Comparação dos métodos de tipagem do HPV por meio de amplificação por PCR usando-se iniciadores tipo-específicos e por sequenciamento direto do produto amplificado

Abstract

The infection by human papilloma virus (HPV) is the most common sexually transmitted disease worldwide, with high-risk viral types associated to cervical carcinogenesis. Although there are several virus typing methods, the best test is still under investigation. This study has compared the effectiveness of type-specific PCR and sequencing aiming at their clinical application. Two hundred and sixty cervical samples of HPV-positive patients were studied by type-specific PCR for types 6, 11,16, 18, 31, 33 and 35 and sequencing. Genotype was identified in 36% of cases by type-specific PCR and in 75% by sequencing. Sequencing was four times more likely to identify the viral type present in positive samples than type-specific PCR (p=0.00). In spite of sequencing being more effective for virus genotyping, this method cannot identify viral types in multiple infections. By combining both methods, we reached a highly sensitive detection (87%), showing that they are complementary methods. Based on these results, in order to genotype clinical samples we propose to start with sequencing and, if necessary, in cases of multiple infections, type-specific PCR should be performed. HPV genotyping plays an important role in guiding the search for specific types to be investigated in routine tests, to allow selecting patients with ahigher risk of developing cervical cancer and to contribute to develop type-specific vaccines.