Infectious Bursal Disease Virus Antibody Research Articles

Efficacy and Safety of an Inactivated Novel Variant Infectious Bursal Disease Virus in Broiler Chickens

The infectious bursal disease virus (IBDV) is severe and highly contagious, causing high mortality and immunosuppression in chickens worldwide. A new novel variant, IBDV (nVarIBDV), has recently emerged in Asian countries, including Malaysia, highlighting the need to develop a new vaccine against this strain due to the inadequacy of existing commercial vaccines in protecting chickens from nVarIBDV infection. Therefore, the current study aimed to evaluate the efficacy and safety of inactivated nVarIBDV as a potential vaccine candidate in broiler chickens. A total of 65 one-day-old Arbo Acres broiler chickens were randomly divided into three groups (five animals in each group with four replications) before the challenge, namely A, B, and C. Groups A and B were immunized subcutaneously at day old with inactivated nVarIBDV (107 EID50/0.2 ml), and Group B was boosted at day 14. Group C was an unimmunized control. The experimental animals were divided into three subgroups and were challenged with pathogenic nVarIBDV (105 EID50/1.0ml) on day 28 post-inoculation through ocular and oral routes. The challenge sub-groups were named ACH, BCH, and CCH, respectively. The live body weight, bursa weight, and blood samples of the chickens were recorded. Gross lesions were examined, and samples of the bursa of Fabricius were collected from all the groups for histological evaluation. All the chickens appeared healthy and normal throughout the trial. Body weight increased in all groups without significant differences. The bursa weight and the bursa-to-body weight ratio of the booster group (Group B) were significantly higher than the non-booster and control groups. Gross lesions were not observed in the investigated groups. The challenged control group had higher bursa lesion scoring than the vaccinated groups. The IBDV antibody titer of challenged chickens in ACH, BCH, and CCH groups was higher than those of unchallenged groups A, B, and C at 35 days post-inoculation. The IBDV antibody titer of challenged chickens in group B was higher than challenged chickens in groups A and C (ACH and CCH). In conclusion, the inactivated nVarIBDV demonstrated safety and efficacy, with the booster Group (B) showing elevated humoral immune responses compared to the non-booster group. Keywords: Antibody, Chicken, Efficacy, Inactivated vaccine, Novel variant infectious bursal disease virus

Detection of infectious bursal disease virus (IBDV) antibodies in backyard poultry by using indirect enzyme linked immunosorbent assay

Infectious bursal disease virus (IBDV) causes infectious bursal disease in poultry and poses a major challenge to the poultry industry globally. This study aimed to measure seroprevalences and so detect exposure to IBDV in backyard poultry in the selected zone of Horro Guduru Wollega. A cross-sectional study was conducted from January 2021 to November 2022. Blood samples were collected for serum extraction from 384 backyard chickens in the Horro and Horro Bulluq districts. IBDV antibody detection was conducted using an indirect ELISA serological diagnostic test. Questionnaires assessed poultry owners? knowledge and health/hygiene management practices regarding the disease. The over all seroprevalence of IBDV was 14.84%. Significant variations in seroprevalence were seen based on district, bird age, bird sex, and flock size. Limited owner experience (just 1-3 years), disposing of carcasses in pits, and poor hygiene on the backyard premises were associated with higher IBDV seroprevalence. In conclusion, IBDV seroprevalence was linked to chicken management practices. Recommendations include improving poultry management among owners to control IBDV. The study indicates backyard poultry in the region have considerable IBDV exposure, and control should focus on improving management practices identified as high-risk, such as pit disposal of carcasses and poor hygiene.

