Date Published: August 5, 2016
Publisher: Public Library of Science
Author(s): Lina Wang, Pengyan Wang, Yan Ren, Jingyun Du, Jianjun Jiang, Xuesong Jia, Chuangfu Chen, Yuanzhi Wang, Maria Lina Tornesello.
Multiple human papillomavirus (HPV) genotypes often coexist within the cervical epithelia and are frequently detected together in various grades of the cervical neoplasia. To date, only a few reports exist on multiple HPV infections of HPV in Xinjiang Uygur Autonomous Region (XUAR). In the present study, we investigated the prevalence of High-Risk HPV (HR-HPV) genotypes and multiple infections. Cervical cytology samples were collected from 428 women who presented cervical abnormalities. Genotyping of HPV was performed by polymerase chain reaction–sequencing based typing (PCR-SBT) using consensus primers and specific primers. Of them, 166 samples were positive for HPV according to PCR results using the consensus primers. These samples contained cervical abnormalities enriched with inflammation (n = 107), cervical intraepithelial neoplasia (CIN) I (n = 19), CINII-III (n = 9) and cervical cancer (n = 31). Of the 166 HPV positive samples as determined by PCR analysis, 151 were further typed by PCR-SBT using 19 pairs of genotype-specific primers. Using this method, 17 different HR-HPV genotypes were identified. The most frequently observed HPV genotypes were HPV16 (44.0%, 73/166), 53 (28.9%, 48/166), 52 (25.3%, 42/166), 58 (22.3%, 37/166) and 35 (17.5%, 29/166). The proportions of single and multiple infections in the HPV-positive specimens were 34.9% and 65.1%, respectively. Multiple HPV types were most prevalent in the inflammatory state (63.0%), followed by cervical cancer (24.1%), CINI (11.1%), and CINII-III (1.9%). The results of our data analyses suggested that i) multiple HPV infection is not necessarily correlated with the severity of cervical abnormalities; and ii) among the multiple HPV infections, double infections combined with HPV16 is the most common. In addition, L1 full-length sequences of the top five high-risk HPV genotypes were amplified and sequenced. According to the L1 sequence of the epidemic genotypes that were amplified, we found that these genotypes contained the sequence point mutation, and that some of these genotypes further showed amino acid modifications. These results provide a basis for the construction of a polyvalent vaccine that is suitable for use in the XUAR, even in economically challenged communities located in China.
Cervical cancer is the second most common malignancy among women and the leading cause of cancer-related death among females worldwide [1, 2]. Epidemiological studies have shown that human papillomavirus (HPV) is the main cause of cervical cancer and precancerous lesions . To date, over 100 HPV genotypes have been identified , and research studies have revealed that the pathogenicity of various strains of HPV is significantly different from each other . Among the various types of HPV, the persistent infection of high-risk HPV (HR-HPV) is closely related to the occurrence of cervical intraepithelial neoplasia (CIN) and cervical cancer . According to epidemiological and molecular biology reports, at least 19 HPV genotypes have been identified as HR-HPV (HPV16, 18, 26, 31, 33, 35, 39, 45, 51, 52, 53, 56, 58, 59, 66, 68, 70, 73 and 82) . These genotypes mostly belong to oncogenic HPV, including alpha-9 (16, 31, 33, 35, 52 and 58) and alpha-7 (18, 39, 45, 59 and 68), which can cause HPV related genital tract tumors . A woman can be repeatedly infected with HPV during her lifetime, which can also co-infect multiple HPV types . In a pooled analysis of 15 areas worldwide, the prevalence of multiple HPV infection averaged about 25% and ranged from 18.5%–46% among HPV-positive women [10–12].
Among the 428 cervical samples analyzed in this study, 166 were found to be HPV-positive DNA as detected using consensus primer. In addition, we found 107 inflammation cases, 19 CINI cases, 9 CINII-III cases, and 31 cervical cancer cases. The prevalence and genotype distribution of the cervical abnormalities are shown in Table 1. Of 166 HPV-positive samples, 151 samples were successfully classified into 17 different HPV genotypes (HPV16, 18, 26, 31, 33, 35, 39, 45, 51, 52, 53, 56, 58, 59, 66, 68 and 73). The most common HPV genotypes were HPV16 (44.0%, 73/166), 53 (28.9%, 48/166), 52 (25.3%, 42/166), 58 (22.3%, 37/166) and 35 (17.5%, 29/166). The distribution and occurrence frequency of different HPV genotypes at different grades of abnormal cervical samples are listed in Table 1. Among them, HPV16, 53, 58 and 52 were the dominant types in the inflammation group, HPV16, 53, 52 and 58 were the dominant types in CINI, HPV33 and 53 were the dominant types in CINII–III. Meanwhile, in the cervical cancer group, the infection rate of HPV16, 52, 53 and 58 were highest. Among the 151 cases, the multiple HPV infections were observed in a total of 109 (65.7%) cases, while single HPV infection was found in 42 (25.3%) samples. Among the 108 cases of multiple HPV infections, the proportion gradually decreased with the increased number of infection genotypes, with 56 cases of double infection, 33 cases of triple infection, 15 cases of quadruple infection, 2 cases of pentagonal infection, and 2 cases of hexagonal infection.
With the development of molecular epidemiology, biological risk factors for abnormal cervical incidence are mainly related to HPV infection. In this study, a total of 166 samples were found to be positive for HPV by PCR-SBT. HPV infection in samples having a background of inflammation, CINI, CINII–II, and cervical cancer were present in 33.6%, 45.2%, 47.4%, and 63.3% of these cases, respectively, which suggested that the positive rate of HPV increased with the severity of the pathological diagnostic grade. Such results indicate that HPV infection is closely related to the occurrence and development of CIN, which is consistent with the previous reports [20, 21]. The positivity rate of HPV increased with the severity of the pathological diagnostic grade, we found that the positive rate of HPV is 63.3% among cervical cancer cases using PCR. We believe that this occurrence is attributed to a theory known as “hit and run.” The previous studies indicated HPV might incite transformation in cells that subsequently lost their HPV DNA sequences during carcinogenesis [22–24]. In addition, the reason for the relatively low positive rate of HPV in cervical cancer cases may be due to the geographical environment and the selection criteria for the samples .