Human papillomavirus: portrait of an invisible enemy

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Human papillomavirus: portrait of an invisible enemy

Research over the past few years have allowed to establish a relationship between cervical cancer and human papillomavirus, sexually transmitted virus. Currently, it is estimated that almost all cases of this type of cancer are associated with these viruses. We look closely at this tiny enemy with Dr. Françoise Thierry Pasteur Institute in Paris.

Portrait of a family of viruses
Not all infections progress to cancer
Dangerous liaisons with the host cell
The risks increase with couples
HPV: portrait of an invisible enemy
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The cervical cancer develops from precancerous lesions called caused by several viruses belonging to the family of human papilloma virus (HPV for Human Papillomavirus). Françoise Thierry, a researcher at the Department of Gene Expression and Diseases of the Pasteur Institute in Paris, tells us more about this virus.

Portrait of a family of viruses
Dr. Thierry explains that: “These viruses are divided into two large families. Some affect the skin and other mucous membranes. Some of these infections are benign (plantar warts or hands), while others may develop into a cancer. ” As often happens with cervical cancer.

Although these sexually transmitted infections are usually benign, in some cases they can lead to precancerous lesions (dysplasia) that, in turn, can evolve to a cervical cancer if not treated on time. Each year there are 258 000 deaths worldwide, of which 550 in Spain. Human papilloma viruses are associated with 80% or 100% of cervical cancers. By contrast, the risk of cancer among uninfected women is almost nonexistent.

Among the different types of virus (known more than 120 genotypes), not everyone has the same carcinogenic. In Europe, the most damaging is definitely the type 16, associated with more than one in two cervical cancers. The other oncogenic HPV types are HPV-18 (20% of cases), less frequent HPV-31, HPV-33 and HPV-35. “We can not say they are less hazardous, they are simply less present in the European context. In Colombia, for example, human papilloma virus causing over half of cancerous lesions of the cervix is HPV-45. There are large geographical variations, “says Dr. Thierry.

Finally, in Europe found Asian or African variants of human papilloma virus. Some studies suggest that they would be more persistent and, therefore, more difficult to remove from the body. Although this issue remains controversial. However, and fortunately, not all HPV infections progress to cancer.

Not all infections progress to cancer
Infections by human papillomaviruses are common in young women and tend to disappear spontaneously. At least one in two sexually active women have been exposed to the virus throughout their life. The virus was detected in 30% of women under 30 and 10% of women above this age. Five years after first sexual intercourse, the risk of being infected increases to 60%, falling and falling to 5-10% after 40-45 years.

HPV infections including those caused by an oncogenic virus usually harmless because the body eliminates them between 6 and 13 months after infection. “There are well known factors that cause the infection spontaneously disappears or, conversely, to develop into a cancer. Today it is estimated that cancer will develop process also depending on the time of infection, “said Dr. Thierry. It is precisely the persistence of HIV infection that causes oncogenic cell abnormalities – the most important marker of tumors.

Dangerous liaisons with the host cell
The oncogenic human papilloma virus differ from the others because it can intervene in the genome and the physiology of the host cell, even to modify it. Pasteur Institute of Paris also appreciated that the E6 and E7 proteins modifying the physiology of the host cells resulting in a carcinogenic process, whereas the opposite effect was E2 (antioncógenica protein that regulates the expression of particular proteins E6 and E7).

According to Dr. Françoise Thierry, problems in balancing the counteracting effects of these two types of viral proteins in cell biology may be one of the triggers of cancer.

Other studies suggest that currently HPV might be associated with other cancers, including prostate, stomach, larynx, esophagus and skin. “Several studies report a significant concentration of HPV-induced skin cancers mainly by the sun. While not yet been able to explain this relationship, it is suspected that the virus may be responsible, “concludes Dr. Thierry. However, also in this case, the exact role of the human papilloma virus is still not identified.

The risks increase with couples
The risk of infection with human papilloma virus (human papillomavirus – HPV) increases with each sex. Scientists at the University of California have studied more than 600 women between 13 and 21 years, who had come to family planning centers. According to these studies, more than half of sexually active women can be infected with HPV within three years. Every relationship growing tenfold the risk of contagion.

The survey reveals other infectious risk factors: besides sexual activity, history of herpes and warts increase the risk while taking oral contraceptives would reduce it by half. But more significantly, this study reframes the relationship between infection and cervical cancer.

This infection is thought to produce changes in cervical cells, called English Low-grade squamous intraepithelial lesions – LSIL, which although benign in most cases, can also be the first stage of early cancers.

But the American study aims other risks HPV and neck cell injury. LSIL risk varies date of HPV infection. It’s more a year. Smoking also appeared as a risk factor to consider. In conclusion, infections with human papillomavirus are necessary but not sufficient for the development of lesions that can cause cervical cancers. The next stage is to discover these other risk factors that, if HPV infection can lead these changes phones.

by, Plantas medicinales’

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