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PubMedDate not supplied

Molecular characterization of infectious bursal disease virus from commercial poultry in the United States and Latin America.

From June 1999 to September 2001, 216 bursal samples from broiler farms in the United States and from countries of Latin America were submitted to the Poultry Diagnostic and Research Center at the University of Georgia for the purpose of genotyping field infectious bursal disease viruses (IBDVs). The reverse transcriptase-polymerase chain reaction (RT-PCR) was used to amplify a 248-bp product, encompassing the hypervariable region of VP2 gene. The genotyping was conducted by restriction fragment length polymorphism (RFLP) analysis with six restriction endonucleases, DraI, SacI, TaqI, Sty, BstNI, and SspI. For the 150 samples received from the United States, 125 samples (83.3%) were RT-PCR positive for the presence of IBDV. One hundred positive samples (80%) had RFLP identical to the variant Delaware E strain, whereas 10 samples (8.0%) exhibited a RFLP pattern similar to this antigenic variant. Other IBDV strains such as Grayson Laboratory strain (GLS), Lukert, PBG-98, Delaware A, and the vaccine strains Sal-1 and D-78 were also detected. Two samples exhibited a pattern similar to the standard challenge (STC) strain, and seven strains (5.6%) were not classified by RFLP. Sixty-six bursal samples previously inactivated with phenol were received from Latin American countries. IBDV strains with analyzed genotypes similar to the Lukert strain were predominantly detected in Mexico. IBDV strains similar to variant E were detected in Colombia and Ecuador. Peru and Venezuela exhibited a higher heterogeneity of IBDV strains due to the detection of classic Delaware type as well as GLS variant strains. IBDV strains detected from Brazil and Dominican Republic exhibited RFLP patterns identical to very virulent IBDV strains prevalent in several countries in Europe, Asia, and Africa.

Animals↗

PubMed2006

Molecular analysis of infectious bursal disease virus from bursal tissues collected on FTA filter paper.

We investigated the feasibility of using FTA filter cards for the storage of bursas of Fabricius containing infectious bursal disease virus (IBDV) and for IBDV detection by reverse transcriptase (RT)-polymerase chain reaction (PCR), and characterization by restriction fragment length polymorphism (RFLP) or nucleotide sequencing. The FTA card is a cotton-based cellulose membrane containing lyophilized chemicals that lyses many types of bacteria and viruses. IBDV was inactivated upon contact with the FTA as shown by the inability of the virus to be propagated in embryonating chicken eggs. Viral RNA in minced bursas or stamped bursas could be amplified by RT-PCR (VP2 gene fragment, 248 base pairs) after storage on FTA for at least 15 days at room temperature or 8 mo at -20 C. Analytical sensitivity of the test was between 0.5-5 ng of RNA template or 5 x 10(1) mean tissue culture infective dose (TCID50)/FTA spot. Detection rate of IBDV in domestic clinical samples collected on FTA or collected by the non-FTA standard procedure was 36.7% and 41.7%, respectively, which represents 88% agreement. Detection of IBDV from FTA cards inoculated with bursal tissues in the laboratory or in the field was 36.7% and 37.1%, respectively. Detection of IBDV from FTA samples when the cards were inoculated with bursal tissues and sent through customs into the United States was 32.9%. Analysis of the amplified products showed that molecular characterization of IBDV by RFLP or nucleotide sequencing is feasible in bursas stored on FTA at 25 C for 1-3 mo or at -20 C for at least 8 mo. The use of FTA for the collection of bursal tissues and simultaneous inactivation of IBDV allows the movement of specimens within the United States and also from outside the United States in compliance with federal regulations and in a manner adequate for molecular characterization.

Animals↗

PubMed1979

Effects of early infectious bursal disease virus infection on immunity to Newcastle disease in adult chickens.

