Modification of infectious bursal disease virus antigen VP2 for cell surface location fails to enhance immunogenicity

Eliciting specific humoral immunity from a plasmid DNA encoding infectious bursal disease virus polyprotein gene fused with avian influenza virus hemagglutinin gene

DNA vaccine coding for infectious bursal disease virus (IBDV) polyprotein gene and that for avian influenza virus (AIV) hemagglutinin (HA) gene have been shown to induce immunity and provide protection against the respective disease. The present study was carried out to determine whether an IBDV polyprotein gene-based DNA fused with AIV HA gene could trigger immune response to both IBDV and AIV. After transfection, VP2 and HA were detected in the cytoplasm and at cell membrane, respectively, by immunofluorescent antibody double staining method, suggesting the fusion strategy did not affect the location of protein expression. VP4 cleavage between VP2 and HA was confirmed by Western blot, indicating the fusion strategy did not affect VP4 function in transfected cells. After vaccination in chickens, the DNA construct VP24-HA/pcDNA induced ELISA and virus neutralizing antibodies against VP2 and hemagglutination inhibition antibody against the HA subtype. The results indicated that a single plasmid construct carrying IBDV VP243 gene-based DNA fused with AIV HA gene can elicit specific antibody responses to both IBDV and AIV by DNA vaccination.

Expression of VP2 gene protein of infectious bursal disease virus detected in Korea

The VP2 gene DNA (1.4 kb in approximate) of a very virulent infectious bursal disease virus (vvIBDV) Chinju strain detected in Chinju, Korea was cloned into the bacmid, a baculovirus shuttle vector, through transposition of the gene from initially cloned pFastBacHTa plasmid, a baculovirus expression vector, and was subsequently expressed in Spodoptera frugiperda (Sf) cells. Biological properties of the expressed VP2 subunit protein were characterized to aid in the development of genetically engineered diagnostic reagents and vaccines against the vvIVDV. When the VP2 DNA-recombinant bacmid was transfected and propagated in the Sf cells, the cells showed no occlusion formation, which is a positive evidence for the insertion of the VP2 DNA into the polyhedrin gene of the bacmid, whereas the occlusions were observed in the cells infected by the Autographa californica nuclear polyhedrosis virus, a wild baculovirus. The expression of VP2 DNA was identified by strong positive reaction in fluorescent antibody test using chicken anti-IBDV serum. The VP2 protein was determined as a polypeptide band with Mr of 48 kDa by the sodium dodecyl-polyacrylamide gel electrophoresis for the lysate of the Sf cells infected with the recombinant bacmid. The VP2 protein was successfully purified from the cell lysate by Ni-NTA affinity chromatography. The expressed VP2 subunit protein reacted specifically with chicken anti-IBDV serum in Western blotting.

DNA vaccination with plasmids containing various fragments of large segment genome of infectious bursal disease virus

The present study was undertaken to determine the effectiveness in including VP2 gene of the large segment genome of infectious bursal disease virus (IBDV) in the DNA vaccine for protection of chickens against infectious bursal disease (IBD). Different fragments of the large segment gene of IBDV standard challenge (STC) strain were successfully amplified by reverse transcription-polymerase chain reaction (RT-PCR) followed by cloning into a eukaryotic expression plasmid vector (pCR3.1) as DNA vaccines. Transient expression of the encoded genes from various constructed plasmids was characterized in COS-7 cells by positive immunofluorescent staining with polyclonal or monoclonal antibody to IBDV. Chickens (1-day old) were intramuscularly injected with the individual plasmid three times at weekly intervals, challenged with IBDV strain STC at 21-day old, and observed for 10 days. Chickens receiving the plasmids containing VP2 genes, including VP243, VP24, or VP2 fragment, did not have clinical signs, mortality, and bursal atrophy and were effectively protected against IBDV infection. On the contrary, chickens receiving plasmids without containing VP2 genes, including VP4, VP3, or VP43 fragment, had marked bursal atrophy and were not protected against IBD. Antigen detection was correlated with protection; chickens protected from IBDV infection had undetectable IBDV antigen in bursae. Enzyme-linked immunosorbent assay (ELISA) antibody titer to IBDV was low or undetectable prior to or after challenge with IBDV in protected chickens receiving the plasmids containing the VP2 gene. The results indicate that inclusion of VP2 gene in the plasmid DNA is essential in achieving effective protection mediated by DNA vaccination against IBDV infection in chickens.

Development of an effective polyvalent vaccine against both Marek's and Newcastle diseases based on recombinant Marek's disease virus type 1 in commercial chickens with maternal antibodies

