ABSTRACT
Highly pathogenic avian influenza viruses (HPAIV) of subtype H5N1 not only cause a devastating disease in domestic chickens and turkeys but also pose a continuous threat to public health. In some countries, H5N1 viruses continue to circulate and evolve into new clades and subclades. The rapid evolution of these viruses represents a problem for virus diagnosis and control. In this work, recombinant vesicular stomatitis virus (VSV) vectors expressing HA of subtype H5 were generated. To comply with biosafety issues the G gene was deleted from the VSV genome. The resulting vaccine vector VSV*ΔG(HA) was propagated on helper cells providing the VSV G protein in trans. Vaccination of chickens with a single intramuscular dose of 2×108 infectious replicon particles without adjuvant conferred complete protection from lethal H5N1 infection. Subsequent application of the same vaccine strongly boosted the humoral immune response and completely prevented shedding of challenge virus and transmission to sentinel birds. The vaccine allowed serological differentiation of infected from vaccinated animals (DIVA) by employing a commercially available ELISA. Immunized chickens produced antibodies with neutralizing activity against multiple H5 viruses representing clades 1, 2.2, 2.5, and low-pathogenic avian influenza viruses (classical clade). Studies using chimeric H1/H5 hemagglutinins showed that the neutralizing activity was predominantly directed against the globular head domain. In summary, these results suggest that VSV replicon particles are safe and potent DIVA vaccines that may help to control avian influenza viruses in domestic poultry.
Subject(s)
Influenza A Virus, H5N1 Subtype/pathogenicity , Influenza in Birds/prevention & control , RNA/administration & dosage , Replicon/genetics , Virion/genetics , Animals , Blotting, Western , Chickens , Female , Fluorescent Antibody Technique , Hemagglutinin Glycoproteins, Influenza Virus/genetics , Hemagglutinin Glycoproteins, Influenza Virus/metabolism , Influenza A Virus, H5N1 Subtype/immunology , Influenza in Birds/immunology , Influenza in Birds/virology , RNA/genetics , RNA, Messenger/genetics , Real-Time Polymerase Chain Reaction , Reverse Transcriptase Polymerase Chain Reaction , Vaccination , Vesiculovirus/genetics , Virus SheddingABSTRACT
The immunopathogenesis of infectious bursal disease virus (IBDV) was investigated in different layer and broiler type chickens in comparison to highly susceptible specific-pathogen-free layers (SPF-Wh-LT) often used for experimental studies. Layer-type chickens (LT) of all genetic backgrounds showed significantly higher IBDV antigen loads in the bursa of Fabricius (BF) compared to broiler type birds (BT) (P<0.05). The variation between IBDV-infected and virus-free birds in the percentage of splenic and intrabursal B cells, T cells and macrophages differed between genetic backgrounds as well as the expression levels of cytokines. The most susceptible SPF-Wh-LT showed high levels of circulating type I IFN starting at 2 days post infection (dpi) up to 7 dpi coinciding with clinical IBD, while less susceptible birds showed a delayed response. Circulating cytokine levels were poorly associated neither with intrabursal nor with splenic mRNA expression of these cytokines. Detected cytokines varied in expression levels and timing between infected groups of different genetic background. These data suggest that variations in the activity of immune cell populations contribute to differences in infectious bursal disease between birds of various genetic backgrounds.
