Determination of the clinical relevance of donor epitope-specific HLA-antibodies in kidney transplantation

In kidney transplantation, survival rates are still partly impaired due to the deleterious effects of donor specific HLA antibodies (DSA). However, not all luminex-defined DSA appear to be clinically relevant. Further analysis of DSA recognizing polymorphic amino acid configurations, called eplets or functional epitopes, might improve the discrimination between clinically relevant vs. irrelevant HLA antibodies. To evaluate which donor epitope-specific HLA antibodies (DESAs) are clinically important in kidney graft survival, relevant and irrelevant DESAs were discerned in a Dutch cohort of 4690 patients using Kaplan-Meier analysis and tested in a cox proportional hazard (CPH) model including nonimmunological variables. Pre-transplant DESAs were detected in 439 patients (9.4%). The presence of certain clinically relevant DESAs was significantly associated with increased risk on graft loss in deceased donor transplantations (p < 0.0001). The antibodies recognized six epitopes of HLA Class I, 3 of HLA-DR, and 1 of HLA-DQ, and most antibodies were directed to HLA-B (47%). Fifty-three patients (69.7%) had DESA against one donor epitope (range 1-5). Long-term graft survival rate in patients with clinically relevant DESA was 32%, rendering DESA a superior parameter to classical DSA (60%). In the CPH model, the hazard ratio (95% CI) of clinically relevant DESAs was 2.45 (1.84-3.25) in deceased donation, and 2.22 (1.25-3.95) in living donation. In conclusion, the developed model shows the deleterious effect of clinically relevant DESAs on graft outcome which outperformed traditional DSA-based risk analysis on antigen level.

The Value of IgM Memory B-Cells in the Assessment of Splenic Function in Childhood Cancer Survivors at Risk for Splenic Dysfunction: A DCCSS-LATER Study

Background

Childhood cancer survivors (CCS) who received radiotherapy involving the spleen or total body irradiation (TBI) might be at risk for splenic dysfunction. A comprehensive screening test for examining splenic dysfunction is lacking.

Objective

We investigated whether IgM memory B-cells could be used to assess splenic dysfunction in CCS who received a splenectomy, radiotherapy involving the spleen, or TBI.

Methods

All CCS were enrolled from the DCCSS-LATER cohort. We analyzed differences in IgM memory B-cells and Howell-Jolly bodies (HJB) in CCS who had a splenectomy (n = 9), received radiotherapy involving the spleen (n = 36), or TBI (n = 15). IgM memory B-cells < 9 cells/µL was defined as abnormal.

Results

We observed a higher median number of IgM memory B-cells in CCS who received radiotherapy involving the spleen (31 cells/µL, p=0.06) or TBI (55 cells/µL, p = 0.03) compared to CCS who received splenectomy (20 cells/µL). However, only two CCS had IgM memory B-cells below the lower limit of normal. No difference in IgM memory B-cells was observed between CCS with HJB present and absent (35 cells/µL vs. 44 cells/µL).

Conclusion

Although the number of IgM memory B-cells differed between splenectomized CCS and CCS who received radiotherapy involving the spleen or TBI, only two CCS showed abnormal values. Therefore, this assessment cannot be used to screen for splenic dysfunction.

Implementation of Early Next-Generation Sequencing for Inborn Errors of Immunity: A Prospective Observational Cohort Study of Diagnostic Yield and Clinical Implications in Dutch Genome Diagnostic Centers

Objective

Inborn errors of immunity (IEI) are a heterogeneous group of disorders, affecting different components of the immune system. Over 450 IEI related genes have been identified, with new genes continually being recognized. This makes the early application of next-generation sequencing (NGS) as a diagnostic method in the evaluation of IEI a promising development. We aimed to provide an overview of the diagnostic yield and time to diagnosis in a cohort of patients suspected of IEI and evaluated by an NGS based IEI panel early in the diagnostic trajectory in a multicenter setting in the Netherlands.

Study Design

We performed a prospective observational cohort study. We collected data of 165 patients with a clinical suspicion of IEI without prior NGS based panel evaluation that were referred for early NGS using a uniform IEI gene panel. The diagnostic yield was assessed in terms of definitive genetic diagnoses, inconclusive diagnoses and patients without abnormalities in the IEI gene panel. We also assessed time to diagnosis and clinical implications.

Results

For children, the median time from first consultation to diagnosis was 119 days versus 124 days for adult patients (U=2323; p=0.644). The median turn-around time (TAT) of genetic testing was 56 days in pediatric patients and 60 days in adult patients (U=1892; p=0.191). A definitive molecular diagnosis was made in 25/65 (24.6%) of pediatric patients and 9/100 (9%) of adults. Most diagnosed disorders were identified in the categories of immune dysregulation (n=10/25; 40%), antibody deficiencies (n=5/25; 20%), and phagocyte diseases (n=5/25; 20%). Inconclusive outcomes were found in 76/165 (46.1%) patients. Within the patient group with a genetic diagnosis, a change in disease management occurred in 76% of patients.

