Investigation of HPV types prevalence by pyrosequencing method in cervical specimens

Investigation of HPV types prevalence by pyrosequencing method in cervical specimens
Fatemeh Kashefi,¹ Mohammad Karbalaie Niya,^2,* Shaghayegh Yazdani,³ Mohammad Shayestehpour,⁴
1. Department of Microbiology, Faculty of Advanced Science and Technology, Tehran Medical Sciences, Islamic Azad University, Tehran, Iran
2. PhD. in Medical Virology, Gastrointestinal and Liver Disease, Research Center(GILDRC), Iran University of Medical Sciences, Tehran, Iran
3. Department of Microbiology, Faculty of Advanced Science and Technology, Tehran Medical Sciences, Islamic Azad University, Tehran, Iran
4. Autoimmune Disease Research Center, Kashan University of Medical Sciences, Kashan , Iran
Introduction: Human papillomaviruses are small, double-stranded DNA viruses that infect the epithelium. More than 120 types of HPV have been identified. Their type's differences are based on the capsid L1 protein. Most HPV types infect the cutaneous epithelium and cause skin warts. About 40 HPV types infect the mucosal epithelium. These are classified according to their epidemiological association with cervical cancer. Infection with low-risk, or non-oncogenic types, such as types 6 and 11, can cause benign or low-risk cervical cell abnormalities, genital warts, and laryngeal papillomas. High-risk or carcinogenic HPV types act as carcinogens in cervical cancer and other anogenital cancers. High-risk types (currently including types 16 and 18, etc.) can cause low-grade abnormalities of cervical cells, high-grade abnormalities of pre-cancerous cervical cells, and anogenital cancers. High-risk types of HPV are diagnosed in 99% of cervical cancers. Type 16 is the cause of approximately 50% of cervical cancers worldwide, and types 16 and 18 together account for about 70% of cervical cancers. High-risk HPV infection is considered essential for the development of cervical cancer, but it alone is not enough to cause HPV infection in most women. In addition to cervical cancer, HPV infection is associated with less common anogenital cancers such as vulvar, vaginal, penile, and anal cancers. The association between HPV and non-genital cancers is less well established, but studies support a role for some pharyngeal cancers in this type of HPV. Cervical cancer is the second leading cause of cancer death in women. In this cancer, more than any other type of malignancy, the effects of prevention, early diagnosis and timely treatment on reducing mortality are evident. In the mid-1970s, the human papillomavirus (HPV) was proposed as the main etiology of cervical cancer. Various studies around the world have shown a strong association between HPV and precancerous and cancerous changes in epithelial cells. Because cell culture and serological methods are of little value in identifying the virus and its variants, the importance of molecular methods, including polymerase chain reaction (PCR), in definitive and early detection of the virus has become apparent. Cervical cancer is a type of cancer that starts in the cervix. The abnormal cells produced can spread to other parts of the body or attack them. There are usually no symptoms at the onset of the disease in the body, but subsequent symptoms may include vaginal bleeding, pelvic pain, or dyspareunia (any painful sexual activity called dyspareunia or painful marital activity). Cervical cancer usually progresses over a period of ten to twenty years following precancerous changes. When HPV stays in the body for several years, it gradually turns some cells in the cervix into cancer cells, and these cells become more progressive. However, many people with human papillomavirus infections do not develop cervical cancer. It is suggested that sexual activity, age of first intercourse and number of sexual partners play an important role in causing this disease. How to diagnose cervical cancer: Diagnosis is made by screening the cervix with a Pap smear and then with a biopsy. Following the diagnosis, medical imaging is performed so that doctors can determine if it has spread. The HPV vaccine protects humans against two strains of the virus, and it is possible that the vaccine could prevent between 65 and 75 percent of cervical cancers. Because there is still a risk of cancer after treatment, it is usually recommended that cervical cells be sampled regularly. Symptoms of cervical cancer include: Pelvic pressure or pain, sciatica, bowel and bladder dysfunction, swelling of the legs.
Methods: In this study, after selecting patients according to the relevant protocol and completing the questionnaire form, 1047 samples of cervical cancer lesions were selected. DNA extraction from paraffin blocks was then performed by standard methods. The presence of HPV virus was detected by PCR. High-risk serotypes of the virus were investigated using pyrosequensing.
Results: Out of 1047 patients with cervical cancer, 160 were positive for HPV infection and 887 were negative. In other words, the prevalence of HPV infection in this population was 15%.
Conclusion: The findings of our study reinforce previous reports of a link between HPV and cervical cancer. Types 6, 11, 16 and 18 were also the most common.
Keywords: HPV, cervical cancer, PCR, Genotyping, Pyrosequencing