Analysis of Human Papillomavirus Type 16 Variants Indicates Establishment of Persistent Infection

Sequence differences in the noncoding region of the human papillomavirus type 16 (HPV-16) genome were displayed using single-stranded conformational polymorphism (SSCP) analysis of polymerase chain reaction (PCR)-amplified material. Two variants accounted for 50%-70% of all HPV-16 variants from 3 cohorts in Seattle. Seventy subjects who were repeatedly HPV-16 DNA-positive over 2-8 4-monthly visits showed an identical SSCP pattern at every visit. Only 10%-20% of the specimens showed evidence of infection by multiple variants when assessed by SSCP. However, cloning and sequencing of the PCR products revealed a substantially higher proportion of specimens with >1 variant. Sequencing many clones from each specimen confirmed that 1 major variant seemed to predominate over time, whereas minor variants appeared more transient. These results suggest that HPV-16 establishes a persistent infection in which a single variant predominates : coinfection with additional HPV-16 variants results in a minor population of HPV-16 genomes.