NY‐ESO‐1 specific antibody and cellular responses in melanoma patients primed with NY‐ESO‐1 protein in ISCOMATRIX and boosted with recombinant NY‐ESO‐1 fowlpox virus

Vaccination strategies based on repeated injections of NY‐ESO‐1 protein formulated in ISCOMATRIX particles (NY‐ESO‐1 ISCOMATRIX) have shown to elicit combined NY‐ESO‐1 specific antibody and T cell responses. However, it remains unclear whether heterologous prime‐boost strategies based on the combination with NY‐ESO‐1 ISCOMATRIX with different NY‐ESO‐1 boosting reagents could be used to increase NY‐ESO‐1 CD8+ or CD4+ T cell responses. To address this question, we carried out a randomized clinical trial in 39 high‐risk, resected melanoma patients vaccinated with NY‐ESO‐1 ISCOMATRIX, and then boosted with repeated injections of either recombinant fowlpox virus encoding full length NY‐ESO‐1 (rF‐NY‐ESO‐1) (Arm A) or NY‐ESO‐1 ISCOMATRIX alone (Arm B). We have comprehensively analyzed NY‐ESO‐1 specific T cells and B cells response in all patients before and after vaccination for a total of seven time points per patient. NY‐ESO‐1 ISCOMATRIX alone elicited a strong NY‐ESO‐1 specific CD4+ T cell and antibody response, which was maintained by both regiments at similar levels. However, CD8+ T cell responses were significantly boosted in 3 out of 18 patients in Arm A after the first rF‐NY‐ESO‐1 injection and such responses were maintained until the end of the trial, while no patients in Arm B showed similar CD8+ T cell responses. In addition, our results clearly identified immunodominant regions in the NY‐ESO‐1 protein: NY‐ESO‐179–102 and NY‐ESO‐1115–138 for CD4+ T cells and NY‐ESO‐185–108 for CD8+ T cells in a large proportion of vaccinated patients. These regions of NY‐ESO‐1 protein should be considered in future clinical trials as immunodominant epitopes. What's New? Cancer vaccines using genetically‐engineered viruses have not been as successful as originally hoped. In this study, the authors asked whether first priming the immune system with antigen alone might improve the success of a viral vector. Melanoma patients were given priming injections of an antigen called NY‐ESO‐1 plus ISCOMATRIX adjuvant. Several patients who then received injections of a fowlpox virus encoding NY‐ESO‐1 had improved CD8+ T‐cell responses, compared to no improvement in patients who simply received more of the isolated antigen.