Cytokines and cell surface receptors as target end points of immunosuppression with cyclosporine A

Comparing Humoral and Cellular Immune Response Against HBV Vaccine in Kidney Transplant Patients

Host protection upon vaccination usually results from the complex interplay of humoral and cellular components of the immune system. Exploring hepatitis B surface antigen (HBsAg)-specific T cell responses and their correlation with humoral responses under immunosuppression, we analyzed 51 renal transplant recipients, differing in HBV vaccine-specific antibody titers (non [NRs]-, low [LRs]-, and high responders [HRs]) and in 22 healthy controls (HCs) in a cross-sectional study. HBsAg-specific T cells were analyzed by flow cytometry according to expression of activation markers CD40L and/or CD69, and the cytokines IFNγ, IL-2, TNFα, and IL-17. No significant differences in responder rate and magnitude of HBsAg-specific T cell responses were found between HCs and HRs. Interestingly, HBsAg-specific Th-cells were also observed in 50% of humoral NRs. Frequencies of HBsAg-specific CD40L+ Th-cells were significantly higher in HRs compared to LRs (p = 0.009) and in LRs in comparison to NRs (p = 0.043). All but NRs showed a predominance of multi-potent HBsAg-specific TNFα+IL-2+ Th-cells. As expected, HBsAg-specific CD8(+) T cells were rarely found. In conclusion, mounting of hepatitis B vaccine-specific T cell responses is possible in kidney transplant recipients despite immunosuppression. Detection of HBV-specific Th-cells in a significant proportion of humoral NRs contributes to the current discussion on conferring immune protection by cellular memory in such patients.

Molybdate modulates mitogen and cyclosporin responses of human peripheral blood lymphocytes

The trace element molybdenum (Mo) is an essential component of key physiological systems in animals, plants and microorganisms. The molybdate oxoanion MoO(4)(2-) has been demonstrated to cause diverse yet poorly understood biochemical and pharmacological effects, such as non-specific inhibition of phosphatases and stabilization of steroid receptors. This study aimed to investigate the effects of molybdate on the activation of human peripheral blood lymphocytes (hPBLs) ex vivo and its potential interaction with the widely used immunosuppressant drug cyclosporin A (CsA). Lymphocyte activation was evaluated by performing multiple experiments determining blastogenesis in cultured peripheral blood lymphocytes obtained from 5 healthy volunteers, following stimulation induced by phytohemagglutinin (PHA), in the absence or presence of 0.05-10 mM sodium molybdate or/and 2.5-30 μg/mL CsA. Blastogenesis was assessed by a morphometric assay based on the relative proportions of unactivated lymphocytes, activated lymphoblasts and cells with aberrant morphology after PHA-induced activation. Molybdate concentrations up to 1 mM showed no effect on lymphocyte blastogenesis, while higher concentrations exerted immunosuppressive actions on cultured hPBLs. Co-administration of 0.1 mM sodium molybdate with CsA, at doses up to 20 μg/mL, induced no alteration in the response of cultured hPBLs to CsA. However, molybdate potentiated the immunosuppressive action of higher CsA concentrations, implying a likely dose-related synergistic interaction of the two agents in PHA-stimulated blood lymphocytes. These observations are indicative of the possible biological importance of molybdate oxoanions in the modulation of hPBL activation that may have pharmacological consequences during the therapeutic application of immunomodulatory drugs.

Individualized monitoring of nuclear factor of activated T cells-regulated gene expression in FK506-treated kidney transplant recipients

BACKGROUND

The suggested key mechanism of both cyclosporine A (CsA) and FK506 is the inhibition of calcineurin phosphatase activity, preventing nuclear factor of activated T cells (NFAT)-translocation into the nucleus of T cells, with a subsequent transcriptional block of crucial cytokine genes. However, the two drugs exert different clinical activities as exemplified by the ability of FK506 to treat acute rejections. Inhibition of calcineurin activity by FK506 occurs in vitro at the same or even higher dose as for CsA; however, the magnitude of clinical and experimental immunosuppression is higher, indicating that FK506 may act in a calcineurin-independent way.

METHODS

To test this hypothesis, we measured the inhibition of NFAT-regulated gene expression in 262 stable kidney transplanted patients after FK506 intake.

RESULTS

Previously, we showed that the optimal degree of NFAT inhibition in patients treated with CsA is between 15% and 30% residual gene expression. A considerable number of patients treated with FK506 do not achieve this level of immunosuppression despite therapeutic drug concentrations. Importantly, FK506 does inhibit protein translation. This insufficient degree of NFAT inhibition was associated with a higher rate of biopsy-proven acute rejection but also with a lower incidence of recurrent infections. Conversion of CsA to FK506 causes immediately reduced inhibition of NFAT-regulated gene expression.