Experimental infection with infectious bursal disease virus (IBDV) at hatching or at 3 weeks of age in White Leghorn chickens without maternally derived antibodies to IBDV resulted in a depression in the antibody response of chickens to Newcastle disease vaccination (NDV) at 4 weeks of age and increased the susceptibility of those birds to challenge with virulent NDV. Infection of non-IBDV immune chickens with IBDV at hatching, but not at 3 weeks of age, also depressed the antibody response of chickens vaccinated at 18, 30, or 42 weeks of age, but had no effect on the susceptibility of those birds to challenge with virulent NDV. Prior exposure to IBDV did not alter disease resistance afforded a bird by NDV vaccination at 18, 30, or 42 weeks of age. However, IBDV infection at hatching did render chickens that were not vaccinated against ND more susceptible to challenge with virulent NDV at 21, 33, or 45 weeks of age than unvaccinated birds which were not infected with IBDV or unvaccinated chickens infected with IBDV at 3 weeks of age.

Age Factors↗

PubMedDate not supplied

In situ hybridization, immunohistochemistry, and in situ reverse transcription-polymerase chain reaction for detection of infectious bursal disease virus.

Development of molecular techniques for the detection of infectious bursal disease virus (IBCV) is an important area of research. An in situ hybridization (ISH) test was developed with a 491-bp cDNA fragment derived from the VP2 gene of IBDV. The fragment was amplified and simultaneously labeled with incorporation of digoxigenin-11-dUTP in a nested polymerase chain reaction (PCR) assay. The resulting digoxigenin-labeled 491-bp nested PCR product was used as probe for ISH to detect and localize IBDV RNA in formalin-fixed, paraffin-embedded bursae of Fabricius from chickens both experimentally infected as well as commercially reared. Bursae from six clinically ill commercial broilers suspected to be IBDV infected were examined by ISH and immunohistochemistry. In two samples, IBDV infection was detected by both ISH and immunohistochemistry, whereas in the other two histologically normal bursae, IBDV was detected only by ISH. Two commercial chickens with atrophied bursae were negative by both ISH and immunohistochemistry. No positive IBDV stained cells were in RNase treated sections from infected birds, uninfected chickens, or reovirus-infected chickens. The ISH test developed herein resulted in important modifications, which makes it superior to other previously published procedures. We also described a direct in situ reverse transcription-polymerase chain reaction method for the amplification and detection of IBDV genome in formalin fixed, paraffin-embedded bursae of Fabricius with a single primer pair with direct incorporation of digoxigenin-11-deoxyuraciltriphosphate (dUTP) into the amplicon. Both molecular tests with their important modifications represent improved detection of IBDV.

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PubMedDate not supplied

Sequence of precursor polyprotein gene (segment A) of infectious bursal disease viruses isolated in Korea.

The coding regions of segment A of two recent Korean very virulent (vv) infectious bursal disease virus (IBDV) isolates (KK1 and KSH) and one atypical IBDV isolate (K310) were amplified by reverse transcriptase-polymerase chain reaction, sequenced, and compared with published sequences for IBDV. The overall amino acid sequence similarity of the KK1 and KSH strains compared with foreign vvIBDV strains was between 97.43% and 98.02%. The KK1 and KSH strains, like vvIBDV strains, share unique amino acid residues at positions 222(A), 256(I), 294(I), and 299(S). The sequence of K310 strain was markedly different from other IBDV strains. The K310 strain had 12, 2, and 1 unique amino acid substitutions in the VP2 hypervariable region, VP4, and VP3 gene, respectively, and 3 of 12 substitutions in a VP2 hypervariable region were found in two hydrophilic regions known to be involved in antigenic determination. Also, the K310 strain had 222(S) and 254(S), which were found in variant IBDV strains. The SWSASGS heptapeptide is conserved in all Korean IBDV isolates. By phylogenetic analysis, KK1 and KSH were categorized in one group with foreign vvIBDV isolates, but K310 isolate was categorized in a separate group that was differentiated from the other IBDV strains compared. The K310 strain seemed to be evolved from a separate lineage of IBDV strain.