Seroprevalence and associated factors of infectious bursal disease (IBD) in indigenous chicken in eastern province in Rwanda

ABSTRACT The status of Infectious bursal disease (IBD) in indigenous chickens and backyard poultry in Rwanda has not been previously elucidated. This cross-sectional study was to determine the seroprevalence of infectious bursal disease in indigenous chickens and to identify the associated factors. The study was been done in three districts in the Eastern province of Rwanda where blood from 364 indigenous chickens were collected. ID Screen® IBD indirect enzyme-linked immunosorbent assay (ELISA) test was used to detect IBD antibodies in these birds. 145 questionnaires were also administered to poultry farmers to obtain information on biosecurity measures and associated factors to IBD outbreaks. The study revealed 48.4% (176/364) prevalence of the chicken with IBDV antibodies with statistical significance (P < .05) among/between location and age groups. The questionnaire revealed that there were other important associated factors which included chicken scavenging for seed as a source of food (59.3% of farmers reported), absence of routine vaccination (53.8%), live chickens are purchased from the open market with no information about IBD outbreaks and vaccination (30.0%), open disposal of dead chickens suspected of IBD (58.9%). IBD virus antibodies are present in indigenous chicken in Eastern Rwanda hence further investigation to better understand the epidemiology of IBD virus in indigenous chickens is desired and more research is needed to identify the role of indigenous chickens in the spread of IBD virus in Rwanda.

Effects of two supplements on rate of infectious bursal disease virus antibody decay and response to a very virulent strain of the virus in pullet chicks

This study evaluated the effects of two supplements on the rate of infectious bursal disease virus (IBDV) antibody decay and response to a very virulent strain of the virus (vvIBDV) in pullet chicks. Two hundred ISA Brown 1-day-old chicks were divided into four groups (AD), each containing 50 birds. Chicks in group A were given supplement A, and B supplement B, from 1-day-old to 42 days of age, while C (positive control) and D (negative control) were not given any supplement. Groups A, B and C were challenged with vvIBDV at 28-days-old. Blood was collected from each bird, serum was obtained and analysed for antibodies against IBDV. The rate of antibody decay and response to vvIBDV were determined. There was significantly higher (p&lt;0.05) antibody titre in chicks of groups A and B than in C and D at days 28, 35 and 42. The rate of antibody decay was lower in chicks of groups A (-57.7%) and B (-65.4%) than in C (-72.1%) and D (-74.2%) at 28-days-old. The antibody response rate was higher in groups A (+76.4%) and B (+71.1%) at 35-days-old. There was lower antibody decline rate in groups A (-22.4%) and B (-29.0%) compared to C (-38.6%) and D (-51.4%) at 42-days-old. These supplements decreased IBD antibody decay, enhanced antibody response to vvIBDV infection and decreased antibody decline by vvIBDV. Therefore, the use of these supplements in IBD outbreaks to enhance immune responses is recommended.

Modeling Infectious Bursal Disease Virus (IBDV) Antigenic Drift In Vitro

Infectious bursal disease virus (IBDV) vaccines do not induce sterilizing immunity, and vaccinated birds can become infected with field strains. Vaccine-induced immune selection pressure drives the evolution of antigenic drift variants that accumulate amino acid changes in the hypervariable region (HVR) of the VP2 capsid, which may lead to vaccine failures. However, there is a lack of information regarding how quickly mutations arise, and the relative contribution different residues make to immune escape. To model IBDV antigenic drift in vitro, we serially passaged a classical field strain belonging to genogroup A1 (F52/70) ten times, in triplicate, in the immortalized chicken B cell line, DT40, in the presence of sub-neutralizing concentrations of sera from birds inoculated with IBDV vaccine strain 2512, to generate escape mutants. This assay simulated a situation where classical strains may infect birds that have suboptimal vaccine-induced antibody responses. We then sequenced the HVR of the VP2 capsid at passage (P) 5 and 10 and compared the sequences to the parental virus (P0), and to the virus passaged in the presence of negative control chicken serum that lacked IBDV antibodies. Two escape mutants at P10 had the same mutations, D279Y and G281R, and a third had mutations S251I and D279N. Furthermore, at P5, the D279Y mutation was detectable, but the G281R mutation was not, indicating the mutations arose with different kinetics.

