Phase 1 study of HPV16-specific immunotherapy with E6E7 fusion protein and ISCOMATRIX™ adjuvant in women with cervical intraepithelial neoplasia☆
Introduction
Cervical cancer is the second commonest female cancer, resulting in over 200,000 deaths annually, the majority of which occur in the developing world. Squamous cervical cancer results from infection of the cervix by “high risk” genotypes of human papillomavirus (HPV) [1], particularly HPV16. It arises from high-grade cervical intraepithelial neoplasia (CIN), which is induced by persistent HPV infection. Cervical cancer can be largely prevented by screening exfoliated cervical cells for cytological abnormalities, and by destructive treatment of identified high grade CIN. However, comprehensive screening programs are limited to developed countries by resource and logistics issues. A more broadly applicable therapeutic approach to persistent cervical HPV infection is therefore desirable.
The average time interval between HPV infection and development of cervical cancer is over 20 years. Cervical cancer incidence is increased by immunosuppression by drugs or by HIV infection, with a latent period in immunosuppressed renal transplant patients of less than 5 years [2]. Thus, host immune responses can control progression of HPV infection to malignancy. HPV encoded non-structural proteins, E6 and E7 are expressed in CIN and cervical cancer, and are able to transform normal epithelium. Infection with HPV can evoke immune responses to these proteins [3]. Immunisation with E7 can control development of E7 expressing tumours in animal models [4], and immune responses to E7 protein can also be induced by immunisation in humans [5]. Thus, an appropriate immune response directed at the E6 and E7 proteins of high risk HPV might eliminate the HPV transformed cells that comprise CIN and hence prevent progression to cervical cancer.
Vaccinia virus expressing a modified non-transforming E6E7 recombinant protein is being tested as immunotherapy for cervical cancer [6]. Attenuated viruses encoding HPV E6 and E7 protein are unlikely to be acceptable vaccine delivery systems for widespread use in humans with non-malignant disease, as these proteins have oncogenic potential. Protein–adjuvant mixtures are the other widely accepted vaccine formulations used in humans. E7 peptides [7], heat shock protein fusions of E7 [8] and E7-GST fusion protein [9] have each been trialled with a variety of adjuvants in humans. However, to date there have been few blinded placebo controlled trials of immunotherapy with HPV16 non-structural proteins, and none have demonstrated a uniform and well characterised antigen specific humoral and cell mediated immune response.
To provide the maximum range of antigenic epitopes from HPV16 and ensure a broad based immune response, we undertook a study of immunotherapy for CIN with HPV16 Immunotherapeutic, a mixture of bacterially derived recombinant E6E7 fusion protein [10] and ISCOMATRIX™ adjuvant [11]. We comprehensively measured immune responses to E6 and E7 protein using well validated assays under good laboratory practice conditions, with all parties blinded to the treatment received by the subjects until all assays were completed. HPV load in the cervix has been identified as a possible surrogate marker for risk of cervical cancer development [12], and reduction in viral load has been reported to precede resolution of HPV associated cervical pathology [13]. In this study we demonstrate that therapy with HPV16 Immunotherapeutic is safe and immunogenic, and that administration may be associated with a reduction in HPV viral load in the cervical epithelium.
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Patient recruitment
Trial participants were recruited from amongst 231 patients attending the gynaecological outpatient departments of four participating hospitals in Brisbane and Melbourne, Australia, between October 1999 and April 2001 for management of cervical cytology consistent with a squamous intraepithelial lesion (SIL). The first 151 patients were screened for cervical HPV16 infection and high grade CIN on biopsy, and 30 subjects with HPV16 and CIN 2 or 3 were identified, of whom six agreed to
Patients
Thirty-one subjects were recruited (mean age 28 years, range 19–57 years). Twenty-four subjects were randomised to active vaccine and they received a total of 56 injections. The seven subjects randomized to placebo received a total of 17 injections. Twenty-six subjects completed treatment as planned (Table 1). Data from all subjects were included in the analysis. The five women who did not complete treatment were assigned to active vaccine. Three women did not receive all injections because of
Discussion
This study demonstrates induction of immune responses to tumour antigens in patients with pre-cancer, using a vaccine combining recombinant antigen with ISCOMATRIX™ adjuvant. This confirms and extends earlier findings that cellular immunity, and specifically cytotoxic T cells, can be induced with ISCOMATRIX™ adjuvant based vaccines in humans [16], [17], and that vaccines based on tumour antigens delivered with this adjuvant are therapeutic in a number of animal tumour models [18].
The E6E7
Acknowledgements
This trial was sponsored by CSL Limited, Parkville, Australia. The authors thank Dr. Gayle Phillips for careful review of cytological and histological specimens from the Brisbane patients.
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ISCOMATRIX™ is a Trade Mark of ISCOTEC AB, a CSL Limited company.