Amino Acid Substitution↗

PubMedDate not supplied

Safety and efficacy of in ovo administration of infectious bursal disease viral vaccines.

In ovo vaccination against Marek's disease virus and infectious bursal disease virus (IBDV) in commercial broilers in the United States is common. Little information exists as to the safety and efficacy of intermediate IBDV vaccines given in ovo. Experiments were initiated to determine the safety and efficacy of three commercially available live intermediate IBDV vaccines by in ovo route. Commonly used vaccines were given at 18 days of embryonation to specific-pathogen-free (SPF) broiler embryos (first and second study) or to commercial broiler embryos (third study) that had maternal antibody against IBDV. When any of the antigenic standard vaccines was given at full dose to SPF embryos, embryonic and 3-wk posthatch mortality increased. Vaccines also caused significant microscopic lesions in the bursa of Fabricius at 1 and 3 wk posthatch. In contrast, there was no adverse effect on embryonic or posthatch mortality when vaccines were given at half dose to SPF or commercial broiler embryos. However, significant microscopic lesions were evident at 1 and 3 wk posthatch in the bursae of SPF embryos given the vaccines at half dose. When vaccines were given at half dose to commercial broiler embryos, lesions were evident at 1 but not 3 wk of age. In the third study, in ovo vaccinated chickens were challenged with either a virulent standard (APHIS) or antigenic variant (variant E) IBDV virus at 3 wk of age. All vaccines produced at least 87% protection against the standard and 60% protection against the variant challenge IBDV, as measured by bursal weight to body weight ratios. This study was the first to examine the safety and efficacy of the three commonly used intermediate IBDV vaccines given in ovo in protection against standard and antigenic variant IBDV challenge viruses.

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PubMedDate not supplied

The exacerbating effect of infectious bronchitis virus infection on the infectious bursal disease virus-induced suppression of opsonization by Escherichia coil antibody in chickens.

Chickens infected with infectious bronchitis virus (IBV) and infectious bursal disease virus (IBDV) commonly develop secondary infection of the respiratory tract with Escherichia coli, resulting in significant economic losses. To understand the host factors that may contribute to the E. coli infection, we investigated macrophage-mediated E. coli phagocytosis, intracellular bacterial killing, and development of opsonizing antibody in previously uninfected chickens and in those infected with IBV, IBDV, and IBDV plus IBV. Macrophages from the peripheral blood and the respiratory tracts of chickens infected with IBV or IBDV plus IBV efficiently performed in vitro phagocytosis of E. coli in the presence of positive-control serum (i.e., E. coli antiserum produced in normal chickens). Those macrophages also had adequate bactericidal activity, indicating that IBV and IBDV infections had not affected their phagocytic activity or bactericidal function. The phagocytic activity of macrophages remained unaffected (P < 0.05) when the positive-control serum was replaced with E. coli antiserum produced in chickens infected with IBV alone. However, when E. coli antisera raised in IBDV-infected and, especially, that produced in IBDV plus IBV-infected chickens were supplemented, the percentage of phagocytosis and number of bacteria ingested per phagocyte were significantly (P < 0.05) less. These results indicate that although IBDV alone has the potential to markedly reduce opsonizing ability of antibody, this effect is significantly (P < 0.05) exacerbated by IBV infection.

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PubMedDate not supplied

Molecular characterization of seven field isolates of infectious bursal disease virus obtained from commercial broiler chickens.

