Radioactive labelling of viruses: an iodination technique preserving biological properties

An iodination procedure suitable for the radioactive labelling of viruses to be used in biological experiments is described. It is characterized by the addition of carrier protein to small amounts of virus before iodination with chloramine T, the use of low concentrations of chemicals, and a rapid purification of the labelled virus to minimize radiation inactivation. Using this procedure, polyoma virus was labelled to a specific activity 100 times greater than that which can be obtained with tritiated amino acids, while its sedimentation coefficient, buoyant density, decapsidation and hamagglutinating activity remained unaffected. Reduction in infectivity, possibly due to radiation inactivation, was slight. Similar results were obtained with adenovirus.