Kinetic And Biologic Properties of Recombinant ChIFN-γExpressed via CELO-Virus Vector

Antibody fragments, expressed by a fowl adenovirus vector, are able to neutralize infectious bursal disease virus

Single-chain variable fragments (scFv) contain the heavy and light chain variable domains of immunoglobulin, joined by a short peptide linker. Previously, our laboratory has produced neutralizing scFv to epitopes of infectious bursal disease virus (IBDV). The in vitro delivery and expression of one of these scFv with and without the C(H)2-C(H)4 Fc domain of chicken IgY attached (scFv-Fc) by a serotype 8 fowl adenovirus (FAdV-8) vector was investigated in the present study. A panel of FAdV-8 vectors was constructed, each containing a different transgene (scFv or scFv-Fc), a different promoter to drive scFv and scFv-Fc transcription (CMVie or the fowl adenovirus major late promoter), and a different sized, right-hand end genomic deletion (52 bp or 2.3 kb). This panel was used to establish what effect these variables had on protein production, viral replication and scFv transcription, as measured by enzyme-linked imunosorbent assay and real-time polymerase chain reaction. Our results showed that, using a FAdV-8 vector containing the optimal CMVie promoter/2.3 kb deletion combination, we successfully expressed a secreted form of both scFv and scFv-Fc that were able to neutralize IBDV both in vitro and in ovo. These studies indicate that the FAdV-8 vector may be a promising candidate to deliver and express therapeutic molecules such as scFv and scFv-Fc in vivo in poultry.

Pivotal role of ChIFNgamma in the pathogenesis and immunosuppression of infectious bursal disease

This study investigates the pivotal role of chicken interferon-gamma (ChIFNgamma) in the pathogenesis and immunosuppression of infectious bursal disease virus (IBDV) infection and is divided into in vivo, ex vivo and in vitro experiments. Two-week-old specific pathogen free chickens were inoculated with the 849VB very virulent strain of IBDV. The levels of systemic ChIFNgamma and chicken interleukin-6 in the serum were followed for 2 weeks during in vivo experiments. Then, splenocytes and bursal cells from infected chickens were analysed for their immunocompetence after mitogenic activation in ex vivo experiments. Finally, in vitro experiments were conducted to assess the direct immunosuppressive effect of ChIFNgamma on splenocytes and peripheral blood lymphocytes from non-inoculated specific pathogen free chickens. Our results reveal that the acute phase of infectious bursal disease coincides, on one hand, with high levels of systemic ChIFNgamma and chicken interleukin-6 and, on the other hand, with a strong inhibition of proliferation and activation of mitogen-stimulated splenocytes from infected chickens, as measured by ChIFNgamma production. Two weeks after viral inoculation, T lymphocytes infiltrating the bursa of Fabricius had recovered their activation capability. Finally, an in vitro study showed that the proliferation of naïve splenocytes and peripheral blood lymphocytes was directly and specifically inhibited by ChIFNgamma. In conclusion, a ChIFNgamma dysregulation occurs in chickens infected with IBDV and the overproduction of ChIFNgamma by T lymphocytes plays a key role in the pathogenesis and immunosuppression induced by this virus.