140 Background: Therapeutic vaccination with HPV type 16 synthetic long peptides (HPV16-SLP) results in T cell–mediated regression of HPV16-induced premalignant lesions but fails to install effective immunity in patients with advanced HPV16-positive cervical cancer. We showed that HPV16-SLP vaccination in mice and in patients with advanced cervical cancer patients fosters robust HPV16-specific T cell responses, when combined with chemotherapy. In this study we noted that a single dose of vaccine 2 weeks into the 2nd cycle of chemotherapy was optimal, because at this time the immunosuppressive myeloid cells were down. Methods: We now completed a chemo-immunotherapy study in a larger number of patients with late stage HPV16+ cervical cancer. Three HPV16-SLP vaccine doses were given 2 weeks after the second, third, and fourth cycles of standard chemotherapy. Cohorts of 12 patients each were vaccinated with each of 4 dose levels (20, 40, 100, and 300 µg/ per peptide) of 13 overlapping HPV16 synthetic long peptides (HPV16-SLP) together covering the length of the 2 E6 and E7 proteins. Results: Robust vaccine-induced HPV16-specific T cell responses as assessed by interferon-g Elispot were observed and were sustained throughout the cycles of chemotherapy. These T cell responses were substantially increased in all patients who received HPV16-SLP . In addition, the chemotherapy augmented recall responses to microbial antigens. Such robust T cell responses were not noted in previous trials when similar patients were vaccinated without timing of vaccination during chemotherapy. A marked correlation was observed between the strength of the vaccine-induced immune response and longer-term clinical outcomes such as overall survival. No such correlation exists between the strength of the T cell response against common recall antigens and survival. In addition, a remarkably high proportion of patients survived beyond 20 months after the start of therapy. Conclusions: These results indicate that the survival advantage is specifically related to the strength of the vaccine-induced T cell response and is not due to generally better immuno-competence. Clinical trial information: NCT02128126.
pDCs efficiently process synthetic long peptides to induce functional virus- and tumour-specific T-cell responses