Biophysical comparison of two canine adenoviruses

The two canine adenoviruses, infectious canine hepatitis (ICH) virus and infectious canine laryngotracheitis (ICL) virus (also designated as Toronto A26/61 virus), were studied with respect to their morphology and the biological properties of their soluble components. The two viruses were found to be composed of soluble components similar to, and carrying biological activities corresponding to, those of the human adenoviruses after fractionation by rate zonal centrifugation and anion-exchange chromatography. The following soluble components were identified: hexons (carrying a common group-specific complement-fixing antigen), penton oligomers (complete soluble hemagglutinin), and penton and fiber monomers (incomplete soluble hemagglutinins). The latter were indicated by hemagglutination enhancement with selected antisera directed against human adenovirus soluble components. Elution characteristics of corresponding components of the two viruses in anion-exchange chromatography experiments were distinctly different. Electron microscopic examination of purified virions and soluble components revealed the fiber component of ICL virus to be 35 to 37 nm in length, and that of ICH virus to be 25 to 27 nm long.