CONCLUSION

We could demonstrate that a considerable number of FK506-treated patients benefit from the drug, irrespective of the potency of NFAT inhibition in T cells by a yet unknown mechanism. Nevertheless, residual expression of NFAT-regulated genes seems to be a useful pharmacodynamic method to monitor FK506 therapy in renal transplant patients.

Individualizing combination of two antiproliferative immunosuppressants with pharmacodynamic modeling of stimulated lymphocyte responses

BACKGROUND

Unpredictable serious adverse events (SAE) of immunosuppression, e.g. nephrotoxicity, with the nephrotoxic immunosuppressants have fostered interest in alternative regimens, which contain two antiproliferative agents, and individualized therapy. However, titration of such combinations to individual needs is not understood.

SPECIFIC AIM

To determine concentration (C) mixtures of mycophenolate mofetil (MMF) and sirolimus (SRL), which produce half-maximal inhibitory effect (EC(50)) on human lymphocytes from individual subjects.

METHODS

Concentration mixtures of MMF (0-5 mug/ml) and SRL (0-30 ng/ml) were incubated with whole blood from each of five healthy human subjects. The intracellular cytokines IL-2, TNF-alpha, and IFN-gamma were measured in PMA-ionomycin-stimulated T-cells (CD4+), while CD54, CD95, CD86, CD25, CD69, and CD71 were measured in pokeweed mitogen-stimulated B-cells, by flow cytometry. Pharmacodynamic (PD) relationships were evaluated using Hill equations modified for single and multidrug regimens, and expressed as EC(50) for each target receptor.

RESULTS

No change was seen in the expression of the T-cell cytokines with either MMF or SRL. Each B-cell receptor was inhibited with increasing concentrations of either MMF or SRL. Each B-cell receptor was also inhibited half-maximally at lower concentrations of MMF in the presence of SRL, than with either agent alone, for the test population of five subjects together, and for each of five individual subjects. However, each subject showed distinctly different amounts of MMF and SRL that needed to be present together, in order to produce an identical inhibitory effect on lymphocyte function.

CONCLUSIONS

PD analysis of biological effect can potentially predict optimal concentration mixtures of two immunosuppressants for individual recipients, and enhance rejection prophylaxis and safety. While this holds promise for drug development efforts, clinical application must await correlation of lymphocyte markers with post-transplant clinical outcomes.

The chemokine MCP-1 and the dendritic and myeloid cells it attracts are increased in the mSOD1 mouse model of ALS

We recently demonstrated increased dendritic cells (potent antigen-presenting cells) and MCP-1 (monocyte, T-cell, and dendritic cell attracting chemokine) levels in ALS spinal cord tissue. Additionally, we presented data suggesting that dendritic cells might be contributing to the pathogenesis. To determine whether MCP-1 and dendritic cells are present in the mSOD1 mouse and how early in the disease process they are involved, we examined mSOD1 and control spinal cord tissue at different ages using real-time RT-PCR and immunohistochemistry. Dendritic cells were present and transcripts elevated in mSOD1 spinal cord beginning at 110 days. MCP-1 mRNA and immunoreactivity were upregulated in mSOD1 neuronal and glial cells as early as 15 days, prior to any evidence of microglial activation. CD68+ cells were present at 39 days of age. Although it is not clear if these responses are protective or injurious, the early increased MCP-1 expression and CD68+ cell presence indicate early preexisting injury.

Pharmacodynamics in the development of new immunosuppressive drugs

Over the past 10-20 years a number of immunosuppressive drugs, such as cyclosporine A, tacrolimus, sirolimus, or mycophenolate mofetil have been approved for clinical use and have been highly successful in preventing or delaying graft rejection. Nevertheless, there is an incessant need for better and safer drugs to improve short-term and long-term outcomes following transplantation. A number of low-molecular-weight molecules that interfere with immune cell functions are in development. These include molecules that inhibit the janus protein tyrosine kinase JAK3, compounds that alter lymphocyte trafficking (the sphingosine-1-phosphate receptor antagonist FTY720), and new malononitrilamides (FK778). All seem to show promising therapeutic potential. Among the biologic agents, there are high expectations for antibodies or recombinant chimeric molecules targeting costimulatory surface molecules or pathways involved in the migration of immune cells. The list of such targets includes the ligand pairs CD28:B7, CD154:CD40, LFA-1:ICAM-1, ICOS:B7RP-1, and VLA-4:VCAM-1. However, the clinical development of drugs for transplantation has proved to be difficult, complex, and time consuming. Therefore, newly emerging drug candidates will also demand better methods for monitoring their efficacy as well as their side effects in vivo. Pharmacokinetics (PK) and pharmacodynamics (PD) are complementary approaches used to select drugs on the basis of their in vivo efficacy as well as safety. Whereas PK monitors the handling of the drug by the body, PD focuses on the biologic effect of the drug on its target. Therefore, PD studies of in vivo efficacy are useful for clinical decisions to determine the optimal dose and type of immunosuppressant. At the preclinical stage, PD is aimed at accelerating the selection of lead compounds via PD-controlled trials in animals. Moreover, PD can help to discover new mechanisms of action for a drug or a drug candidate. However, its full potential has not been used, mainly because of laborious and time-consuming methodology. This review focuses on established and novel PD/PK approaches to assess immunosuppressive compounds in the context of new evolving drugs or drug combinations.

