The Human Papillomavirus (HPV) in Human Pathology: Description, Pathogenesis, Oncogenic Role, Epidemiology and Detection Techniques

Persistent infection by human papilloma virus (HPV) is considered to be the main causative agent of cervical cancer and other anogenital cancers. Of more than 30 genotypes capable of infecting the anogenital tract it is estimated that, worldwide, HPV 16 and 18 cause 70 percent of the cervical cancers. So far, more than 100 types and subtypes of HPVs have been wholly or partially sequenced. All of them, approximately 40 types, have been isolated from lesions to the lower genital tract and between 15 and 20, according to different studies, have been detected in carcinomas. According to their oncogenic risk, they are classified as low-risk HPV (LR-HPV) and high-risk HPV (HR-HPV). We must take into account that certain viral types may appear in cancerous lesions as a result of a co-infection and not be the causative etiologic agents for tumour transformation. As is logical, epidemiological studies attribute important population variations to the prevalence and cause/effect of different viral types, however, there is no doubt about the high prevalence or involvement of types 16 and 18 in high level pathologies and carcinomas in our population.

The detection of HPV DNA through techniques of Molecular Biology, regardless of the method used, are based on the specificity of the complementarity among the nucleic acids. A DNA sequence has the ability to specifically hybridise with other DNAs or RNAs so specifically that at a certain temperature they only form hybrids if 100 percent of the bases are complementary. The way of detecting these hybrids, the composition of the DNA probes, and the existence or not of amplification of the signal mark the difference between the different detection techniques. The assessment of the viral load, integration, and other molecular parameters are shaping up as excellent complementary diagnoses in daily clinical practice.