Comparison by restriction enzyme analysis of three fowl adenoviruses of varying pathogenicity

Restriction enzyme studies have been used to divide the fowl adenoviruses (FAV) into 5 groups - A, B,C,D and E. More detailed restriction enzyme studies of a series of group E FAV field isolates showed that these methods could differentiate between mildly and hypervirulent FAV belonging to this group. We have mapped the genomes of the hypervirulent (CFA 40) and two of the mildly virulent FAV (CFA 44 and CFA 3), using 11 different restriction enzymes: HindIII, BglII, XbaI, NdeI, SpeI, DraI, NotI, StuI, NheI, SfiI, and AvrII. Comparison of the three maps showed that the CFA 3 genome was approximately 3.5 kb smaller than that of CFA 44 and CFA 40. This size difference was discounted as a likely cause of the reduced pathogenicity of CFA 3 as the other mildly virulent virus, CFA 44, was the same size as the hypervirulent CFA 40. Other variations between the three viruses occurred in the region of the hexon and 100 K genes, but further studies are required to determine the significance of these variations in pathogenicity.