α4β7 Integrin Is Upregulated on CD8+ Effector Memory T-Cells in Children with Gut Gvhd Prior to Clinical Symptoms and Represents a Therapeutic Target in Pediatric Allogeneic HSCT Patients

Abstract

Background α4β7 integrin is expressed on T-cells which migrate to gut-associated lymphoid tissues. Expression of α4β7 integrin is elevated on memory T-cells in adult hematopoietic stem cell transplant (HSCT) recipients at diagnosis of GI GVHD. No pediatric data exist regarding α4β7 integrin expression before or at onset of GVHD. We hypothesized that α4β7 integrin expression on effector memory T-cells (TEMs) would be elevated in patients before acute GI GVHD symptoms compared to patients without GVHD and may be a useful therapeutic target for the prevention of acute GI GVHD. Methods Cryopreserved T-cells were characterized in 48 children who developed acute GI GVHD (n=22), isolated skin GVHD (n=12) and no GVHD (n=14). In patients with GVHD, T-cells were characterized prior to HSCT, one week before GVHD and at GVHD diagnosis. In patients without GVHD, samples were analyzed at baseline and day+30 after HSCT. Samples were incubated with fluorochrome conjugated monoclonal antibodies directed against CD3, CD8, CCR7, α4β7 integrin and CD45RA. TEMs were defined as CD3+, CCR7-, CD45RA- lymphocytes. Co-expression of trafficking markers implicated in GI GVHD (CCR5, CCR9), and liver GVHD (CXCR6 and CCR5) were also assessed. Samples were analyzed on an LSR Fortessa flow cytometer (BD Biosciences). Data were analyzed using FCS Express (De Novo Software). Surface expression of all markers were compared using the Mann Whitney U-test. Patients with skin GVHD and no GVHD were grouped for analysis. Patients with at least 200 absolute CD8+ T-cell events were deemed evaluable. Results Twenty patients with GI GVHD, 8 with skin GVHD and 10 patients without GVHD had at least 200 absolute CD8+ events and were evaluable. Demographics of patients are shown in Figure 1. Expression of α4β7 integrin on CD8+ TEMs was upregulated in patients with GI GVHD compared to the No GI GVHD (skin GVHD + no GVHD) group one week prior to clinical symptoms (p=0.02; Figure 2A). Co-expression of CCR5 and CCR9 with α4β7 integrin was also higher on CD8+ TEM cells in the GI GVHD group compared to No GI GVHD group (p Conclusion α4β7 integrin is elevated on CD8+ TEMs prior to acute GI GVHD symptoms and co-expression of intestinal trafficking-specific markers such as CCR5 and CCR9 are also elevated prior to acute GVHD in pediatric patients. Our data suggest a rationale for the blockade of α4β7 integrin or the dual blockade of α4β7 integrin and CCR5 with clinically available therapeutics (maraviroc and vedolizumab) for acute GI GVHD prevention in pediatric allogeneic HCT patients.