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Abstract
The avian adeno-associated virus (AAAV) is a replication defective non-pathogenic virus proved useful as a viral vector for gene delivery. The first set of studies aimed the development recombinant AAAV virions expressing the hemagglutinin-neuraminidase (HN) protein of Newcastle disease virus (NDV) or the viral protein 2 (VP2) of infectious bursal disease virus (IBDV). Transgene expression of the viral proteins was confirmed and the recombinant viruses tested for immunogenicity and protection. The birds vaccinated with the recombinant virions showed IBDV and NDV specific antibodies and up to 80% protection against virulent challenge. The second set of studies aimed to characterize the Villegas-Glisson / University of Georgia (VG/GA) strain of NDV. The VG/GA strain was detected in the respiratory and intestinal tract of chickens with a preferential tropism for the latter. The VG/GA strain and the LaSota strain (used for comparison) induced NDV specific immunoglobulin A (IgA) at the upper respiratory tract. The IgA levels in the trachea were higher for LaSota strain, while in the bile and intestine were higher for the VG/GA strain. Early vaccination with the VG/GA strain afforded 95 to 100% protection against lethal challenge, equivalent to the protection conferred by LaSota strain. Full genome sequence analysis classified the VG/GA strain within class II, genotype II viruses, which include most of the classic vaccine strains. The third study investigated the feasibility of using Flinders Technology Associates filter paper (FTA cards) to collect allantoic fluid (AF) and chicken tissue samples for NDV molecular detection. The FTA cards allowed NDV identification from AF with titter of 10 ELD50/ml and tissue imprints from experimentally infected birds. The FTA cards are suitable for collecting and transporting NDV positive samples, providing a reliable source of RNA for molecular characterization and a hazard free sample. Index words: Newcastle disease virus, infectious bursal disease, avian adeno-associated virus, hemaglutinin-neuraminidase, viral protein 2, VG/GA strain, FTA card