Engineered Lactococcus lactis biovaccine containing NY-ESO-1 long peptides as potent immunotherapeutics

Peptide vaccines have potential for tumour immunotherapy but face challenges in clinical trials, such as human leukocyte antigen limitations, potential cytotoxic T lymphocyte tolerance, short T-cell response duration, weak immune response, and other issues. Optimizing the antigens of peptide vaccines and selecting an effective delivery system are crucial for enhancing their antitumour effects. 3 multiepitope long peptides (NLP) targeting the NY-ESO-1 antigen were screened using bioinformatics methods. An engineered <i>Lactococcus lactis</i> strain (FOLactis) expressing FMS-like tyrosine kinase 3 ligand and the costimulator OX40 ligand was previously developed to activate immune cells. In this study, FOLactis was utilized as a biological carrier for NLP via Mg²⁺-based metal-organic frameworks to stimulate innate and adaptive immunity. The FOL-M@NLP were characterized, and various tumour models were established to assess the antitumour efficacy of the biovaccine. The preliminary mechanism of the immune effect induced by FOL-M@NLP was studied both <i>in vivo</i> and <i>in vitro</i>. The biovaccine FOL-M@NLP was effectively taken up by antigen-presenting cells (APCs). APCs were activated, activating the T-cell response. When FOL-M@NLP was administered subcutaneously <i>in vivo</i>, their antitumour activity was superior to that of NLP and FOLactis alone. The biovaccine improved the immune infiltrating state of the tumour microenvironment and metastasis niche, inhibited tumor progression and prevented recurrence. It is demonstrated that FOL-M@NLP serves as a potent and safe antitumour platform that enhances antigen peptide delivery and facilitates the advancement of therapeutic biological vaccine platforms.