HPV type 6

Human papillomavirus (HPV) is associated with a wide range of diseases: from skin warts to life-threatening cancers. HPV type 6 refers to non-oncogenic viruses, that is, cancer does not cause.

[1], [2], [3]

Structure HPV type 6

All types  of human papillomavirus  Papovaviridae have the same structure, and HPV 6 type virions also exist in the form of an icosahedral capsid with a diameter of 52-55 nm, built of several dozen units of the structural proteins L1 and L2 - self-organizing pentamer capsomers.

An unprotected lipid envelope capsid contains one circular DNA molecule of the viral genome, consisting of two chains or filaments linked by proteins of cell nuclei - histones. The genome contains approximately eight open reading frames (ORFs) that are all transcribed from a single DNA strand.

HPV 6, like other papillomaviruses, is characterized by high epitheliotropicity, adaptability to the host and protection from the cell-mediated immune response. By expressing viral genes and replicating its DNA, it neutralizes the immunocompetent cells of the epidermis (T cells, macrophages / monocytes, etc.) and penetrates into the keratinocytes of the stratified epithelium of the skin of the anogenital zone and the oral cavity. The life cycle of the virus, first of all, its lytic phase, is associated with the differentiation of basal cells, which ensure the proliferation of skin tissue cells.

For replication, HPV has proteins (E1- E7) - recognizing its onset, regulating gene transcription and stimulating differentiating skin cells to replicate the DNA doubling period, that is, the S-phase of the cell cycle.

A specific feature of the papillomavirus type 6, as a low oncogenic risk virus, is the absence of aggressive inactivation of cellular tumor suppressor proteins p53 and pRb with its potential oncogenic proteins E6 and E7, which do not lead to the launch of the program of malignant differentiation of skin cells and their mutation (occurring in cancerous types HPV).

In addition, this virus has a latent phase of the life cycle, when, after the initial infection, the division of viruses ceases. At this stage, their genes can remain passive for a long time, being in the cytoplasm or the nucleus of the host cells, in the form of separate structures of episomal DNA. However, the virus is able to reactivate the process of DNA replication without re-infection of the person.

How is HPV 6 transmitted? Most often, the virus spreads through the skin contact between an infected and an uninfected person - sexually.

Read also -  Human papillomavirus: structure, life cycle, how it is transmitted, prevention

[4], [5], [6], [7], [8], [9], [10], [11], [12], [13], [14]

Symptoms

Infection with HPV 6 can be severe, subclinical or latent. Its symptoms on the skin and mucous membrane - anywhere on the external genitals, in the anal area and even in the mouth - are clinical manifestations of low-grade squamous intraepithelial lesions, which are diagnosed as  condylomata  acuminate or  genital warts.

They appear on the skin of the vulva, vagina, cervix, groin, penis, scrotum, or perianal area. They may have the appearance of a hyperkeratotic macula, plaque or papule of a different color; often look like fleshy soft formations, sometimes similar to cauliflower in miniature. They are always contagious; in most cases, painless, but can cause discomfort and irritation with itching; may increase in size, remain unchanged for years, spontaneously regress.

When the formation becomes very large (5–10 cm) and spreads to deeper tissues, it is called the giant warts Buschke and Loewenstein. This benign formation is most common in men in the head of the penis and foreskin, but is also possible as a perianal lesion in women.

HPV type 6 in men, for details, see -  Genital warts in men.

Details on HPV type 6 in women in the publication -  Genital warts in women.

Activation of the HPV 6 DNA replication process and pregnancy links the state of physiologically determined immunosuppression, which contribute to relapses, as well as accelerated reproduction and growth of genital  condylomas. In most cases, after birth, they spontaneously regress. All the details in the material -  Papillomas during pregnancy.

But their presence in pregnant women can lead to intrapartum infection (during childbirth) and such a rare manifestation of HPV type 6 in a child, such as laryngeal papillomas or recurrent  laryngeal papillomatosis, which makes breathing difficult, may be accompanied by coughing and problems with swallowing.

[15], [16], [17], [18], [19], [20], [21], [22]

Diagnostics

Methods such as electron microscopy, cell culture and some immunological methods that use the diagnosis of viral infections are not suitable for detecting HPV.

For visualization of subclinical genital HPV-associated lesions, acetic acid test is performed: placing gauze wipes moistened with a 3-5% solution of acetic acid on the affected area (10 minutes) makes invisible flat genital lesions visible (they turn white).

False positive results are common and can result from focal parakeratosis in candidiasis, psoriasis, or lichen planus.

Important methods for diagnosing HPV type 6 are biopsy and  tests for human papillomavirus.

Quantitative determination of HPV 6 can be carried out by real-time polymerase chain reaction (qPCR) - kinetic monitoring of viral DNA amplification. Although it is not always possible to determine the specific type of virus.

Also read -  Human papillomavirus infection: detection of human papillomavirus.

[23], [24], [25], [26], [27], [28], [29], [30]

Treatment

Treatment of human papillomavirus  should not be understood as drug therapy for persistent human papillomavirus infection (there are simply no such drugs), but as a treatment for visible warts.

According to experts, an average of 56% of cases of squamous intraepithelial lesions of HPV 6, three years after their detection, there is spontaneous regression of lesions that can recur after different periods of time, especially against the background of weakened immunity.

External treatments are used in the treatment, in particular, Podofillin solution, various  papillomas ointments. Perhaps surgical treatment using cryo-, electro-and laser methods of  removing genital warts.

Detailed information in the article -  Review of effective methods of treatment of genital warts

Regarding systemic immunotherapy for HPV infection, there is no consensus among physicians. For example, the combination drug Immunostimulating Action Isoprinosine with HPV 6 (other trade names - Inosine Pranobex, Groprinosin, Gropivirin, Groprim, Neoprinozin, Dimepranol, Normomed, Inosiplex, Methisoprinol) can be prescribed as an additional therapy. Manufacturers equate immunomodulatory drugs to antiviral, assuring their etiotropic action. Although among the components of  Isoprinosine  - inosine, 4-acetamidobenzoic acid and N-dimethylamino-2-propanol - no one pharmacologically affects papillomaviruses. In addition, the last ingredient refers to the precursors of psychotropic drugs.

Prevention HPV type 6

Experts suggest that a significant part of the population as a whole is subclinical infected with one or more types of HPV that are transmitted through sexual contact.

Therefore, prevention includes protected sexual intercourse - the use of condoms, although it is partially effective: warts can easily spread from areas not covered by a condom.

Vaccination will protect against HPV 6 -  Vaccination against human papillomavirus  with Gardasil vaccine 9).

[31], [32], [33], [34], [35], [36], [37], [38], [39]

Forecast

The presence of genital warts is not associated with an increased risk of future cancer. However, the HPV virus cannot be eliminated: even after the removal of warts, almost a third of patients have recurrences of genital warts.

[40], [41], [42], [43], [44], [45], [46], [47]