HPV 51: A candidate for type-replacement following vaccination?

BackgroundHuman papilloma virus (HPV) infection is known to be a necessary cause of cervical cancer and is found in 99.7% of invasive cervical carcinomas. Current HPV vaccines protect against infection from strains 16 and 18. Baseline prevalence studies are important for the measurement of prophylactic vaccine impact and type-replacement monitoring. Between 2009-2010 the HPV research group in collaboration with Cervical Screening Wales conducted the Base HPV 2009 study to determine baseline prevalence in unvaccinated women aged 20-22 in Wales. Preliminary analysis of results showed that in single HPV infection, 16 was the most prevalent high-risk strain followed by 18 and 51. This high prevalence of HPV 51 has not been observed in previous studies from Wales and is not a common finding elsewhere. This study aims to determine whether the high prevalence of HPV 51 observed in the Base HPV 2009 study is a true finding and if HPV 51 should be considered a candidate for type-replacement post-vaccination. MethodsThe first 100 single and 100 multiple HPV 51 positive liquid-based cytology (LBC) samples from the Base HPV 2009 study were selected for re-analysis. Each sample underwent DNA extraction and was tested using two methods: 1) Repeat of original methodology using GP5+/6+ HPV 51 PCR-ELISA. 2) HPV 51 E7 PCR. Data were then correlated with age, social deprivation score and cytology. 5 samples were excluded from analysis. ResultsDirect repeat of HPV 51 PCR-EIA identified 146 of 195 (75.0%) samples as HPV 51 positive. E7 PCR identified 166 of 195 (85.1%) samples as HPV 51 positive. When classified by cytological grade, the prevalence of confirmed HPV 51 increased with grade. ConclusionsThis study confirms that the prevalence of HPV 51 observed in the Base HPV 2009 study population is truly high and warrants further consideration. There is limited evidence on the cross-protection for 51 offered by the current HPV vaccine and it represents a potential candidate for type-replacement following vaccination. This study highlights the need for further longitudinal investigation into the regional and global prevalence of HPV 51. The data would recommend HPV 51 to be considered in future multivalent vaccines.