Natural killer cell functional genetics and donor-specific antibody-triggered microvascular inflammation

Antibody-mediated rejection (ABMR) is a leading cause of graft failure. Emerging evidence suggests a significant contribution of natural killer (NK) cells to microvascular inflammation (MVI). We investigated the influence of genetically determined NK cell functionality on ABMR development and activity. The study included 86 kidney transplant recipients subjected to systematic biopsies triggered by donor-specific antibody detection. We performed killer immunoglobulin-like receptor typing to predict missing self and genotyped polymorphisms determining NK cell functionality (FCGR3AV/F158 [rs396991], KLRC2wt/del, KLRK1HNK/LNK [rs1049174], rs9916629-C/T). Fifty patients had ABMR with considerable MVI and elevated NK cell transcripts. Missing self was not related to MVI. Only KLRC2wt/wt showed an association (MVI score: 2 [median; interquartile range: 0-3] vs 0 [0-1] in KLRC2wt/del recipients; P = .001) and remained significant in a proportional odds multivariable model (odds ratio, 7.84; 95% confidence interval, 2.37-30.47; P = .001). A sum score incorporating all polymorphisms and missing self did not outperform a score including only KLRC2 and FCGR3A variants, which were predictive in univariable analysis. NK cell genetics did not affect graft functional decline and survival. In conclusion, a functional KLRC2 polymorphism emerged as an independent determinant of ABMR activity, without a considerable contribution of missing self and other NK cell gene polymorphisms.

The kinetics of Torque Teno virus plasma load following calcineurin inhibitor dose change in kidney transplant recipients

Torque Teno virus (TTV) is nonpathogenic, highly prevalent, and reflects the immune status of its host. Thus, TTV plasma load was suggested for the guidance of immunosuppression post solid organ transplantation. The present study was designed to determine the kinetics of TTV following changes in calcineurin inhibitor (CNI) dose. A total of 48 adult recipients of a kidney graft transplanted at the Medical University of Vienna between 2018 and 2019 with isolated changes in CNI dose were selected from the prospective TTV-POET trial. TTV plasma load was quantified by in-house PCR. At Day 30 following CNI dose adaptation (median 33% of daily dose) no changes in TTV load were noted. However, at Day 60, following CNI dose reduction a lower TTV load of 6.4 log10 c/mL (median; interquartile range [IQR] 4.9-8.1) compared with the baseline of 7.1 log10 c/mL (IQR 5.3-8.9) was noted (p = 0.001); there was also a trend toward a higher TTV load following CNI increase (6.6 log10 c/mL, IQR 4.1-9.7 vs. 5.2 log10 c/mL, IQR 4.5-6.8; p = 0.09). The data suggested that TTV load changes become noticeable only 2 months after CNI dose adaptation, which might be the ideal time point for TTV load monitoring.

Efficacy and safety of mTOR inhibition in cutaneous sarcoidosis: a single-centre trial

BACKGROUND

Sarcoidosis is an inflammatory condition that can affect various organs and tissues, causing the formation of granulomas and subsequent functional impairment. The origin of sarcoidosis remains unknown and there are few treatment options. Mechanistic target of rapamycin (mTOR) activation is commonly seen in granulomas of patients across different tissues and has been shown to induce sarcoidosis-like granulomas in a mouse model. This study aimed to examine the efficacy and safety of the mTOR inhibitor sirolimus as a treatment for cutaneous sarcoidosis.

METHODS

We did a single-centre, randomised study treating patients with persistent and glucocorticoid-refractory cutaneous sarcoidosis with sirolimus at the Vienna General Hospital, Medical University of Vienna (Vienna, Austria). We recruited participants who had persistent, active, and histologically proven cutaneous sarcoidosis. We used an n-of-1 crossover design in a placebo-controlled, double-blind topical treatment period and a subsequent single-arm systemic treatment phase for 4 months in the same participants. Participants initially received either 0·1% topical sirolimus in Vaseline or placebo (Vaseline alone), twice daily. After a washout period, all participants were subsequently administered a 6 mg loading dose followed by 2 mg sirolimus solution orally once daily, aiming to achieve serum concentrations of 6 ng/mL. The primary endpoint was change in the Cutaneous Sarcoidosis Activity and Morphology Index (CSAMI) after topical or systemic treatment. All participants were included in the safety analyses, and patients having completed the respective treatment period (topical treatment or systemic treatment) were included in the primary analyses. Adverse events were assessed at each study visit by clinicians and were categorised according to their correlation with the study drug, severity, seriousness, and expectedness. This study is registered with EudraCT (2017-004930-27) and is now closed.

FINDINGS

16 participants with persistent cutaneous sarcoidosis were enrolled in the study between Sept 3, 2019, and June 15, 2021. Six (37%) of 16 participants were men, ten (63%) were women, and 15 (94%) were White. The median age of participants was 54 years (IQR 48-58). 14 participants were randomly assigned in the topical phase and 2 entered the systemic treatment phase directly. Daily topical treatment did not improve cutaneous lesions (effect estimate -1·213 [95% CI -2·505 to 0·079], p=0·066). Systemic treatment targeting trough serum concentrations of 6 ng/mL resulted in clinical and histological improvement of skin lesions in seven (70%) of ten participants (median -7·0 [95% CI -16·5 to -3·0], p=0·018). Various morphologies of cutaneous sarcoidosis, including papular, nodular, plaque, scar, and tattoo-associated sarcoidosis, responded to systemic sirolimus therapy with a long-lasting effect for more than 1 year after treatment had been stopped. There were no serious adverse events and no deaths.

INTERPRETATION

Short-term treatment with systemic sirolimus might be an effective and safe treatment option for patients with persistent glucocorticoid-refractory sarcoidosis with a long-lasting disease-modulating effect. The effect of sirolimus in granulomatous inflammation should be investigated further in large, multi-centre, randomised clinical trials.

FUNDING

Vienna Science and Technology Fund, Austrian Science Fund.

Morphologic and Molecular Features of Antibody-Mediated Transplant Rejection: Pivotal Role of Molecular Injury as an Independent Predictor of Renal Allograft Functional Decline

Current knowledge about the factors correlating with functional decline and subsequent failure of kidney allografts in antibody-mediated rejection (ABMR) is limited. We conducted a cohort study involving 75 renal allograft recipients diagnosed with late ABMR occurring at least 6 months after transplantation. The study aimed to examine the correlation of molecular and histologic features with estimated glomerular filtration rate (eGFR) trajectories and death-censored graft survival. We focused on sum scores reflecting histologic ABMR activity versus chronicity and molecular scores of ABMR probability (ABMRProb), injury-repair response (IRRAT) and fibrosis (ciprob). In multivariable Cox analysis, a Banff lesion-based chronicity index (ci+ct+cg[x2]; hazard ratio per interquartile range [IQR]: 1.97 [95% confidence interval: 0.97 to 3.99]) and IRRAT (1.93 [0.96 to 3.89]) showed the strongest associations with graft failure. Among biopsy variables, IRRAT exhibited the highest relative variable importance and emerged as the sole independent predictor of eGFR slope (change per IQR: -4.2 [-7.8 to -0.6] mL/min/1.73 m2/year). In contrast, morphologic chronicity associated with baseline eGFR only. We conclude that the extent of molecular injury is a robust predictor of renal function decline. Transcriptome analysis has the potential to improve outcome prediction and possibly identify modifiable injury, guiding targeted therapeutic interventions.