Sero-Prevalence and Risk Factors for Infectious Bursal Disease in Local Chicken on Backyard Production System in Selected Districts of Ilubabor Zone, South Western Ethiopia

Introduction Gumboro is an acute, highly contagious, and immunosuppressive viral disease of young chickens less than 17-weeks. However, in local chicken flocks of Ilubabor, there is no known sero-status of the disease. Methods To address this information gap, a cross-sectional study was conducted in local backyard chicken flocks of three districts of Ilubabor Zone where chick mortality and morbidity were a big problem. The objectives of the study were to estimate the seroprevalence of infectious bursal disease virus (IBDV) and to assess its risk factors. Result Out of 418 serum samples tested, 180 were positive and the overall chicken level seroprevalence of the IBDV antibody in the study area was found to be 43.10% (95% CI: 38.40-47.85) and flock-level seroprevalence was 45.63% (73/160) (95%CI: 37.91-53.34) with almost all test positive flock chickens were seropositive. Multivariable analysis at chicken level showed that the odds of IBDV seroprevalence was significantly high in Metu and Bilo Nopa districts, in purchased, in female and adult chickens. Also, it was high at flock level in chickens mixed with exotic breeds, in flocks having greater than 5 chickens. Conclusion This study shows that IBDV is circulating in the chicken population of Ilubabor at a high prevalence level. Therefore, further studies on serotypes and strains of IBDV identification should be carried out to design suitable control and prevention measures.

A Cross-Sectional Seroepidemiological Study on Infectious Bursal Disease in Backyard Chickens in the Mymensingh District of Bangladesh.

Infectious bursal disease (IBD) is a highly contagious disease that causes significant economic loss in chickens. A cross-sectional study was conducted in the Mymensingh district of Bangladesh to determine the seroprevalence of IBD virus (IBDV) antibodies in backyard chickens and their association with different epidemiological risk factors. A total of 460 serum samples were randomly collected from backyard chickens that had not been previously vaccinated against IBDV. The collected sera were examined using an enzyme-linked immunosorbent assay (ELISA). Data on epidemiological risk factors were collected through face-to-face interviews with owners and subjected to both uni- and multivariable risk analyses to determine their association with IBDV infection. Using ELISA, the overall seroprevalence of IBDV antibodies in backyard chickens was 83.4% (95% confidence interval: 79.8%–86.6%), among which, a significantly higher seroprevalence was recorded in females (83.4%, 345/350), 4–6 weeks age group (95.3%, 244/256), and unhealthy (95.0%, 57/60) backyard chickens than those of males, other age groups, and healthy chickens, respectively. Furthermore, chickens reared in free-ranging housing systems (93.3%, 280/300) and poor-conditioned houses (98.0%, 147/150) showed a significantly higher seropositivity of IBDV antibodies than those reared in separated housing systems and other hygienic-conditioned houses, respectively. Moreover, compared with their counterparts, a higher but nonsignificant seroprevalence of IBDV antibodies was observed in backyard chickens that were selected from Fulbaria Upazila (88.8%; 80/90) and which were brought from the marketplace (85.7%, 60/70). A higher seropositivity of IBDV antibodies was shown to be statistically associated with various critical epidemiological risk factors, indicating that field strains of IBDV were exposed in backyard chickens and could be readily transferred horizontally. Proper prevention and control methods, villagers' awareness of IBD, and the rapid and widespread use of seroepidemiological investigations could help to reduce the spread of IBDV infection in backyard chickens.

Characterizations of glucose-rich polysaccharides from Amomum longiligulare T.L. Wu fruits and their effects on immunogenicities of infectious bursal disease virus VP2 protein

