Long-Term Redistribution of Peripheral Lymphocyte Subpopulations after Switching from Calcineurin to mTOR Inhibitors in Kidney Transplant Recipients

Tacrolimus: Physicochemical stability challenges, analytical methods, and new formulations

Tacrolimus, a potent immunosuppressant, is widely used in several formulations to treat organ rejection in transplant patients. However, its physicochemical stability poses significant challenges, including thermal instability, photostability issues, low solubility, and drug-excipient incompatibility. This review article focuses on the details of these challenges and discusses the analytical methods employed to study tacrolimus stability, such as thermal, spectroscopic, and chromatographic methods in different formulations. New formulations to enhance tacrolimus stability are explored, including lipid-based nanocarriers, polymers, and thin film freezing. Researchers and formulators can optimize tacrolimus formulations to improve efficacy and patient outcomes by understanding and addressing these stability challenges.

Pharmacodynamic Effect of mTOR Inhibition-based Immunosuppressive Therapy on T- and B-cell Subsets After Renal Transplantation

Background

The mammalian target of rapamycin inhibitor (mTORi) therapy after kidney transplantation is solely monitored pharmacokinetically, not necessarily reflecting PI3K-Akt-mTOR pathway blockade efficacy leading to potential under-or overimmunosuppression.

Methods

In this cross-sectional study, phosphoflow cytometry was used to determine the efficacy of mTOR inhibition in peripheral T- and B-lymphocyte subsets by assessing p70S6 kinase (p70S6K) phosphorylation in renal transplant recipients upon treatment with a combination of either mTORi and calcineurin inhibitors (n = 18), or mTORi with mycophenolic acid (n = 9). Nine dialysis patients with end-stage renal disease and 17 healthy age-matched volunteers served as controls.

Results

mTORi treatment reduced p70S6K phosphorylation in CD4+, CD8+ T, and CD19+ B cells compared with healthy controls (HCs). Subpopulation analysis of CD4+ T cells and CD19+ B cells revealed a significant reduction of p70S6K phosphorylation in CD4+CD45RA-CD25- Th cells (P < 0.05), CD24hiCD38hi transitional B cells (P < 0.001), CD24+CD38- memory B cells (P < 0.001), and CD24intCD38int-naive B cells (P < 0.05) upon mTORi treatment, whereas CD4+CD45RA-CD25++CD127- regulatory T cells and CD24-CD38hi plasmablasts were not affected. Compared with mTORi + mycophenolic acid therapy, mTORi + calcineurin inhibitor treatment exhibited an even stronger inhibition of p70S6K phosphorylation in CD4+CD45RA-CD25- Th cells and CD8+ T cells. However, trough levels of mTORi did not correlate with p70S6K phosphorylation.

Conclusions

mTORi selectively inhibited p70S6K phosphorylation in select lymphocyte subtypes. Assessing p70S6K phosphorylation by phosphoflow cytometry may serve as an approach to understand cell subset specific effects of mTORi providing detailed pharmacodynamic information for individualizing immunosuppression.

Targeting regulatory T cell metabolism in disease: Novel therapeutic opportunities

Regulatory T cells (Tregs) are essential for immune homeostasis and suppression of pathological autoimmunity but can also play a detrimental role in cancer progression via inhibition of anti-tumor immunity. Thus, there is broad applicability for therapeutic Treg targeting, either to enhance function, for example, through adoptive cell therapy (ACT), or to inhibit function with small molecules or antibody-mediated blockade. For both of these strategies, the metabolic state of Tregs is an important consideration since cellular metabolism is intricately linked to function. Mounting evidence has shown that targeting metabolic pathways can selectively promote or inhibit Treg function. This review aims to synthesize the current understanding of Treg metabolism and discuss emerging metabolic targeting strategies in the contexts of transplantation, autoimmunity, and cancer. We discuss approaches to gene editing and cell culture to manipulate Treg metabolism during ex vivo expansion for ACT, as well as in vivo nutritional and pharmacological interventions to modulate Treg metabolism in disease states. Overall, the intricate connection between metabolism and phenotype presents a powerful opportunity to therapeutically tune Treg function.