A multicentre, patient- and assessor-blinded, non-inferiority, randomised and controlled phase II trial to compare standard and torque teno virus-guided immunosuppression in kidney transplant recipients in the first year after transplantation: TTVguideIT

BACKGROUND

Immunosuppression after kidney transplantation is mainly guided via plasma tacrolimus trough level, which cannot sufficiently predict allograft rejection and infection. The plasma load of the non-pathogenic and highly prevalent torque teno virus (TTV) is associated with the immunosuppression of its host. Non-interventional studies suggest the use of TTV load to predict allograft rejection and infection. The primary objective of the current trial is to demonstrate the safety, tolerability and preliminary efficacy of TTV-guided immunosuppression.

METHODS

For this purpose, a randomised, controlled, interventional, two-arm, non-inferiority, patient- and assessor-blinded, investigator-driven phase II trial was designed. A total of 260 stable, low-immunological-risk adult recipients of a kidney graft with tacrolimus-based immunosuppression and TTV infection after month 3 post-transplantation will be recruited in 13 academic centres in six European countries. Subjects will be randomised in a 1:1 ratio (allocation concealment) to receive tacrolimus either guided by TTV load or according to the local centre standard for 9 months. The primary composite endpoint includes the occurrence of infections, biopsy-proven allograft rejection, graft loss, or death. The main secondary endpoints include estimated glomerular filtration rate, graft rejection detected by protocol biopsy at month 12 post-transplantation (including molecular microscopy), development of de novo donor-specific antibodies, health-related quality of life, and drug adherence. In parallel, a comprehensive biobank will be established including plasma, serum, urine and whole blood. The date of the first enrolment was August 2022 and the planned end is April 2025.

DISCUSSION

The assessment of individual kidney transplant recipient immune function might enable clinicians to personalise immunosuppression, thereby reducing infection and rejection. Moreover, the trial might act as a proof of principle for TTV-guided immunosuppression and thus pave the way for broader clinical applications, including as guidance for immune modulators or disease-modifying agents.

TRIAL REGISTRATION

EU CT-Number: 2022-500024-30-00.

Levels of donor-derived cell-free DNA and chemokines in BK polyomavirus-associated nephropathy

BACKGROUND

BK polyomavirus-associated nephropathy (BKPyVAN) carries a risk of irreversible allograft injury. While detection of BK viremia and biopsy assessment are the current diagnostic gold standard, the diagnostic value of biomarkers reflecting tissue injury (donor-derived cell-free DNA [dd-cfDNA]) or immune activation (C-X-C motif chemokine ligand [CXCL]9 and CXCL10) remains poorly defined.

METHODS

For this retrospective study, 19 cases of BKPyVAN were selected from the Vienna transplant cohort (biopsies performed between 2012 and 2019). Eight patients with T cell-mediated rejection (TCMR), 17 with antibody-mediated rejection (ABMR) and 10 patients without polyomavirus nephropathy or rejection served as controls. Fractions of dd-cfDNA were quantified using next-generation sequencing and CXCL9 and CXCL10 were detected using multiplex immunoassays.

RESULTS

BKPyVAN was associated with a slight increase in dd-cfDNA (median; interquartile range: .38% [.27%-1.2%] vs. .21% [.12%-.34%] in non-rejecting control patients; p = .005). Levels were far lower than in ABMR (1.2% [.82%-2.5%]; p = .004]), but not different from TCMR (.54% [.26%-3.56%]; p = .52). Within the BKPyVAN cohort, we found no relationship between dd-cfDNA levels and the extent of tubulo-interstitial infiltrates, BKPyVAN class and BK viremia/viruria, respectively. In some contrast to dd-cfDNA, concentrations of urinary CXCL9 and CXCL10 exceeded those detected in ABMR, but similar increases were also found in TCMR.

CONCLUSION

BKPyVAN can induce moderate increases in dd-cfDNA and concomitant high urinary excretion of chemokines, but this pattern may be indistinguishable from that of TCMR. Our results argue against a significant value of these biomarkers to reliably distinguish BKPyVAN from rejection.

Emerging drugs for antibody-mediated rejection after kidney transplantation: a focus on phase II & III trials

INTRODUCTION

Antibody-mediated rejection (ABMR) is a leading cause of kidney allograft failure. Its therapy continues to be challenge, and no treatment has been approved for the market thus far.

AREAS COVERED

In this article, we discuss the pathophysiology and phenotypic presentation of ABMR, the current level of evidence to support the use of available therapeutic strategies, and the emergence of tailored drugs now being evaluated in systematic clinical trials. We searched PubMed, Clinicaltrials.gov and Citeline's Pharmaprojects for pertinent information on emerging anti-rejection strategies, laying a focus on phase II and III trials.

EXPERT OPINION

Currently, we rely on the use of apheresis for alloantibody depletion and intravenous immunoglobulin (referred to as standard of care), preferentially in early active ABMR. Recent systematic trials have questioned the benefits of using the CD20 antibody rituximab or the proteasome inhibitor bortezomib. However, there are now several promising treatment approaches in the pipeline, which are being trialed in phase II and III studies. These include interleukin-6 antagonism, CD38-targeting antibodies, and selective inhibitors of complement. On the basis of the information that has emerged so far, it seems that innovative treatment strategies for clinical use in ABMR may be available within the next 5-10 years.

MO1023: Effects of Bortezomib on Complement Fixation and IGM Reactivity in Late Abmr — Results of A Randomized Controlled Trial (The Borteject Trial)

BACKGROUND AND AIMS

Late antibody-mediated rejection (ABMR) is a cardinal cause of kidney allograft failure. Currently, there is no proven effective treatment for this type of rejection. In a recent randomized controlled trial, we have reported no meaningful effect of plasma cell-directed treatment using the proteasome inhibitor bortezomib on the clinical course of late ABMR (BORTEJECT trial; ClinicalTrials.gov, NCT01873157; Eskandary et al. J Am Soc Nephrol, 2018; 29: 591). Treatment had also no significant effect on IgG type donor-specific antibody (DSA) patterns, possibly due to rapid reconstitution of the allospecific plasma cell repertoire. To further dissect the impact of bortezomib on donor-specific B cell alloimmunity, we here sought to investigate whether and to what extent bortezomib impacts the dynamics of specific alloreactivity patterns, in particular, the course of IgM type DSA and complement-activating capability of detected DSA.

