Bronchoalveolar lavage cytokine-based risk stratification of minimal acute rejection in clinically stable lung transplant recipients

https://doi.org/10.1016/j.healun.2021.05.017Get rights and content

Background

Acute cellular rejection (ACR) remains the most significant risk factor for chronic lung allograft dysfunction (CLAD). While clinically significant or higher-grade (≥A2) ACR is generally treated with augmented immunosuppression (IS), the management of clinically stable grade A1 ACR remains controversial. At our center, patients with clinically stable grade A1 ACR are routinely not treated with augmented IS. While the overall outcomes in this group of patients at our center are equivalent to patients with stable A0 pathology, CLAD and death rates remain overall high. We hypothesized that a distinct cytokine signature at the time of early minimal rejection state would be associated with worse outcomes. Specifically, we aimed to determine whether bronchoalveolar lavage (BAL) biomarkers at the time of first clinically stable grade A1 ACR (CSA1R) are predictive of subsequent CLAD or death.

Methods

Among all adult, bilateral, first lung transplants, performed 2010-2016, transbronchial biopsies obtained within the first-year post-transplant were categorized as clinically stable or unstable based on the presence or absence of ≥10% concurrent drop in forced expiratory volume in 1 second (FEV1). We assessed BAL samples obtained at the time of CSA1R episodes, which were not preceded by another ACR (i.e., first episodes). Twenty-one proteins previously associated with ACR or CLAD were measured in the BAL using a multiplex bead assay. Association between protein levels and subsequent CLAD or death was assessed using Cox Proportional Hazards models, adjusted for relevant peri-transplant clinical covariates.

Results

We identified 75 patients with first CSA1R occurring at a median time of 98 days (range 48.5-197) post-transplant. Median time from transplant to CLAD or death was 1247 (756.5-1921.5) and 1641 days (1024.5-2326.5), respectively. In multivariable models, levels of MCP1/CCL2, S100A8, IL10, TNF-receptor 1, and pentraxin 3 (PTX3) were associated with both CLAD development and death (p < 0.05 for all). PTX3 remained significantly associated with both CLAD and death after adjusting for multiple comparisons.

Conclusion

Our data indicate that a focused BAL protein signature, with PTX3 having the strongest association, may be useful in determining a subset of CSA1R patients at increased risk and may benefit from a more aggressive management strategy.

Section snippets

Study design

This was a single-center, retrospective cohort study based on prospectively collected BAL samples. The study was approved by the Institutional Research Ethics Board (Approval number 15-9531-AE). The study population consisted of all adult, bilateral, first lung transplant recipients at Toronto General Hospital who underwent a lung transplant operation between January 1, 2010, and December 31, 2016, and had a minimum of 2 post-transplant forced expiratory volume in 1 second (FEV1) measurements.

Statistical analysis

Demographic characteristics were assessed as counts and percentages for categorical variables and as standard measures (median and interquartile range) for continuous variables. For the primary analysis, univariable and multivariable Cox Proportional Hazards models were used for evaluating the association of BAL protein levels with time from first CSA1R to CLAD or death/retransplant. For time to CLAD analyses, patients who died without CLAD were censored at their date of death. For time to

Study population and patient characteristics

Of all adult, bilateral, first lung transplant recipients who underwent a transplant operation between January 1, 2010, and December 31, 2016, 104 patients with clinically stable first A1 ACR, not preceded by ≥A1 ACR, were included in the pool of potential participants for the primary analysis (Figure 1). After excluding 29 patients (concurrent infection, missing BAL samples, or biopsy obtained after CLAD diagnosis), we identified 75 patients with a first CSA1R, occurring at a median time of 98

Discussion

In this unique cohort of patients with a first, clinically stable, untreated, minimal AR, at a median time of 3 months post-transplant, we were able to identify a protein signature associated with progression to CLAD or death/retransplant. Using a hypothesis-driven approach, we identified 7 individual biomarkers associated with subsequent CLAD and 12 associated with subsequent death. Five of these markers (IL10, PTX 3, S100A8, TNF-R1, and MCP1/CCL2) demonstrated a strong predictive capacity for

Authors' contributions

TM conceived the research concept, supervised the project, oversaw data analysis, and made critical revisions to the manuscript. LL designed and supervised the study, analyzed the data, and wrote the manuscript. EH performed all statistical analyses and made critical revisions to the manuscript. LL, MA, WK, JT, RG collected and organized the clinical data and revised the final manuscript. LL, SH, KZ organized samples for analysis, and together with KB, SM carried out the multiplex assay and

Disclosure statement

The authors of this manuscript have no conflicts of interest to disclose.

The authors would like to thank the Toronto Lung Transplant Program Biobank team for helping with sample collection and retrieval.

This research was supported in part by a grant from The Canadian Institutes of Health Research (#149094, to TM and SJ), a grant from The Physicians’ Services Inc. Foundation (#17–22, to LL and TM), and by a Cystic Fibrosis Canada grant (#12787, to LL).

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