Post-transplant cyclophosphamide prevents xenogeneic graft-versus-host disease while depleting proliferating regulatory T cells

peer reviewe

Predictors of neutralizing antibody response to BNT162b2 vaccination in allogeneic hematopoietic stem cell transplant recipients.

peer reviewedBACKGROUND: Factors affecting response to SARS-CoV-2 mRNA vaccine in allogeneic hematopoietic stem cell transplantation (allo-HCT) recipients remain to be elucidated. METHODS: Forty allo-HCT recipients were included in a study of immunization with BNT162b2 mRNA vaccine at days 0 and 21. Binding antibodies (Ab) to SARS-CoV-2 receptor binding domain (RBD) were assessed at days 0, 21, 28, and 49 while neutralizing Ab against SARS-CoV-2 wild type (NT50) were assessed at days 0 and 49. Results observed in allo-HCT patients were compared to those obtained in 40 healthy adults naive of SARS-CoV-2 infection. Flow cytometry analysis of peripheral blood cells was performed before vaccination to identify potential predictors of Ab responses. RESULTS: Three patients had detectable anti-RBD Ab before vaccination. Among the 37 SARS-CoV-2 naive patients, 20 (54%) and 32 (86%) patients had detectable anti-RBD Ab 21 days and 49 days postvaccination. Comparing anti-RBD Ab levels in allo-HCT recipients and healthy adults, we observed significantly lower anti-RBD Ab levels in allo-HCT recipients at days 21, 28 and 49. Further, 49% of allo-HCT patients versus 88% of healthy adults had detectable NT50 Ab at day 49 while allo-HCT recipients had significantly lower NT50 Ab titers than healthy adults (P = 0.0004). Ongoing moderate/severe chronic GVHD (P  0.5, P < 0.01) and more weakly with the number of follicular helper T cells (r = 0.4, P = 0.01). CONCLUSIONS: Chronic GVHD and rituximab administration in allo-HCT recipients are associated with reduced Ab responses to BNT162b2 vaccination. Immunological markers could help identify allo-HCT patients at risk of poor Ab response to mRNA vaccination. TRIAL REGISTRATION: The study was registered at clinicaltrialsregister.eu on 11 March 2021 (EudractCT # 2021-000673-83)

Azacytidine augments regulatory T cells and prevents experimental xenogeneic graft-versus-host disease.

The demethylating agent 5-azacytidine (AZA) has proven its efficiency in myeloid malignancies treatment. Recently, several studies have shown that AZA also presents an immunomodulatory activity, mainly through the induction of regulatory T cells (Treg) differentiation from conventional T cells. Treg promotion is a promising treatment option for graft-versus-host disease (GVHD) following hematopoietic stem cell transplantation. In this way, AZA has been shown to reduce GVHD in mouse-to-mouse transplantation models. However, the impact of AZA on human GVHD remains elusive as well as its effects on human Treg and on the other T cell subsets in vivo. Here we report AZA impact on GVHD in a xeno-transplantation model of the disease and describe the overall effects of the drug on human T cells in vivo. When administered to NSG mice receiving 2.107 human PBMC intravenously, AZA successfully ameliorated both survival (p < 0.001) and GVHD score. Flow cytometry analyses showed that this improvement may be mediated through an anti-proliferative effect of AZA on human T cells while these cells presented an increased activation state. We also observed a significant decrease of Th1 and 2 differentiation, assessed by RT-qPCR and cytokines secretion assays, and a reduced production of granzyme B and perforin 1 by cytotoxic T cells. As expected, AZA dramatically augmented Treg frequency while we could also observe a promotion of their IL-2 mediated proliferation over conventional T cells. Interestingly, Th17 frequency was not affected by AZA, therefore increasing the balance Treg/Th17. Finally our data suggest that AZA-induced Treg may have an improved suppressive activity and present long-term stability in vivo. Altogether our findings suggest that AZA may be a promising treatment option for GVHD in the clinical setting

The tumor-specific antigens landscape in acute myeloid leukemia

In theory, tumor-specific antigens (TSAs) represent ideal targets for cancer immunotherapy, but none have been identified in acute myeloid leukemia (AML) so far. We have recently designed a proteog-enomic approach allowing the identification of MHC class I-associated peptides deriving from any reading frame of all genomic regions (not only from exons). Using this approach, we could identify 82 TSAs from 18 primary human AML samples. All these TSAs derived from unmutated transcripts which were aberrantly expressed by allegedly non-coding regions of the genome (that would have been missed by conventional exome-based approaches). In agreement with previous reports showing that high intron retention is a key feature in AML, we found that introns were the main source of TSAs (54.8%). The TSAs were presented by 24 different HLA allotypes, together covering 98,04% of the world population. The examination of the expression of the RNAs coding for the TSAs showed that most of them (68%) were expressed by at least 50% of AML samples in the “The Cancer Genome Atlas” (TCGA) cohort while all of them were either expressed at very low levels or not expressed at all in normal tissues (from the “Genotype-Tissue Expression” (GTEx) project). We have yet to discover the specific epigenetic changes leading to TSA expression in cancer cells. Meanwhile, we propose that vaccination against ab-errantly expressed TSAs could be used to treat a vast majority of patients, with minimal risks of collateral damage to healthy normal tissues

Proteomic study of hypertriglyceridemia impact on mice liver metabolism

L’hypertriglycéridémie est une pathologie largement répandue chez l’homme sédentarisé. Elle se définit comme un taux plasmatique de triglycérides (TAG) anormalement élevé (supérieur à 200 mg/dl). La souris transgénique HuApoC-III est un animal modèle idéal pour l’étude de l’hypertriglycéridémie indépendamment des effets confondants qui y sont généralement associés (en particulier l’obésité et la résistance à l’insuline). En effet, elles sont hypertriglycéridémiques mais ne sont ni obèses ni résistantes à l’insuline. Dans la continuité d’une étude des adaptations mitoprotéomiques hépatique à une hypertriglycéridémie sévère (taux de TAG supérieur à 500 mg/dl) récemment menée par notre laboratoire, nous avons caractérisé par une technique de protéomique comparative, le 2DDIGE, les adaptations protéomiques de la membrane interne mitochondriale et du protéome cellulaire à ce même type d’hypertriglycéridémie, chez la souris HuApoC-III. Comme prédit lors de notre étude antérieure, le protéome de la membrane interne s’est avéré ne présenter aucune modification de sa composition entre les souris HuApoC-III et sauvages. Comme il a été rapporté que les souris HuApoC-III présentent une vitesse de respiration mitochondriale à l’état III sur succinate similaire à celle des souris sauvages, cette invariance de la composition protéique de la membrane interne pourrait refléter des altérations de sa composition lipidique ou de sa structure. L’analyse du protéome cellulaire total a permis de confirmer l’augmentation de la capacité du catabolisme des acides aminés et de la glycolyse suggérée par nos résultats antérieurs. Cette augmentation, accompagnée de l’augmentation de la capacité de la β- oxydation également décrite antérieurement, permettrait d’augmenter le taux de production d’acétyl-CoA, de glycérol-3-phosphate et d’ATP fin de supporter la production élevée de TAG des hépatocytes des souris HuApoC-III. Cette analyse a par ailleurs révélé que les hépatocytes des souris HuApoC-III présentent un stress oxydatif cytoplasmique, une probable accumulation de fer intracytoplasmique et une prolifération accrue. Ce stress oxydatif pouvant induire des lésions cellulaires et tissulaires ainsi que l’inflammation du foie, nous proposons que les souris HuApoC-III présentent une fibrose hépatique