METHOD

The BORTEJECT trial was a randomized, placebo-controlled parallel group trial designed to investigate whether two cycles of bortezomib (each cycle: 1.3 mg/m2 intravenously on days 1, 4, 8 and 11) were able to halt the progression of IgG-DSA-positive late ABMR. A total of 44 recipients were randomly assigned to receive bortezomib (n = 21) or placebo (n = 23). In the present re-analysis of biobanked serum samples obtained in the context of the trial, we applied modified single antigen bead assays to assess IgM-DSA and, in addition, complement (C1q) binding. To estimate antibody/complement binding, levels of mean fluorescence intensity (MFI) were recorded. IgM DSA was defined in relation to donor/recipient HLA typing, independently of IgG reactivity patterns.

RESULTS

At baseline, the complement-fixing capability of the immunodominant IgG DSA did not differ between groups. Thirty of 44 patients had detectable IgM DSA at baseline, and we observed a considerable overlap of IgG and IgM DSA specificities (22/30) without group differences. IgM DSA levels were also similar between groups.

Bortezomib treatment did not affect the complement-fixing capability of IgG DSA over time. Similarly, there was no effect on the course of IgM-DSA. There were also no significant differences between groups when analysing percentage changes.

CONCLUSION

A limited course of bortezomib as a sole treatment strategy may not be sufficient to impact on DSA levels, including the evolution of IgM type DSA and the complement-binding capability of detected alloreactivity patterns. Our study results, which may mirror the lack of clinical efficacy, reinforce the need for the development of innovative new strategies to effectively target plasma cells and halt the progression of ABMR.

MO1022: Torque Teno Virus Load in Kidney Transplantation: Association with Donor and Recipient Characteristics and Clinical Follow-Up Data

BACKGROUND AND AIMS

The apathogenic and torque teno virus (TTV) is associated with the state of immunosuppression in solid organ transplant recipients. After kidney transplantation, quantification of TTV viral load may serve as a risk stratification tool for allograft rejection and infectious events. Besides a robust and independent association between recipient age, sex and TTV load, respectively, limited data exists on other potential determinants of TTV load. This trial was designed to analyse the association between TTV and detailed recipient and donor baseline characteristics and clinical follow-up parameters.

METHOD

This retrospective analysis included all 386 consecutive adult recipients of a kidney allograft transplanted between 1 January 2016 and 30 June 2018 at the Medical University Vienna from the prospective observational TTV-POET trial (institutional review board approval number: 1785/2016; German Clinical Trials Registry number: DRKS00012335). For the present analysis, we included TTV measures before transplantation (d0), at month 1 (m1), at month 3 (m3) and at month 12 (m12) after transplantation. TTV DNA was extracted from patient plasma and assessed by real-time PCR with laboratory-developed primers. TTV load was associated with recipient and donor baseline characteristics and follow-up data.

RESULTS

The median recipient and donor age at transplantation was 55 years. A total of 135 (35%) kidney allograft recipients were female; 74 patients (19%) had a history of prior kidney transplantation; and 318 patients (82%) received a deceased donor kidney transplant. A total of 34 patients (9%) had pre-formed donor-specific antibodies (DSA); 19 patients (5%) received an AB0-incompatible transplant. For the whole cohort, 1-year patient survival was 95.6% and 1-year death censored graft survival was 94.8%.

Baseline TTV load (d0) was lower in female recipients (P = 0.003) and higher in older recipients {β 0.033, [95% confidence interval (95% CI) 0.002–0.066]; P = 0.039}. Baseline TTV load was not associated with recipient body mass index and a history of immunological causes of end-stage renal disease and diabetes mellitus, respectively. TTV load within the first year after kidney transplantation did not show an association with the prevalence of preformed DSA, induction treatment, AB0-incompatibility and HLA-mismatch, respectively. Our trial detected an association between donor age and TTV load. Recipients from older donors showed higher TTV loads (m1, β 0.037, 95% CI 0.008–0.065, P = .01; m3, β 0.04, 95% CI 0.012–0.068, P = .005; m12, β 0.065, 95% CI 0.028–0.01, P = .001). There was no association between TTV load during the first year after transplantation and donor sex. When investigating the association between TTV load and clinical follow-up data, TTV levels showed a negative correlation with peripheral blood leukocyte and lymphocyte counts during the first year after transplantation [lymphocytes: m1, β –0.867, 95% CI –1.367–0.364, P = .01; m3, β –0.985, 95% CI –1.709–0.260, P = .008; m12, β –1.304, 95% CI –2.156–0.452, P = .003; data on leukocytes not shown). These findings might reflect the role of lymphocytes for TTV control. Additionally, TTV viral load negatively correlated with the estimated glomerular filtration rate (MDRD) within the first year after kidney transplantation (m1, β –0.043, 95% CI –0.066–0.02, P < .001; m3, β –0.024, 95% CI –0.049–0.001, P = .06; m12, β –0.078, 95% CI –0.111–0.045, P < .001). One might speculate that a higher eGFR might be a proxy for a healthier donor being more capable of controlling TTV infection. TTV viral load was associated with tacrolimus trough levels in month 12 after transplantation (β 1.262, 95% CI 0.0221–0.250; P = .019), but not with the amount of mycophenolic acid dosage.

CONCLUSION

This study revealed an association between TTV viral load and distinct baseline donor and recipient characteristics and clinical follow-up data, including kidney function. Further analysis, especially longitudinal assessment of TTV levels, may help to further dissect the interplay between TTV viral load and the state of immunosuppression in patients undergoing kidney transplantation.

Early Estimated Glomerular Filtration Rate Trajectories After Kidney Transplant Biopsy as a Surrogate Endpoint for Graft Survival in Late Antibody-Mediated Rejection

Background

Late antibody-mediated rejection (ABMR) after kidney transplantation is a major cause of long-term allograft loss with currently no proven treatment strategy. Design for trials testing treatment for late ABMR poses a major challenge as hard clinical endpoints require large sample sizes. We performed a retrospective cohort study applying commonly used selection criteria to evaluate the slope of the estimated glomerular filtration rate (eGFR) within an early and short timeframe after biopsy as a surrogate of future allograft loss for clinical trials addressing late ABMR.

Methods

Study subjects were identified upon screening of the Vienna transplant biopsy database. Main inclusion criteria were (i) a solitary kidney transplant between 2000 and 2013, (ii) diagnosis of ABMR according to the Banff 2015 scheme at >12 months post-transplantation, (iii) age 15-75 years at ABMR diagnosis, (iv) an eGFR > 25 mL/min/1.73 m2 at ABMR diagnosis, and (v) a follow-up for at least 36 months after ABMR diagnosis. The primary outcome variable was death-censored graft survival. A mixed effects model with linear splines was used for eGFR slope modeling and association of graft failure and eGFR slope was assessed applying a multivariate competing risk analysis with landmarks set at 12 and 24 months after index biopsy.

