Avian adeno‐associated virus (AAAV) and fowl adenoviruses (FAV): Studies of viral interactions in chicken cell cultures

Abstract

As the growth kinetics of avian adeno-associated virus (AAAV) in chicken cells demonstrate the three serotypes of fowl adenovirus (FAV), FAV -1, -5 and -8, provide complete helper activity for the production of infectious AAAV. Under one step conditions, the growth cycle of AAAV in primary chicken kidney cell (CKC) cultures is characterised by an eclipse phase of 8 hours and an exponential increase of the virus infectivity by 4 to 5 logs until 24 hours post-adsorption (p.a.). These growth characteristics do not depend on the serotype of FAV used as helper. In chicken embryo fibroblast (CEF) cultures the eclipse phase is prolonged to 12 hours p.a. and the virus infectivity increases only by 2 logs. In addition, the low efficiency of plating of FAV -1 in this cell system does not allow one step growth curves for AAAV. In CKC and CEF cultures coinfected with FAV and AAAV the multiplication of helper FAV is reduced. The degree of growth inhibition depends on the AAV multiplicity used. Sequential infection of CKC cultures with FAV -1 and AAAV modifies the AAAV growth cycle, i.e. there is a time reduction of the eclipse phase and a decrease of the virus yield. Infectious AAAV was determined by an indirect immunofluorescence assay and infectious FAV by a plaque assay.