Microvascular inflammation in the absence of human leukocyte antigen-donor-specific antibody and C4d: An orphan category in Banff classification with cytotoxic T and natural killer cell infiltration

Isolated microvascular inflammation (iMVI) without HLA donor-specific antibodies or C4d deposition in peritubular capillaries remains an enigmatic phenotype that cannot be categorized as antibody-mediated rejection (ABMR) in recent Banff classifications. We included 221 kidney transplant recipients with biopsies with ABMR (n = 73), iMVI (n = 32), and normal (n = 116) diagnoses. We compared peripheral blood leukocyte distribution by flow cytometry and inflammatory infiltrates in kidney transplant biopsies among groups. Flow cytometry showed fewer lymphocytes and total, CD4+, and CD8+ peripheral T cells in iMVI compared with ABMR and normal cases. ABMR and iMVI had fewer total natural Killer (NK) cells but more NKG2A+ NK cells. Immunohistochemistry indicated that ABMR and iMVI had greater CD3+ and CD68+ glomerular infiltration than normal biopsies, whereas CD8+ and TIA1+ cells showed only increased iMVI, suggesting they are cytotoxic T cells. Peritubular capillaries displayed more CD3+, CD56+, TIA1+, and CD68+ cells in both ABMR and iMVI. In contrast, iMVI had less plasma cell infiltration in peritubular capillaries and interstitial aggregates than ABMR. iMVI displayed decreased circulating T and NK cells mirrored by T cell and NK cell infiltration in the renal allograft, similar to ABMR. However, the lesser plasma cell infiltration in iMVI may suggest an antibody-independent underlying stimulus.

Alloimmune risk assessment for antibody-mediated rejection in kidney transplantation: A practical proposal

Kidney transplantation is the treatment of choice for patients with end-stage renal disease. Although an improvement in graft survival has been observed in the last decades with the use of different immunosuppressive drugs, this is still limited in time with antibody-mediated rejection being a main cause of graft-loss. Immune monitoring and risk assessment of antibody-mediated rejection before and after kidney transplantation with useful biomarkers is key to tailoring treatments to achieve the best outcomes. Here, we provide a review of the rationale and several accessible tools for immune monitoring, from the most classic to the modern ones. Finally, we end up discussing a practical proposal for alloimmune risk assessment in kidney transplantation, including histocompatibility leukocyte antigen (HLA) and non-HLA antibodies, HLA molecular mismatch analysis and characterization of peripheral blood immune cells.

Influence of CYP3A5, IL-10 polymorphisms and metabolism rate on tacrolimus exposure in renal post-transplant recipients

Aim: To investigate the influence of CYP3A5 and IL-10 polymorphisms on tarcolimus metabolism and renal function for renal transplantation recipients at a stable period. Methods: CYP3A5 and IL-10 polymorphisms, together with other clinical factors, were collected for 149 renal transplantation patients at postoperative stable period. Statistics analysis was performed to explore key factors affecting tarcolimus metabolism. Results: CYP3A5 6986A >G and IL-10 -819C >T significantly impacted tacrolimus metabolism (p < 0.001). CYP3A5 6986A >G G allele and IL-10 -819C >T T allele were associated with poorer tacrolimus metabolic capability. Patients with various tacrolimus metabolism rates presented little difference in renal functions at stable period. Conclusion: Genotyping of CYP3A5 and IL-10 might benefit the precision dosage of tacrolimus for renal transplantation recipients.

Simultaneous Determination of Six Immunosuppressants in Human Whole Blood by HPLC-MS/MS Using a Modified QuEChERS Method

A high-performance liquid chromatography-tandem mass spectrometry method was established for the simultaneous determination of mycophenolic acid, mycophenolate mofetil, tacrolimus, rapamycin, everolimus and pimecrolimus in human whole blood by optimizing the QuEChERS (Quick, Easy, Cheap, Effective, Rugged, and Safe) preparation method. Whole blood was extracted into ethyl acetate, salted out with anhydrous magnesium sulfate, and purified with ethylenediamine-N-propyl silane adsorbent. The supernatant was evaporated under nitrogen until dry and finally reconstituted in methanol. Chromatographic separation was performed on an Agilent Poroshell 120 EC-C18 column in methanol (mobile phase A)-water (optimized for 0.1% acetic acid and 10 mM ammonium acetate, mobile phase B) at a 0.3 mL·min−1 flow rate. Electrospray ionization and positive ion multiple reaction monitoring were used for detection. The time for of analysis was 13 min. The calibration curves range of tacrolimus, rapamycin, everolimus and pimecrolimus were in the range of 1−100 ng·mL−1, mycophenolate mofetil in the range of 0.1−10 ng·mL−1 and mycophenolic acid at 10−1000 ng·mL−1. All correlation coefficients were >0.993. The coefficients of variation (CV, %) for inter-day and intra-day precision were less than 10%, while the spiked recoveries were in the range of 92.1% to 116%. Our method was rapid, sensitive, specific, and reproducible for the simultaneous determination of six immunosuppressants in human whole blood. Importantly, our approach can be used to monitor drug concentrations in the blood to facilitate disease treatment.