Specific-pathogen-free sentinel birds were used as an initial biological system to isolate infectious bursal disease virus (IBDV) field isolates from commercial broiler farms exhibiting recurrent respiratory problems and poor performance. Reverse transcription (RT)-polymerase chain reaction (PCR) was used to amplify a 248-bp product encompassing the hypervariable region of the IBDV VP2 gene. Restriction fragment length polymorphism (RFLP) analysis of the RT-PCR products was performed with the restriction endonucleases DraI, SadI, TaqI, StyI, BstNI, and SspI. Two isolates (619 and 850) exhibited a RFLP pattern characteristic of Delaware variant E IBDV. Restriction enzyme digestion for four isolates (625, 849, 853, and 11,153) revealed unmatched RFLP patterns when compared with reference IBDV strains. Nucleotide and deduced amino acid sequence analyses of the VP2 hypervariable region for these six isolates revealed identity (96.3% up to 98%) with Delaware E variant IBDV strain. However, serine at position 254, which is characteristic of Delaware variant strains, was substituted by asparagine in these six isolates. The seventh IBDV isolate (9109) also exhibited a unique RFLP pattern, which included the SspI restriction site, which is characteristic of very virulent (vv) IBDV strains. Nucleotide and amino acid sequence analyses of the hypervariable region for this isolate revealed identity (90%) with the standard challenge strain. However, the leucine residue at position 294 was substituted by isoleucine. This substitution corresponds to one of the amino acids that are conserved in the vvIBDV strains. Antigenic index studies of the predicted amino acid sequence of the hypervariable region of VP2 from isolates 619, 625, 849, 850, 853, and 11,153 exhibited a profile almost identical to variant E, whereas the isolate 9109 exhibited a profile characteristic of standard IBDV strains.

Amino Acid Sequence↗

PubMedDate not supplied

Response of B congenic chickens to infection with infectious bursal disease virus.

Six congenic lines of chickens that differ from the parental inbred line RPRL-15I5 for genes in the major histocompatibility (B) complex were used to study the influence of the B haplotypes on the response of chickens to infection with virulent infectious bursal disease virus (IBDV) at 1 day or 4 weeks of age, and on the antibody response to vaccination with live or inactivated oil-emulsion (OE) IBDV vaccines at 7 weeks of age. IBDV-induced immunodepression and lesions in the bursa, spleen, and thymus in chickens infected with virus at 1 day of age were of the same degree of severity, regardless of line of chickens used. The response of blood cells to the mitogens phytohemagglutinin-M and concanavalin A was elevated in chickens infected with IBDV at 1 day of age. In an experiment conducted to study the effect of the B haplotype on IBDV infection in 4-week-old chickens, B congenic line C-12 (B12B12) showed the highest susceptibility to clinical IBD, with mortality of 79%. No detectable difference in the serological response to vaccination with live or OE IBDV vaccines was noted among chickens of various congenic lines. We conclude that the B haplotypes may influence IBDV-induced mortality, but not immunodepression or severity of lesions in lymphoid organs, or the antibody response to live or OE IBDV vaccines.

Animals↗

PubMedDate not supplied

Response of susceptible versus immune chicks to killed, live-modified, and wild infectious bursal disease virus vaccines.

Modified infectious bursal disease virus (IBDV) administered ocularly to either susceptible or passively immune chicks did not induce protection against bursal atrophy by wild IBDV, while intramuscular (IM) or intrabursal (IB) injection protected susceptible chickens. No protection was obtained in passively immune chickens vaccinated IM or IB. Susceptible and passively immune chickens vaccinated with a single dose of killed-virus suspension (KVS) did not become resistant to wild IBDV challenge. A killed-virus multiple emulsion (KVME) induced partial protection (3/5) against challenge 28 days after subcutaneous vaccination of three-day-old susceptible chickens. At 35 and 42 days old, all susceptible chickens were protected by KVME. Protection by passive antibodies was observed in unvaccinated, KVS-, and KVME-vaccinated chickens challenged at 10 and 17 days of age. Protection was only partial in passively immune chickens vaccinated with KVME after passive antibodies were no longer protective to unvaccinated and KVS-vaccinated chicks. Modified IBDV was detected two days post-IB inoculation only in the bursa of Fabricius of susceptible chickens, while wild IBDV was found also in the thymus, spleen, and blood. No evidence of virus was found in immune chickens inoculated IB with modified IBDV. The growth of wild IBDV was limited to the bursa of Fabricius in immune chickens. Furthermore, the intensity of fluorescence, as well as the number of positive bursa cells, was low when compared with fluorescence in the bursa of susceptible chickens infected with wild IBDV.

