting a decreased cold-induced ascites incidence in broiler progeny from hyperthyroid (HYPER) breeder hens, and a controversy on the effects of hyperthyroidism on immunocompetence, the present study was conducted to determine the probable adverse effect of induced maternal hyperthyroidism on immune function in progeny chicks. Breeder hens (n = 88) were randomly allotted to the control or HYPER groups and received common or thyroxine (T4)-added (1 mg/L) water, respectively. The hens were artificially inseminated, and hatching eggs (n = 924) were incubated. Thereafter, the male hatchlings (n = 288) were reared for 42 d, and several cellular and humoral immune responses were evaluated at standard or low ambient temperature. Prevaccination antibody titers to Newcastle disease, infectious bronchitis, and infectious bursal disease virus were higher in HYPER chicks during 1 wk of age, although not different in their dams. For primary response to SRBC administered at 7 d of age, HYPER chicks recorded higher total, IgM (d 14), and IgG (d 21) anti-SRBC antibody titers. Higher cutaneous basophilic hypersensitivity response in HYPER chicks (d 10) was not observed at 35 d of age. Carbon clearance assay showed no difference, but in vitro lymphoproliferative response to concanavalin A was higher in 19-d-old HYPER chicks, independent of temperature treatment. An increase in lymphocyte percentage coincided with a decreased heterophil percentage and heterophil to lymphocyte ratio (d 14) in the HYPER group. The weight of lymphoid organs in progeny was not influenced by the oral exposure of dams to extra T4. Independent of T4 treatment, cold exposure was generally associated with decreased immune functions at early stages. The data suggested that oral exposure of broiler breeder hens to 1 mg/L of T4 not only had no adverse effect on immune function, but also modulated early adaptive immune responses in progeny chicks for which the causal mechanisms remain to be unraveled.

Omega-3 polyunsaturated fatty acids enrichment alters performance and immune response in infectious bursal disease challenged broilers.

BACKGROUND: Infectious bursal disease (IBD) results in economic loss due to mortality, reduction in production efficiency and increasing the usage of antibiotics. This study was carried out to investigate the modulatory roles of dietary n-3 polyunsaturated fatty acids (PUFA) enrichment in immune response and performance of IBD challenged broiler chickens. METHODS: A total of 300 day old male broiler chicks were assigned to four dietary n-3 PUFA ascending levels as the treatment groups (T1: 0.5; T2: 8.0; T3: 11.5; T4: 16.5) using combinations of tuna oil and sunflower oil. All diets were isocaloric and isonitrogenous. On day 28, all birds were challenged with IBD virus. Antibody titer, cytokine production, bursa lesion pre and post-challenge and lymphoid organ weight were recorded. RESULTS: On d 42 the highest body weight was observed in the T2 and T3 and the lowest in T4 chickens. Feed conversion ratio of the T2 broilers was significantly better than the other groups. Although productive parameters were not responded to the dietary n-3 PUFA in a dose-dependent manner, spleen weight, IBD and Newcastle disease antibody titers and IL-2 and IFN-γ concentrations were constantly elevated by n-3 PUFA enrichment. CONCLUSIONS: Dietary n-3 PUFA enrichment may improve the immune response and IBD resistance, but the optimum performance does not coincide with the optimum immune response. It seems that dietary n-3 PUFA modulates the broiler chicken performance and immune response in a dose-dependent manner. Thus, a moderate level of dietary n-3 PUFA enrichment may help to put together the efficiency of performance and relative immune response enhancement in broiler chickens.

Immunomodulatory and hepatoprotective role of feed-added Berberis lycium in broiler chicks.

