Human papillomavirus

Human papillomavirus

HPV causes genital warts and cervical Cancer!

In 2008, Har­ald Zur Hausen won the Nobel Prize in Phys­i­ol­o­gy or Med­i­cine for his dis­cov­ery that prac­ti­cal­ly all cas­es of cer­vi­cal can­cer are due to a long-term infec­tion with any of sev­er­al strains of human papil­lo­mavirus (HPV). He also won the 2013 Soci­ety for Gen­er­al Micro­bi­ol­o­gy Prize Medal. Here’s an inter­view with Dr. Zur Hausen:

Here is a video that gives an overview of the HPVs:

We now have effec­tive vac­cines against the strains of HPV that are respon­si­ble for most cas­es of cer­vi­cal can­cer. One of these vac­cines also pre­vents the strains that are respon­si­ble for benign gen­i­tal warts. These vac­cines are remark­ably safe. They are most effec­tive when they are giv­en to patients who have not yet been exposed to those strains of HPV. That’s why the HPV vac­cines should be giv­en to pre­teen girls and boys—before they are old enough to have sex­u­al activ­i­ty.

Why the vaccine trials did not count actual cancers

Many peo­ple have com­plained that the clin­i­cal tri­als of the HPV vac­cine have used the num­ber of pre­can­cer­ous lesions, as opposed to actu­al can­cers, as an end­point. How­ev­er, there was a prac­ti­cal rea­son for this: You would expect ZERO can­cers in either group: the vac­ci­nat­ed and the unvac­ci­nat­ed. The women in the clin­i­cal tri­als were being so close­ly mon­i­tored that any cer­vi­cal lesion would be found and removed before it became malig­nant.

The HPV infec­tion can cause a wart-like lesion on the out­er sur­face of the cervix, which is the neck of the womb. These lesions con­sist of abnor­mal, HPV-infect­ed cells. The dan­ger­ous strains of HPV block some of the process­es that would nor­mal­ly cause an abnor­mal cell to com­mit sui­cide. Because these process­es are blocked, the HPV virus can enable its host cells to sur­vive, even though they are defec­tive. Unfor­tu­nate­ly, this means that the host cells can sur­vive long enough to col­lect enough muta­tions to become malig­nant. It takes about 10 years for the lesion to become malig­nant.

Why the HPV vaccine is important

If you could find and remove all of these pre­can­cer­ous lesions before they become malig­nant, you could pre­vent all cer­vi­cal can­cers. That is why the reg­u­la­to­ry author­i­ties let the vac­cine spon­sor use the num­ber of pre­can­cer­ous lesions as the end­point in the study. Unfor­tu­nate­ly, not all women get reg­u­lar pelvic exams, and some lesions can be missed dur­ing an exam.  Also, HPV can cause lesions that are hard­er to diag­nose at a cur­able stage. That’s why vac­ci­na­tion is impor­tant.

Since the vac­cine is so effec­tive, it can actu­al­ly stop the tar­get­ed strains of HPV from cir­cu­lat­ing among the next gen­er­a­tion. Ulti­mate­ly, we will judge the val­ue of the HPV vac­cine by see­ing how sharply the num­ber of cer­vi­cal can­cers and oth­er can­cers drops in the coun­tries that vac­ci­nat­ed their young peo­ple against HPV.


Pho­to by AJC1