Results

A total of 70 allografts from 68 patients were included. An eGFR loss of 1 ml/min/1.73 m2 per year significantly increased the risk for allograft failure, when eGFR slopes were modeled over 12 months [HR 1.1 (95% CI: 1.01-1.3), p = 0.020] or over 24 months [HR 1.3 (95% CI: 1.1-1.4), p = 0.001] after diagnosis of ABMR with landmarks set at both time points. Covariables influencing graft loss in all models were histologic evidence of glomerulonephritis concurring with ABMR as well as the administration of anti-thymocyte globulin (ATG) at the time of transplantation.

Conclusion

Our study supports the use of the eGFR slope modeled for at least 12 months after biopsy-proven diagnosis of late ABMR, as a surrogate parameter for future allograft loss. The simultaneous occurrence of glomerulonephritis together with ABMR at index biopsy and the use of ATG at the time of transplantation-likely representing a confounder in pre-sensitized recipients-were strongly associated with worse transplant outcomes.

Safety, tolerability, and efficacy of monoclonal CD38 antibody felzartamab in late antibody-mediated renal allograft rejection: study protocol for a phase 2 trial

BACKGROUND

Antibody-mediated rejection (ABMR) is a cardinal cause of renal allograft loss. This rejection type, which may occur at any time after transplantation, commonly presents as a continuum of microvascular inflammation (MVI) culminating in chronic tissue injury. While the clinical relevance of ABMR is well recognized, its treatment, particularly a long time after transplantation, has remained a big challenge. A promising strategy to counteract ABMR may be the use of CD38-directed treatment to deplete alloantibody-producing plasma cells (PC) and natural killer (NK) cells.

METHODS

This investigator-initiated trial is planned as a randomized, placebo-controlled, double-blind, parallel-group, multi-center phase 2 trial designed to assess the safety and tolerability (primary endpoint), pharmacokinetics, immunogenicity, and efficacy of the fully human CD38 monoclonal antibody felzartamab (MOR202) in late ABMR. The trial will include 20 anti-HLA donor-specific antibody (DSA)-positive renal allograft recipients diagnosed with active or chronic active ABMR ≥ 180 days post-transplantation. Subjects will be randomized 1:1 to receive felzartamab (16 mg/kg per infusion) or placebo for a period of 6 months (intravenous administration on day 0, and after 1, 2, 3, 4, 8, 12, 16, and 20 weeks). Two follow-up allograft biopsies will be performed at weeks 24 and 52. Secondary endpoints (preliminary assessment) will include morphologic and molecular rejection activity in renal biopsies, immunologic biomarkers in the blood and urine, and surrogate parameters predicting the progression to allograft failure (slope of renal function; iBOX prediction score).

DISCUSSION

Based on the hypothesis that felzartamab is able to halt the progression of ABMR via targeting antibody-producing PC and NK cells, we believe that our trial could potentially provide the first proof of concept of a new treatment in ABMR based on a prospective randomized clinical trial.

TRIAL REGISTRATION

EU Clinical Trials Register (EudraCT) 2021-000545-40 . Registered on 23 June 2021.

CLINICALTRIALS

gov NCT05021484 . Registered on 25 August 2021.

Comparison of SARS-CoV-2 Antibody Response 4 Weeks After Homologous vs Heterologous Third Vaccine Dose in Kidney Transplant Recipients: A Randomized Clinical Trial

IMPORTANCE

Fewer than 50% of kidney transplant recipients (KTRs) develop antibodies against the SARS-CoV-2 spike protein after 2 doses of an mRNA vaccine. Preliminary data suggest that a heterologous vaccination, combining mRNA and viral vector vaccines, may increase immunogenicity.

OBJECTIVE

To assess the effectiveness of a third dose of an mRNA vs a vector vaccine in KTRs who did not have antibodies against the SARS-CoV-2 spike protein after 2 doses of an mRNA vaccine.

DESIGN, SETTING, AND PARTICIPANTS

This was a single center, single-blinded, 1:1 randomized clinical trial of a third dose of vaccine against SARS-CoV-2, conducted from June 15 to August 16, 2021, in 201 KTRs who had not developed SARS-CoV-2 spike protein antibodies after 2 doses of an mRNA vaccine. Data analyses were performed from August 17 to August 31, 2021.

INTERVENTIONS

mRNA (BNT162b2 or mRNA-1273) or vector (Ad26COVS1) as a third dose of a SARS-CoV-2 vaccine.

MAIN OUTCOMES AND MEASURES

The primary study end point was seroconversion after 4 weeks (29-42 days) following the third vaccine dose. Secondary end points included neutralizing antibodies and T-cell response assessed by interferon-γ release assays (IGRA). In addition, the association of patient characteristics and vaccine response was assessed using logistic regression, and the reactogenicity of the vaccines was compared.

RESULTS

Among the study population of 197 kidney transplant recipients (mean [SD] age, 61.2 [12.4] years; 82 [42%] women), 39% developed SARS-CoV-2 antibodies after the third vaccine. There was no statistically significant difference between groups, with an antibody response rate of 35% and 42% for the mRNA and vector vaccines, respectively. Only 22% of seroconverted patients had neutralizing antibodies. Similarly, T-cell response assessed by IGRA was low with only 17 patients showing a positive response after the third vaccination. Receiving nontriple immunosuppression (odds ratio [OR], 3.59; 95% CI, 1.33-10.75), longer time after kidney transplant (OR, 1.44; 95% CI, 1.15-1.83, per doubling of years), and torque teno virus plasma levels (OR, 0.92; 95% CI, 0.88-0.96, per doubling of levels) were associated with vaccine response. The third dose of an mRNA vaccine was associated with a higher frequency of local pain at the injection site compared with the vector vaccine, while systemic symptoms were comparable between groups.

CONCLUSIONS AND RELEVANCE

This randomized clinical trial found that 39% of KTRs without an immune response against SARS-CoV-2 after 2 doses of an mRNA vaccine developed antibodies against the SARS-CoV-2 spike protein 4 weeks after a third dose of an mRNA or a vector vaccine. The heterologous vaccination strategy with a vector-based vaccine was well tolerated and safe but not significantly better than the homologous mRNA-based strategy.

TRIAL REGISTRATION

EudraCT Identifier: 2021-002927-39.

Torque Teno Virus Load Is Associated With Subclinical Alloreactivity in Kidney Transplant Recipients: A Prospective Observational Trial

BACKGROUND

Nonpathogenic torque teno viruses (TTVs) are highly prevalent in transplant recipients and associated with immunosuppression. Studies in kidney transplant patients have proposed assessment of TTV load for risk stratification of clinically overt graft rejection. The value of TTV quantification in the context of subclinical rejection has not been evaluated.

METHODS

In this prospective trial, 307 consecutive kidney transplant recipients were subjected to per-protocol monitoring of plasma TTV. TTV was analyzed in the context of protocol biopsies (n = 82), scheduled 1 year posttransplantation.

RESULTS

TTV load at the time of biopsy was lower in recipients with rejection (n = 19; according to Banff, including borderline changes suspicious for acute T cell-mediated rejection) than those without rejection (n = 63) whereby each log increase in TTV copies/mL decreased the risk for rejection by 9% (risk ratio 0.91, 95% confidence interval, 0.85-0.97; P = 0.004). Development of chronic lesions (cg, cv, ci, ct, ah, ptcml) was associated with the number of days with a TTV load <1 × 106 copies/mL between months 3 and 12 posttransplant (β 0.07, 95% confidence interval, 0.01-0.14; P = 0.02).