Animals↗

PubMedDate not supplied

Characteristics and serologic studies of two serotypes of infectious bursal disease virus in turkeys.

Two serotypes of infectious bursal disease virus (IBDV) were distinguished using the virus-neutralization test. An IBDV isolate from chickens, two commercial IBDV vaccine viruses, and an IBDV isolate from turkeys were designated serotype I. Two IBDV isolates from turkeys were designated serotype II. A common antigen shared by serotype I and serotype II viruses was detected using an indirect immunofluorescent assay. The virions of both IBDV serotypes were determined to be nonenveloped icosahedrons with diameters ranging from 58 to 60 nm. The virion densities of one serotype I isolate and two serotype II isolates were similar (1.32 g/ml). Twenty-three turkey breeder flocks and 22 commercial turkey flocks from Ohio, North Carolina, and Indiana were tested for antibodies to the two IBDV serotypes. Seventy percent of the 23 breeder flocks had antibody titers to serotype I, and 75% had antibody titers to serotype II. None of the 22 commercial flocks had antibodies to serotype I, and 77% had antibody titers to serotype II. Antibodies to serotype I were detected only in breeder flocks that were vaccinated using a commercial serotype I IBDV vaccine. Only antibodies to serotype II viruses were naturally widespread in the flocks tested.

Animals↗

PubMedDate not supplied

Efficacy of three live vaccines against highly virulent infectious bursal disease virus in chickens with or without maternal antibodies.

Since 1990, highly virulent infectious bursal disease virus (IBDV), which induces high mortality, has been infecting even vaccinated flocks in Japan. We report the efficacy of three live vaccines that are available in Japan. Two mildly attenuated strains (A and B) and one intermediate strain (C) were each tested both in specific-pathogen-free (SPF) chickens and in commercial chickens that have maternal antibodies against IBDV. Chickens were vaccinated at 20 days old and challenged with highly virulent IBDV 10 days post-vaccination. Protection was determined 7 days after challenge by measuring bursa/body weight ratios, histopathological lesions, and antibody responses to IBDV. All three lie vaccines conferred protection to SPF chickens. However, only vaccine C protected 100% of vaccinated commercial chickens against highly virulent IBDV; Vaccines A and B respectively protected three-fourths and none of vaccinated commercial chickens from severe bursal lesions. Vaccines A, B, and C and highly virulent IBDV induced bursal lesions in 3%, 0%, 23%, and 61% of inoculated commercial chickens, respectively. These results suggest that serological determination of the optimum vaccination time for each flock is required to effectively control highly virulent IBDV in the field. The optimum vaccination timing could be approximated by titrating the maternal IBDV antibodies of 1-day-old chicks by an enzyme-linked immunosorbent assay or by an agar gel precipitin test.

Animals↗

PubMedDate not supplied

Antigenic and immunogenic properties of baculovirus-expressed infectious bursal disease viral proteins.

Genomic segment A of the variant Md infectious bursal disease virus (IBDV) was amplified by reverse transcriptase/polymerase chain reaction, cloned, and expressed in the baculovirus expression system. Three different baculovirus recombinants expressing the genes encoding VP2, VP2/VP4, and the complete polyprotein (VP2/VP4/VP3) were prepared. The three antigens were used in separate enzyme-linked immunosorbent assays, and each detected antibodies against the variant IBDV strains Md, Del-A, Del-E, and GLS and the classic IBDV strain D78 throughout a 14-wk period following vaccination. Eight-week-old specific-pathogen-free (SPF) chickens were inoculated subcutaneously using the VP2/VP4 or VP2/VP4/VP3 baculovirus recombinant or wild-type baculovirus-infected insect cell lysates. Virus-neutralizing antibodies were detected in the VP2/VP4 and VP2/VP4/VP3 baculovirus-inoculated birds at 13 days postinoculation (PI) and at 43 days PI when titrated against Md IBDV. No virus-neutralizing antibody titer was observed in the negative controls or wild-type baculovirus-inoculated birds. One-week-old SPF chickens were inoculated with the VP2, VP2/VP4/VP3 baculovirus recombinants or wild-type baculovirus-infected insect cell lysates. The birds were boosted 2 wk later and challenged at 4 wk of age with 0.5 ml/bird classic STC IBDV (10(2) median embryo infective dose [EID50]/ml) or variant Md IBDV (10(5) EID50/ml) via the oral/nasal route. The VP2 and VP2/VP4/VP3 baculovirus-inoculated birds were partially protected against challenge with the classic STC IBDV. The birds were protected against clinical disease and death but not bursal damage, whereas the wild-type baculovirus-inoculated birds exhibited clinical signs of disease, 13% mortality, and bursal damage. When challenged with the variant Md IBDV, neither the VP2, VP2/VP4/VP3 baculovirus recombinants nor the wild-type baculovirus elicited protection against bursal damage and atrophy.