Easy-to-use, accurate and flexible individualized Bayesian limited sampling method without fixed time points for ciclosporin monitoring after liver transplantation

BACKGROUND

New methods to estimate the systemic exposure to ciclosporin such as the level 2 h after dosing and limited sampling formulas may lead to improved clinical outcome after orthotopic liver transplantation. However, most strategies are characterized by rigid sampling times.

AIM

To develop and validate a flexible individualized population-pharmacokinetic model for ciclosporin monitoring in orthotopic liver transplantation.

METHODS

A total of 62 curves obtained from 31 patients at least 0.5 year after orthotopic liver transplantation were divided into two equal groups. From 31 curves, relatively simple limited sampling formulas were derived using multiple regression analysis, while using pharmacokinetic software a two-compartment population-pharmacokinetic model was derived from these same data. We then tested the ability to estimate the AUC by the limited sampling formulas and a different approach using several limited sampling strategies on the other 31 curves. The new approach consists of individualizing the mean a priori population-pharmacokinetic parameters of the two-compartment population-pharmacokinetic model by means of maximum a posteriori Bayesian fitting with individual data leading to an individualized population-pharmacokinetic limited sampling model. From the individualized pharmacokinetic parameters, AUC(0-12h) was calculated for each combination of measured blood concentrations. The calculated AUC(0-12h) both from the limited-sampling formulas and the limited-sampling model were compared with the gold standard AUC(0-12h) (trapezoidal rule) by Pearson's correlation coefficient and prediction precision and bias were calculated.

RESULTS

The AUC(0-12h) value calculated by individualizing the population-pharmacokinetic model using several combinations of measured blood concentrations: 0 + 2 h (r(2) = 0.94), 0 + 1 + 2 h (r(2) = 0.94), 0 + 1 + 3 h (r(2) = 0.92), 0 + 2 + 3 h (r(2) = 0.92) and 0 + 1 + 2 + 3 h (r(2) = 0.96) had excellent correlation with AUC(0-12h), better than limited sampling formulas with less than three sampling time points. Even trough level with limited sampling method (r(2) = 0.86) correlated better than the level after 2 h of dosing (r(2) = 0.75) or trough level (r(2) = 0.64) as single values without limited sampling method. Moreover, the individualized population-pharmacokinetic model had a low prediction bias and excellent precision.

CONCLUSION

Multiple rigid sampling time points limit the use of limited sampling formulas. The major advantage of the Bayesian estimation approach presented here, is that blood sampling time points are not fixed, as long as sampling time is known. The predictive performance of this new approach is superior to trough level and that after 2 h of dosing and at least as good as limited sampling formulas. It is of clear advantage in busy out-patient clinics.

Enhanced donor-specific alloreactivity occurs independently of immunosuppression in children with early liver rejection

To determine whether early acute cellular rejection (ACR) is associated with sub-optimal immunosuppression in children with liver transplants (LTx).

METHODS

Twenty-five children with primary LTx after pre-transplant rabbit anti-thymocyte globulin (rATG), and steroid-free tacrolimus (TAC) were evaluated. Mitogen-stimulated T- and B-cell responses and mixed lymphocyte response to donor and third-party antigens were performed at several time points between two consecutive TAC doses. TAC concentrations (C) associated with half-maximal effect (EC(50)) on lymphocytes was determined by pharmacodynamic equations.

RESULTS

Mean age was 7.2 +/- 6.2 years, mean time to lymphocyte function studies was 25 +/- 19 days. Acute rejection occurred at a mean interval of 31 +/- 19 days after LTx. Rejectors (n = 16) demonstrated significantly higher EC(50) of TAC for the intra-cellular IFN-gamma in T cells (p = 0.005) and its CD8+ sub-population (p = 0.027) as well as the co-stimulatory/activation receptor CD54 on B cells (p = 0.0001). The response of recipient lymphocytes to donor antigen was significantly higher in rejectors, compared with non-rejectors (p = 0.015). The patient groups demonstrated no differences in third-party MLR, or in C of TAC.

