According to the World Health Organization, cervical cancer is the fourth most common cancer in the world and will kill more than 443,000 people worldwide by 2030, of which nearly 90% in Sub-Saharan Africa. This high incidence may be justified by the lack of an adequate structure for diagnosis, screening and treatment (Castellsague et al., 2007). In Senegal, cervical cancer is the second most common cancer in women (ICO / IARC HPV Information Center, 2019), and we have reported here a pilot study exclusively dedicated to the distribution of HPV genotypes among Senegalese women affected. Cervical cancer. Given that papillomaviruses cannot be cultivated in vitro, nor detectable by serological tests, molecular biology techniques represent a tool of choice for their detection and genotyping. Real-time PCRs were therefore chosen as the molecular approach but also the basic method, namely sequencing. This study has been submitted to the journal BMC inféctious Disease, and is awaiting an editorial decision.
All cervical samples taken from women with histologically confirmed cervical cancer had at least one HPV genotype detected. This result is justified because it is now accepted that certain human papillomaviruses are responsible for genital infections which can lead, after several tens of years, to cancer of the cervix. The most common types of HPV detected in women with one or more HPV infections were HPV 16 (consistently detected in all of our patients), 18 (83%), 45 (33%), 33 (31% ), 59 (28%), 35 (12%), 31 (11%), 58 (8%), 39 and 73 (4%), 44, 54 and 68 (3%) and the rest less than 1% . The high prevalence of HPV16 and HPV18 reported in our study was expected, as these types are the two most common types of HPV worldwide (de Sanjose et al., 2010; Li et al., 2011; de Oliveira et al, 2013; Deny et al, 2014; Lagheden et al., 2018; Liao et al., 2018). Several studies (Ho et al., 1998; Muñoz et al., 2004; IARC, 2005) have shown that genotypes 16 and 18 are responsible for 70.7% of cervical cancers, which explains why they were chosen as target for HPV vaccines. This percentage corresponds to the estimate of the worldwide distribution of the genotypes of human papillomaviruses responsible for invasive cancers (Muñoz et al. 2004). This result agrees with that of Missaoui et al, 2010 who found that HPV 16 is the most frequent virus among invasive squamous cell carcinomas (47.6%, p = 0.001) and adenocarcinomas (80%, p <0.001) in North Africa (Tunisia). On the other hand, in Central Africa more precisely in Cameroon, the prevalence of the HPV 16 and HPV 18 genotypes represented 30.8% (Tebeu et al., 2018). It also emerges that HPV 45 was very present in our study (33%) which is in line with certain studies (Mejia et al., 2015; Wang et al., 2018; Schisler et al., 2018; Long et al., 2018 ), which had shown that other genotypes (HPV45, 58, 52) had been reported as the second most common.
We also noted that most women were infected with at both high risk HPV (75, 83%). This high co-detection rate is notably due to the high sensitivity of the Chippron real-time PCR test, which targeted a wide range of genotypes, but also to the fact that almost all of our patients were on a polygamous diet. Indeed, the association of co-functions and cervical cancer risk co-factors has shown that polygamy may involve the diversity of the genotypes noted as well as the high number of co-infections. Overall, it has been noted that the proportion of multiple HPV infections has increased in recent years from 4% to 15% (Li et al., 2011), reflecting the use of newer tests more likely to detect multiple infections in recent studies. Multiple HPV infections could, in part, explain the peculiar aggressiveness and rapid progression of cervical cancer disease seen in Senegalese women, as it has been reported as an independent predictor of longer survival. low in another study (Genta et al., 2017). However, the mechanism of the influence of multiple HPV infections on patient survival is not fully understood. We also noted that co-infections with more than 2 types of HR-HPV were particularly prevalent in patients aged 45-55, possibly due to viral persistence or latent HPV reactivation (Simon and Poppe 2008 ; Dufit et al., 1991). Our observations are comparable to those in the African study of histologically confirmed cancer cases, which found the average age of patients to be 48.5 years with a peak in the age group of 41-50 years, or 38.1% of detection of invasive cervical cancer, could currently be around 45-74 years. On the other hand, in countries where screening is organized, invasive cancer is discovered at an average age of 55 years. These figures correspond to the age of the patients at the time of diagnosis of the disease. Regarding marital status, multiple HR-HPV co-infections were significantly more frequent in polygamists. We also noted that women with more than six pregnancies were prone to multiple co-infections. Both results are consistent with previous results which clearly indicated that multiple pregnancies and high number of sexual partners increased the risk of HPV infection and persistence (IARC, 2016).
Based on the new Gardasil-9® vaccine which operates against 9 HPV genotypes (6, 11, 16, 18, 31, 33, 45, 52 and 58), only 5 cases of CHF were exclusively associated with non- vaccines types. Thus, in view of the results obtained in the present study, the use of this nonavalent vaccine could provide effective results in the prevention of cervical cancer in adolescent girls or young Senegalese, in the hope of preventing up to at 95% of CHF. However, additional studies including more patients are needed to better assess the real impact of this nonavalent vaccine.
Regarding the prospects for vaccination, the relatively high prevalence of the types present in nonavalent vaccines (genotypes 16, 18, 31, 33, 45 and 58), Gardasil 9 shows that the latter could constitute a clear advance in the prevention of cervical cancer. infection of the uterus and papilloma virus (HPV) but also an additional means of screening in Senegal in order to reduce the risk of cervical cancer due to genotypes 16 and 18, which are among the known causes most frequent pre-cancerous lesions of the Matterhorn.
In sum, the overall frequency of HPV types detected in women with cervical cancer in Senegal was high for HPV16 and HPV18. Multiple infections were also very common. Determining the viral load of genotypes by quantitative methods would probably help to get an idea of the types or combinations of associated types that are more carcinogenic in Senegal.