Broad antigenicity exhibited by some isolates of avian adenovirus

Ten of 16 isolates of avian adenovirus could be readily classified as members of serotypes 2, 5, or 7. However, 6 exhibited broad neutralization reactions which created typing problems. Detailed studies of these interactions revealed that our prototype for serotype 5 (i.e., T-8; subsequently found to be an "intermediate" strain) contributed to this broad cross-reactivity because it shared antigens with members of serotypes 5 and 7. As a result of this study, TR-59 or 58-1 is recommended as the suitable prototype for the serotype 5 viruses. The 6 broadly reactive isolates were classified as serologic "variants" of serotypes 5 and 7.