CONCLUSIONS

Independent of the amount of immunosuppressant, ACR of liver allografts in children is associated with enhanced donor-specific alloreactivity. This is accompanied by a cytotoxic T-cell sub-population with increased requirement for TAC.

Modeling individual variation in biomarker response to combination immunosuppression with stimulated lymphocyte responses-potential clinical implications

BACKGROUND

In mitogen-stimulated lymphocyte responses (sLR), cytokines and cell-surface receptors in peripheral human blood lymphocytes (PBL) are sensitive to cyclosporine (CsA), and can predict its in vivo effect with pharmacodynamic (PD) modeling. This is not known for multiple-agent combinations.

METHODS

Twenty-five concentration mixtures of CsA (0-1200 ng/ml) plus sirolimus (SRL, 0-30 ng/ml) were added to whole blood from five normal human subjects (NHS) for effect on a limited array of six targets. Effect-concentration relationships were analyzed with E(max) PD equations, and expressed as the range of concentration mixtures associated with one-half of maximal inhibitory effect (EC(50)) on a model biomarker target. This predicted range was examined to see whether it contained representative concentration mixtures of these two drugs, which were associated with a stable post-transplant outcome in a logistic regression model of 1039 clinical trial patients.

RESULTS

PD analyses suggested that in NHS samples containing CsA+SRL (n=5), (1) PMA-Ionomycin-stimulated T-cell expression of intracellular IL-2, TNF-alpha, and IFN-gamma was inhibited by CsA, and minimally by SRL, and (2) the two agents inhibited pokeweed mitogen (PWM)-stimulated B-cell expression of CD54 and CD95, but not CD86 (ICAM-1, Fas antigen, and B7.2), synergistically. With CD54 as the model biomarker, contour plots also predicted a wide range of concentration mixtures of the two agents across which an EC(50) could be predicted for CsA+SRL in a population (e.g., CsA-72 ng/ml+SRL 15 ng/ml, n=5), as well as in the individual subject (e.g., CsA-0 ng/ml+SRL-13.75 ng/ml in NHS-D310). Logistic regression analysis of clinical outcomes in 1039 patients suggested that the concentration mixture of CsA congruent with 50-150 ng/ml+SRL congruent with 10 ng/ml was associated with a stable post-transplant course. The EC(50) contour plot for CD54 suggested a nearly identical CsA concentration of 120 ng/ml in the presence of 10 ng/ml of sirolimus.

CONCLUSIONS

Our data suggest that pharmacodynamic evaluation of immunosuppressive agents with biomarkers may be an efficient process with which to characterize immunosuppressive effect of combination agents in individual patients and in patient populations.

Controlled clinical trial to assess the response of recent heroin abusers with chronic hepatitis C virus infection to treatment with interferon alpha-n2b

BACKGROUND

Chronic infection with hepatitis C virus (HCV) is the most common infectious disease among heroin abusers, but it is recommended that specific treatment with interferon be delayed until at least 6 to 12 months after the end of drug addiction.

OBJECTIVE

We investigated the response of heroin abusers to interferon treatment shortly after the end of detoxification treatment with methadone.

METHODS

We studied 2 homogeneous groups of white Italian patients with chronic HCV infection: former male heroin abusers and males without a history of drug addiction. Tumor necrosis factor, interleukin-1beta, interleukin-2, activated monocytes, anti-HCV antibodies, HCV RNA, and alanine aminotransferase levels were assessed. Standard treatment was initiated with 5 MU interferon alpha-n2b administered subcutaneously once daily for 8 weeks. Patients with negative HCV-RNA findings at the end of 8 weeks received further treatment with 5 MU TIW subcutaneously for an additional 48 weeks.

RESULTS

Thirty of 47 patients in group A (former heroin abusers) and 30 of 30 patients in group B (controls) completed the study. Heroin abusers presented a significantly enhanced response to treatment compared with the controls. After 8 weeks, HCV-RNA test results were negative in 27 of 30 patients in group A (90.0%) and in 25 of 30 in group B (83.3%) (P = NS). Onset of relapse occurred significantly later in heroin abusers (mean [SD], 53 [3] weeks) than in controls (26 [2] weeks) (P < 0.05). Cytokine levels and activated CD11 antigen-expressing monocytes were significantly (P < 0.001) higher in heroin abusers than controls.

CONCLUSION

Heroin abusers with chronic HCV infection were successfully treated with interferon alpha-n2b soon after the end of detoxification treatment.