Predicting Risk of Infection in Patients Receiving CAR-T for Aggressive Lymphoma: A Study Exploring the Utility of Immune Profiling
Authors: Reynolds Gemma K , Williams Lewis , Anderson Mary Ann , Dowling Mark R , Minson Adrian , Dickinson Michael J. , Thursky Karin A , Harrison Simon J , Slavin Monica A , Doerflinger Marcel , Teh Benjamin W 
Published: December 2024

Introduction
Comprehensive immune profiling may enable personalized infection-risk prediction in patients (pts) receiving chimeric antigen receptor T-cell (CAR-T) therapy for aggressive lymphoma. Our exploratory study evaluated whether patterns of cytokine expression could predict early and late infections following CAR-T treatment.
Methods
Pts with diffuse large B-cell lymphoma (DLBCL) treated with standard-of-care CAR-T between 2019 - 2023 were consented and included. Demographic, treatment-related variables and infection events were recorded. Infection episodes were classified as clinically or microbiologically defined.1
Blood samples were collected at apheresis (baseline) and day 30 (D30) post CAR-T infusion. Peripheral blood mononuclear cells were isolated, and either re-stimulated with phorbol myristate acetate and ionomycin, or left untreated for 48 hours. Induced cytokines were measured with a Luminex xMAP System.
The relationship between early infections (baseline-D30), and stimulated and unstimulated cytokine levels from baseline PBMCs, was evaluated in a multivariable regression that controlled for median therapies, baseline HT score,2 and CAR-T product. Cytokine levels at D30 were similarly evaluated as predictors of late infections occurring in the following 3 -months, controlling for tocilizumab exposure and prolonged neutropenia (≤0.5x106 for ≥14 days). Logistic Firth's regressions were performed, with Bonferroni adjustment for multiple comparisons.
Results
20 pts (70% male) with DLBCL received axicabtagene (n=10) or tisagenlecleucel (n=10), with a median of 3 prior therapies (IQR:3 - 4.25). 55% had undergone prior autologous stem-cell transplant.
17 infections (15pts), 47% grade≥3, occurred in the study period, 76% before D30. 85% of early infections were microbiologically confirmed; 54% bacterial, 27% viral, 18% fungal. All late infections were microbiologically confirmed; 2 bacterial and 2 viral infections.
80 cytokines were examined across 9,600 cytokine-stimulant combinations. At baseline, triggering receptor expressed on myeloid cells (TREM1) and IL-1α were correlated with early all-cause infection (R2= -0.45, p=0.016; R2= -0.40 p=0.039). In univariate analysis (adjusted p=0.025), higher TREM1 levels were significantly associated with lower infection risk (p=0.01) in both stimulated and unstimulated samples. In multivariable analysis, higher TREM1 levels from stimulated cells, were associated with a lower risk of subsequent early infection (p=0.017) controlling for median therapies, CAR-T product and baseline HT. Every 500pg/mL increase in TREM-1 levels following stimulation was associated with a 25% reduced risk of infection. TREM1 levels from unstimulated samples did not predict infections in multivariable analysis.
On day 30, monocyte chemoattractant protein-1 (MCP1) release at D30 was moderately correlated with late infections (R2= .46, p=0.005) and significantly associated in univariable analysis (p=0.04). In stimulated samples, a 500pg/mL increase of MCP1 was associated with 2-fold increase in subsequent late infection rates (p=0.013, HR=2.23) controlling for cumulative tocilizumab exposure and prolonged neutropenia. MCP1 from unstimulated samples was not significantly associated with late infections in the multivariable model.
Conclusion
Our exploratory study is the first to evaluate whether cytokine levels were associated with subsequent infections following CAR-T. We identify two cytokines significantly associated with infections in multivariable analysis. TREM1 increases in early sepsis,3-5 but in our study, higher TREM1 levels following stimulation was significantly associated with lower infection rates. TREM1 levels following stimulation in vitro may reflect the amplitude, and perhaps adequacy, of the immune response against a future pathogen. Additionally, higher MCP-1 levels have also been associated with acute infection,6-8 and D30 levels predicted a higher risk of late infection risk in our cohort. Most late infections in our cohort occurred within 6 weeks, thus higher MCP1 may have reflected early subclinical infection. Our study has limitations. Our sample size may be underpowered to detect statistical significance of some effects while accounting for disease and treatment factors. Validation of the predictive efficacy of TREM1 and MCP1 in future cohorts is warranted.