The relationship between the soluble antigens and the virion of adenovirus type 3: VI. Further characterization of antigenic sites available at the surface of virions

Abstract

Absorption experiments demonstrated the presence of antigenic sites at the surface of virions of adenovirus type 3 which were not carried by spontaneously occurring soluble components. These unique sites were identified by use of virion antigen in neutralization and hemagglutination-inhibition (HI) tests with rabbit hyperimmune sera in the presence of sheep anti-rabbit serum and in complement-fixation tests. Antibodies against vertex capsomers (represented by an antipenton serum absorbed with purified fibers) or against fibers carried negligible neutralizing activity. However, efficient neutralization occurred when both kinds of antibodies were present simultaneously, i.e., as in antipenton and antidodecon sera, or when anti-rabbit serum was added. The possible occurrence of cross-reacting antigenic sites at the surface of virions was examined in HI tests with purified virions and soluble hemagglutinin of eight different human adenovirus serotypes, including at least two types for each one of Rosen's subgroups. Rabbit hyperimmune sera against virions and purified soluble components were employed, and a sheep anti-rabbit serum was added to the HI tests in order to increase their sensitivity. Low-degree cross-reactions of subgroup-specific nature were identified. They were demonstrated to be due to the occurrence of vertex capsomer-associated subgroup-specific antigen(s). An antiserum against type 11 dodecons was found to display some capacity to neutralize virions of type 3 in the presence of anti-rabbit serum. This heterotypic neutralization is proposed to be caused by the subgroup-specific antibodies against vertex capsomers demonstrated by HI tests.