Nano‐particle vaccination combined with TLR‐7 and ‐9 ligands triggers memory and effector CD8+ T‐cell responses in melanoma patients

Optimal vaccine strategies must be identified for improving T‐cell vaccination against infectious and malignant diseases. MelQbG10 is a virus‐like nano‐particle loaded with A‐type CpG‐oligonucleotides (CpG‐ODN) and coupled to peptide_16–35 derived from Melan‐A/MART‐1. In this phase IIa clinical study, four groups of stage III‐IV melanoma patients were vaccinated with MelQbG10, given (i) with IFA (Montanide) s.c.; (ii) with IFA s.c. and topical Imiquimod; (iii) i.d. with topical Imiquimod; or (iv) as intralymph node injection. In total, 16/21 (76%) patients generated ex vivo detectable Melan‐A/MART‐1‐specific T‐cell responses. T‐cell frequencies were significantly higher when IFA was used as adjuvant, resulting in detectable T‐cell responses in all (11/11) patients, with predominant generation of effector‐memory‐phenotype cells. In turn, Imiquimod induced higher proportions of central‐memory‐phenotype cells and increased percentages of CD127⁺ (IL‐7R) T cells. Direct injection of MelQbG10 into lymph nodes resulted in lower T‐cell frequencies, associated with lower proportions of memory and effector‐phenotype T cells. Swelling of vaccine site draining lymph nodes, and increased glucose uptake at PET/CT was observed in 13/15 (87%) of evaluable patients, reflecting vaccine triggered immune reactions in lymph nodes. We conclude that the simultaneous use of both Imiquimod and CpG‐ODN induced combined memory and effector CD8⁺ T‐cell responses.