The aim of this study is to explore the characterization of Amomum longiligulare T.L. Wu fruits polysaccharide (ALP) and their immune enhancement effects. Two homogeneous polysaccharides (ALP1 and ALP2) were isolated from the fruits. The structural characterization results showed that ALP1 (26.10 kDa) and ALP2 (64.10 kDa) were both mainly composed of glucose. Furthermore, ALP1 was consisted of (1,2)-α-D-Glcp, (1,2,3)-α-D-Glcp and T-α-D-Glcp, while ALP2 was consisted of T-α-D-Glcp, (1,3)-α-D-Glcp and (1,3,6)-α-D-Glcp. Afterwards, the immune enhancement effects of two polysaccharides were evaluated by determining their effects on immunogenicities of infectious bursal disease virus (IBDV) VP2 protein. Chickens were immunized with IBDV VP2 protein accompanied with ALP1/ALP2. And the results indicated both ALP1 and ALP2 promoted the weights and bursa of fabricius indexes of chickens. In addition, both two polysaccharides increased specific IBDV antibody levels, while ALP1 possessed higher immune enhancement ability and was expected to be an adjuvant for IBDV VP2 protein.

SEROLOGICAL SURVEY OF INFECTIOUS BURSAL DISEASE ANTIBODY IN LOCAL CHICKEN

Serological evidence for infectious bursal disease virus antibody in local chicken in Ago-Iwoye area of Ogun State was detected using agar gel precipitation test. 51 out of the 98 sera samples tested were positive for precipitating antibody against infectious bursal disease.

Generation of recombinant VP3 protein of infectious bursal disease virus in three different expression systems, antigenic analysis of the obtained polypeptides and development of an ELISA test.

Infectious bursal disease virus (IBDV), which infects young chickens, is one of the most important pathogens that harm the poultry industry. Evaluation of the immune status of birds before and after vaccination is of great importance for controlling the disease caused by this virus. Therefore, the development of low-cost and easy-to-manufacture test systems for IBDV antibody detection remains an urgent issue. In this study, three expression systems (bacteria, yeast, and human cells) were used to produce recombinant VP3 protein of IBDV. VP3 is a group-specific antigen and hence may be a good candidate for use in diagnostic tests. Comparison of the antigenic properties of the obtained polypeptides showed that the titres of antibodies raised in chickens against bacteria- or human-cell-derived recombinant VP3 were high, whereas the antibody level against yeast-derived recombinant VP3 was low. The results of an enzyme-linked immunosorbent assay (ELISA) of sera from IBDV-infected chickens demonstrated that the recombinant VP3 produced in E. coli would be the best choice for use in test systems.

Research Note: Detection of infectious bursal disease virus antibodies in free-living wild birds in Zaria, Nigeria

Infectious bursal disease virus (IBDV) is an immunosuppressive pathogen of poultry causing great economic losses to the poultry industry. In this study, the IBDV antibodies were detected in captured free-living wild birds in Zaria, Nigeria. One hundred and fifty free-living wild birds, comprising 30 birds each of 5 different species, were sampled over a period of 9 months. Blood samples were collected from each bird, and harvested sera were tested for IBDV antibodies using enzyme-linked immunosorbent assay. Results indicated IBDV seroprevalences in speckled pigeon (6.67%) and cattle egret (3.33%). In conclusion, the detection of IBDV antibodies in free-living wild birds in this study is indicative of previous natural exposure of these birds to the virus. These species of wild birds could therefore serve as carriers of these viruses and, consequently, transmit these viruses to chickens.

Comparative in vivo pathogenicity study of an ITA genotype isolate (G6) of infectious bursal disease virus.

