Full HPV typing by a single restriction enzyme

Background: Restriction fragment length polymorphism (RFLP) methods for genotyping genital human papillomavirus (HPV) are considered labor consuming and constrained by the reduced set of restriction enzymes capable of detecting specific mutations. However, we think that these methods have not taken full advantage of the high diversity of the known restriction enzymes. Objective: We have set out to find the best restriction enzyme for HPV typing. Study design: An extensive search for enzymes was carried out by combining statistical methods and database information. The search maximized the discrimination between high- and low-risk types by examining the sequence of the L1 gene flanked by primers MY09/11. Different electrophoretic resolutions and two variations of the RFLP method were considered. Results: HpyCH4V is the best enzyme for discriminating between risk types. Moreover, HpyCH4V generates different patterns for virtually all the HPV types. The typical pattern consists of two or three fragments, which facilitates typing in mixed infections. The typing of a set of clinical samples confirmed the expectations. Conclusions: This result illustrates the possibilities of statistical methods to exploit the high diversity of restriction enzymes in order to classify samples in a pre-established hierarchy of types for which DNA sequences are known.