A One-FilterThree-Probe Assay for Defective Interference (DI) Effects of Naturally Occurring Core Internal Deletion (CID) Variants of Human Hepatitis

“Incomplete particles” were discovered during successive undiluted passages of the influenza viruses (1 ). In general, these incomplete particles contain a less than full-length genome and are replication-defective. They can be rescued by, and interfere with, the replication of homologous helper viruses. Another important characteristic of incomplete particles is their ability to enrich their proportion in the total viral yield in cells infected with wild-type and incomplete viruses (2 –4 ). Based on these properties, Huang and Baltimore defined these biologically active incomplete particles as defective interfering (DI) particles and the replication-competent homologous helper viruses as standard viruses (5 ).