Recently, a new genotype of infectious bursal disease virus (IBDV), named ITA, was detected in IBD-vaccinated Italian broilers. Genome characterization revealed ITA to be a genetically different IBDV, belonging to genogroup 6 according to a recently proposed IBDV classification. The currently available clinical data do not allow any definition of the degree of pathogenicity of the ITA-IBDV isolates. In the present study, a pathogenicity trial was conducted by the oral inoculation of specific-pathogen-free (SPF) chickens. Birds were housed in poultry isolators and inoculated at 35days of age with an ITA-IBDV isolate (35 birds) or a strain belonging to the G1a genogroup as a comparison (35 birds). Control birds (25 birds) were contextually mock-inoculated with sterile water. Birds were observed daily for clinical signs and at 0, 7, 14, 21 and 28days post-inoculation (dpi) were bled for IBDV antibody detection. At 2, 4, 7, 14, 21 and 28dpi, five birds from each of the inoculated groups, and three from the control group, were euthanized and subjected to a post-mortem examination; the bursa:body weight and thymus:body weight ratios were calculated. Microscopic lesions of the bursa and thymus were scored on the basis of lymphoid necrosis and/or depletion or cortex atrophy, respectively. Both viruses induced a subclinical course of disease, as neither clinical signs nor mortality were recorded during the study, even in the presence of typical IBDV gross and microscopic lesions. Bursal damage, measured by the bursa:body weight ratio, was more noticeable and precocious after ITA-IBDV inoculation. Histopathology scores of the bursa, indicative of rapid lymphoid depletion, confirmed the aggressiveness of the ITA-IBDV strain in this organ. This study showed that, although the ITA-IBDV strain tested causes infection with a subclinical course, it induces severe damage to lymphoid tissues. Therefore, its circulation in birds might be a threat for the poultry industry and may jeopardize the success of the production cycle.

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.

Assessment of antibody assay methods in determination of prevalence of infectious bursal disease among local chickens and guinea fowls in Kwara state, North Central Nigeria.

Aim:This study aimed to assess available assay methods for infectious bursal disease (IBD) diagnosis and seromonitoring in local birds. It also sought to know the prevalence of IBD antibodies among local chickens and guinea fowls in Kwara state, North Central Nigeria.Materials and Methods:Sera were obtained from local chickens and guinea fowls and IBD virus (IBDV) antibodies were assayed using enzyme-linked immunosorbent assay (ELISA), indirect hemagglutination (IHA) test, and agar gel immunodiffusion (AGID) test.Results:A total of 265 sera were obtained from local birds during dry and wet seasons. ELISA recorded the highest prevalence of 81.1% (215/265) while IHA and AGID detected IBDV antibodies in 183 (69.1%) and 122 (46%) birds, respectively. Significant differences were established for IBD-positive sera based on the assay method used, bird species, and seasons.Conclusion:This study indicated that ELISA is the most sensitive and reliable assay method while AGID is the least. It also showed that there is a high prevalence of IBDV antibodies among local birds which were not vaccinated, and this implies a high IBDV activity among these bird species in the study area. This may have significant epidemiological implications on the spread of the virus to exotic bird reared in the rural areas on a commercial scale. Thus, this study suggests continuous surveillance, awareness campaign, and advocacy for vaccination of indigenous birds against IBD.

The effects of dietary soybean isoflavone on immunity in Chinese yellow-feathered broilers challenged with infectious bursal disease virus

AbstractTo investigate the effects of soybean isoflavone (SI) on immunity in infectious bursal disease virus (IBDV)-infected broilers, chicks were fed the same basal diet supplemented with 0 (non-infected control), 0 (infected control), 10, 20 or 40 mg/kg SI for 44 days. At 21 days old, chickens were inoculated with bursal infectious dose causing 50% morbidity of the IBDV BC 6/85 strain by the eye-drop and nasal route (except for non-infected controls). Results showed that, over 1–23 days post-infection (dpi), there was a significant interaction between SI supplementation level and time: high-level SI supplementation increased peripheral T lymphocyte proliferation, percentages of CD3+, CD4+and CD8+T lymphocytes, CD4+to CD8+ratio, serum concentrations of IgA, IgM and IgG, and IBDV antibody titres. Except for serum IgA and IgM, these variables increased over time with far higher values at 23 dpi than earlier. Compared with non-infected controls, IBDV inoculation decreased peripheral T lymphocyte proliferation at 3 dpi, percentages of CD3+, CD4+and CD8+T lymphocytes, and serum IgG, IgM concentration at 23 dpi, and increased IBDV antibody titres at 7, 15 and 23 dpi. Supplemental SI quadratically increased peripheral T lymphocyte proliferation, CD4+to CD8+ratio and serum IgA concentration at 3 dpi, percentages of CD3+, CD4+and CD8+T lymphocytes at 3 and 23 dpi, and serum IgM concentration and IBDV antibody titres at 23 dpi. These results indicate that dietary SI improved cellular and humoral immunity of IBDV-infected birds and may enhance resistance of Yellow-feathered broilers to infectious diseases.

