Occurrence of multiple types of human papillomavirus in genital tract lesions. Analysis by in situ hybridization and the polymerase chain reaction.

More than 22 types of human papillomavirus (HPV) have been detected in genital tract squamous cell intraepithelial lesions. Seven of two hundred eighty-six (2.4%) genital tract tissues in which HPV DNA was detected by in situ hybridization contained two or more different HPV types. When analyzed by site, 5 of 204 (2.4%) of cervical intraepithelial lesions were infected by more than one type, compared with 2 of 82 (2.4%) of vulvar lesions. The rate for low-grade lesions was similar (5/218; 2.3%) to that for high-grade lesions (2/68; 2.9%). In contrast, two different HPV types were detected in 6/33 (18%) of tissues by the polymerase chain reaction (PCR) using type-specific primers for eight HPV types. It is concluded that infection by one HPV type is rarely associated with concurrent 'active' infection by a second HPV type, even though DNA of a different viral type can be detected by PCR in about one fifth of such cases. Further study is required to determine if an existing HPV infection can inhibit replication by a different HPV type.