How is human papillomavirus HPV infection

Kak peredaetsya papillomavirusnaya infekciya VPCH

Cervical cancer is a rare and late complication of trivial viral infections. However, the disease is a source of suffering and is a serious medical and social problem. Each year the disease affects 400,000 women in Europe – about 50 thousand, mostly hurt young (30 to 50 years), half of them will die from this diagnosis. In our country each year get sick more than 1,000 women die of about 400. In recent years, this issue was reviewed by the international and domestic medical experts.

Let's also see what is – human papillomavirus that can lead to cancer, how is HPV infection, which types are the most dangerous.

The HPV virus

This virus is capable to meet and be transferred in all vertebrates, but each species — specific. HPV is probably accompanied by a person over millions of years of evolution of the human species. It exists in the form of infectious particles – virions – with a diameter of 55 nm, the surface of which (the capsid) is shaped symmetrical icosahedron with 72 pentagonal surfaces. A structural unit is called the nucleocapsid.

The virus contains a circular double-double-stranded DNA genome (the biological substrate of memory of 7900 base pairs) without the lipid shell, only the shell proteins (L1, L2, and histones).

The virus is relatively stable and durable, due to which – it is easily transmissible. In a humid environment to become infected is equal to several months. Biological memory is implemented by creating proteins.

The functions of the individual proteins

  1. E1 – protein of the beginning of virus replication,
  2. E2 – protein regulator of transcription of the virus,
  3. E3 – likely meaningless,
  4. E4 – a protein release of infectious virions in the environment (which determines the possibility of Contracting),
  5. E5 – oncogene growth factor, protection against the cytotoxic T-lymphocytes,
  6. E6 – inactivates cellular integrity of the tread, the cellular protein p53, activates telomerase,
  7. E7 inactivates the tumor suppressor protein PRB cells, destroys cells,
  8. E8 – possible factor latent viral infection in the basal epithelial cells,
  9. L1 – construction of the main structural protein of the viral shell (capsid),
  10. L2 protein shell of the viral DNA into the virion.

Classification of HPV virus

Kak peredaetsya papillomavirusnaya infekciya VPCH

Current typological classification of viruses of HPV based on sequence analysis, clinical and pathological consequences of infection, functional and genetic characteristics: a virus is a self-sufficient, independent of pathogen. The infection can be detected morphologically, by hybridization, polymerase chain reaction, immunohistochemistry (antibodies against the antigen encoded by the L1 gene).

Once infected with HPV, the virus replicates exclusively in the skin or mucous membranes of the genital organs, the anus, the mouth and the respiratory tract. Separate types of HPV always infected anatomical localization, where the core of the local epithelial cell specific viral genome is actively rewrite. The immune response is cellular in nature, specific to particular types of viruses. To viremia with seeding in remote areas does not reach.

Manifestations

During productive infection comes to a local hyperproliferative keratinocytes, sometimes with obvious manifestations, but the infection often occurs without symptoms. HPV is a necessary cause of carcinogenesis of epithelial tumors in the anogenital region (indicated in carcinoma of the cervix in 99.7% identical in the metastases and the primary lesion often cause in vitro transformation of cells, viral genome is actively transcribed).

The anatomical substrate, gateway (transmission path), and then cultivation and soil inoculation of virus are minor injuries of the skin or mucous membranes. The virus can fill every evolutionary niche in which the immune response is ineffective.

What is the connection between HPV and cervical carcinoma?

Nearly 100% of all cases of cancer of this type responds to infection by the virus HPV. This infection, the most common methods of infection which include sex, is a widespread phenomenon.

The highest number of infected is the female population in the age group of 20-25 years (about 50%) and 45-50 years of age. Up to 80% of people throughout life infectedHPV, in most cases, people become infected soon after the beginning of sexual life. Usually within 12-18 months of a person's immune system copes with infection.

Up to 80% of all people are subject to HPV infection in their lifetime. Some of them repeatedly.

Route of transmission

The most common way, how is papillomavirus, presented to the sexual act.

Kak peredaetsya papillomavirusnaya infekciya VPCH

Be transmitted virus and no sexual activity (for example, through a contaminated towel or linen), but the probability is quite rare (these ways HPV is transmitted, for example, should be considered in children).

In any sexual activity and, in particular, by sexual contact creates cracks on the genitals, which are "conduits" for the transmission. Infection can occur in sexually active girls, not having sexual relations because the infection is able to anestis, for example, through contaminated fingers of the partner.

  1. Primarily, HPV is transmitted through sexual intercourse (90%).
  2. Condom is not able to 100% protect from infection, but its use reduces the risk of infection.
  3. The period from infection to manifestation of symptoms usually ranges from weeks to six months, sometimes longer.
  4. In a large percentage of infected people do not manifest any signs of infection.

By testing for the presence of HPV in cancer of the cervix has been proven that the immune system a large percentage of women are capable of 12-18 months to deal with contamination, therefore, it has been suggested that the male immune system can fight the infection within the same time.

Risk factors for transformation

The main factor is the contact with the HPV virus and its retention (i.e. persistence) in the tissue. In addition, there are other factors that increase the relative risk of cell transformation:

  1. Sexual behavior and number of sexual partners in their lifetime.
  2. Ethnically given a genetic predisposition (differences of haplotype leukocyte antigen HLA).
  3. A greater number of full-term babies in young women (cervical injury, immunosuppression).
  4. The presence of pathogens of other sexually transmitted infections (some genotypes of chlamydia).
  5. Cigarette Smoking and immune disorders (in particular, human immunodeficiency virus, HIV).
  6. Initiation of sexual activity during somatic changes at puberty
  7. Eating disorders with low levels of alpha-tocopherol and vitamin C antioxidants.
  8. Search non-participation in screening programs.

Light a precancerous change of squamous epithelium, arising from the impact of HPV low risk, in most cases, heal spontaneously, or long-term stagnation. Only in 10% of cases, the process worsens and develops into a severe precancerous condition and approximately 0.15% in cancer.

Glandular epithelial lesions are rare (relative to squamous cell 1:50), but can occur faster. The natural evolution of HPV infection is identical with the development of precancerous lesions. Then the most serious is HPV type 16.

How to protect against HPV infection?

Currently, the most effective protection against HPV is vaccination. In the domestic market affordable vaccine Cervarix (Cervarix) and Gardasil (Gardasil). Cervarix protects against HPV 16 and 18, Gardasil – against HPV 6, 11, 16 and 18.

Vaccines are only prophylactic (preventive) measure, not a therapeutic effect and do not affect the current infection. Therefore, it is best to administer the vaccine to women before they become sexually active. Vaccination is useful to already sexually active women, as the risk of new infection is maintained throughout life.

Kak peredaetsya papillomavirusnaya infekciya VPCH

The effectiveness of the vaccine among sexually active women is the same, long an HPV infection acquired through vaccination greatly reduces its effectiveness. However, for HPV-positive women or women who have already suffered the infection, the vaccine may be useful. Most infections are temporary and only lead to the formation of very small amounts of protective antibodies, therefore, without vaccination, the formation of precancerous changes due to re-infection by a virus of the same type.

A very effective means of protection against many sexually transmitted diseases is the condom. Its regular use reduces the risk of infection, however, does not eliminate it. Transmission of HPV occurs through contact with skin outside the area protected by the condom.

The best strategy possible protection against infection is represented by vaccination, moderate sexual life and strict adherence to basic rules of hygiene.