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Longitudinal Studies of a B-Cell-Derived Signature of Tolerance in Renal Transplantation

ABSTRACT: The development of reliable biomarkers of transplant tolerance would enhance the safety and feasibility of clinical trials and potentially also facilitate management of patients on standard immunosuppressive therapies. To this end, we examined peripheral blood samples of spontaneously tolerant renal transplant recipients, as well as patients enrolled in two interventional tolerance trials, using multiparameter flow cytometry and gene expression analysis. Repeat analysis of samples from a previously reported tolerant cohort, as well as newly identified tolerant patients, confirmed that tolerance was associated with increased expression of B cell-associated genes relative to immunosuppressed patients with stable renal function. This was not accounted for merely by an increase in total B cell numbers, but appeared to be the result of increased frequencies of transitional and naïve B cells. Moreover, serial measurements demonstrated that this pattern persisted over several years. Importantly, patients rendered tolerant via induction of transient mixed chimerism, and those weaned to low levels of immunosuppression, showed similar increases in the expression of selected B cell genes as did spontaneously tolerant individuals. Collectively, these findings support the notion that alterations in B cells may be a common theme for tolerant kidney transplant recipients, and a useful immune monitoring tool in prospective trials. The MassARRAY QGE (Sequenom) multiplexed primer and competitive template designs and analysis were reported previously.

ORGANISM(S): Homo sapiens

PROVIDER: GSE66612 | GEO | 2015/09/30

SECONDARY ACCESSION(S): PRJNA277456

REPOSITORIES: GEO

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Project description:Immunosuppression is needed in HLA identical sibling renal transplantation. We conducted a tolerance trial in this patient cohort using Alemtuzumab induction, donor hematopoietic stem cells, tacrolimus/mycophenolate immunosuppression converted to sirolimus, planning complete drug withdrawal by 24 months post-transplantation. After an additional 12 months with no immunosuppression, normal biopsies and renal function, recipients were considered tolerant. Twenty recipients were enrolled. Of the first 10 (>36 months post-transplantation), 5 had immunosuppression successfully withdrawn for 16-36 months (tolerant), 2 had disease recurrence and 3 had subclinical rejection in protocol biopsies (non-tolerant). Microchimerism disappeared after 1 year, and CD4+CD25highCD127-FOXP3+ T cells and CD19+IgD/M+CD27- B cells increased to 5 years post-transplantation in both groups, whereas immune/inflammatory gene expression pathways in the peripheral blood and urine were differentially downregulated in tolerant compared to non-tolerant recipients. Therefore, in this HLA identical renal transplant tolerance trial, absent chimerism, Treg and Breg immunophenotypes were indistinguishable between tolerant and non-tolerant recipients, but global genomic changes indicating immunomodulation were observed only in tolerant recipients. A total of 46 PBMC samples representing blood draws from four time points in the first 9 recipients were processed for microarray analysis (The Scripps Research Institute, La Jolla, CA). The analyzed time points were: immediately pre-operatively in the absence of immunosuppression (n=9); post-operatively at 1 year (n=8, range 11-13 months); at 2 years (n=12, range 18-25 months); >3 years (n=17, range 32-48 months). (At year 2 and at > 3 years, repeated samples were obtained from individual subjects, and at one year, one subject had a technically unsatisfactory sample.) To discount the effects of immunosuppression on gene expression, microarray data were included on whole blood from 18 healthy human subjects (controls: GSE40586; NCBI Gene Expression Omnibus [GEO] repository).