HPV is a pathogen that most of us come into contact with during our lifetime. Infection with it may be different - some people do not develop any symptoms, others have various warts, and in others, HPV can lead to neoplastic diseases, e.g. cervical cancer. Effective methods of treating HPV infection have not been found so far, only methods of preventing infection with this microorganism are known.
HPV(human papillomavirus,human papillomavirus ) is extremely widespread among the human population - it is estimated that the overwhelming majority people become infected with this pathogen throughout their lives.
The HPV virus is such an important microorganism for human he alth that even the Nobel Prize was awarded for its discovery. It was received by Harald Zur Hausen, a German virologist who not only discovered HPV, but also characterized its role in the pathogenesis of cervical cancer, and participated in the development of a vaccine against HPV.
Contents:
- HPV virus: construction
- HPV virus: routes of infection
- HPV virus: effects of infection
- HPV: diseases
- HPV: How can papilloma promote cancer?
- HPV virus: diagnosis of papilloma infection
- HPV: treatment
- HPV: prevention
HPV virus: construction
HPV belongs to the familyPapillomaviridae . Its virion is bare, has icosahedral symmetry, and is 55 nanometers in diameter. The genetic material of the human papilloma is double-stranded DNA, appearing in a circular form.
There are over 200 types of HPV - they differ, for example, in a tendency to infect the skin and mucous membranes, but also with oncogenic potential (i.e. the ability to induce neoplastic transformation of infected cells).
HPV virus: routes of infection
In fact, it is relatively easy to get infected with HPV - it is even considered that HPV infection is the most common sexually transmitted infection. Transmission of the pathogen between people may be the result of close skin-to-skin contact.
The HPV virus is quite resistant to various environmental conditions, therefore infection may also occur as a result ofuse of items (e.g. towels) used by a person infected with this pathogen.
Transmission of infection can also occur during pregnancy - it happens that a pregnant woman, who is a carrier of HPV, transmits the pathogen to a child even before his birth. There is also the possibility of transmission from mother to child during labor.
There are several factors that increase the risk of contracting the human papillomavirus - they are:
- having sexual contact with multiple partners
- having sex with a person who has had multiple sexual partners
- weakened immunity (due to HIV infection or taking immunosuppressive drugs)
- presence of some damage on the skin or mucous membranes (e.g. minor wounds)
HPV virus: effects of infection
Human papilloma, as mentioned above, is tropic to human epithelial cells. It initially infects cells of the basal epithelial layer. Over time, these structures migrate to higher layers, accompanied by processes related to viral replication - eventually, daughter virions are released from dead epithelial cells.
In some people, HPV infection is temporary and it wears off after some time (then there may not even be any lesions). In others, persistent HPV infection may occur, leading to the appearance of various skin lesions, which, even after spontaneous resolution, may recur due to the presence of papillomavirus DNA in epithelial cells.
However, before any lesions possibly occur in a person infected with HPV, the pathogen must develop in the body for some time. This is known as the incubation period, and it lasts an average of three months, although it can last either 6 weeks or even 2 years.
HPV: diseases
Human papilloma can be the cause of many different dermatological problems, but not only. The HPV virus can cause diseases such as:
- skin warts (units such as common warts, flat warts or foot warts can be mentioned here)
- genital warts (referred to as genital warts, most cases are associated with HPV types 6 and 11 infections; genital warts can be both small and flat, and can take the form of large, cauliflower-shaped structures)
- epidermoplasia verruciformis (a genetic disease associated with HPV types 5 and 8 infection, papillary lesions may transform with agefor squamous cell carcinoma)
- recurrent respiratory papillomatosis (an uncommon unit in which the course of changes typically occurs within the larynx, its form occurs in childhood and develops in adulthood)
- changes in the mouth (such as squamous cell papillomas or common warts)
- intraepithelial neoplasia (it may apply to the cervix, but also to the vagina, anus, vulva and penis)
- neoplastic diseases (e.g. cervical cancer, rectal cancer or penile cancer, but also head and neck cancers, such as e.g. tonsil cancer or epiphyseal cancer)
HPV: How can papilloma promote cancer?
Some types of HPV have a lower oncogenic potential, others a greater oncogenic potential. The most dangerous types of HPV are HPV 16, 18, 31 as well as 33, 45 and 56.
The risk of neoplastic transformation occurs when the genetic material of the virus integrates with the DNA of the host cells. Then, proteins other than those in the normal replication of the virus are produced - viral proteins E6 and E7 are of major importance in oncogenesis.
With their high production, the divisions of HPV-infected human cells may be stimulated - these divisions are uncontrolled and may ultimately result in the occurrence of one of the above-mentioned neoplastic diseases.
This is because the aforementioned viral proteins block the activity of human suppressor proteins, whose task is to protect against uncontrolled cell division - here we are talking about the TP53 and RB proteins.
It should be emphasized here that not every patient who develops HPV infection within the cervix will develop cancer of this organ.
Even 8 out of 10 such infections heal spontaneously, and what's more - it also happens that the process of carcinogenesis will start, and eventually the changes caused by the human papilloma will reverse anyway.
However, there are no known factors that cause some women infected with HPV to eventually develop cancer, and in others the changes disappear after some time.
HPV virus: diagnosis of papilloma infection
Most diseases caused by the HPV virus - eg skin warts - can be identified just by assessing the morphology of such changes. In the case of diagnostics of HPV infections within the cervix, colposcopy and cytological examinations are used (for which a cervical smear is taken).
It is also possible to perform tests to assess the presence of the genetic material of the virusin tissue samples obtained from the patient.
HPV: treatment
So far, no drugs have been found that would be able to cure HPV infection. Most pathogen-induced diseases resolve completely spontaneously after a long and varied period of time.
If the patient wishes to eliminate unsightly skin lesions, various physical methods of their removal (such as cryotherapy or laser therapy) can be used, as well as chemical methods of their removal (e.g. using preparations containing podophyllotoxin or chloroacetic acid). On the other hand, HPV-induced neoplasms are treated in a variety of ways - for example, cervical cancer can be treated surgically as well as with the use of chemo- or radiotherapy (where the choice of treatment depends primarily on the stage of the disease at the time of diagnosis).
HPV: prevention
HPV infection cannot be cured - yes, it can pass spontaneously, but it can also be prevented at all. For this purpose, be careful when having sexual contact (e.g. remember to use condoms or avoid casual intercourse), and avoid contact with the skin of people who have visible changes potentially caused by HPV.
There is, however, a special method of preventing infection by the HPV virus - we are talking about vaccinations here.
There are several types of them - bi-, four- and 9-valent HPV vaccines are available (the greater the valency, the more types of HPV virus vaccination protects against - all protect against the most oncogenic types of HPV, i.e. 16 and 18).
Vaccination is recommended primarily to girls and young women, but there is more and more talk that boys and young men may also benefit from vaccination. Sources:
- "Obstetrics and gynecology", vol. 2, scientific editor G. H. Bręborowicz, Wyd. Medical PZWL, Warsaw 2015
- "Infectious diseases", edited by A. Kowal-Piaskowska and I. Mozer-Lisewska, Ed. Scientific UM im. Karol Marcinkowski in Poznań, Poznań 2016
- Broniarczyk J. et al., Structure and properties of the human papillomavirus, Biotechnology 3 (90), 126-145, 2010