Human papillomavirus: structure, life cycle, as transmitted, prevention
One of the most common infections is the human papillomavirus. Consider its main types, the risk of oncogenicity, symptomatology, methods of diagnosis and treatment.
HPV is highly specific to the human body infection from the family Papovaviridea, that is, the papoviruses of subgroup A. Its carrier is every sixth person on the planet. The fine heat-stable exciter well survives in the external environment and is resistant to thermal treatments. Has a high ability to infect multilayer epithelium: skin, mucous membranes, cylindrical lung epithelium, prostate and cervical canal.
To date, medicine has known more than 120 serotypes of the virus, 35 affects the skin and mucous membranes. Some serotypes have oncogenicity, that is, the ability to cause cancerous degeneration of the affected tissues.
- Low oncogeneity - 6, 11, 42, 43, 44, 73.
- High oncogeneity - 16, 18, 31, 33, 35, 39, 45, 51, 52, 56, 58, 59, 66, 68.
Getting into the human body, the virus spreads through the bloodstream, penetrates into the DNA of the cell and disrupts their normal functioning. The infected cell begins to actively divide and expand, because of what on the affected area there are characteristic growths.
According to medical statistics, HPV infection is most common during transmission during sexual intercourse. Only in the last 7-10 years the number of infected has grown more than 10 times. The disease requires comprehensive diagnosis and treatment.
Structure of the human papillomavirus
HPV has small virions without a membrane shell, with a diameter of not more than 30 nm. That is, its size is 5 times less than the influenza virus and HIV, which have a membrane envelope. The genetic material of papillomavirus is DNA in which about 8000 base pairs and a variety of protein compounds. The genome is a double-stranded molecule, packed with histomes, that is, cellular proteins that participate in the compaction of DNA in the nucleus.
The genes of the virus encode several types of proteins, each of which performs certain functions in its life cycle. Isolate early proteins (E), which are responsible for the regulatory functions and multiplication of infected cells and late proteins (L), performing structural functions.
The structure of the virus corresponds to these types of proteins:
- E1-E8 - are involved in DNA replication, are synthesized immediately after infection. They are manifested by the granularity of the skin in which they accumulate.
- L1-L2 - form the structure of the virus. Responsible for the formation of the outer shell (capsid), which penetrates the stratum corneum of the epidermis.
The protein structures involved in oncogenesis are especially dangerous:
- E6 - disables the tumor suppressor of p53 healthy cells, causing excessive proliferation of cellular structures. E6 leads to a sharp decrease in p53 and degenerative processes.
- E7 - binds Rb, that is, the oncosphere, responsible for slowing down the enzymatic reactions of uncontrolled cell division.
E6 and E7 lead to uncontrolled growth of cells, causing tumor formation. In this case, the E2 protein stops this pathological process, but this ability is lost immediately after the genome infects the human cell.
Because of the complex structure, HPV is not easy to cultivate under laboratory conditions. This is due to the fact that the virus particles are formed only in living organisms or complex organotypic cultures that are similar to human cells.
Life cycle of the human papillomavirus
The infectious process and the life cycle of the human papilloma virus are based on the self-reproduction of infectious virions. In the normal course of the pathological process, there is a close relationship between the cycle of viral DNA replication and the life cycle of the infected cell of the human body. Papillomavirus disrupts replication of cellular DNA, laying down a program of reproducing its own infected cells with increased infectious activity.
In the process of inhibiting replication, there is a high probability of changing the cycle of infection and transforming it into a malignant tumor. If the life cycle is disrupted or interrupted, the development of infectious virions becomes impossible.
In an infected cell, HPV exists in two forms:
- Episomal - is outside the chromosomes of the infected cell, has a low risk of oncogenicity.
- Integrated - viral DNA is embedded in the cell chromosome. This form is malignant.
Depending on the intracellular form of infection, such variants of the course of the infectious process are possible:
- The latent (latent) course is HPV in episomal form, but does not cause pathological changes and has no clinical manifestations.
- Papillomas are an infection in the episomal form. The number of cells of the basal layer increases, which leads to the appearance of skin outgrowths of different localization.
- Dysplasia - virions are in episomal and integrated form.
- Carcinoma - the virus is in an integrated form. Appear atypical cells, indicating the development of malignant processes in the body.
The incubation period from infection to the appearance of the first symptom can be from ½ month to several years. It is possible to develop several genotypes in the body at the same time. In some cases, within 6-12 months after infection, self-healing occurs, that is, a violation of viral DNA replication.
How is the human papillomavirus transmitted?
