Single cell tracking of gadolinium labeled CD4(+) T cells by laser ablation inductively coupled plasma mass spectrometry

Cellular therapy is emerging as a promising alternative to conventional immunosuppression in the fields of haematopoietic stem cell (HSC) transplantation, autoimmune disease and solid organ transplantation. Determining the persistence of cell-based therapies in vivo is crucial to understanding their regulatory function and requires the combination of an extremely sensitive detection technique and a stable, long-lifetime cell labelling agent. This paper reports the first application of laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) to perform single cell detection of T cell populations relevant to cellular immunotherapy. Purified human CD4+ T cells were labelled with commercially available Gd-based MRI contrast agents, Omniscan® and Dotarem®, which enabled passive loading of up to 108 Gd atoms per cell. In mixed preparations of labelled and unlabelled cells, LA-ICP-MS was capable of enumerating labelled cells at close to the predicted ratio. More importantly, LA-ICP-MS single cell analysis demonstrated that the cells retained sufficient label to remain detectable for up to 10 days post-labelling both in vitro and in vivo in an immunodeficient mouse model

Table_1_External validation of biomarkers for immune-related adverse events after immune checkpoint inhibition.xlsx

Immune checkpoint inhibitors have revolutionized treatment of advanced melanoma, but commonly cause serious immune-mediated complications. The clinical ambition of reserving more aggressive therapies for patients least likely to experience immune-related adverse events (irAE) has driven an extensive search for predictive biomarkers. Here, we externally validate the performance of 59 previously reported markers of irAE risk in a new cohort of 110 patients receiving Nivolumab (anti-PD1) and Ipilimumab (anti-CTLA-4) therapy. Alone or combined, the discriminatory value of these routine clinical parameters and flow cytometry biomarkers was poor. Unsupervised clustering of flow cytometry data returned four T cell subsets with higher discriminatory capacity for colitis than previously reported populations, but they cannot be considered as reliable classifiers. Although mechanisms predisposing some patients to particular irAEs have been described, we are presently unable to capture adequate information from pre-therapy flow cytometry and clinical data to reliably predict risk of irAE in most cases.</p

DataSheet_1_External validation of biomarkers for immune-related adverse events after immune checkpoint inhibition.pdf

Immune checkpoint inhibitors have revolutionized treatment of advanced melanoma, but commonly cause serious immune-mediated complications. The clinical ambition of reserving more aggressive therapies for patients least likely to experience immune-related adverse events (irAE) has driven an extensive search for predictive biomarkers. Here, we externally validate the performance of 59 previously reported markers of irAE risk in a new cohort of 110 patients receiving Nivolumab (anti-PD1) and Ipilimumab (anti-CTLA-4) therapy. Alone or combined, the discriminatory value of these routine clinical parameters and flow cytometry biomarkers was poor. Unsupervised clustering of flow cytometry data returned four T cell subsets with higher discriminatory capacity for colitis than previously reported populations, but they cannot be considered as reliable classifiers. Although mechanisms predisposing some patients to particular irAEs have been described, we are presently unable to capture adequate information from pre-therapy flow cytometry and clinical data to reliably predict risk of irAE in most cases.</p