Enhancing melanoma treatment through systemic delivery of an immune boosting Staphylococcus epidermidis strain.

A unique strain of Staphylococcus epidermidis, AIT01 (AIT, Airway Immune Trainer), identified in our previous research, has demonstrated immune-boosting properties. This study aimed to evaluate the systemic immune-modulatory effects and potential anti-tumor properties of this immune-enhancing skin microbiota strain. A series of ex vivo and in vivo experiments were conducted to assess immune cell proliferation, cytokine production, and anti-tumor efficacy. In ex vivo studies, splenocytes treated with the bacterial lysate or culture supernatant of the strain showed significantly increased viability in a concentration-dependent manner. Flow cytometry analysis revealed increased populations of dendritic cells, NK cells (Natural killer cells), and γδ T cells, with enhanced cytokine production, particularly IFN-γ (Interferon-γ) and perforin, in the lysate-treated group. When administered via intraperitoneal and intravenous routes in vivo, mice showed significant inhibition of melanoma growth upon receiving the bacterial lysate. Notably, pre-treatment demonstrated superior efficacy compared to post-treatment. Furthermore, the combination of the bacterial lysate with anti-PD-1 (anti-Programmed cell death protein-1) monoclonal antibody further suppressed tumor growth compared to anti-PD-1 monotherapy. These findings suggest that the AIT01 lysate enhances immune cell proliferation and cytokine production, contributing to its potent anti-tumor effects. The systemic delivery of this immune-boosting skin microbiota strain, particularly in combination with anti-PD-1 therapy, holds promise as an effective immunotherapeutic strategy against melanoma.