Genetic heterogeneity of the human papovaviruses BK and JC

We have examined the structure and infectivity of BKV and JCV genomes from prototype strains after cell culture passage and of BKV genomes from primary isolates. Genomic structures were determined by restriction endonuclease analysis of molecularly cloned DNA. Infectivity was determined by transfection of the cloned genomes into urine‐derived epithelial cells and assaying for viral proteins and virus production. Prototype BKV DNA, which was cloned after 14 passages in three different cell lines, contained no alterations in restriction enzyme sites and was infectious. In contrast, prototype JCV acquired changes in the late region of the genome during passage in cell culture and the cloned DNA was not infectious. Urine‐derived cells were used to isolate virus from the urine of two renal transplant patients and one asymptomatic individual. The genome of the virus isolated from the normal individual was indistinguishable from prototype BKV except for a 60‐base pair deletion, which was localized between 0.62 and 0.72 map units. Two isolates from transplant patients differed from each other and from prototype BKV at a number of restriction enzyme cleavage sites located in the early region and were infectious. Genomes containing deletions from 100 to 600 base pairs were also cloned but were not infectious.