Delivery of avian cytokines by adenovirus vectors

A fowl adenovirus serotype 8 (FAV-8) recombinant was constructed by inserti ng an expression cassette consisting of the FAV major late promoter/splice leader sequences (MLP/SL), the chicken interferon-gamma (ChIFN-gamma) gene and SV40 polyA into sites in the right hand end of the FAV-8 genome. One re combinant (A3-13) was constructed by an insertion of ChIFN-gamma into a 1.3 kilobase pair (kbp) deletion which removed a putative open reading frame ( ORF) with identity to the CELO (FAV serotype 1) 36 kDa homologue. A second recombinant (S4) removed a further 0.9 kbp and a third recombinant (AAI) wa s constructed in a small 50 base pair (bp) SpeI deletion. The recombinants displayed differing growth characteristics in CK monolayers. A3-13 grew slo wly and only attained a titre of 10(5) pfu/ml, S4 had intermediate growth a nd AAI showed wild type growth kinetics. These differing growth properties indicated that removal of the 36 kDa homologue had an effect on growth in v itro. Supernatants from CK monolayers infected with the recombinant virus w ere assayed for the production of ChIFN-gamma. Detectable levels of ChIFN-g amma were observed in supernatants as early as 24 h post infection (p.i.), peaked at 48 h p.i. and this level was maintained for at least 10 days. The level of production of ChIFN-gamma correlated with each recombinant's grow th characteristics in vitro. Chickens treated with rFAV-ChIFN-gamma showed increased weight gains compared to controls and suffered reduced weight los s when challenged with the coccidial parasite Eimeria acervulina. (C) 2000 Elsevier Science Ltd. All rights reserved.