The tumorigenesis of bovine adenovirus type 3 was studied using either the wild type strain or three isolated virus clones and one experimentally induced variant, with the following results:
The wild type strain produced non-progressive, solid or cystic tumors which induced neutralizing antibodies.
The three cloned virus strains produced progressive, always solid tumors without the formation of neutralizing antibodies.
The experimentally induced variant proved to be non-tumorigenic and differed in its antigenic composition.
It is concluded that bovine adenovirus type 3 represents a heterogenic population of virus particles with different tumorigenic potentialities.
Type 3 bovine adenovirus WBR1 strain was found to be tumorigenic for hamsters (Darbyshire, 1966). In this species the virus induced both solid tumors that did not appear to grow but remained static after reaching a size of 20–30 mm, and tumors of cystic type that regressed within 10 days leaving back small subcutaneous nodules. Stimulated by this observation we assumed the wild type strain of type 3 bovine adenovirus to be a mixture of genetically different virus particles.