Transmission of HPV is from a sick person to a healthy one. Infection occurs with close personal contact, during intercourse or during the labor process from mother to child.
There are ways of penetrating the infection into the body:
- Contact with infected skin or mucous membranes.
- Use of personal use of the infected.
- Wearing shoes or clothes of the patient.
- Visiting saunas, swimming pools and other common areas with high humidity.
According to medical statistics, the most common way of transmitting HPV is unprotected sexual intercourse. In this case, infection occurs regardless of the type of contact (vaginal, oral, anal). The virus penetrates the body through microdamages of the mucous membranes and epidermis. If growths occur in the oral cavity, then this may indicate infection during a kiss or oral sex. Men are more likely to infect women. In this case, infection is possible only if there is papillomas and warts on the genitals.
When infected from mother to child, papillomatosis is transmitted intranatally or when the child passes through the birth canal. The baby can have anogenital warty growths and warts on the inner surface of the larynx and pharynx, complicating the process of breathing. Also, infection can occur during lactation. The ways of household transmission of the virus are extremely rare. This is due to the fact that in the environment the infection exists for a short time.
Since human papillomavirus does not have a high infectiousness, infection occurs when certain factors act:
- Reducing the protective forces of the immune system.
- Violation of barrier functions of the epidermis or mucous membranes.
- Violation of the microflora of the intestine or vagina.
- STDs (papillomatosis acts as a secondary infection).
- Exacerbation of chronic diseases.
- Frequent stress or harmful working conditions.
- Non-compliance with personal hygiene.
- The use of drugs that suppress the immune system.
Throughout life a person can infect several genotypes of infection simultaneously. The above factors lead to an increase in infection. Infected cells begin to multiply actively, causing skin growths of various forms and localizations.
Immunity
To date, papillomatosis is one of the most common diseases. People with a strong immune system can be carriers of the virus for a long period of time without even knowing it.
It is the immunity that acts as a factor in protecting the body from pathogens. A timely immune response leads to the destruction of the pathogen, which does not have time to infect the basal cells of the epithelium.
There are a number of factors that undermine immunity and contribute to infection and activation of the virus:
- Frequent respiratory viral infections and infectious and inflammatory lesions of the body.
- Intensive exercise.
- Psychoemotional stress and stress.
- Subcooling the body.
- Abuse of alcohol, smoking and other bad habits.
Decreased immunity provides active growth of papillomatous neoplasms. In order to prevent this, we show the use of immunomodulators and vitamin, which contribute to the speedy recovery and elimination of the virus from the body.
Prevention of the human papillomavirus
Any disease is much easier and more important to prevent than treat. Prevention of human papilloma virus is based on a healthy lifestyle and strengthening of immunity. It is the immune system that plays a decisive role in the appearance of HPV infection. With a weakening of protective forces, the body weakens, creating a favorable background for infectious lesions.
Prevention of papillomatosis and other diseases is reduced to such simple rules:
- Healthy lifestyle.
- Lack of bad habits.
- Proper balanced nutrition.
- Secured sex and a regular partner.
- Absence of stress and other emotional shocks.
- Timely treatment of any diseases.
- Vaccination.
- Regular preventive examinations at the doctor.
The above recommendations relate to the prevention of the first level. To prevent the infection of HPV with high carcinogenic risk, there are special vaccines. They contain viral proteins-antigens, under the influence of which the body produces specific antibodies that contribute to the destruction of the infection when it occurs.
There are also secondary preventive measures, which include: visual and cytological screening to detect a virus and monitor the dynamics of its development. If the results of these tests are positive, the patient is assigned a comprehensive set of diagnostic tests. Typically, this PCR, biopsy, colposcopy and a number of other methods.
Tertiary prophylaxis is performed when HPV infection of high oncogenic risk is infected. The patient should take a smear every six months for a cytology within three years after infection. If the results are negative, the test is taken once a year for life.
Vaccination against human papillomavirus
One of the methods of preventing papillomatosis is vaccination. Vaccination against the papilloma virus is used to prevent the infection of HPV with a high carcinogenic risk - it's 16 and 18 type. Vaccination is advisable to be carried out until the first sexual contacts, that is, in adolescence from 16 to 23 years.
It should be noted that if the virus is already present in the body, then the effect of the injection is zero. But many scientists believe that the introduction of a vaccine to already infected patients facilitates the course of the virus and speeds up the recovery process.
Vaccination involves the inoculation with one of these drugs:
- Cervarix
An adsorbed recombinant vaccine for the prevention of diseases caused by the human papillomavirus. It contains a mixture of virus-like particles of strain 16 and 18. The effectiveness of the drug is based on its adjuvant system. Provides cross-protection of the body against any manifestation of HPV, which can be detected cytologically.