An earlier report (M. Sakaguchi et al., Vaccine 16:472-479, 1998) showed that recombinant Marek's disease virus type 1 (rMDV1) expressing the fusion (F) protein of Newcastle disease virus (NDV-F) under the control of the simian virus 40 late promoter [rMDV1-US10L(F)] protected specific pathogen-free chickens from NDV challenge, but not commercial chickens with maternal antibodies against NDV and MDV1. In the present study, we constructed an improved polyvalent vaccine based on MDV1 against MDV and NDV in commercial chickens with maternal antibodies. The study can be summarized as follows. (i) We constructed rMDV1 expressing NDV-F under the control of the MDV1 glycoprotein B (gB) promoter [rMDV1-US10P(F)]. (ii) Much less NDV-F protein was expressed in cells infected with rMDV1-US10P(F) than in those infected with rMDV1-US10L(F). (iii) The antibody response against NDV-F and MDV1 antigens of commercial chickens vaccinated with rMDV1-US10P(F) was much stronger and faster than with rMDV1-US10L(F), and a high level of antibody against NDV-F persisted for over 80 weeks postvaccination. (iv) rMDV1-US10P(F) was readily reisolated from the vaccinated chickens, and the recovered viruses were found to express NDV-F. (v) Vaccination of commercial chickens having maternal antibodies to rMDV1-US10P(F) completely protected them from NDV challenge. (vi) rMDV1-US10P(F) offered the same degree of protection against very virulent MDV1 as the parental MDV1 and commercial vaccines. These results indicate that rMDV1-US10P(F) is an effective and stable polyvalent vaccine against both Marek's and Newcastle diseases even in the presence of maternal antibodies.

Protection of chickens against very virulent infectious bursal disease virus (IBDV) and Marek's disease virus (MDV) with a recombinant MDV expressing IBDV VP2

To develop a herpes virus vaccine that can induce immunity for an extended period, a recombinant Marek's disease (MD) virus (MDV) CVI-988 strain expressing infectious bursal disease virus (IBDV) host-protective antigen VP2 at the US2 site (rMDV) was developed under the control of an SV40 early promoter. Chickens vaccinated with the rMDV showed no clinical signs and no mortality and 55% of the chickens were considered protected histopathologically after challenge with very virulent IBDV (vvIBDV), whereas all of the chickens vaccinated with the conventional IBDV vaccine showed no clinical signs and were protected. Chickens vaccinated with the CVI-988 or chickens in the challenge control showed severe clinical signs and high mortality (70-75%) and none of them were protected. Also, the rMDV conferred full protection to chickens against vvMDV just as the CVI-988 strain did, whereas 90% of the challenge control chickens died of MD. Antibody levels against IBDV and MDV following the vaccination increased continuously for at least 10 weeks. No histopathological lesions in the rMDV-vaccinated chickens and no contact transmission of the rMDV to their penmates were confirmed. These results demonstrate that an effective and safe recombinant herpesvirus-based IBD vaccine could be constructed by expressing the VP2 antigen at the US2 site of the CVI-988 vaccine strain.

Recombinant fowlpox viruses coexpressing chicken type I IFN and Newcastle disease virus HN and F genes: influence of IFN on protective efficacy and humoral responses of chickens following in ovo or post-hatch administration of recombinant viruses

We have constructed recombinant (r) fowl pox viruses (FPVs) coexpressing chicken type I interferon (IFN) and/or hemagglutinin-neuraminidase (HN) and fusion (F) proteins of Newcastle disease virus (NDV). We administered rFPVs and FPV into embryonated chicken eggs at 17 days of embryonation or in chickens after hatch. Administration of FPV or rFPVs did not influence hatchability and survival of hatched chicks. In ovo or after hatch vaccination of chickens with the recombinant viruses resulted in protection against challenge with virulent FPV and NDV. Chickens vaccinated with FPV or FPV-NDV recombinant had significantly lower body weight 2 weeks following vaccination. This loss in body weight was not detected in chickens receiving FPV-IFN and FPV-NDV-IFN recombinants. Chickens vaccinated with FPV coexpressing IFN and NDV genes produced less antibodies against NDV in comparison with chickens vaccinated with FPV expressing NDV genes.

The structural proteins of infectious pancreatic virus are not glycosylated

The major capsid protein, VP2, of infectious pancreatic necrosis virus, a nonenveloped icosahedral virus, contains six N-glycosylation consensus sequences (Asn-X-[Thr/Ser]). Since VP2 contains the major virus-neutralizing epitopes, the possible role for glycosylation in capsid formation and antigenicity was examined. The carbohydrate content of the virion proteins was determined by chemical detection, pulse-chase experiments,[3H]mannose labeling, and alteration of protein migration on sodium dodecyl sulfate-polyacrylamide gels after tunicamycin treatment. No glycosylation of any virion protein was observed when the carbohydrate nature of the glycoprotein of infectious hematopoietic necrosis virus was detected.

Antigen specificity of the ovine cytotoxic T lymphocyte response to bluetongue virus

Bluetongue virus (BTV), an arbovirus transmitted by midges, can cause serious disease in sheep. Both virus neutralizing antibody and cytotoxic T lymphocytes (CTL) have been shown to have a role in protective immunity. In this study, the antigen specificity of CTL from BTV-immune sheep has been determined using recombinant vaccinia viruses expressing individual BTV antigens. The results show that, in the sheep studied thus far, the serotype-specific outer coat protein, VP2, and the non-structural protein, NS1 are major immunogens for CTL, with VP5 (an outer coat protein) and NS3 being minor immunogens. No VP7 (a major group-reactive inner coat protein) specific CTL were detected. The CTL from sheep immunized with serotype 1 were cross-reactive and able to recognize target cells infected with other BTV serotypes. Further work demonstrated that the cross-reactive CTL recognized NS1, but not VP2.