ISOLATION OF A FULLY INFECTIOUS VARIANT OF PARVOVIRUS H-1 SUPPLANTINGTHE STANDARD STRAIN IN HUMAN-CELLS

A variant H-1 virus, designated H-1 dr virus, was isolated from stock of the standard H-1 virus strain propagated in the newborn human kidne y cell line NB-E, Molecular cloning and sequence analysis revealed an in-frame deletion at map positions 39 to 41. This deletion affects the open reading frames encoding the nonstructural proteins NS-1 and NS-2 and the untranslated leader sequence of the R3 transcripts encoding t he capsid proteins, In addition, K-1 dr virus harbors a 58-nucleotide duplication inboard from the right-hand terminal palindrome. Internal deletions and terminal reiterations are hallmarks of H-1 virus type I variants that typically are defective interfering particles. Indeed, H -1 dr virus was found to progressively supplant the standard strain in serially coinfected NB-E cell cultures. However, H-1 dr virus differe d from previously described type I variants in its full infectivity, a s was apparent from its ability to give yields of replication and prog eny virus production that were similar to those of the standard virus strain in NB-E cells. Hence, the interference of H-1 dr virus in tie p ropagation of standard H-1 virus in coinfected cells was not accompani ed by a drop in the titer of infectious virus. Moreover, H-1 dr virus proved to induce the same pathogenic effects in newborn hamsters as th e standard virus strain did.