HPV related infections
Acronym for Human Papilloma Virus, HPV is involved in hyperprolifrative lesions localized in various mucosal and skin regions, including the vulva, cervix, vagina, anus, and lining of the mouth and throat;
It is believed that HPV infections are among the most frequent sexually transmitted diseases: it is estimated that a large part of women (between 75 and 90%) have contracted the virus at least once in their life. It should be emphasized that, fortunately, the efficiency of the immune system of many women is able to eradicate the virus without the need for pharmacological intervention.
The probability that the Papilloma Virus infection is not eradicated in a short time by the immune system is strongly conditioned by the contracted HPV genotype and is clearly higher for the variants with high oncogenic risk.
Microbiological analysis
The HPV virion is a pathogen devoid of pericapsid (naked virus), with an icosahedral structure: it is covered by an icosahedral capsid with a diameter of 50 nm. The capsid, in turn, is made up of 72 capsomers (12 pentamers and 60 hexamers), originating a 5-pointed protuberance, with a sort of central core. There are two proteins that form the capsid:
- Protein L1, or major protein, common to all variants of Human Papillomavirus: it constitutes 80% of the virus proteins. It is believed possible that most antibodies are produced against this protein.
- Minor protein or L2: completes the remaining 20%. It is not constant in the various forms of Human Papillomavirus.
From microbiological scientific research, it is observed that 7,900 base pairs make up a single molecule of the viral genome: the DNA of the virus is circular and covalently closed.
Genotypes and classification
The term Papilloma it is composed of a prefix "papilla", of Latin derivation, and a suffix "-oma", which literally means "tumor pustule".
The Papilloma Viruses, extremely heterogeneous in terms of composition, belong to the family of Papillomaviridae and the genre of Papilloma virus.
There are numerous strains of Papilloma Virus: to date, over 120 have been identified, but it is assumed that the number of genotypes is constantly growing. Among the more than 100 scientifically isolated serotypes of Papilloma virus, a classification has been made into 16 groups, distinguished by the letters of the Greek alphabet between A and P. More precisely, these viruses are classified on the basis of several factors:
- nucleotide sequence
- phylogenetic position
- oncogenic potential
Furthermore, the Papilloma Viruses are cataloged according to the site of action: some exert their pathogenic power at the skin level (mainly HPV type beta), others are specific for causing damage to the mucous membranes (HPV alpha).
Human Papillomavirus genotypes are also classified into three levels, depending on the possible oncogenic risk:
- Some of the high oncogenic risk HPV genotypes are HPV 13, HPV 16, HPV 18, HPV 31, HPV 33, HPV 35, HPV 39, HPV 45, HPV 51, HPV 52, HPV 56, HPV 58, HPV 59, HPV 68, HPV 73, HPV.
- HPV 26, 53 and 66 are categorized as "probable high risk genotype"
- The other HPV genotypes, in particular 6 and 11 (the most common), present a very low risk of tumor degeneration: these are, in fact, the genotypes involved in the formation of genital warts.
Fortunately, the vast majority of viruses belonging to the Papillomaviridae it does not cause dangerous or alarming lesions, just think of skin warts which, although annoying, are certainly not among the serious dermatological lesions. Among the papilloma viruses, however, a small minority is accused of inducing a malignant transformation of the cells involved, therefore cancer, especially at the level of the cervix, anus, esophagus, larynx and oral cavity.
The image below clearly shows that HPV 16 is the serotype responsible for the greatest number (53.5%) of cervical carcinomas attributable to the human papilloma virus; the additional contribution of HPV 18 is 17.2%: as anticipated, HPV 16 and HPV 18 are therefore responsible, alone, for over 70% of cervical carcinomas attributable to human papilloma virus.
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After breast cancer, malignant cancer due to HPV is the most common among women: it is estimated that every year, in our country, more than 3,000 new women are affected by this form of cancer that affects the neck of the uterus.