When the full vaccination is carried out on a special schedule, the drug promotes the formation of specific antibodies to the virus in the body. Immunoglobulins are detected in 100% of patients who underwent a course of inoculation.
- Indications for use: prevention of cervical cancer in patients 10-25 years old, prevention of acute and chronic infections associated with Human papillomavirus, as well as cellular pathologies involving the development of flat atypical cells of unknown etiology, cervical intraepithelial neoplasia and precancerous conditions in patients 10-25 years.
- Method of administration: the vaccine is administered to the deltoid muscle region. Intravenous and intradermal administration is contraindicated. Before vaccination, an organoleptic control of the preparation should be carried out and shaken thoroughly to obtain an opaque white suspension. The drug is administered in three stages with a single dose of 0.5 ml. At primary grafting the schedule of 0-1-6 month adheres.
- Side effects: pain at the injection site, increased fatigue, dizziness, disorders of the gastrointestinal tract and the musculoskeletal system, skin allergic reactions. There is also a risk of anaphylactic reactions.
- Contraindications: hypersensitivity to vaccine components, acute hyperthermia, relapses of chronic diseases. With special care, grafting should be carried out with thrombocytopenia and disorders of the blood coagulation system. The vaccine is not suitable for treating existing lesions caused by HPV types 16 and 18. Cervarix injections during pregnancy and lactation are not carried out. There have been no cases of overdose.
The vaccine is produced in a syringe with a single dosage. Store the drug should be in the refrigerator for three years from the date it was manufactured.
- Gardasil e Gardasil 9
The drug Gardasil is an antigenic set of papillomaviruses 6, 11, 16 and 18 types. Promotes the activation of the immune system for the formation of antiviral antibodies and immunological protection of the body. Gardasil® 9 is a 9-valent recombinant human papillomavirus vaccine. It is active against such strains of infection: 6, 11, 16, 18, 31, 33, 45, 52, 58. Both inoculations provide cross-protection against genotypes that are not present in the preparation: 31, 33, 35, 39, 45, 51, 52, 56, 58 and 59.
- Indications for use: prevention of infection with Human papillomavirus, prevention of cancer and precancerous conditions of the cervix, vulva, anus, penis. Recommended for vaccination of patients from 9 to 45 years.
- Method of application: the vial with the solution is shaken and checked for absence of foreign inclusions. The solution is typed into a syringe and injected intramuscularly into the delta of the shoulder or the anterolateral region of the thigh. After the procedure, the patient should be under medical supervision for 30 minutes. Injections are carried out according to specially designed schemes. The standard scheme is 0-2-6 months, accelerated 0-1-4 months.
- Side effects: itching, swelling and tenderness at the injection site, headaches, fever, fainting, anaphylaxis, inflammation in the pelvic organs, thromboembolism, urticaria, gastroenteritis and others. In the case of an overdose, the severity of the above reactions increases.
- Contraindications: intolerance of active components, violation of blood coagulability, pregnancy and lactation, treatment with anticoagulants.
Gardasil and Gardasil 9 are available as a suspension in vials with a dosage of 0.5 ml each.
The vaccines described above are certified and passed all necessary checks. The vaccination is carried out in the conditions of the dispensary in compliance with the rules of asepsis and antiseptics.
Using a condom to prevent HPV infection
The main way to transmit HPV is unprotected sex with an infected person. Clinical studies have established that the use of a condom for the prevention of papillomavirus is highly effective. With this method of contraception, infection occurs in about 30% of cases. The risk of infection during sex without using a condom is 90%. Transmission of HPV through a condom often occurs after anal sex, but not vaginal.
Also it should be taken into account that pathogens are present in all biological fluids of the human body: saliva, mucus, etc. Therefore, if one of the partners on the mucosa of the oral cavity has growths characteristic of the disease, infection is possible not only with oral sex, but also with a kiss.
As for sex during the treatment of papillomatosis , intimacy is possible after destructive methods of sanitizing papillomas, condylomas or warts and after a course of antiviral treatment to suppress infection activity. In this case, sex should only be with the use of barrier contraception to prevent repeated relapses or infection of the partner.
Forecast
Human papillomavirus is one of the most common diseases with a hidden course. The prognosis of this pathology when infected with strains with low and medium oncogeneity is favorable. If it occurred by infection with HPV of the third group (high carcinogenicity), the outcome of the disease depends on its early diagnosis and treatment.