Immunocytochemical detection of HPV16 E7 in cervical smear

Cervical cancer is characterized by a long period of preclinical dysplasia or carcinoma in situ progressing into invasive cancer. Although Papanicolaou (Pap) smear test has contributed significantly to the early detection of precursor lesions, the cytological screening has inherent problems that produce considerable false negative/positive results. Since the infection of high-risk type of human papillomavirus (HPV) is strongly associated with cervical cancer, we investigated the feasibility of an immunostaining test to detect cells infected by HPV in cervical smear. We produced monoclonal antibodies against HPV16 E7 in mice by repeated injections with the recombinant HPV16 E7. Western blot analysis and immunocytochemical assay demonstrated that the selected monoclonal antibody, mAb (130-9-7), reacts specifically with cultured cervical cancer cell lines infected by HPV16. Specific staining was observable with the HPV16-positive smear specimens obtained from the cervical cancer patients, whereas no staining was detected with the HPV-negative smear specimens. To achieve the desired sensitivity, specificity and reproducibility, we modified and optimized the conventional immunocytochemical procedure for cervical smear specimens. Our results suggest that this immunostaining method for detecting high-risk HPV in cervical smear may be used as a strategy to distinguish a high-risk group, especially those patients with low grade cytological abnormality.