The Study On Genetic Engineering Prophylactic Vaccine Of Human Papillomavirus 18

Cervical cancer and precancerous cervical lesions threaten human health, especially in women. Clinical, molecular, and epidemiological investigations demonstrated that human papillomavirus (HPV) is a major cause of cervical cancer and cervical dysplasia . Virtually all cervical cancers (99%) are related to high-risk HPVs, it is found that most commonly types are HPV16,18, 31, and 45 . About 470,000 cases of cervical cancer were diagnosed worldwide each year, and about half of them were dead. In the U.S. alone, 50 million Pap tests are performed each year, among them, 1.2 million cases of low-grade dysplasia (cervical intraepithelial neoplasia [CIN]1), 300,000 cases of high-grade dysplasia (CIN2/3) and 10,000 cases of cervical cancer were identified The total health care cost associated with the screening and treatment of cervical cancer in the U.S. is estimated to be $6 billion per year. Although screening has dramatically reduced the incidence of this disease in the developed world, it is still estimated that there will be 3,710 deaths from cervical cancer in the U.S. during 2005.In areas of the world where most women do not have access to regular gynecological care and screening, cervical cancer is ranked in second only after breast cancer as a cancer-related cause of death Current treatment of cervical dysplasia is limited to excisional or ablative procedures that remove or destroy cervical tissue. These procedures have efficacy rates of approximately 90%, but are associated with morbidity and high expense. Additionally, surgical treatments can remove only the dysplastic tissue, leaving normal-appearing HPV-infected tissue untreated It is therefore desirable to eradicate this infection by using a vaccine, as was done previously with great success with hepatitis B vaccine. Preventive vaccination of adolescents before they first encounter HPV aims at this target. However, already-infected women as well as patients suffering from advanced cervical cancer could also benefit from therapeutic vaccinations under development. The quadrivalent human papillomavirus(Type 6/11/16/18) recombinant vaccine from Merck company, whose tradename is Gardasil, has been approved for use by Food and Drug Administration(FDA) on June 8,2006.The bivalent HPV from GlaxoSmithKline is in phase III clinical study and may be approved for use in 2007.This paper described that the whole L1 gene with preferred condons for P.pastoris was rebuilt and A-T rich regions were abolished. The gene was cloned into pAO819 and expression vectors with one copy and two copies of 18L1 gene were constructed in vitro. The recombinant vectors were lineared and transformed into GS115 yeast cells and screened in the presence of G418. BMGY/BMMY were used for induction and expression of L1 protein. Mouse antibody of HPV18L1 was used to identify the expressed products by western blotting. Ten clones were found to produce L1 protein which can be identified with chemoluminescence Western blot. The expressed protein with a relative molecular of 55000Dr reacted with HPV antisera. The VLPs of HPV18 were observed by electron microscope. HPV type 18 L1 peotein was successfully expressed in P.pastoris. This study lay foundations for future animal experiments and clinical trial.