Variations in the prevalence of isolated human papillomavirus genotype in cervical cancer specimens: a review

The uterine cervix represents a pathologically important part of the uterus because of the high prevalence of cervical cancer worldwide. The epithelium of the cervix can be infected by sexually transmitted oncogenic types of human papillomavirus (HPV). These virus cause persistent infection of the cervical epithelial cells and this leads to viral cytopathic changes associated with atypia (koilocytic atypia) in the infected cells. This is referred to as squamous intraepithelial lesions which can be low grade or high grade depending on the severity of koilocytic atypia. There are three categories of oncogenic human papillomavirus. These include the high-risk, low-risk and undetermined-risk human papillomaviruses. There are up to 19 types of high-risk human papillomaviruses that have been identified. These include types 16, 18, 26, 31, 33, 35, 39, 45, 51, 52, 53, 56, 58, 59, 66, 67, 68, 69, 70, 73 and 82. More than 90% of cervical cancer is caused by high-risk human papillomaviruses. These viral subtypes are isolated more often from cervical cancer specimen than the low-risk subtypes. There are several low-risk HPVs including types 6, 11, 40, 42, 43, 44, 54, 55, 57, 61, 62, 70, 70, 71, 72, 74, 81, 83, 84 and 89. They have been isolated from cervical cancer specimens in some cases. They have been known to be responsible for more than 90% benign cervical lesions such as condylomata accuminata. There are also undetermined-risk human papillomaviruses for cervical cancer such as types 2a, 3, 7, 10, 13, 27, 28, 29, 30, 34, 86, 87, 90 and 91. The common prevalent HPV genotypes are HPV 16, 18, 31, 33 and 45. But HPV45 have not been isolated from cervical sample specimens in some regions in the globe like southern Nigeria and Ivory Coast. HPV 16 and 18 have consistently been the most prevalent HPV subtypes isolated from the cervical specimen in most part of the world. Several studies done in Nigeria, Japan, Kenyan and Canada have shown HPV 16 and 31 as the commonest HPV genotypes isolated from cervical cancer specimen. The study by de Vuyst et al in Kenya show an equal prevalence of HPV 31 and 45. Objective: To do a review on the variations in the prevalence of isolated human papillomavirus genotype in cervical cancer specimens. Methodology: Literature search was done using google search and the following keywords were used in the search - prevalence, human papillomavirus, genotype, cervical and cancer. The literatures obtained were analyzed and used for this review. Conclusion: It is clear that the prevalent HPV genotypes involved in the etiology of cervical cancer in the various part of the world vary. Therefore, there is need to develop vaccines that would be able to protect women and men from HPV infections of the variable HPV genotypes. The specific HPV vaccines available do not protect against infections caused by other types of HPV that it is not specific for. With the growing knowledge of the prevalent HPV genotypes in various region of the world, a day for the perfect vaccine that would eliminate cervical cancer globally will come soon.