CONCLUSIONS

This trial demonstrates an association between TTV and subclinical graft rejection in kidney transplant recipients. A TTV load <1 × 106 copies/mL suggests suboptimal immunosuppression.

Diagnostic value of donor-derived cell-free DNA to predict antibody-mediated rejection in donor-specific antibody-positive renal allograft recipients

Circulating donor‐specific antibodies (DSA) do not necessarily indicate antibody‐mediated rejection (ABMR). Here, we evaluated the diagnostic value of donor‐derived cell‐free DNA (dd‐cfDNA) as an add‐on to DSA detection. The study included two independent cohorts of DSA⁺ kidney allograft recipients, 45 subclinical cases identified by cross‐sectional antibody screening (cohort 1), and 30 recipients subjected to indication biopsies (cohort 2). About 50% of the DSA⁺ recipients had ABMR and displayed higher dd‐cfDNA levels than DSA⁺ABMR⁻ recipients (cohort 1: 1.90% [median; IQR: 0.78–3.90%] vs. 0.52% [0.35–0.72%]; P < 0.001); (cohort 2: 1.20% [0.82–2.50%] vs. 0.59% [0.28–2.05%]; P = 0.086). Receiver operating characteristic (ROC) analysis revealed an area under the curve (AUC) of 0.89 and 0.69 for dd‐cfDNA, and 0.88 and 0.77 for DSA mean fluorescence intensity (MFI), respectively. In combined models, adding dd‐cfDNA to DSA‐MFI or vice versa significantly improved the diagnostic accuracy. Limited diagnostic performance of dd‐cfDNA in cohort 2 was related to the frequent finding of other types of graft injury among ABMR⁻ recipients, like T cell‐mediated rejection or glomerulonephritis. For dd‐cfDNA in relation to injury of any cause an AUC of 0.97 was calculated. Monitoring of dd‐cfDNA in DSA⁺ patients may be a useful tool to detect ABMR and other types of injury.

Anti-interleukin-6 antibody clazakizumab in late antibody-mediated kidney transplant rejection: effect on cytochrome P450 drug metabolism

Targeting interleukin-6 (IL-6) is a promising strategy to counteract antibody-mediated rejection (ABMR). In inflammatory states, IL-6 antagonism was shown to modulate cytochrome P450 (CYP), but its impact on drug metabolism in ABMR treatment was not addressed so far. We report a sub-study of a phase 2 trial of anti-IL-6 antibody clazakizumab in late ABMR (ClinicalTrials.gov, NCT03444103). Twenty kidney transplant recipients were randomized to clazakizumab versus placebo (4-weekly doses; 12 weeks), followed by a 9-month extension where all recipients received clazakizumab. To study CYP2C19/CYP3A4 metabolism, we administered pantoprazole (20 mg intravenously) at prespecified time points. Dose-adjusted C₀ levels (C₀ /D ratio) of tacrolimus (n = 13) and cyclosporin A (CyA, n = 6) were monitored at 4-weekly intervals. IL-6 and C-reactive protein were not elevated at baseline, the latter was then suppressed to undetectable levels under clazakizumab. IL-6 blockade had no clinically meaningful impact on pantoprazole pharmacokinetics (area under the curve; baseline versus week 52: 3.16 [2.21-7.84] versus 4.22 [1.99-8.18] μg/ml*h, P = 0.36) or calcineurin inhibitor C₀ /D ratios (tacrolimus: 1.49 [1.17-3.20] versus 1.37 [0.98-2.42] ng/ml/mg, P = 0.21; CyA: 0.69 [0.57-0.85] versus 1.08 [0.52-1.38] ng/ml/mg, P = 0.47). We conclude that IL-6 blockade in ABMR - in absence of systemic inflammation - may have no meaningful effect on CYP metabolism.

A Randomized Clinical Trial of Anti-IL-6 Antibody Clazakizumab in Late Antibody-Mediated Kidney Transplant Rejection

BACKGROUND

Late antibody-mediated rejection (ABMR) is a leading cause of transplant failure. Blocking IL-6 has been proposed as a promising therapeutic strategy.

METHODS

We performed a phase 2 randomized pilot trial to evaluate the safety (primary endpoint) and efficacy (secondary endpoint analysis) of the anti-IL-6 antibody clazakizumab in late ABMR. The trial included 20 kidney transplant recipients with donor-specific, antibody-positive ABMR ≥365 days post-transplantation. Patients were randomized 1:1 to receive 25 mg clazakizumab or placebo (4-weekly subcutaneous injections) for 12 weeks (part A), followed by a 40-week open-label extension (part B), during which time all participants received clazakizumab.

RESULTS

Five (25%) patients under active treatment developed serious infectious events, and two (10%) developed diverticular disease complications, leading to trial withdrawal. Those receiving clazakizumab displayed significantly decreased donor-specific antibodies and, on prolonged treatment, modulated rejection-related gene-expression patterns. In 18 patients, allograft biopsies after 51 weeks revealed a negative molecular ABMR score in seven (38.9%), disappearance of capillary C4d deposits in five (27.8%), and resolution of morphologic ABMR activity in four (22.2%). Although proteinuria remained stable, the mean eGFR decline during part A was slower with clazakizumab compared with placebo (-0.96; 95% confidence interval [95% CI], -1.96 to 0.03 versus -2.43; 95% CI, -3.40 to -1.46 ml/min per 1.73 m2 per month, respectively, P=0.04). During part B, the slope of eGFR decline for patients who were switched from placebo to clazakizumab improved and no longer differed significantly from patients initially allocated to clazakizumab.

CONCLUSIONS

Although safety data indicate the need for careful patient selection and monitoring, our preliminary efficacy results suggest a potentially beneficial effect of clazakizumab on ABMR activity and progression.

New concepts in chronic antibody-mediated kidney allograft rejection: prevention and treatment

PURPOSE OF REVIEW

Chronic antibody-mediated rejection (AMR) is a cardinal cause of transplant failure, with currently no proven effective prevention or treatment. The present review will focus on new therapeutic concepts currently under clinical evaluation.

RECENT FINDINGS

One interesting treatment approach may be interference with interleukin-6 (IL-6) signaling to modulate B-cell immunity and donor-specific antibody (DSA) production. Currently, a large phase III randomized controlled trial is underway to clarify the safety and efficacy of clazakizumab, a high-affinity anti-IL-6 antibody, in chronic AMR. A prevention/treatment strategy may be costimulation blockade using belatacept to interfere with germinal center responses and DSA formation. In a recent uncontrolled study, belatacept conversion was shown to stabilize renal function and dampen AMR activity. Moreover, preliminary clinical results suggest efficacy of CD38 antibodies to deplete plasma and natural killer cells to treat AMR, with anecdotal reports demonstrating at least transient resolution of active rejection.