Multi-year serological evaluation of three viral agents in the Adélie Penguin (Pygoscelis adeliae) on Ross Island, Antarctica

Serological assays are commonly used in wildlife health studies to screen for exposure of an individual or a population to infectious agents. Such assays can therefore provide useful information regarding the health status of an individual or for determining the prevalence of a pathogen within a population. In this study, serological assays of three viral agents have been conducted on the Adelie Penguin (Pygoscelis adeliae) on Ross Island, Ross Sea, Antarctica. We sampled adult Adelie Penguins during three consecutive summer breeding seasons (2010–2011, 2011–2012 and 2012–2013), and tested those samples for antibodies to avian influenza A virus, Newcastle disease virus, and infectious bursal disease virus. No antibodies were detected for avian influenza A virus in any season. Two samples in 2012–2013 were positive for Newcastle disease virus antibodies and a total of 10 samples were positive for infectious bursal disease virus antibodies during this study. This information establishes baseline data for these three viruses in Adelie Penguins at this location and can be used for future comparisons of disease prevalence in this population.

Serological survey of Infectious Bursal Disease Antibodies amongst birds in Keffi, Nassarawa State, Nigeria

Infectious Bursal Disease (IBD) is an acute, immunosuppressive disease of significant threat to the poultry industry in Nigeria and vaccination has been reported as the best method of control. This study was conducted between November and December 2015 to establish the occurrence of infectious bursal disease antibodies in exotic chickens from some selected backyard poultry farms and local chickens slaughtered in keffi central market, Nassarawa State. Sera collected randomly from two hundred birds were subjected to Agar Gel Precipitation Test (AGPT) for qualitative analysis at the virology laboratory (FCVMLT), National Veterinary Research Institute, Vom. The assay showed 35% of exotic birds had IBD virus antibodies while local birds indicated absence of detectable antibodies with significant P&lt;0.05 breed association (Χ2= 42.5, df=2). However, there was no association (P&gt;0.05) with age in both breeds and IBDV antibodies (Χ2=0.802, 3.13, df=1). The presence of antibodies in exotic breeds suggests evidence of post vaccination protective antibodies due to sero-conversion rather than anti-IBDV antibodies associated with disease. Absence of infectious bursal disease virus antibodies in local birds suggests high vulnerability to potential IBD outbreaks posing a risk of financial losses to stakeholders. In conclusion, this sero-survey of Infectious bursal disease antibodies in exotic birds suggest evidence of vaccination and the need to vaccinate local birds. Awareness campaign program amongst rural and backyard poultry keepers in the study community on the need to protect their commercial exotic and free scavenging birds against infectious bursal disease is thus recommended.

The immune enhancement activity of exopolysacharide from marine bacteria on the IBDV immune response induced by B87 vaccine

Abstract Infectious bursal disease (IBD), which is caused by infectious bursal disease virus (IBDV), is a fatal or immunosuppressive disease of young chickens. Immunization is still an important way to prevent the outbreak of the disease. The purpose of this study was aimed to investigate the immune enhancement activity of two kinds of exopolysacharide (EPS), on the IBDV immune response induced by an IBD vaccine (B87). B87 vaccine plus EPS or B87 only were performed twice (at 7 and 14-day old) on commercial Three-Yellow-Chickens. The antibodies and IL-1 level were evaluated after immunization. The vvIBDV challenging was performed at 28-day old. The protection were assessed at 3 and 7 days post infection (dpi). The results showed that IBDV antibodies and IL-1 level in 04 EPS+B87 and 09 EPS+B87 groups were significantly higher than B87 group. Further, the IL-1 level in groups received EPS only were significantly higher than the group received PBS only. High levels of IBDV antibody and IL-1 lasted at least for 5 weeks. After challenged with vvIBDV, the morbidity in 04 EPS+B87 and 09 EPS+B87 groups was 20%, lower than any other. The BBIX of bursa and thymus in 04 EPS+B87 and 09 EPS+B87 groups were significantly higher than the B87 group but lower than negative control, suggested that either the 04 and 09 EPS might have the ability to repair the immune organ damages induced by B87 vaccine. The trend of T cells (both CD4+ and CD8+) and B cells number, and the viral load, at 3 and 7 dpi, respectively, were consistent with the changing trend in BBIX value. We concluded that either 04 or 09 EPS showed the activity of immune enhancement in Three-Yellow-Chickens, the combination of EPS and B87 could induce higher titers of anti-IBDV antibody and protect chickens from vvIBDV challenge.

