Results of the ABLE/PBMTC 1202 studies demonstrate biological differences between cGvHD and late aGvHD

Chronic graft-versus-host disease (cGvHD) is the most serious non-relapse complication affecting up to 25% of pediatric and 60% of adult hematopoietic stem cell transplant (HSCT) survivors.¹ It may lead to irreversible organ damage and has a high mortality rate.¹ Clinically, it is sometimes difficult to distinguish from late acute GvHD (L-aGvHD). Therefore, the National Institutes of Health Consensus Criteria (NIH-CC) has been developed to better diagnose cGvHD. According to the NIH-CC, L-aGvHD is distinct from cGvHD with symptoms limited to the involvement of skin, liver, and gastrointestinal system without sclerotic changes after Day +100 post-transplant.²

To better understand the differences between L-aGvHD and cGvHD, the Applied Biomarker in Late Effects of Childhood Cancer/Pediatric Blood and Marrow Transplantation Consortium (ABLE/PBMTC 1202; NCT02067832) studies evaluated the immune profiles associated with the development of L-aGvHD and cGvHD in pediatric patients.³

Methods³

• Patients (N = 302) were enrolled in 27 pediatric transplant centers. Of these, 241 were evaluable for prognostic biomarkers at 100 days after HSCT and were placed into six groups:
  • Control group: no L-aGvHD and no cGvHD (n = 132)
    • no previous aGvHD (immune tolerant group; n = 87)
    • previous aGvHD resolved by Day 100 (n = 45)
  • L-aGvHD group (n = 58)
    • active L-aGvHD Day +100 -114 (n = 28)
    • L-aGvHD after Day +114 (n = 30)
  • cGvHD group (n = 51)
    • active cGvHD before Day +114 (n = 10)
    • cGvHD after Day +114 (n = 41)
• At 100 days after HSCT, immune phenotypic (T, B and NK cells sub-populations) and cytokine analysis was performed for each patient

Results³

No biomarker differences in cGvHD cases meeting NIH-CC vs those cases not meeting NIH-CC

• In the cGvHD group after Day +114, six patients did not meet formal NIH-CC, but had enough cGvHD features that the ABLE study committee agreed these patients had cGvHD (called “non-NIH-CC” cases)
• The authors compared the immune profile of the non-NIH-CC group (n = 6) with the NIH-CC group (n = 35). As no significant differences between the two groups were observed, subsequent analyses of the cGvHD group included both the non-NIH-CC patients and NIH-CC patients

Differences in immune profiles at Day 100 between patients developing L-aGvHD and patients developing cGvHD after Day 114

• Biomarker changes in cGvHD group (as compared to control group):
  • decrease in overall B cell counts, as well as in transitional T2 and T3 B cells, CD21^low B cells and in classic activated cytolytic CD56^dim NK cells
  • increase in the percentages of peripheral naïve CD4⁺, naïve PD1⁺ CD8⁺ T cells, activated T cells (CD3⁺ CD69⁺) in children who developed cGvHD after Day 114, and increase in ST2 and sCD13
• Biomarker changes in L-aGvHD group (as compared to no control group):
  • similar decrease in transitional B cell as observed in cGvHD
  • increase in unswitched memory B cells and in a cytolytic CD56^bright NK population (granzyme B high)
  • decrease in peripheral Tc cells
• This comparison confirmed that cGvHD is distinct from L-aGvHD with a decrease in NK_reg cells and B cells, and an increase in naïve CD4+ Tc cells, Th cells, and sCD13

Impact of previous aGvHD on Day 100 biomarker profile of patients with L-aGvHD or cGvHD

In order to analyze the impact of previous aGvHD on Day 100 biomarkers to identify patients at risk of L-aGvHD or cGvHD, the control group was separated into two groups, an “immune tolerant” group (n = 87), and another group with previous aGvHD resolved by day 100 (n = 45)

• Biomarker profiles from immune tolerant patients or patients with previous GvHD did not reveal markers associated with L-aGvHD or cGvHD
• cGvHD markers maintained significance, regardless of prior aGvHD including increased activated classic (CD56^dim) NK cells and ST2 and decreased transitional T3 B cells, CD21^low B cells, and NK_reg cells

Differences in immune profiles between patients who had active L-aGvHD or active cGvHD between Days 100–114 and patients developing L-aGvHD and cGvHD after Day 114

• Active L-aGvHD between Days 100–114 compared L-aGvHD after Day 114 saw an:
  • increase in sCD13 and ST2
  • decrease in overall B cell numbers, transitional B cells, IgD⁺ CD27⁺ B cells, and CD31⁺ naïve T_reg cells
• Active cGvHD between Days 100–114 compared to the cGvHD cohort that will develop cGvHD after Day 114:
  • increase in transitional T3 B cells, memory Th cells, and PD-1^- memory T_reg cells
  • decrease in PD-1⁺ memory T_reg cells

Impact of age on the Day 100 immune profiles in patients at risk for future cGvHD

To evaluate the impact of age on the Day 100 biomarkers patterns, each of the subject groups (cGvHD and controls) were divided at their respective median age (~12.5 years old and nine years old) and analyzed for each age group. Comparing younger cGvHD vs younger controls, the authors observed:

• a decrease in transitional B cell populations and elevation in ST2 and sCD13 in both younger and older patients with cGvHD
• by contrast, in the older population no increase in the CD56^dim NK cells, activated T cells, or naïve T cells or a decrease in NK_reg cells and CD21^low B cells was detected

Day 100 immune profiles does not predict early or late onset of cGvHD

To examine the impact of the onset time of cGvHD on the Day 100 immune profile, the cGvHD subjects were divided into an early onset group (≤ 166 days after HSCT) and a later onset group. There were no major differences between the early and the late onset group.

t-Distributed Stochastic Neighbour Embedding (t-SNE) on the Day 100 immune profiles to visualize differences between cGvHD, aGvHD, and controls

t-SNE, a method where subjects with similar biomarker values are clustered together, reveals differences between subject groups. This analysis showed that the cGvHD group and control group tend to cluster in opposite location of the plot, with the L-aGvHD group was located between these two groups.

Conclusions³

• Patients with clinical signs of cGvHD which meet NIH-CC cohort do not differ from those that do not meet NIH-CC, indicating that NIH-CC criteria to diagnose cGvHD may require modifications
• The comprehensive analyses of immune profile, plasma markers and t-SNE analysis suggest that L-aGvHD is a transition stage towards progression to cGvHD
• While both cGvHD and L-aGvHD, had decreased transitional B cells and increased cytolytic NK cells, cGvHD presented with additional cytokine, T, NK, and B cell abnormalities
• One critical factor in the development of cGvHD appeared to be the loss of NK_reg cells and increase in naïve Th cells at Day 100
• The authors proposed a model where naïve Th cell during L-aGvHD progress into PD1^- naïve Th cells at cGvHD onset, and naïve T_reg cells seen in L-aGvHD mature into memory T_reg cells during progression to cGvHD
• The comprehensive immune profile approach may allow to better identify patients at risk for cGvHD, with the possibility of early interventions using pre-emptive therapy
• A limitation of the study is its focus on children and adolescents, which mandates similar studies in adults