The Henles hypothesized that EBV lingered in some lymphatic cells, slowly transferring the virus to other cells. While zur Hausen expressed interest in studying EBV, he had little experience with the required research procedures. Zur Hausen worked with a different virus, the adenovirus, to familiarize himself with lab procedures. The adenovirus most commonly causes respiratory illness, though it can also lead to infections of the bladder or digestive system.
The Henles taught zur Hausen how to use a method, nucleic acid hybridization, to identify and analyze DNA, as well as how to use other methods to detect viral DNA in sample cells.
Using those methods, zur Hausen looked for chromosome mutations in human cells infected with the adenovirus. He also analyzed chromosomal differences in human lymphoblastoids, which are immature cells that eventually become different types of white blood cells.
While still working on his research with the adenovirus, zur Hausen began researching EBV. He analyzed Burkitt's lymphoma cells using an electron microscope , which bounces electrons off a specimen to create a high quality image of that specimen. When he did so, he discovered EBV in the cancerous cells. Zur Hausen's analysis further supported the hypothesis that EBV played a significant role in Burkitt's lymphoma. Zur Hausen's second son, Axel, was born in He led an independent lab group and continued to research EBV.
Zur Hausen proposed the virus only became activated in certain cells. Rather, EBV-infected lymphatic cells lived longer than uninfected cells, enabling them to grow and reproduce more than normal, a sign of cancer. He showed that viruses, as genetic information within human tumor cells, can initiate tumor growth by potentially modifying the genes of the host cells.
During his time as chairman, zur Hausen began to study the causes of cervical cancer. Scientists had hypothesized that herpes-simplex 2 virus HSV-2 , a sexually transmitted infection that commonly results in genital warts, caused cervical cancer. Researchers had agreed that genital warts were most often caused by sexually transmitted infections.
Zur Hausen conducted his own research experiments using nucleic acid hybridization to search for HSV-2 DNA in cervical cancer tumor samples. After failing to produce evidence of HSV-2 DNA in tumor samples, zur Hausen began investigating another sexually transmitted infection as the cause of cervical cancer, the human papilloma virus HPV. Zur Hausen reviewed medical reports of women with HPV-caused genital warts developing cervical cancer. The medical reports linked HPV-caused genital warts to cervical cancer.
Using those findings, zur Hausen published his theory that HPV caused cervical cancer Also in , zur Hausen's third son Gerrit was born.
From onward, zur Hausen confirmed his theory that HPV causes cervical cancer. When he published his hypothesis that HPV caused cervical cancer in , zur Hausen theorized that genital warts caused by HPV infections led to cervical cancer.
From through , zur Hausen and his research team analyzed genital wart samples and discovered two new types of HPV in the samples, HPV 6 and He also divorced his first wife and married Ethel-Michele de Villiers, one of the members of his research team. Zur Hausen and his research team continued investigating genital wart samples and cervical cancer samples.
They found that HPV 6 and 11 were prevalent in genital wart samples, whereas HPV 16 and 18 were prevalent in cervical cancer samples.
Initial tests were inconclusive but the team published a preliminary report of their work in and eventually identified several HPV types. In zur Hausen was appointed chairman of the Institute of Virology of the University of Freiburg. He took most of his team with him, including Lutz Gissmann and Ethel-Michele de Villiers, who would later become his wife.
By they had reached HPV, which they discovered was present in around half of cervical cancer cases. The following year they isolated HPV, accounting for a further fifth of cases. Fortunately this view later changed and the HPV vaccine became available in One reason for this may be the incorporation of virus genes into the genes of host cells.
Harald zur Hausen demonstrated in that cervical cancer in humans is caused by certain types of papilloma viruses wart viruses , the genes from which are incorporated into the host cells' DNA.
This discovery made it possible to develop a vaccine against cervical cancer, which had been the second most common tumor disease in women. Photo: U.
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