Definition of an HPV18/45 cross‐reactive human T‐cell epitope after DNA immunisation of HLA‐A2/KB transgenic mice

Abstract

Although human papillomavirus (HPV) types 16 and 18 are the most common types associated with cervical cancer worldwide, other related HPV types such as HPV 35, 45 and 58 have significant prevalence in geographically distinct populations. For development of global prophylactic and therapeutic vaccine strategies, it is important to study immune responses against these viruses and to define the degree of cross-reactivity between related HPV types. To investigate the potential for T cell cross-reactivity after vaccination, HLA-A2/K b transgenic mice were immunised with DNA plasmid constructs containing HPV18 and 45 E6 and E7.Splenocytes from immunised mice were tested in direct ELIspot assays against overlapping pools of HPV 18 peptides. Immunisation with either HPV18 or HPV45 E6 DNA produced dominant T cell responses against an epitope (KCIDFYSRI) that was shared between HPV18 and HPV45. This peptide was shown to bind to HLA-A*0201 but not D b or K b molecules on the cell surface. Furthermore this peptide was shown to be immunogenic in vitro to human T cells from 2 out of 3 HLA-A2 1 healthy donors. Collectively, these results demonstrate that HPV 18 and 45 E6 DNA vaccines are immunogenic in mice and demonstrate that cross-reactive T cell responses against closely related HPV types can be induced in vivo. The use of the HLA-A2/K b transgenic mice allowed definition of an HLA-A*0201 binding peptide epitope that would have been rejected on the basis of predicted major histocompatibility complex binding affinity. ' 2005 Wiley-Liss, Inc.Key words: HPV; CTL; cervical cancer; epitope; cross-reactivity Human papillomavirus (HPV) infection is strongly associated with the development of virtually all cervical cancers, 1 and some head, neck 2 and skin cancers. 3 Cervical cancer is the 2nd leading cause of female cancer mortality worldwide, with an estimated 400,000 new cases every year. 4 The global burden of cervical cancer has lead to much research into prophylactic and therapeutic vaccines. Despite encouraging recent data with prophylactic vaccines, 5 there is still a need to develop therapeutic approaches for cancer and to address the considerable burden of recurrent HPVassociated anogenital neoplasias.Cell-mediated immunity is important in the control of HPV infection, as HPV-associated cervical lesions are more prevalent in immunosuppressed individuals. 6,7 Furthermore, regression of HPV-induced warts is associated with lymphocytic infiltration in man and animal models. 8 CD8 1 cytotoxic T lymphocytes (CTL) are known to protect against persistent viruses, 9 but importantly can also mediate tumour regression in animal models 10,11 and in a limited number of clinical studies in man. 12-14 CD8 1 CTL recognise endogenously processed peptides bound to major histocompatibility complex (MHC) class I molecules on tumour cells. 15 For oncogenic HPV types, the intracellular E6 and E7 proteins provide attractive targets because of their persistent and obligate expression in tumour cells. 16 Therapeutic approaches have largely ta...

Cellular immunity induced by a novel HPV18 DNA vaccine encoding an E6/E7 fusion consensus protein in mice and rhesus macaques

“…The homology of E6 and E7 proteins within each class suggest the possibility that a broad coverage may be achieved by using a HPV 16 or HPV18 vaccine. In fact, a shared T cell epitope (KCIDFYSRI) that bound to HLA-A*0201 but not D b or K b molecules between HPV 18 and 45 was identified (31). In order to maximize potential immune cross-reactivity, especially at the T-cell level, we generated a HPV 18 consensus E6 and E7 DNA immunogen.…”

Characterization of HPV18 E6-specific T cell responses and establishment of HPV18 E6-expressing tumor model

“…Of note, the HPV18-E6 antigenic epitope characterized in this study, HPV18-E6aa67-75, has been evaluated by McCarthy et al and was suggested to be presented via HLA-A2 MHC molecules [17]. In their study, McCarthy et al .…”

“…While the MHC class I restriction of HPV18-E6aa67-75 epitope in naïve C57BL/6 mice has not been previously explored, an earlier publication evaluated the MHC class I restriction of this epitope in HLA-A2/KB transgenic mice and determined that this peptide sequence binds mainly to HLA-A2 [17]. We demonstrated that pcDNA3-HPV-18-E6 vaccination generated E6aa67-75 epitope-specific CD8+ T cell response in naïve C57BL/6 mice (Figure 1).…”

“…While the current study focused on characterizing the immune response against HPV18-E6aa67-75 since this epitope has been previously reported to be presented in mice [16, 17], other studies have reported the observation of HPV18-E6 specific immune response in human or in human MHC restricted fashion. For example, Chen et al has previously identified that HPV18-E6 epitopes aa54-62 and aa84-92 can bind to HLA-A11 [25].…”

A Novel Tumor Antigen Derived from Enhanced Degradation of Bax Protein in Human Cancers

“…On the basis of their HLA-A2 binding, only these 4 Bax peptides would be predicted to be candidate T-cell epitopes. However, we included all the candidate HLA-A2 peptides in subsequent experiments because we have previously shown that even peptides with poor or low binding in the T2 assay can be T-cell epitopes (16,20).…”