Challenges and Opportunities for Biomarkers of Clinical Response to AHSCT in Autoimmunity

Abstract

Autoimmunity represents a broad category of diseases that involve a variety of organ targets and distinct autoantigens. For patients with autoimmune diseases who fail to respond to approved disease-modifying treatments, autologous hematopoietic stem cell transplantation (AHSCT) after high-dose immunosuppressive therapy provides an alternative strategy. Although more than 100 studies have been published on AHSCT efficacy in autoimmunity, the mechanisms that confer long-term disease remission as opposed to continued deterioration or disease reactivation remain to be determined. In a phase II clinical trial, high-dose immunosuppressive therapy combined with autologous CD34+ hematopoietic stem cell transplant in treatment-resistant, relapsing-remitting multiple sclerosis (RRMS) resulted in 69.2% of participants achieving long-term remission through 60 months follow-up. Flow cytometry data from the 24 transplanted participants in the high-dose immunosuppression and autologous stem cell transplantation for poor prognosis multiple sclerosis (HALT-MS) trial are presented to illustrate immune reconstitution out to 36 months in patients with aggressive RRMS treated with AHSCT and to highlight experimental challenges inherent in identifying biomarkers for relapse and long-term remission through 60 months follow-up. AHSCT induced changes in numbers of CD4 T cells and in the composition of CD4 and CD8 T cells that persisted through 36 months in participants who maintained disease remission through 60 months. However, changes in T cell phenotypes studied were unable to clearly discriminate durable remission from disease reactivation after AHSCT, possibly due to the small sample size, limited phenotypes evaluated in this real-time assay, and other limitations of the HALT-MS study population. Strategies and future opportunities for identifying biomarkers of clinical outcome to AHSCT in autoimmunity are also discussed.

Trial registration: ClinicalTrials.gov NCT00288626.

Keywords: T cells; autoimmunity; biomarkers; flow cytometry; immune cell reconstitution; immune tolerance; multiple sclerosis.

Figures

Figure 1

Impact of autologous hematopoietic stem cell transplantation (AHSCT) on numbers of circulating lymphocyte populations through 36 months follow-up. Absolute cell numbers per microliter of whole blood were analyzed for (A) CD8 T cells, (B) CD4 T cells, (C) CD19 B cells, (E) CD56dim NK cells, and (F) CD56hi NK cells. (D) CD4/CD8 ratios were calculated from absolute cell numbers (A,B). Flow data were plotted after log transformation for normalization of these variables. Data shown are mean values for the group that maintained remission through 60 months post-AHSCT. The black line represents the Loess Regression fitted curve with a span = 0.7, and its 95% confidence band colored in gray. Paired t-test was used to examine persistent changes at 36 months from pretherapy numbers within the group that maintained remission through 60 months post-AHSCT (n = 15). CD4 T cells, CD4/CD8 T cell ratio, and CD56dim NK cells were reduced from pretherapy numbers at 36 months post-AHSCT. Individual lines for the seven participants who experienced disease reactivation prior to 60 months post-AHSCT are plotted using different symbols to indicate the type of disease activity and different colored lines to indicate the time to first multiple sclerosis (MS) disease activity. For additional details including flow cytometry data without log-transformation, see https://www.itntrialshare.org/HALTMS_fimmu_fig1.url.

Figure 2

Impact of autologous hematopoietic stem cell transplantation (AHSCT) on the composition of circulating CD4 and CD8 T cells through 36 months follow-up. Percentages of CD27+CD45RO− naive CD4 (A) and CD8 (B) T cells, CD27+CD45RO+ central memory CD4 (C) and CD8 (D) T cells, CD27−CD45RO+ effector memory CD4 (E) and CD8 (F) T cells, (G) CD31+CD45RA+CD45RO− CD4 recent thymic emigrants (RTEs), (H) CD27−CD45RO− long-term memory CD8 T cells, (I) CD56−CD57+CD28− CD8 T cells, and (J) CD56+CD57+CD28− CD8 T cells. Flow data were plotted after log transformation for normalization of these variables. Data shown are mean values for the group that maintained remission through 60 months post-AHSCT. The black line represents the Loess Regression fitted curve with a span = 0.7, and its 95% confidence band colored in gray. Paired t-test was used to examine sustained changes at 36 months from pretherapy numbers within the group that maintained remission through 60 months post-AHSCT (n = 15). AHSCT induced persistent changes in relative proportions of central memory and RTE phenotypes in reconstituted CD4 T cells. In reconstituted CD8 T cells, sustained alterations in proportions of central memory, CD56−CD57+CD28− (senescent) and CD56+CD57+CD28− (cytotoxic) phenotypes were observed. Individual lines for the seven participants who experienced disease reactivation before 60 months post-AHSCT are plotted using different symbols to indicate the type of disease activity and different colored lines to indicate the time to first multiple sclerosis (MS) disease activity. For additional details including flow cytometry data without log-transformation, see https://www.itntrialshare.org/HALTMS_fimmu_fig2.url.

Figure 2

Impact of autologous hematopoietic stem cell transplantation (AHSCT) on the composition of circulating CD4 and CD8 T cells through 36 months follow-up. Percentages of CD27+CD45RO− naive CD4 (A) and CD8 (B) T cells, CD27+CD45RO+ central memory CD4 (C) and CD8 (D) T cells, CD27−CD45RO+ effector memory CD4 (E) and CD8 (F) T cells, (G) CD31+CD45RA+CD45RO− CD4 recent thymic emigrants (RTEs), (H) CD27−CD45RO− long-term memory CD8 T cells, (I) CD56−CD57+CD28− CD8 T cells, and (J) CD56+CD57+CD28− CD8 T cells. Flow data were plotted after log transformation for normalization of these variables. Data shown are mean values for the group that maintained remission through 60 months post-AHSCT. The black line represents the Loess Regression fitted curve with a span = 0.7, and its 95% confidence band colored in gray. Paired t-test was used to examine sustained changes at 36 months from pretherapy numbers within the group that maintained remission through 60 months post-AHSCT (n = 15). AHSCT induced persistent changes in relative proportions of central memory and RTE phenotypes in reconstituted CD4 T cells. In reconstituted CD8 T cells, sustained alterations in proportions of central memory, CD56−CD57+CD28− (senescent) and CD56+CD57+CD28− (cytotoxic) phenotypes were observed. Individual lines for the seven participants who experienced disease reactivation before 60 months post-AHSCT are plotted using different symbols to indicate the type of disease activity and different colored lines to indicate the time to first multiple sclerosis (MS) disease activity. For additional details including flow cytometry data without log-transformation, see https://www.itntrialshare.org/HALTMS_fimmu_fig2.url.