Animals↗

PubMed2001

Induction of apoptosis in vitro by the 17-kDa nonstructural protein of infectious bursal disease virus: possible role in viral pathogenesis.

Infectious bursal disease virus (IBDV) causes severe immunodeficiency in young chickens by destroying the precursors of antibody-producing B cells in the bursa of Fabricius. It has been shown that IBDV infection induces apoptosis in chicken embryo and tissue culture cells. We previously reported that an IBDV mutant lacking the expression of 17-kDa nonstructural (NS) protein exhibited decreased apoptotic effects in cell culture as compared to the parental IBDV, suggesting that the NS protein may be involved in induction of apoptosis. Here, we report that the NS protein of IBDV alone is capable of inducing apoptosis in cell culture. Transfection of chicken B-lymphocyte cell line (RP9) and chicken embryo fibroblast cells with a plasmid DNA, containing the NS protein gene under the control of the immediate-early promoter-enhancer region of human cytomegalovirus, induced programmed cell death in both cell lines. Apoptosis changes, such as chromatin condensation, DNA fragmentation, and the appearance of apoptotic nuclear bodies, were observed in cell cultures 48-h posttransfection. As reported earlier, the mutant IBDV grew to lower titers with slower replication kinetics and lower cytopathogenicity when compared to that of the parental virus. Here, we demonstrate that the mutant virus is closely associated with cells and its yield from the supernatant was approximately 30-fold lower than the wild-type due to increased cell association, indicating a deficiency in lysis of virus-infected cells. Taken together, our results indicate that the NS protein of IBDV is highly cytotoxic, which brings about the release of the viral progeny from cells, and thus play an important role in viral pathogenesis.

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PubMed1992

Naturally occurring-neutralizing monoclonal antibody escape variants define the epidemiology of infectious bursal disease viruses in the United States.

A panel of two non-neutralizing and six neutralizing monoclonal antibodies (Mabs) were used in antigen-capture enzyme immunoassays (AC-ELISA) to examine the antigenicity of 1301 wild type infectious bursal disease viruses (IBDV) isolated from different poultry flocks throughout the United States over a three year period. Analysis of these isolates with protective, neutralizing Mabs directed against the VP2 structural protein of IBDV showed that four antigenically distinct groups of serotype 1 IBDV could be separated on the basis of the presence or absence of one or more Mab defined, conformation-dependent, multivalent neutralization site. AC-ELISA reactivity patterns of the Mabs with isolates demonstrated that IBDV field populations were relatively antigenically homogeneous per premise isolation. Geographically, various antigenic species were more or less prevalent, or nearly absent. Competition analysis with neutralizing Mabs coupled with AC-ELISA results suggested that neutralization epitopes for IBDV are distinct, spatially arranged, yet closely linked. Of 5 Mab defined neutralization epitopes, shown to be related to protection from virulent challenge by Classic IBDV strains isolated prior to 1985, only two of the epitopes remain unaltered on the most recent emergent variant field strain of IBDV isolated.

