Health Talk: The 2008 Nobel Prize in medicine
This year, the highly esteemed Nobel Prize for Physiology or Medicine was awarded to Harald zur Hausen for the discovery of the human papilloma viruses (HPV), which cause cervical cancer, and Françoise Barré-Sinoussi and Luc Montagnier for the discovery of human immunodeficiency virus (HIV). Hausen shares half of the award, while Sinoussi and Montagnier share a quarter of the award each.
These discoveries are considered some of the most significant revelations in the history of medicine. Hausen discovered that HPV is responsible for 70 percent of cervical cancers worldwide. By discovering the Acquired Immune Deficiency Syndrome (AIDS) virus in 1983, Barré-Sinoussi and Montagnier showed the urgent need of diagnostic tests to control the disease.
According to the National Cancer Institute, cervical cancer is the second most common cancer in women. In the 1970s, Hausen claimed that HPV may be responsible for cervical cancer.
Hausen discovered that the DNA of HPV could be present in a non-productive state in tumors. This means that this DNA is not expressed and is inactive; hence no external symptoms of viral infection are observed. However, as Hausen proved, this integration of the HPV DNA with the host’s DNA leads to cancer.
Hausen also found that HPV is a heterogeneous family of viruses, which means that the viruses differ in their genetic sequences so that only a few types of HPV actually cause cancer. This helped scientists understand the mechanism of HPV-induced cancer and led to the development of vaccines for curing such cancers.
It took Hausen 10 long years to detect the viruses because it was very hard to search for them. The virus was hard to detect in patients as the viral DNA rarely integrated completely with the DNA of the host cells. After intensive research, in 1983, he cloned two types of HPV — HPV 16 and 18 — from patients with cervical cancer. These were found to be present in about 70 percent of the cervical cancer cases around the world. This discovery of infection due to HPV is vital to medical sciences because HPV is the most commonly sexually transmitted agent. Statistics from the National Cancer Institute state that around 15 out of the 40 HPV types that generally infect the genital tract are responsible for cervical cancer in women. About 100 types of HPV have been discovered to date.
Hausen’s discovery laid down mechanisms for HPV-induced cancer and the scientific community has benefited a lot because of this discovery. Vaccines that provide 95 percent protection from infection by the HPV 16 and 18 types were the result of this novel discovery. They have proved to be very helpful in treating a large proportion of the women who acquire cervical cancer each year.
Barré-Sinoussi and Montagnier started their search for a causative agent for the immunodeficiency virus in 1981. It was believed that swollen lymph nodes were a characteristic of early stages of infection by the immunodeficiency virus. The two scientists took this as their starting point. They isolated and cultured these lymph node cells. They then found direct signs of retrovirus infection as they detected the retroviral enzyme, reverse transcriptase, in the cultures. When they treated lymphocytes from both diseased and healthy donors with this isolated virus, they found that the lymphocytes got infected and died. The retrovirus they discovered is what is now known as HIV. As a result of the discovery, information about methods for cloning the HIV genome, interactions of the virus with the host, details of the replication cycle, and methods to diagnose infected patients were made available to the world.
A difficulty faced while isolating the virus is that it constantly changes and hides its genome in the host lymphocyte DNA. Therefore, the virus cannot be eradicated easily even after long-term antiviral treatment. But the ample information available about these unique viral hosts provides excellent incentives for future vaccine developments and possibly more Nobel Prizes.