BACKGROUND: A large number of plants and their isolates have been shown to potentiate immunity. Some plants exert anti-inflammatory and anti-stress effects, others hepatoprotective activity. In this study, 320 1-day-old broiler chicks were randomly divided into four major groups A, B, C and D and fed rations supplemented with 0, 15, 20 and 22.5 g Berberis lycium kg⁻¹ ration respectively. Each group was further divided into two subgroups, one vaccinated against Newcastle disease (ND) and infectious bursal disease (IBD), the other non-vaccinated. Antibody titre against IBD and ND, relative weight of lymphoid organs, post-challenge morbidity and mortality, serum hepatic enzymes and total serum protein were observed. RESULTS: Group C had higher anti-IBD and anti-ND antibody titres. Relative bursa weight in groups C and D was higher until day 28, but birds in group C performed better at later stages of examination. Relative spleen weight was highest in group C. During initial stages there was no effect on relative thymus weight, but at later stages the effect was significant. Groups C and D performed similarly in terms of relative thymus weight. The birds were challenged to field IBD through intramuscular injection at a dose rate of 0.5 mL per bird. Post-challenge morbidity was lowest in groups C and D, while treatment significantly (P < 0.001) affected mortality amongst affected (morbid) birds. Levels of serum alanine aminotransferase and alkaline phosphatase were lowest in group C. Serum protein was similar in all groups and in both vaccinated and non-vaccinated broiler chicks. CONCLUSION: Berberis lycium added to feed at 20 g kg⁻¹ is effective in improving immunity against ND and IBD as well as liver function in broiler chicks.

Antox® and Bactofort® mitigated the haematological alterations induced by a very virulent infectious bursal disease virus in chicks.

The study investigated the mitigating effects of two probiotics on blood parameters of ISA Brown chicks inoculated with a very virulent infectious bursal disease virus (vvIBDV). Two hundred chicks were assigned into four groups of 50 birds each. Groups A and B were administered Antox® in water and Bactofort® in feed daily from 1 to 42 days of age and inoculated with a vvIBDV at 28 days and C and D served as positive and negative controls, respectively. Blood samples were examined for changes in packed cell volume (PCV), haemoglobin concentration (Hb), red blood cell (RBC), total white blood cell (TWBC), heterophil and lymphocyte counts seven days post inoculation. The PCV between groups A and C differed (P < 0.05) and in group B it was higher (P < 0.05) than that of group C. The Hb concentration between groups A, B and C differed (P < 0.05). There was a difference (P < 0.05) in RBC counts between groups A, B, C. Differences in TWBC between group A and C were significant (P < 0.05) and TWBC in group B was higher (P < 0.05) than that of group C. There was a significant difference in heterophil (P < 0.05) and lymphocyte (P < 0.05) count between group A and C, and B and C. Heterophil/lymphocyte ratio was significantly higher in positive control compared to groups A, B, C. Antox® and Bactofort® mitigated the deleterious effects of vvIBDV on blood parameters and can assist in cases of IBD outbreak.

Detection of infectious bursal disease virus (IBDV) antibodies using chimeric plant virus-like particles.

The aim of the present study is to use Physalis mottle virus (PhMV) coat protein (CP) as a scaffold to display the neutralizing epitopes of Infectious bursal disease virus (IBDV) VP2. For this, three different chimeric constructs were synthesized by replacing the N-terminus of PhMV CP with tandem repeats of neutralizing epitopes of IBDV VP2 and expressed in Escherichia coli. Expression analysis revealed that all the three recombinant chimeric coat protein subunits are soluble in nature and self-assembled into virus-like particles (VLPs) as evidenced through sucrose density gradient ultracentrifugation. The chimeric VLPs were characterized by various biochemical and biophysical techniques and found that they are stable and structurally sound. When the chimeric VLPs were used as coating antigen, they were able to detect IBDV antibodies. These results indicated that the chimeric VLPs can be used as potential vaccine candidates for the control of IBDV, which needs to be further evaluated in animal models.

Effects of IBDV infection on expression of ghrelin and ghrelin-related genes in chicken.

