Immune mechanisms involved in inducing remission in Crohn’s disease patients undergoing hematopoietic stem cell transplant

Abstract

Crohn’s disease [CD] is a chronic inflammatory disease of the intestinal tract with considerable heterogeneity among affected patients in terms of disease phenotype and therapeutic responses. Despite the increase in the number of drugs approved for the management of CD, a significant percentage of patients remain unresponsive or lose response over time to treatments, and eventually require surgery to control disease activity and/or complications. Nonetheless, in a fraction of these refractory patients, intestinal resection may not be possible due to disease location, extension or previous surgeries. For such patients, autologous hematopoietic stem cell transplantation [HSCT] represents a potential salvage therapy despite the risks associated with this procedure.

Stem cell transplantation is an accepted therapy for hematological disorders, aplastic anemia and immunodeficiencies. In the context of autoimmune diseases, the serendipitous benefits of transplantation were initially reported in patients suffering from both immune-mediated diseases and hematological disorders. This led to trials that have shown the efficacy of autologous HSCT in treating an array of autoimmune diseases including refractory severe multiple sclerosis, systemic lupus erythematosus, juvenile idiopathic arthritis, rheumatoid arthritis and, more recently, CD.

The benefit of HSCT in autoimmunity is thought to originate from the ability of intense immune depletion to eliminate auto-reactive cells regardless of their specificity. This would lead to de novo generation of immune cells that could re-establish tolerance, although no objective evidence of this ‘resetting’ has been reported thus far. To explore this hypothesis, we group of CD patients [n = 18] receiving autologous HSCT, with 50% of them achieving endoscopic drug-free remission. To elucidate the mechanisms driving efficacy, we monitored changes after HSCT in blood and intestine immune-cell composition. CD patients [n = 22] receiving anti-tumor necrosis factor [TNF]-α were included for comparison.

Severe immune ablation followed by HSCT induced dramatic changes in both peripheral blood T and B cells in all patients regardless of the efficacy of the treatment. Endoscopic remission at week 52 following HSCT was associated with significant intestinal transcriptional changes. A comparison of the remission signature with that of anti-TNFα identified both common and unique genes in the HSCT-induced response. Based on deconvolution analysis of intestinal biopsy transcriptome data, we show that response to HSCT, but not to anti-TNFα, is associated with an expansion of naïve B-cells, as seen in blood, and a decrease in the memory resting T- cell content. As expected, endoscopic remission, in response to both HSCT and anti-TNFα, led to a significant reduction in intestinal neutrophil and M1 macrophage content. HSCT dramatically renewed the pre-existing T-cell receptor [TCR] repertoire; however, persistent high-frequency TCR clones were detected in all patients in both blood and biopsy throughout the first year of follow-up. The number of persistent resident T cell clonotypes in tissue after treatment decreased in patients that achieve endoscopic remission. Furthermore, we found that low TCR peripheral diversity at baseline, and up to 1 year after HSCT, were associated with a lack of response to the immunoablative protocol. Peripheral blood immune remodeling after HSCT does not predict efficacy. In contrast, a profound intestinal T-cell depletion that is maintained long after transplant is associated with mucosal healing following HSCT, but not anti-TNFα.

Se ha demostrado la eficacia del trasplante hematopoyético de células madre (THCM) en pacientes con enfermedad de Crohn severamente refractaria. La hipótesis aceptada es que el proceso de THCM elimina células auto-reactivas, devolviendo así la tolerancia. No obstante, no existen estudios específicos y exhaustivos sobre la reconstitución inmune en pacientes con enfermedad de Crohn tratados con THCM. En esta tesis, monitorizamos una cohorte de 18 pacientes con enfermedad de Crohn refractaria que recibieron trasplante autólogo de células madre hematopoyéticas, de los cuales el 50% consiguieron la remisión endoscópica sin tratamiento de mantenimiento. Para elucidar los mecanismos que determinan la eficacia, monitorizamos los cambios después de THCM en la composición de células inmunes tanto en sangre como en tejido intestinal.

Como resultado, observamos que la ablación inmune producida durante el TCMH induce cambios dramáticos en las células T y B en sangre en todos los pacientes, independientemente de la eficacia del tratamiento. La remisión endoscópica en la semana 52 posterior al TCMH se asoció con cambios transcripcionales intestinales significativos. Una comparación de la transcripción en remisión con la de la remisión inducida por fármaco identificó genes comunes y únicos en la respuesta inducida por el TCMH. A través de un análisis de deconvolución de los datos del transcriptoma de la biopsia intestinal, mostramos que la respuesta al TCMH, pero no a fármaco inmuno- modulador, se asocia con una expansión de las células B naïve y una disminución en el contenido de células T memoria. Como se esperaba, la remisión endoscópica, en respuesta a tanto a TCMH como a fármaco, condujo a una reducción significativa en el contenido de neutrófilos intestinales y macrófagos M1

La remodelación inmune de la sangre periférica después del TCMH no predice la eficacia. No obstante, la depleción de las células T intestinales mantenida un año después del trasplante se asocia con la curación mucosa después del TCMH.