SUMMARY

There are promising concepts on the horizon for the prevention and treatment of chronic AMR. The design of adequately powered placebo-controlled trials to clarify the safety and efficacy of such new therapies, however, remains a big challenge, and will rely on the definition of precise surrogate endpoints predicting long-term allograft survival. Mapping the natural history of AMR would greatly help the understanding of who would derive benefits from treatment.

Torque teno virus for risk stratification of graft rejection and infection in kidney transplant recipients-A prospective observational trial

The nonpathogenic and ubiquitous torque teno virus (TTV) is associated with immunosuppression in solid organ transplant recipients. Studies in kidney transplant patients proposed TTV quantification for risk stratification of graft rejection and infection. In this prospective trial (DRKS00012335) 386 consecutive kidney transplant recipients were subjected to longitudinal per-protocol monitoring of plasma TTV load by polymerase chain reaction for 12 months posttransplant. TTV load peaked at the end of month 3 posttransplant and reached steady state thereafter. TTV load after the end of month 3 was analyzed in the context of subsequent rejection diagnosed by indication biopsy and infection within the first year posttransplant, respectively. Each log increase in TTV load decreased the odds for rejection by 22% (odds ratio [OR] 0.78, 95% confidence interval [CI] 0.62-0.97; P = .027) and increased the odds for infection by 11% (OR 1.11, 95% CI 1.06-1.15; P < .001). TTV was quantified at a median of 14 days before rejection was diagnosed and 27 days before onset of infection, respectively. We defined a TTV load between 1 × 10⁶ and 1 × 10⁸ copies/mL as optimal range to minimize the risk for rejection and infection. These data support the initiation of an interventional trial assessing the efficacy of TTV-guided immunosuppression to reduce infection and graft rejection in kidney transplant recipients.

P1643TORQUE TENO VIRUS FOR RISK STRATIFICATION OF SUBCLINICAL GRAFT REJECTION AFTER KIDNEY TRANSPLANTATION- A PROSPECTIVE STUDY

Background and Aims

Non-invasive monitoring strategies are insufficient to detect patients at risk for subclinical graft rejection after kidney transplantation. The highly prevalent and non-pathogenic Torque Teno virus (TTV) reflects the immunocompetence of its host: high level viraemia indicates strong and low level viraemia weak immunosuppression, respectively. Thus TTV replication might serve as a candidate for immunologic monitoring.

Method

To analyze the association between TTV and subclinical kidney graft rejection, an interim analysis of the prospective “TTV POET” cohort study (DRKS00012335) was performed including data available until 31/01/2019. All consecutive kidney graft recipients transplanted at the Medical University Vienna since 01/12/2016 (n=308) with a protocol biopsy 12 months after transplantation (n=47; median 12.4 months) and stable graft function were included. Biopsy results according to current BANFF classification were analyzed in the context of peripheral blood TTV levels quantified by PCR.

Results

Graft function was excellent (median eGFR MDRD: 57 ml/min/1.73m2, urinary PKR: 92 mg/g). Twenty recipients (43%) had subclinical rejection (borderline TCMR, n=16; ABMR, n=3; TCMR type I, n=1). TTV level quantified at the date of biopsy was lower in recipients with rejection compared to recipients without rejection. The risk for rejection increased by 11% with each log level decrease in TTV copies/ml (RR 0.89, 95% CI 0.85-0.93; p&lt;0.001). Differences in TTV levels were evident not only at the date of biopsy, but already 6 weeks earlier. Patients with biopsies showing chronic leasons, suggesting ongoing allo-reactivity, had a longer period of time with TTV levels &lt;1x106 copies/ml.

Conclusion

Our data suggests an association between TTV level and subclinical graft rejection at 12 months after kidney transplantation. Future clinical trials are necessary to test the potential of TTV guided immunosuppression to reduce subclinical rejection.

P1624TORQUE TENO VIRUS FOR RISK STRATIFICATION OF GRAFT REJECTION AND INFECTION IN KIDNEY TRANSPLANT RECIPIENTS - A PROSPECTIVE OBSERVATIONAL TRIAL

Background and Aims

The non-pathogenic and ubiquitous Torque Teno virus (TTV) is associated with immunosuppression in solid organ transplant recipients. Studies in kidney transplant patients proposed TTV quantification for risk stratification of graft rejection and infection. This prospective observational trial was designed to assess the potential of TTV load for risk prediction of both, infection and rejection in the first year after transplantation. The objective of this trial was to provide TTV cut-off level to define an optimal TTV range as a basis for a randomised controlled interventional trial to test the efficacy of TTV-guided immunosuppression.

Method

Within this trial (DRKS00012335) all 386 adult (≥18 years of age) consecutive kidney graft recipients transplanted at the Medical University Vienna, Austria, between January 1st 2016 and June 31st 2018. were subjected to longitudinal per protocol TTV monitoring. In total 3265 TTV measurements were taken and 71 biopsy proven graft rejections (defined by BANFF classification) and 472 clinically relevant infections were documented in the first year post-transplant. After reaching steady state at the end of post-transplant month 3, peripheral TTV plasma load was analyzed in the context of subsequent rejection and infection by rt-PCR.

Results

Patients with allograft rejection had lower levels of TTV compared to patients without rejection (median 3.5x106 c/mL, IQR 1.7x105-1.3x108 c/ml vs. median 2.5x108 c/mL, IQR 5.8x106-9.3x108 c/mL; P = .028) in subsequent biopsies. TTV load in individuals experiencing an infectious event in the subsequent observation period was higher compared to patients without infection (median 3.9x108 c/mL, IQR 7.9x106-3.3x109 c/mL vs. median 2.6x107 c/mL, IQR 1.3x106-9.2x108 c/mL; P &lt; .001). Of note, TTV was quantified several weeks before rejection diagnosis and infection onset. Each log increase in TTV load decreased the odds for rejection by 22% (OR 0.78, 95% CI 0.62-0.97; P = .027) and increased the odds for infection by 11% (OR 1.11, 95% CI 1.06-1.15; P &lt; .001). The association of TTV and infection and rejection, respectively was not altered by confounding or effect modification. A TTV load between 106 and 108 copies/mL was defined as optimal range to minimize the risk for rejection and infection.

Conclusion

These data support the initiation of an interventional trial assessing the efficacy of TTV-guided immunosuppression to reduce infection and graft rejection in kidney transplant recipients.

