Module 2 Human Papillomavirus Vaccine
----a recombinant DNA vaccine to prevent cervical cancer
which is caused by infection of Human Papillomavirus
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Related topics: diseases, cell cycle and division, body defense mechanisms, applied genetics, techniques in modern biotechnology, biotechnology in medicine, bioethics Guiding questions: |
Introduction
About 12,000 women are diagnosed with cervical cancer 子宮頸癌 every year and 4,000 women die from this disease. Cervical cancer is caused by Human Papillomavirus (HPV) 人類乳頭狀瘤病毒 infection through sexual activities. To prevent cervical cancer, one may consider having HPV vaccine. For traditional vaccine made from attenuated 減毒 virus, it may still be a chance that the attenuated virus becomes virulent 惡性的 again. Following the invention of recombinant DNA technology 重組DNA技術, recombinant vaccine can help to eliminate the chance of being infected while triggering primary immune response for host protection.
What is Human Papillomavirus and what is its relation with cervical cancer?
Genital human Papillomavirus (HPV) is the most common sexually transmitted infection through body fluid or direct skin to skin contact with someone who has HPV. HPV causes changes in the cells of the cervix, causing a condition called cervical dysplasia 子宮脛不典型增生. If untreated, it will progress to cervical cancer. There are about 100 types of HPV that can affect genitals, including cervix, penis and scrotum, so man can also be infected by HPV. Among the 100 types of HPV, 13 of them are considered as high risk of causing cervical cancer.
Cancer is a disease in which abnormal cells divide without control and cancer is able to invade other tissues. Cancer cells can spread to other part of the body through the blood and lymph.
Classification of cancer:
- Benign 良性 (NOT cancerous)
- A mass of extra tumor grow at one place
- Not invading other tissue
- Malignant 惡性 (cancerous)
- Able to invade and damage nearby tissue
- Spread to other part of the body through blood or lymph
Tumor Grades:
Grade |
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GX |
Grade cannot be assessed (Undetermined grade) |
G1 |
Well-differentiated (Low grade) |
G2 |
Moderately differentiated (intermediate grade) |
G3 |
Poorly differentiated grade (High grade) |
G4 |
Undifferentiated grade (High grade) |
* Information taken from the National Cancer Institute, the American Joint Committee recommends the following guidelines for grading tumors based on microscopic appearance of the cancer cells.
There are usually no symptoms for people infected with HPV and the most common sign is the presence of warts 疣 in the genital area. The signs of infection usually appear weeks, months or even years after virus infection.
Diagnosis of HPV
The followings show 3 ways of HPV diagnosis:
- Pap test
子宮頸抹片檢查
A sample of cells is removed from the cervix. Then, the cells are examined under a microscope to look for any changes in the cells. This can be done in the absence of genital warts.
- Colposcopy
陰道鏡檢查
An instrument called colposcope 陰道鏡 shines a light and magnifies the view of the cervix. Cells infected with HPV will turn to white in testing solution. This allows cells to be seen more easily.
- HPV DNA test
The genetic material (DNA) of HPV within the cells is directly tested. The type of HPV connected to cervical cancer can be identified through this test. The cells used for this test can be taken from the cells used for Pap test.
Vaccine of HPV
- Work of a Vaccine
3 shots of HPV vaccine are given to protect against HPV infection and HPV-related diseases. Two vaccines (Cervarix and Gardasil) have been shown to protect against most cervical cancers in women. Gardasil also protect against genital warts and cancers of the anus, vagina and vulva 外陰 and it can also be available for men.
- HPV vaccine as a recombinant vaccine
Recombinant vaccine 重組疫苗 refers to the vaccine that contains only the antigen but not the attenuated toxin or modified virus or bacterium. The vaccine can trigger the primary immune response of the recipient without the worries of being infected as in traditional vaccine technology. Besides HPV vaccine, another recombinant vaccine currently used by human is Hepatitis B vaccine.
To learn more about recombinant DNA technology and its application in the production of HPV vaccine, please click here . - Future development of recombinant vaccine
The use of recombinant vaccine can help to reduce the risk of vaccine infection as there are no real infectious organisms being injected. Moreover, the production cost is lower as the vector virus is more stable, easier to grow and store than the attenuated virus used in traditional vaccine.
However, the cost of developing a new recombinant vaccine is high and there is a potential danger of making a genetically modified organism while producing recombinant vaccine.
Can you suggest more Pros and Cons of developing recombinant DNA vaccine and how it is affecting our health, society and environment? What are the roles of each party on this issue?