Infectious antibody-reovirus complexes.

Populations of reovirus type 1 could not be completely neutralized by exposure to specific antiviral serum. Aggregation of reovirions before or after exposure to neutralizing antibody was discarded as a possible explanation for the phenomenon observed. Anti-rabbit serum and equilibrium zonal density gradient centrifugation were used to show that the residual infectious fraction consisted of infectious antibody-virion complexes. Electron microscopy and equilibrium density gradient centrifugation of stock virus preparations were used to attempt to determine whether the infectious virus-antibody complexes resulted from the combination of antibody with virus particles which differed from neutralizable virions either morphologically or with regard to buoyant density. Although electron micrographs revealed the presence of three morphologically distinct classes of virus particles, density gradient centrifugation resulted in only one infectious peak. Density gradient centrifugation of virus exposed to antibody resulted in only one infectious peak which consisted of virus-antibody complexes.