sybr-green-i and Uterine-Cervical-Dysplasia

Human papilloma virus (HPV) load and physical status are considered useful parameters for clinical evaluation of cervical squamous cell neoplasia. However, the errors implicit in HPV gene quantification by PCR are not well documented. We have undertaken the first rigorous evaluation of the errors that can be expected when using SYBR green qPCR for quantification of HPV type 16 gene copy numbers. We assessed a modified method, in which external calibration curves were generated from a single construct containing HPV16 E2, HPV16 E6 and the host gene hydroxymethylbilane synthase in a 1:1:1 ratio.. When testing dilutions of mixed HPV/host DNA in replicate runs, we observed errors in quantifying E2 and E6 amplicons of 5-40%, with greatest error at the lowest DNA template concentration (3 ng/microl). Errors in determining viral copy numbers per diploid genome were 13-53%. Nevertheless, in cervical keratinocyte cell lines we observed reasonable agreement between viral loads determined by qPCR and Southern blotting. The mean E2/E6 ratio in episome-only cells was 1.04, but with a range of 0.76-1.32. In three integrant-only lines the mean E2/E6 ratios were 0.20, 0.72 and 2.61 (values confirmed by gene-specific Southern blotting). When E2/E6 ratios in fourteen HPV16-positive cervical carcinomas were analysed, conclusions regarding viral physical state could only be made in three cases, where the E2/E6 ratio was < or = 0.06.. Run-to-run variation in SYBR green qPCR produces unavoidable inaccuracies that should be allowed for when quantifying HPV gene copy number. While E6 copy numbers can be considered to provide a useable indication of viral loads, the E2/E6 ratio is of limited value. Previous studies may have overestimated the frequency of mixed episomal/integrant HPV infections.

Topics: Base Sequence; Benzothiazoles; Calibration; Carcinoma, Squamous Cell; Cell Line, Tumor; Diamines; DNA-Binding Proteins; DNA, Viral; Female; Gene Dosage; Human papillomavirus 16; Humans; Hydroxymethylbilane Synthase; Molecular Sequence Data; Oncogene Proteins, Viral; Organic Chemicals; Papillomavirus Infections; Polymerase Chain Reaction; Quinolines; Repressor Proteins; Uterine Cervical Dysplasia; Uterine Cervical Neoplasms; Viral Load

In this study we developed an in situ protocol for quantitative detection of high-risk human papillomavirus (HPV), based on direct in situ polymerase chain reaction (PCR) with SYBR Green I labeling and GeneAmp 5700 Sequence Detection System technology. This protocol was applied on cytological specimens of patients with cervical intraepithelial neoplasia (CIN) and squamous cell carcinoma (SCC). We performed direct in situ quantitative PCR on cell smears, uninfected human skin fibroblasts, Hela and Caski cells. After in situ amplification, slides were counterstained with propidium iodide and analyzed under a fluorescent microscope in order to localize high-risk HPV and verify preservation of morphology. After PCR optimization, we obtained the following results. The Hela cells showed values ranging from 15 to 33 copies of high-risk HPV per cell, the Caski cell line from 220 to 300 high-risk HPV copies per cell and the cell smear (both CIN and SCC) around 20-35 copies of high-risk HPV per cell. No high-risk HPV amplification was detected in uninfected human fibroblasts, healthy controls, non-amplification control, and non-specific primer control. A positive intranuclear high-risk HPV amplification was detected in cell smears from 20 patients with CIN and 10 with SCC. In conclusion, our in situ quantitative protocol for high-risk HPV detection on cell smears combines both quantitative data and in situ localization of the target, with preservation of morphology. For this reason it could be used as a rapid screening tool when both morphological and quantitative results are requested on the same slide.

Topics: Benzothiazoles; Carcinoma, Squamous Cell; Diamines; Female; Fluorescent Dyes; HeLa Cells; Humans; In Situ Hybridization, Fluorescence; Organic Chemicals; Papillomaviridae; Polymerase Chain Reaction; Quinolines; Sensitivity and Specificity; Tumor Cells, Cultured; Uterine Cervical Dysplasia; Uterine Cervical Neoplasms