Non-invasive Chemokine Detection: Improved Prediction of Antibody-Mediated Rejection in Donor-Specific Antibody-Positive Renal Allograft Recipients

Background: Screening for donor-specific antibodies (DSA) has limited diagnostic value in patients with late antibody-mediated rejection (ABMR). Here, we evaluated whether biomarkers reflecting microcirculation inflammation or tissue injury-as an adjunct to DSA detection-are able to improve non-invasive ABMR monitoring. Methods: Upon prospective cross-sectional antibody screening of 741 long-term kidney transplant recipients with a silent clinical course, 86 DSA-positive patients were identified and biopsied. Serum and urine levels of E-selectin/CD62E, vascular cell adhesion molecule 1 (VCAM-1), granzyme B, hepatocyte growth factor (HGF), C-C motif chemokine ligand (CCL)3, CCL4, C-X-C motif chemokine ligand (CXCL)9, CXCL10, and CXCL11 in DSA-positive recipients were investigated applying multiplexed bead-based immunoassays. Results: Diagnosis of ABMR (50 patients) was associated with significantly higher levels of CXCL9 and CXCL10 in blood and urine and of HGF in blood. Overall, urinary CXCL9 had the highest diagnostic accuracy for ABMR (area under the receiver operating characteristic curve: 0.77; accuracy: 80%) and its combined evaluation with the mean fluorescence intensity of the immunodominant DSA (DSAmax MFI) revealed a net reclassification improvement of 73% compared to DSAmax MFI alone. Conclusions: Our results suggest urinary CXCL9 testing, combined with DSA analysis, as a valuable non-invasive tool to uncover clinically silent ABMR late after transplantation.

Immunoadsorption Combined with Membrane Filtration to Counteract Early Treatment-Refractory Antibody-Mediated Rejection

INTRODUCTION

Immunoadsorption (IA) represents a therapeutic option for acute antibody-mediated rejection (ABMR) after kidney transplantation. The addition of membrane filtration (MF) to enhance elimination of macromolecular components that potentially contribute to rejection, such as key complement component C1q and alloreactive IgM, may be an effective strategy to further improve its therapeutic efficiency.

RESULTS

Here we present 4 consecutive patients with episodes of HLA donor-specific antibody-positive ABMR nonresponsive to cycles of 6-16 sessions of IA treatment. Rejection episodes were characterized by severe microvascular injury (high-grade microcirculation inflammation and/or signs of thrombotic microangiopathy) and evidence of intense complement activation in peritubular capillaries (diffuse C4d-positivity). IA combined with MF led to substantial morphologic improvement (follow-up biopsies: g + ptc and C4d scores ≤1) and stabilization of allograft function.

CONCLUSIONS

Our findings provide evidence for an effect of combination of IA + MF in refractory early acute/active ABMR in kidney transplant recipients.

Torque Teno Virus for Risk Stratification of Acute Biopsy-Proven Alloreactivity in Kidney Transplant Recipients

Background

Drug-induced immunosuppression in kidney transplant recipients is crucial to prevent allograft rejection, but increases risk for infectious disease. Immunologic monitoring to tailor immunosuppressive drugs might prevent alloreactivity and adverse effects simultaneously. The apathogenic torque teno virus (TTV) reflects the immunocompetence of its host and might act as a potential candidate for a holistic monitoring.

Methods

We screened all 1010 consecutive patients from the prospective Vienna Kidney Transplant Cohort Study for availability of allograft biopsies and adequately stored sera for TTV quantification by polymerase chain reaction.

Results

Patients with acute biopsy-proven alloreactivity according to the Banff classification (n = 33) showed lower levels of TTV in the peripheral blood compared to patients without rejection (n = 80) at a median of 43 days before the biopsy. The risk for alloreactivity decreased by 10% per log level of TTV copies/mL (risk ratio, .90 [95% confidence interval, .84–.97]; P = .005). TTV levels >1 × 10⁶ copies/mL exclude rejection with a sensitivity of 94%. Multivariable generalized linear modeling suggests an independent association between TTV level and alloreactivity.

Conclusions

TTV is a prospective biomarker for risk stratification of acute biopsy-proven alloreactivity in kidney transplant recipients and might be a potential tool to tailor immunosuppressive drug therapy.

Determinants of the intercept and slope of glomerular filtration rate in recipients of a live donor kidney transplant

Background

Donor kidney function is considered a critical determinant of allograft survival after live donor (LD) kidney transplantation, but its independent impact on the evolution of graft function is less well defined. The objective of this study was to dissect the relative contribution of LD kidney function to baseline estimated glomerular filtration rate (eGFR) of recipients and its decline.

Methods

In this study 91 LD kidney transplantations performed between 2007 and 2015 were included. The eGFR of donated kidneys (eGFR-dk) was calculated from total LD eGFR (eGFR-dt) based on the results of isotope nephrography. Recipient eGFR (eGFR-r) determined 6‑monthly until 36 months posttransplantation served as dependent variable in mixed linear models estimating changes in baseline allograft function (intercept) and eGFR‑r slope. Models were adjusted either for eGFR-dk or eGFR-dt, in addition to other potential confounders.

Results

Overall, unadjusted mean eGFR‑r at baseline (6 months) and its annual decline in allograft function were 56.5 mL/min/1.73 m² and −0.2 mL/min/1.73 m², respectively. In multivariate analysis, eGFR-dk impacted on baseline eGFR‑r (0.6 mL/min/1.73 m² mean estimated increase per unit; P = 0.02) but not on its slope. In the eGFR-dt-adjusted model, a marginal effect was observed for LD age (P = 0.05). Both models identified antibody-mediated rejection (ABMR) as the strongest risk factor of accelerated loss of allograft function (eGFR‑r slope: approximately −6 mL/min/1.73 m² per year; P ≤ 0.02).

Conclusion

Donor-related characteristics, most prominently the function of donated kidneys and LD age, were predictive of eGFR at baseline. The ABMR was identified as the cardinal cause of progressive deterioration of allograft function.

Quantification of Torque Teno Virus Viremia as a Prospective Biomarker for Infectious Disease in Kidney Allograft Recipients

Background

Drug-induced immunosuppression following kidney transplantation is crucial to prevent allograft rejection, but increases risk for infectious disease. Tailoring of drug dosing to prevent both rejection and infection is greatly desirable. The apathogenic and ubiquitous torque teno virus (TTV) reflects immunocompetence of the host and might be a potential candidate for immunologic monitoring.

Methods

To assess TTV as an infection biomarker, virus load was prospectively quantified in peripheral blood of 169 consecutive renal allograft recipients at the Medical University Vienna.

Results

Patients with infection showed higher TTV levels compared to patients without infection (4.2 × 10⁸ copies/mL [interquartile range, IQR, 2.7 × 10⁷–1.9 × 10⁹] vs 2.9 × 10⁷ [IQR 1.0 × 10⁶–7.2 × 10⁸]; P = .006). Differences in TTV load became evident almost 3 months before infection (median 77 days, IQR 19–98). Each log level of TTV copies/mL increased the odds ratio for infection by 23% (95% confidence interval 1.04–1.45; P = .014). TTV >3.1 × 10⁹ copies/mL corresponded to 90% sensitivity to predict infections. Logistic regression demonstrated independent association between TTV levels and infection.

Conclusions

TTV quantification predicts infection after kidney transplantation and might be a potential tool to tailor immunosuppressive drug therapy.