Seroprevalence of infectious bursal disease virus antibodies in some species of poultry in Maiduguri, Nigeria

This study was aimed at determining the antibodies of IBDV in some poultry species in Maiduguri, Nigeria. A total of 944 serum samples were collected from village chickens, broilers, layers, ducks, turkeys and geese in Maiduguri and tested for IBDV antibodies using inzyme linked Immunosorbent assay (ELISA) and a seroprevalence of 46.6% was recorded. The species distribution showed that 33.4% of local chickens (134/401), 67.3% of layers (35/52), 50.8% of broilers (159/313), 60.6% of turkeys (77/127), 65.5% of ducks (19/29) and 72.7% of geese (16/22) sampled were positive for IBDV antibodies. Males showed a seroprevalence of 70% while females recorded 30%. IBDV seropositive sera showed that samples from broilers reacted with 31.5% middle OD values and turkeys with 9.4% middle OD values. Samples from other species reacted with lower OD values. Samples from other species reacted with lower OD values. Presence of IBDV antibodies in species other than chickens suggested that different bird species might have IBDV and could serve as reservoirs for IBDV transmission. Because of this threat to poultry industry, there is need for continuous surveillance of IBDV in all poultry species so as to institute effective preventive measures against the disease. Keywords: ELISA, Infectious bursal disease virus, IgG, Poultry species, Serum samples

Recombinant VP2 expressed in baculovirus and adjuvanted with TIR-TLR7: a vaccine candidate against infectious bursal disease virus

Currently, a variety of immunostimulatory molecules are used as adjuvants in combination with poor immunogenic recombinant infectious bursal disease virus (IBDV) vaccine antigen. TIR domain of Toll-like receptors (TLRs) triggers the interleukin-1 (IL-1) signaling cascade which plays a critical role in immune responses against infectious agents. For this study, the bacmid DNA pBac-VP2 of a field isolate was generated and transfected to Sf9 insect cells to produce recombinant VP2 (rVP2). In addition, based on in silico analysis, the cDNA encoding the conserved TIR domain of TLR7 (TIR-TLR7) contain the IL-1 receptor was synthesized and used as an adjuvant. We further evaluated the ability of rVP2/TIR-TLR7 vaccine candidate to induce specific immune responses in specific pathogen-free (SPF) chickens and compared the efficacy by challenging with the virulent IBDV. The results indicate that rVP2/TIR-TLR7-adjuvanted vaccine elicited humoral immune responses and protected chickens against IBDV infection. Higher levels of neutralizing IBDV antibody titers were observed in chickens intramuscularly immunized with rVP2/TIR-TLR7 than those injected with rVP2 alone. The antibody titers were higher in chickens which received booster injection. Furthermore, chickens immunized with rVP2/TIR-TLR7 in the prime and boost groups had significant protection against a virus challenge. The survival rate was 70 and 90% after the primary and booster rVP2/TIR-TLR7 vaccinations, respectively, and indicated that they were protected from virus challenge. Despite the unvaccinated control group, the immunized chickens with rVP2/TIR-TLR7 did not show any clinical signs and histopathological changes of the bursa. Our results demonstrate that TIR-TLR7 is a potential vaccine adjuvant and can induce antigen-specific immune responses induced by rVP2 for protection against IBDV infection.