The ability of a heat-inactivated whole virus from a highly virulent infectious bursal disease virus (hvIBDV) and VP2 protein from hvIBDV expressed in E. coli provided protection against a hvIBDV challenge in specificpathogen- free (SPF) chickens. Six out of seven chickens that were injected three times with crude VP2 protein developed significant antibody titer against IBDV. However, only four out of the seven chickens survived the hvIBDV challenge. Despite showing low antibody titer profiles, all chickens immunized with the heat-inactivated whole virus also survived the challenged with hvIBDV. However, all of these chickens had bursal atrophy and mild to moderate depletion of lymphocytes. Thus, antibodies raised against IBDV VP2 protein expressed in E. coli and denatured IBDV proteins induced some degree of protection against mortality but not against bursal damage following challenge with hvIBDV.
Animals ; Antibodies, Viral/blood ; Birnaviridae Infections/immunology/prevention & control/*veterinary/virology ; Chickens ; Enzyme-Linked Immunosorbent Assay/veterinary ; Escherichia coli/genetics ; Immunization/standards/*veterinary ; Infectious bursal disease virus/genetics/*immunology/pathogenicity ; Poultry Diseases/*immunology/prevention&control/virology ; Recombinant Proteins/genetics/*immunology ; Specific Pathogen-Free Organisms ; Vaccines, Attenuated/immunology/pharmacology ; Vaccines, Synthetic/immunology/pharmacology ; Viral Structural Proteins/biosynthesis/genetics/*immunology ; Viral Vaccines/*immunology/pharmacology

Classical swine fever virus (CSFV) causes a highly contagious disease among swine that has an important economic impact worldwide. CSFV strain LOM is an attenuated virus of low virulent strain of Miyagi isolated from Japan in 1956. Eight DNA fragments representing the genome of the CSFV strain LOM were obtained by RT-PCR. These were used to determine the complete nucleotide sequence and construct a full-length cDNA clone which was called Flc-LOM. Sequence analysis of the recombinant clone (Flc-LOM) revealed the presence of eight mutations, resulting in two amino acid substitutions, when compared to the parental sequence. RNA transcripts of both LOM and Flc-LOM were directly infectious in PK-15 cells. The rescued Flc-LOM virus grew more slowly than the parental virus, LOM, in the cells. Intramuscular immunization with Flc-LOM was safe and highly immunogenic in pigs; no clinical signs or virus transmission to sentinel animals were observed after 35 days. CSFV-specific neutralizing antibodies were detected 14 days post-infection. After challenge with the virulent CSFV strain SW03, pigs immunized with Flc-LOM were shown to be fully protected. Thus, our newly established infectious clone of CSFV, Flc-LOM, could serve as a vaccine candidate.
Animals ; Antibodies, Viral/blood ; Base Sequence ; Cell Line ; Classical Swine Fever/immunology/*virology ; Classical swine fever virus/*genetics/immunology/pathogenicity ; Cloning, Molecular ; DNA, Complementary/genetics/immunology ; Immunization/methods/standards/veterinary ; Molecular Sequence Data ; Neutralization Tests/veterinary ; RNA, Viral/chemistry/genetics ; Recombinant Proteins/immunology ; Reverse Transcriptase Polymerase Chain Reaction/veterinary ; Sequence Analysis, DNA ; Specific Pathogen-Free Organisms ; Swine ; Virulence