Georgia Beasley

Isolated limb infusion (ILI) using melphalan and dactinomycin (actinomycin D) was developed as a simplified and minimally invasive alternative to the traditional, more invasive, and elaborative isolated limb perfusion (ILP) to treat unresectable metastatic melanoma confined to the limb. An increasing number of centers around the world have reported their results using the procedure. Reports from different centers have shown that the procedure is safe, with mild-to-moderate regional toxicity, and results in satisfactory response rates. When comparing ILI and ILP, it must be borne in mind that ILI is often performed in significantly older patients and in patients with higher stages of disease, which decreases the likelihood of a favorable response. Even in this era of effective systemic therapies for metastatic melanoma, ILI is still worthwhile and a relatively straightforward, single-treatment option to treat locally recurrent or in-transit metastatic melanoma involving a limb. Due to its minimally invasive nature, ILI is an ideal platform to test new drugs and drug combinations. Potential exists to further improve ILI response rates when combined with novel therapies.

BACKGROUND: Antitumor mechanisms of CD4+ T cells remain crudely defined, and means to effectively harness CD4+ T-cell help for cancer immunotherapy are lacking. Pre-existing memory CD4+ T cells hold potential to be leveraged for this purpose. Moreover, the role of pre-existing immunity in virotherapy, particularly recombinant poliovirus immunotherapy where childhood polio vaccine specific immunity is ubiquitous, remains unclear. Here we tested the hypothesis that childhood vaccine-specific memory T cells mediate antitumor immunotherapy and contribute to the antitumor efficacy of polio virotherapy. METHODS: The impact of polio immunization on polio virotherapy, and the antitumor effects of polio and tetanus recall were tested in syngeneic murine melanoma and breast cancer models. CD8+ T-cell and B-cell knockout, CD4+ T-cell depletion, CD4+ T-cell adoptive transfer, CD40L blockade, assessments of antitumor T-cell immunity, and eosinophil depletion defined antitumor mechanisms of recall antigens. Pan-cancer transcriptome data sets and polio virotherapy clinical trial correlates were used to assess the relevance of these findings in humans. RESULTS: Prior vaccination against poliovirus substantially bolstered the antitumor efficacy of polio virotherapy in mice, and intratumor recall of poliovirus or tetanus immunity delayed tumor growth. Intratumor recall antigens augmented antitumor T-cell function, caused marked tumor infiltration of type 2 innate lymphoid cells and eosinophils, and decreased proportions of regulatory T cells (Tregs). Antitumor effects of recall antigens were mediated by CD4+ T cells, limited by B cells, independent of CD40L, and dependent on eosinophils and CD8+ T cells. An inverse relationship between eosinophil and Treg signatures was observed across The Cancer Genome Atlas (TCGA) cancer types, and eosinophil depletion prevented Treg reductions after polio recall. Pretreatment polio neutralizing antibody titers were higher in patients living longer, and eosinophil levels increased in the majority of patients, after polio virotherapy. CONCLUSION: Pre-existing anti-polio immunity contributes to the antitumor efficacy of polio virotherapy. This work defines cancer immunotherapy potential of childhood vaccines, reveals their utility to engage CD4+ T-cell help for antitumor CD8+ T cells, and implicates eosinophils as antitumor effectors of CD4+ T cells.

<jats:p>&lt;p&gt;Trial Schema&lt;/p&gt;</jats:p>