aGvHD

CCR7 as a potential therapeutic target for GvHD – results from preclinical models

Acute graft-versus-host disease (aGvHD) is a major complication following hematopoietic stem cell transplant (HSCT) that contributes to high non-relapse mortality. The disease process is initiated by the migration of donor T cells to the host secondary lymphoid organs and their activation by allo-antigens on host antigen-presenting cells (APC).1 CCR7, a chemokine receptor, and its ligands CCL19 and CCL21 expressed by donor T cells is critically important for lymph node specific homing and activation of T cells by APCs.2

Previous reports demonstrated that a high proportion of CCR7+ donor T-cell subsets in the graft was an independent risk factors for aGvHD and correlated with poorer outcome.3

A study published by Carlos Cuesta-Mateos and colleagues explored whether apheresis with a low proportion of CCR7+ cells or blocking the function of CCR7 with an anti-human CCR7 monoclonal antibody (mAb) could prevent or treat aGvHD in preclinical models.4

Methods
  • Apheresis samples were stained with a panel of antibodies including anti-CD45RA, anti-CD62L, anti-CD3, anti-CD4 to identify the following T cell subsets:
    • T cells considered as primary mediators of aGVHD
      • CCR7+ naïve T cells (TN)
      • central memory T cells (TCM)
    • T cells associated with responses against infections and graft-versus-leukemia (GvL) effect
      • CCR7- effector memory T cells (TEM)
      • CCR7- CD45RA+ TEM cells (TEMRA)
  • Migration and complement-dependent cytotoxicity (CDC) assays were performed on peripheral blood mononuclear cells (PBMC) from apheresis samples
  • Xenogeneic models of aGvHD were induced by engrafting human (h) PBMC in sub-lethally irradiated NSG mice
Main findings

In total, 103 donor–recipient pairs who underwent allogeneic hematopoietic stem cell transplantation (allo-HSCT) were analyzed. Transplant characteristics are presented in Table 1.

Table 1. Selected transplant characteristics

Characteristics

Patients, %

Diagnosis of the underlying disease (Relapse rate, %)

Myelodysplastic syndrome

Acute lymphoid leukemia

Acute myeloid leukemia

Hodgkin lymphoma

Non-Hodgkin Lymphoma

Chronic lymphocytic leukemia

Multiple myeloma

 

27 (17)

9 (33)

44 (22)

9 (33)

8 (25)

2 (0)

2 (50)

Gender matching

Male to male

Female to female

Other

 

35

18

47

Donor type

HLA-identical sibling

HLA-identical (10/10) unrelated

HLA mismatched (9/10) unrelated

 

30

46

24

Source of graft

BMSC

PBSC

Infused CD34+ 106/kg of recipient weight

Infused CD3+ 106/kg of recipient weight

 

5

95

5.23

22.07

Conditioning regimen

Myeloablative

No Myeloablative

 

68

32

GvHD prophylaxis

CsA and MTX

CsA and MMF

CsA

 

87

11

2

BMSC, bone marrow stem cells; CsA, cyclosporin A; MMF, mycophenolate mofetil; MTX, methotrexate; PBSC, peripheral blood stem cells;

Correlating rate of transfused CCR7+ cells with induction of GvHD in humans and mice

In patients, apheresis with < 3.6% of CD4+ CCR7+ cells showed low risk of developing aGvHD, with 87.88% (75.23–100%) of patients not developing the complication. The cut off for CD8+ CCR7+ was < 2.2% cells in the apheresis, with 88.57% (76.60–100%) of patients free from chronic (c)GvHD.

In contrast, xenograft models of GvHD demonstrated that lowering the proportion of CCR7+ cells used for apheresis failed to prevent or delay GvHD. The median overall survival (OS) was 14 days for animals engrafted with apheresis products containing ≤3% of CD4+ CCR7+ (n = 6) vs 13 days for mice with apheresis around 20% of CCR7+ cells.

Using anti-CCR7 mAb impairs CCR7+ TN and TCM cells chemotaxis and induces CDC

The addition of anti-CCR7 mAb to PBMC reduced the migration of CCR7+ TN and TCM cells stimulated with CCL19 or CCL21. CCR7 ligands and anti-CCR7 mAb did not induce responses in TEM and TEMRA cells which were CCR7-. Moreover, in vitro assays using anti-CCR7 mAb with fresh hPBMC from apheresis demonstrated strong depletion of CCR7+ but not CCR7- human TN and TCM cells via CDC.

CCR7+ T-cells are not involved in CMV reactivation and GvL effect

In patients, the levels of donor CCR7+ T cells in the apheresis did not correlate with cytomegalovirus (CMV) reactivation within the first six months after transplantation or with a relapse of the underlying disease.

Anti-hCCR7 mAb prevents aGvHD in xenograft models

In xenogenic models of aGvHD induced by engrafting of hPBMC, early administration of anti-CCR7 mAb, after hPBMC inoculation, prevented the development of aGvHD. Animals treated later than on Day 5 after engraftment had infiltration of human T cells in all tissues, which was, however, lower than in control mice.

  • In animals that started treatment two hours before engraftment and had additional four doses given every three days, there was an increased median OS with the anti-hCCR7 mAb vs control (30 days vs 12 days; p = 0.0025)
  • In animals that started treatment on Day 5 after engraftment and had additional four doses administered, anti-hCCR7 mAb was able to reverse first clinical signs of aGvHD and provide survival benefit compared to control treatment (median OS of 33 days vs 18 days; p = 0.0211)
  • In animals that started treatment on Day 3, Day 7, or Day 10 after engraftment and had additional four doses given every three days, best responses were seen at Day 3 (median OS of 26 days with anti-hCCR7 mAb vs 12 days with control; p = 0.0026) compared to Day 7 (median OS 18 days vs 12 days, respectively; p = 0.0742) and Day 10 (median OS 17 days vs 12 days, respectively; p = 0.0181)
Conclusions

The authors of the article demonstrated that selective targeting of CCR7 with antibodies is a feasible and promising way to prevent donor T-cell migration to secondary lymphoid organs and to reduce the severity of aGVHD. Importantly, CCR7+ T cells seem not to be involved in the GvL effect or CMV reactivation. Other than in humans, xenograft models suggest that even small amounts of CCR7+ T cells can induce GvHD. The most profound anti-aGvHD effect was observed in transplanted mice, when an anti-hCCR7 mAb was administrated within the first five days after transplantation. This novel prophylactic approach could offer a benefit to patients in haploidentical settings, who have a particularly large unmet need for safe and effective therapies preventing GvHD.

References
  1. Beilhack A. et al. Prevention of acute graft-versus-host disease by blocking T-cell entry to secondary lymphoid organs. Blood. 2008 Mar 1;111(5):2919–28. DOI: 10.1182/blood-2007-09-112789
  2. Förster R. et al. CCR7 coordinates the primary immune response by establishing functional microenvironments in secondary lymphoid organs. Cell. 1999 Oct 1;99(1):23–33. DOI: 10.1016/s0092-8674(00)80059-8
  3. Portero-Sainz I. et al. A high migratory capacity of donor T-cells in response to the lymph node homing receptor CCR7 increases the incidence and severity of GvHD. Bone Marrow Transplant. 2017 May;52(5):745–752. DOI: 10.1038/bmt.2016.342
  4. Cuesta-Mateos C. et al. Evaluation of therapeutic targeting of CCR7 in acute graft-versus-host disease. Bone Marrow Transplant. 2020 Feb 21. DOI: 10.1038/s41409-020-0830-8
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