Physical state of human papillomavirus type 16 in cervical intraepithelial lesions and cancers determined by two different quantitative real-time PCR methods.

Abstract

The aim of this study was to analyse the correlation between a new multiplex qPCR assay and a reference qPCR assay for assessment of the human papillomavirus (HPV16) load and the viral genome status. The study was performed on 100 HPV16 positive samples containing premalignant lesions and carcinomas. HPV16 E2 and E6 gene loads were assessed by two PCR methods. The load of E2 and E6 was normalized to the cell number by qPCR targeting the RNase P open reading frame. The physical state of the viral genome was determined as a ratio of E2/E6 copies number per cell. Among 100 samples analysed, there were no statistically significant differences in the E2 and E6 viral load evaluated by multiplex qPCR and qPCR, the correlation coefficients were 0.98 and 0.97, respectively. There were 19% of samples with the integrated, 73% with mixed and 8% with episomal state of viral genome detected by multiplex qPCR and 17%, 79%, 4%, respectively, found by qPCR. Prevalence of integrated and episomal forms estimated by multiplex qPCR was higher than the one obtained by qPCR (Chi2, p < 0.0001), but in samples with premalignant and malignant diagnoses no significant differences were demonstrated regardless of the methods used. Sensitivity and specificity of multiplex qPCR were 93.7% and 100% as compared with qPCR, the positive predictive value was 100%. In summary, the multiplex qPCR assay in respect of HPV16 load and the frequency of viral genome status was shown to be a sensitive and specific reference method. Simultaneous estimation of E2 and E6 genes in one reaction tube reduces the cost of testing.