Animals↗

PubMed2003

Antigenic and genetic diversity of early European isolates of Infectious bursal disease virus prior to the emergence of the very virulent viruses: early European epidemiology of Infectious bursal disease virus revisited?

Eleven Polish and Hungarian isolates of Infectious bursal disease virus (IBDVs) obtained in the 70/80s (early IBDV) and in the 90s (recent IBDV) were characterized in an Antigen-Capture-ELISA with a panel of neutralizing monoclonal antibodies (Mabs), and by nucleotide sequencing of the VP2 variable domain (vVP2). The viruses were compared with reference IBDV strains, among others with Faragher 52/70 (F52/70, classical, isolated 1970), 89163 (typical very virulent-vvIBDV, isolated 1989) and 91168 (antigenically modified vvIBDV, isolated 1991). Only one of the early isolates (Hungarian strain P1) proved antigenically and genetically similar to F52/70. Other early isolates exhibited no reactivity versus Mabs 3, 4, 5 and/or 8 and had a common previously unrecognized combination of amino acid changes in vVP2. The recent isolates all proved antigenically and genetically related to typical vvIBDV strain 89163, except the Polish isolate 93/35 which proved related to the 91168 strain although no epidemiological relationship had been documented between these viruses in the field. Phylogenetic analysis confirmed that the non-P1 early IBDVs represent a previously unrecognized group among serotype 1 IBDVs. It is discussed whether these early isolates are derivatives of the F52/70-like viruses that might still be present in the field, or whether they represent early IBDV strains that might have been present prior to and progressively replaced by the F52/70-like viruses, as the latter have been replaced by vvIBDVs in the late eighties.

Amino Acid Sequence↗

PubMed1991

Genome cloning and analysis of the large RNA segment (segment A) of a naturally avirulent serotype 2 infectious bursal disease virus.

The genome of infectious bursal disease virus (IBDV) of serotype 2 (strain OH) has been cloned, and 3171 nucleotides of genome segment A cDNA sequence have been determined for the first time. Sequence homology of OH-IBDV with the most distant serotype 1 IBDV at the nucleotide level is 83.1%, and the amino acid sequence homology of the polyprotein is 89.6%. Alignment of the polyprotein amino acid sequences showed the hypervariable region in VP2 to be 151-152 amino acid residues long in IBDV. A second variable region, 37 amino acid residues long, was identified in the N-terminal third of the IBDV VP2 molecule. IBDV strains, like the IPNV strains, also contain inverted repeats that may form stem-and-loop structures in the 5' noncoding sequences. These inverted repeats are variable between the two IBDV serotypes, particularly at the AT basepairs.

Animals↗

PubMed1992

Characterization of nonradioactive hybridization probes for detecting infectious bursal disease virus.

Reverse transcription followed by the polymerase chain reaction was used to amplify a fragment of infectious bursal disease virus (IBDV) strain P3009 genome. The amplified DNA fragment was annealed into the plasmid pUC18 and used to transform Escherichia coli strain JM109. A clone that contained IBDV-specific nucleotide sequences was selected and designated pC23. The DNA fragment within pC23 was 320 base pairs in length and designated C23. Radiolabeled probes prepared from C23 hybridized to genome segment A of strain P3009 by a northern-blot hybridization assay. Biotin-labeled probes prepared from C23 and pC23 either by using nick translation (designated C23/NT and pC23/NT, respectively) or by direct introduction of biotin molecules into C23 and pC32 (designated C23/BH and pC23/BH, respectively) were used in the dot blot hybridization assay for detecting IBDV strains. All four biotinylated probes detected three serotype 1 viruses and one serotype 2 IBDV. However, they did not cross-react with nucleic acids extracted from mock-infected cells or from seven unrelated avian viruses. Probe pC23/BH detected as little as 0.04 ng of IBDV RNA, while the other three probes were less sensitive and detected approximately 1 ng of IBDV RNA. In addition, the probe pC23/BH detected IBDV RNA in bursa tissues from commercial broiler raising farms following the dot blot hybridization.

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