Biological Characterization of Structural Components of Adenovirus type 12

Two products with a large mass and five different soluble components of adenovirus type 12 have been identified. The former were virus particles and empty capsids, which both carried group-specific complement-fixing (CF) antigen and were active as complete haemagglutinins (HAs). Their buoyant densities in CsCl were 1·330 to 1·340 and 1·295 to 1·305, respectively. The soluble components were identified as hexons, pentons, isolated fibres, dimers of fibres and isolated vertex capsomeres. Hexons were trypsin-resistant, ther-mostable and carried group-specific CF antigen; ultrastructurally they resembled hexons of other human adenoviruses. Pentons were active as an incomplete HA, causing agglutination in the presence of heterologous antisera against representative members of all three subgroups of adenoviruses. Furthermore, they were trypsin-sensitive and thermolabile. Isolated fibres represented another incomplete HA, exhibiting agglutinating activity only in the presence of antisera against members of subgroup III, e.g. type 2. This component was also identified as the dominating type-specific CF antigen. The length of fibres was estimated as 28 to 32 nm. by electron microscopy. The dimers of fibres represented a complete HA, the activity of which became apparent only after other material was removed. Both isolated fibres and their dimers were trypsin-resistant and thermostable. The assumed pentons and fibre dimers occurred in too low concentration to allow ultrastructural identi-fication. Isolated vertex capsomeres were demonstrated by a haemaggluti- nation enhancement antibody consumption test. They were completely destroyed by trypsin treatment and exhibited a moderate thermostability. Electron microscopy confirmed the presence of capsomere-like structures. These structures occasionally displayed a five-sided contour, thereby differing from hexons.

The sequence of elution of different components from an anion exchanger was: isolated vertex capsomeres, hexons + pentons, fibres and dimers of fibres. In zonal centrifugation experiments the components sedimented at decreasing rates in the following order: hexons, pentons+isolated vertex capsomeres, dimers of fibres and isolated fibres. Probably on account of the morphological characteristics of the various components they presented a different pattern of elution in exclusion chromatography. Dimers of fibres, pentons and even isolated fibres were eluted before hexons. The position of the peak activity of type 12 fibres in the elution diagram was similar to that of types 1, 2 and 5 fibres.