The therapeutic challenge of late antibody-mediated kidney allograft rejection

Late antibody‐mediated rejection (ABMR) is a cardinal cause of kidney allograft failure, manifesting as a continuous and, in contrast with early rejection, often clinically silent alloimmune process. While significant progress has been made towards an improved understanding of its molecular mechanisms and the definition of diagnostic criteria, there is still no approved effective treatment. In recent small randomized controlled trials, therapeutic strategies with promising results in observational studies, such as proteasome inhibitor bortezomib, anti‐C5 antibody eculizumab, or high dose intravenous immunoglobulin plus rituximab, had no significant impact in late and/or chronic ABMR. Such disappointing results reinforce a need of new innovative treatment strategies. Potential candidates may be the interference with interleukin‐6 to modulate B cell alloimmunity, or innovative compounds that specifically target antibody‐producing plasma cells, such as antibodies against CD38. Given the phenotypic heterogeneity of ABMR, the design of adequate systematic trials to assess the safety and efficiency of such therapies, however, is challenging. Several trials are currently being conducted, and new developments will hopefully provide us with effective ways to counteract the deleterious impact of antibody‐mediated graft injury. Meanwhile, the weight of evidence would suggest that, when approaching using existing treatments for established antibody‐mediated rejection, “less may be more”.

Clazakizumab in late antibody-mediated rejection: study protocol of a randomized controlled pilot trial

Background

Late antibody-mediated rejection (ABMR) triggered by donor-specific antibodies (DSA) is a cardinal cause of kidney allograft dysfunction and loss. Diagnostic criteria for this rejection type are well established, but effective treatment remains a major challenge. Recent randomized controlled trials (RCT) have failed to demonstrate the efficacy of widely used therapies, such as rituximab plus intravenous immunoglobulin or proteasome inhibition (bortezomib), reinforcing a great need for new therapeutic concepts. One promising target in this context may be interleukin-6 (IL-6), a pleiotropic cytokine known to play an important role in inflammation and adaptive immunity.

Methods

This investigator-driven RCT was designed to assess the safety and efficacy of clazakizumab, a genetically engineered humanized monoclonal antibody directed against IL-6. The study will include 20 DSA-positive kidney allograft recipients diagnosed with ABMR ≥ 365 days after transplantation. Participants will be recruited at two study sites in Austria and Germany (Medical University of Vienna; Charité University Medicine Berlin). First, patients will enter a three-month double-blind RCT (1,1 randomization, stratification according to ABMR phenotype and study site) and will receive either clazakizumab (subcutaneous administration of 25 mg in monthly intervals) or placebo. In a second open-label part of the trial (months 4–12), all patients will receive clazakizumab at 25 mg every month. The primary endpoint is safety and tolerability. Secondary endpoints are the pharmacokinetics and pharmacodynamics of clazakizumab, its effect on drug metabolism in the liver, DSA characteristics, morphological ABMR lesions and molecular gene expression patterns in three- and 12-month protocol biopsies, serum/urinary biomarkers of inflammation and endothelial activation/injury, Torque Teno viral load as a measure of overall immunosuppression, kidney function, urinary protein excretion, as well as transplant and patient survival.

Discussion

Currently, there is no treatment proven to be effective in halting the progression of late ABMR. Based on the hypothesis that antagonizing the effects of IL-6 improves the outcome of DSA-positive late ABMR by counteracting DSA-triggered inflammation and B cell/plasma cell-driven alloimmunity, we suggest that our trial has the potential to provide proof of concept of a novel treatment of this type of rejection.

Trial registration

ClinicalTrials.gov, NCT03444103. Registered on 23 February 2018 (retrospective registration).

Electronic supplementary material

The online version of this article (10.1186/s13063-018-3158-6) contains supplementary material, which is available to authorized users.

Longitudinal assessment of HLA and MIC-A antibodies in uneventful pregnancies and pregnancies complicated by preeclampsia or gestational diabetes

The significance of antibodies directed against paternal epitopes in the context of obstetric disorders is discussed controversially. In this study anti-HLA and anti-MIC-A antibodies were analysed in sera of women with uneventful pregnancy (n = 101), preeclampsia (PE, n = 55) and gestational diabetes (GDM, n = 36) using antigen specific microbeads. While two thirds of the women with uneventful pregnancy or GDM were HLA and MIC-A antibody positive in gestational week 11 to 13 with a modest increase towards the end of pregnancy, women with PE showed an inverse kinetic: 90% were HLA antibody positive in gestational week 11 to 13 and only 10% showed HLA reactivities at the end of the pregnancy. HLA antibody binding strength was more pronounced in gestational week 14 to 17 in patients with PE compared to women with uneventful pregnancy (maximum median fluorescence intensity of the highest ranked positive bead 7403, IQR 2193–7938 vs. 1093, IQR 395–5689; p = 0.04) and was able to predict PE with an AUC of 0.80 (95% CI 0.67–0.93; p = 0.002). Our data suggest a pathophysiological involvement of HLA antibodies in PE. HLA antibody quantification in early pregnancy may provide a useful tool to increase diagnostic awareness in women prone to develop PE.

PAI-1 (Plasminogen Activator Inhibitor-1) Expression Renders Alternatively Activated Human Macrophages Proteolytically Quiescent

OBJECTIVE

Macrophages are versatile immune cells capable of polarizing into functional subsets depending on environmental stimulation. In atherosclerotic lesions, proinflammatory polarized macrophages are associated with symptomatic plaques, whereas Th2 (T-helper cell type 2) cytokine-polarized macrophages are inversely related with disease progression. To establish a functional cause for these observations, we analyzed extracellular matrix degradation phenotypes in polarized macrophages.

APPROACH AND RESULTS

We provide evidence that proinflammatory polarized macrophages rely on membrane-bound proteases including MMP-14 (matrix metalloproteinase-14) and the serine protease uPA (urokinase plasminogen activator) together with its receptor uPAR for extracellular matrix degradation. In contrast, Th2 cytokine alternatively primed macrophages do not show different proteolytic activity in comparison to unpolarized macrophages and lack increased localization of MMP-14 and uPA receptor to the cell membrane. Nonetheless, they express the highest amount of the serine protease uPA. However, uPA activity is blocked by similarly increased expression of its inhibitor PAI-1 (plasminogen activator inhibitor 1). When inhibiting PAI-1 or when analyzing macrophages deficient in PAI-1, Th2 cytokine-polarized macrophages display the same matrix degradation capability as proinflammatory-primed macrophages. Within atherosclerotic lesions, macrophages positive for the alternative activation marker CD206 express high levels of PAI-1. In addition, to test changed tissue remodeling capacities of alternatively activated macrophages, we used a bleomycin lung injury model in mice reconstituted with PAI-1^-/- bone marrow. These results supported an enhanced remodeling phenotype displayed by increased fibrosis and elevated MMP activity in the lung after PAI-1 loss.

CONCLUSIONS

We were able to demonstrate matrix degradation dependent on membrane-bound proteases in proinflammatory stimulated macrophages and a forced proteolytical quiescence in alternatively polarized macrophages by the expression of PAI-1.