ANALYSIS OF IMMUNE RESPONSES TO HPV-16 E2 PEPTIDES IN NATURAL HISTORY STUDIES OF HUMAN PAPFLLOMA VIRUS INDUCED CERVICAL LIESIONS

Abstract

The main goal of this project was to investigate T cell responses to human papillomavirus type 16 (HPV-16) E2 peptides in women infected with HPV at different stages of disease and to determine whether the presence and frequency of these responses were associated with disease status. Studies analyzing responses to E2 in patients with HPV-associated disease are limited, thus a need for further baseline investigations was necessary. T helper (Th) cell and Cytotoxic T Lymphocyte (CTL) responses to HPV-16 E2 have previously been reported in small population studies involving individuals with HPV infection (Edwards et al. 1995), as well as in healthy controls (de Jong et al. 2002), however, characterization of these immune responses to human papillomavirus (HPV) at different stages of disease is of crucial importance in defining correlates of protection or progression to disease. In terms of immune intervention, the E6 and E7 oncoproteins are major targets in high-grade cervical intraepithelial neoplasia (CIN) and cervical carcinoma, because these proteins are constitutively expressed and are required for maintenance of the transformed state. However, in the context of productive infections and low-grade CIN, the E2 protein is just as attractive a target because it is highly expressed at this stage of infection, exhibiting an expression pattern comparable to its high-grade CIN counterparts E6 and E7. The monitoring of immune responses to E2 may contribute to identification of correlates of protection to HPV-associated disease, which may be relevant to the development of therapeutic strategies that can be employed to successfully eradicate HPV infection and resulting HPV-induced neoplasia. In a population of HPV infected women with high-grade and low-grade lesions (53/110), cell mediated immune responses against overlapping sequences of E2 peptides covering the entire protein sequence were analyzed using lymphoproliferation assays (LPAs). An equivalent number of women with no clinical indications of cervical lesions (57/110) were also analyzed. In general, cases (29/110; designated as ≥ CIN 2) responded differently than controls (81/110; designated as <CIN 2). Observations ranging from a number of individuals responding positively to the E2 peptide (referenced by stimulation indices (S1s) greater than 2) to number of reactive peptide panels responding per individual, revealed a trend for an overall decrease for cases ≥ CIN 2) when compared to resulting data for controls (< CIN 2) regarding immune response and. clinical disease status. These conclusions reveal that there is an association between immune response to E2 and disease status, substantiating the need for further investigation in this area of interest. In addition, evidence of correlations between immune reactivity to .mitogenic (PHA) and antigenic stimuli (FLU and E2 protein) support the need for further testing to investigate whether similar correlations could be found against other antigenic stimuli, which would further substantiate continuing reports of decrease in immune response to HPV in advanced cervical disease and its potential implications in clinical outcome.