Human papillomavirus. Detection and prevention of infection

Abstract

Human papillomaviruses (HPVs) are composed of a big group of over hundred related viruses. Some of them can cause warts, and some can in worst case lead to cancer. High-risk HPVs can cause several types of cancer such as: cervical cancer, anal cancer, oropharyngeal cancers (cancers of the middle part of throat, including the soft palate, the base of the tongue, and the tonsils), vaginal cancer, vulvar cancer and penile cancer. The high-risk HPVs cause approximately 5 % of all cancers worldwide. It is well known that oral cancer is related to tobacco and alcohol use. On the other hand, HPVs seem to be linked to many of the cases of oral cancer. In Norway 57 % of oropharyngeal cancers are related to HPV infections. Nearly 70 % of all humans will be infected by HPV during life. Most of HPV infections go away on their own, but some infections persist and can cause cellular changes in the infected tissues. The identification of HPV nowadays relies on molecular biology techniques. This is because it cannot be propagated in tissue cultures. HPV has a well-known physical structure and an organization of genes, making the tests of choice for detecting HPV from clinical specimens based on nucleic acid probe technology. The detection methods can be divided into target amplification methods and signal amplification methods. Polymerase chain reaction (PCR) is the most commonly used tool in the detection of HPVs DNA. Since 2009, a vaccine (Gardasil) against 4 types of HPVs has been offered to 12-year-old females in Norway. The main purpose of this vaccine was to prevent the occurrence of cervical cancer among Norwegian females. It is estimated that 100 % of all cervical cancers are related to HPV infections. About 10 000 Norwegian females get diagnosed with mild cervical cell changes every year. About 300 Norwegian females are diagnosed with cervical cancer each year, and every year about 70 Norwegian females die because of cervical cancer. HPV 16 and 18 are considered the main cause of about 70 % of cervical cancer, and HPV 6 and 11 are found in cases mostly related to genital warts. The HPV vaccine is now also offered to Norwegian females born between year 1991 and 1996, 20-25 years of age. Some studies have suggested that the HPV vaccine can protect against HPV infections caused by oral transmission of the virus.