CD4+ T-cell response against human papillomavirus type 16 E6 protein is associated with a favorable clinical trend

The association between the CD8+ T-cell responses to human papillomavirus type 16 (HPV-16) E6 protein and a favorable clinical trend has been demonstrated previously. The roles of human papillomavirus (HPV)-specific CD4+ T-cell responses and of regulatory T-cells (Tregs) were examined. Subjects with a recent history of abnormal Papanicolaou smear were eligible, and colposcopy-guided biopsy was performed at enrollment. Interferon-γ enzyme-linked immunospot assay and fluorescent-activated cell sorter analysis to measure the frequencies of Tregs were performed. Subjects with histological diagnoses of cervical intraepithelial neoplasia 1, 2, or 3 were considered to have short-term persistence of cervical abnormality and were called "persistors" (n = 51) while those of normal histology were designated to be "regressors" (n = 33). A significantly higher percentage CD4+ T-cell response was detected in the regressors (15/33 or 45.5%) compared with the persistors (10/51 or 19.6%) (P = .015) for the E6 peptides but not for the E7 peptides. The CD4+ responses to certain E6 regions [E6(16-40), E6(91-115), E6(106-130), and E6(136-158)] were also significantly higher in the regressors. Although there was no difference in the frequencies of Tregs between the two groups, low frequencies of Tregs were significantly associated with positive CD4+ T-cell responses within certain E6 regions [E6(16-40), E6(31-55), E6(76-100), E6(91-115), and E6(106-130)]. The CD4+ and CD8+ T-cell responses to the HPV-16 E6 protein are associated with a favorable clinical trend. The HPV-16 E6 protein should be incorporated in the design of an HPV therapeutic vaccine.