Ghrelin is a peptide hormone that plays a modulatory role in the immune system. Studies have demonstrated that mammal ghrelin level is influenced by pathological status. However, it has not been reported whether chicken ghrelin level changes during pathogen infection. This study was designed to investigate changes of ghrelin levels in chickens infected with infectious bursal disease virus (IBDV) and to explore the relationship between ghrelin changes and bursal damage, and inflammatory cells infiltration induced by IBDV. The results showed that (1) plasma ghrelin concentration increased after IBDV infection. It reached a peak at 10443.6 ± 2612.9 pg/mL on 2 dpi, which was about 100-fold as high as that of the control. Then it decreased sharply on 3 dpi, which was only 31.7% as that of 2 dpi, and remained stable until 5 dpi. Meanwhile, ghrelin and ghrelin-related gene, ghrelin-o-acyltransferase (GOAT), and growth hormone secretagogue receptor (GHSR) mRNA expression levels in bursa were also increased after IBDV infection, and reached the peak on 2 dpi at 149, 28.8, and 117.2-fold higher than that of the control, respectively. Then they decreased and remained at a higher status. Correlation analysis showed that plasma ghrelin concentration and ghrelin, GOAT, and GHSR mRNA expressions in bursa were strongly associated with IBDV VP2 mRNA expression in bursa. (2) The damage of bursa was the most severe on 5 dpi with a histopathological score of 12. It had no direct correlation with plasma ghrelin level and ghrelin, GOAT, and GHSR mRNA expressions in bursa. However, the number of inflammatory cells infiltrating into bursa, which was the highest on 2 and 3 dpi, showed significant a positive correlation with the ghrelin and GHSR mRNA expression. Presumably chicken ghrelin may function as an anti-inflammatory factor. In conclusion, IBDV infection upregulates the expression of ghrelin and ghrelin-related gene in chickens, and chicken ghrelin may play an important regulatory role during pathogen infection.

Tissue distribution, shedding and environmental detection of infectious bursal disease virus genome following infection of meat chickens at two ages.

OBJECTIVE: To compare the effects of infectious bursal disease virus (IBDV) infection of commercial meat chickens at 0 and 16 days old (d.o.) and determine if IBDV vRNA is quantifiable in litter and dust samples. METHODS: Ross meat chickens (n = 60) were orally infected or not with IBDV at 0 or 16 d.o. Blood and faecal samples were collected longitudinally to 28 days post infection (dpi) from six chickens and tissues collected weekly from three euthanased chickens. Relative bursal weight was recorded postmortem. IBDV antibody titres in sera were measured using ELISA and VCN was determined in tissues, faeces, litter and dust using qRT-PCR. RESULTS: Chickens infected at 16 d.o. had earlier and more severe bursal atrophy, earlier and higher IBDV vRNA load in lymphoid organs and an earlier and greater antibody response to infection than those infected at 0 d.o. Faecal shedding of IBDV between 2 and 6 dpi was observed in both groups followed by cessation with the 0 d.o. group and re-initiation of shedding at 28 dpi. IBDV was readily detected and quantified in litter and dust samples. CONCLUSIONS: The presence of significant maternal antibody (MAb) titres in 0 d.o. chickens provided protection against IBDV replication and bursal atrophy at 7 and 14 days post infection. The reduced titres of MAb present at 16 d.o. did not prevent rapid IBDV replication and early marked bursal atrophy. The observed resistance of 0 d.o. chickens is likely to be a combination of MAb inhibition of IBDV and true age resistance of neonatal chicks. Measurement of IBDV in litter and dust may have research or diagnostic application.

Effect of infectious bursal disease virus insult on iron, copper, and zinc concentration in liver, bursa of Fabricius, spleen, pancreas, and serum of chickens.

The effect of a systemic disease on the dynamics of iron, zinc, and copper in chickens fed ad libitum was examined by infecting 10-day-old specific pathogen-free chickens with infectious bursal disease virus (IBDV). Liver, bursa of Fabricius, pancreas, spleen, and serum were sampled in 10 controls and 10 challenged chickens at 3-day intervals postinfection (PI) for 15 days. The samples were analyzed using atomic absorption spectroscopy. Serum levels were similar to that reported in the literature. Concentrations of iron and zinc did not change significantly in the pancreas, but there was an increase in copper in infected pancreatic tissue on days 9 and 15 PI. Iron concentration in the spleen showed a significant increase on days 6, 9, and 15 PI, whereas zinc was only significantly increased on day 15 PI. There was no significant change in copper concentrations in the spleens of infected chickens vs. controls. This finding is in line with previously reported data. The results showed that the liver was not a major tissue where iron and zinc were sequestered, as previous data have shown in mammals. Instead, the bursa of Fabricius had significantly increased levels of both iron and zinc in infected tissue vs. control tissue from 9 days PI on. Furthermore, the bursa had increased levels of copper in the latter portion of the study. These findings suggest that the bursa of Fabricius rather than the liver is the major organ for metallic ion sequestering during IBDV infection.