Conclusion

In this cohort, the highest yields of NGS based evaluation for IEI early in the diagnostic trajectory were found in pediatric patients, and in the disease categories immune dysregulation and phagocyte diseases. In cases where a definitive diagnosis was made, this led to important disease management implications in a large majority of patients. More research is needed to establish a uniform diagnostic pathway for cases with inconclusive diagnoses, including variants of unknown significance.

Antibodies against ARHGDIB are associated with long-term kidney graft loss

The clinical significance of non-HLA antibodies on renal allograft survival is a matter of debate, due to differences in reported results and lack of large-scale studies incorporating analysis of multiple non-HLA antibodies simultaneously. We developed a multiplex non-HLA antibody assay against 14 proteins highly expressed in the kidney. In this study, the presence of pretransplant non-HLA antibodies was correlated to renal allograft survival in a nationwide cohort of 4770 recipients transplanted between 1995 and 2006. Autoantibodies against Rho GDP-dissociation inhibitor 2 (ARHGDIB) were significantly associated with graft loss in recipients transplanted with a deceased-donor kidney (N = 3276) but not in recipients of a living-donor kidney (N = 1496). At 10 years after deceased-donor transplantation, recipients with anti-ARHGDIB antibodies (94/3276 = 2.9%) had a 13% lower death-censored covariate-adjusted graft survival compared to the anti-ARHGDIB-negative (3182/3276 = 97.1%) population (hazard ratio 1.82; 95% confidence interval, 1.32-2.53; P = .0003). These antibodies occur independently from donor-specific anti-HLA antibodies (DSA) or other non-HLA antibodies investigated. No significant relations with graft loss were found for the other 13 non-HLA antibodies. We suggest that pretransplant risk assessment can be improved by measuring anti-ARHGDIB antibodies in all patients awaiting deceased-donor transplantation.

Allocation to highly sensitized patients based on acceptable mismatches results in low rejection rates comparable to nonsensitized patients

Whereas regular allocation avoids unacceptable mismatches on the donor organ, allocation to highly sensitized patients within the Eurotransplant Acceptable Mismatch (AM) program is based on the patient's HLA phenotype plus acceptable antigens. These are HLA antigens to which the patient never made antibodies, as determined by extensive laboratory testing. AM patients have superior long-term graft survival compared with highly sensitized patients in regular allocation. Here, we questioned whether the AM program also results in lower rejection rates. From the PROCARE cohort, consisting of all Dutch kidney transplants in 1995-2005, we selected deceased donor single transplants with a minimum of 1 HLA mismatch and determined the cumulative 6-month rejection incidence for patients in AM or regular allocation. Additionally, we determined the effect of minimal matching criteria of 1 HLA-B plus 1 HLA-DR, or 2 HLA-DR antigens on rejection incidence. AM patients showed significantly lower rejection rates than highly immunized patients in regular allocation, comparable to nonsensitized patients, independent of other risk factors for rejection. In contrast to highly sensitized patients in regular allocation, minimal matching criteria did not affect rejection rates in AM patients. Allocation based on acceptable antigens leads to relatively low-risk transplants for highly sensitized patients with rejection rates similar to those of nonimmunized individuals.

Development and Validation of a Multiplex Non-HLA Antibody Assay for the Screening of Kidney Transplant Recipients

The best treatment for patients with end-stage renal disease is kidney transplantation. Although graft survival rates have improved in the last decades, patients still may lose their grafts partly due to the detrimental effects of donor-specific antibodies (DSA) against human leukocyte antigens (HLA) and to a lesser extent also by antibodies directed against non-HLA antigens expressed on the donor endothelium. Assays to detect anti-HLA antibodies are already in use for many years and have been proven useful for transplant risk stratification. Currently, there is a need for assays to additionally detect multiple non-HLA antibodies simultaneously in order to study their clinical relevance in solid organ transplantation. This study describes the development, technical details and validation of a high-throughput multiplex assay for the detection of antibodies against 14 non-HLA antigens coupled directly to MagPlex microspheres or indirectly via a HaloTag. The non-HLA antigens have been selected based on a literature search in patients with kidney disease or following transplantation. Due to the flexibility of the assay, this approach can be used to include alternative antigens and can also be used for screening of other organ transplant recipients, such as heart and lung.

Pretransplant C3d-Fixing Donor-Specific Anti-HLA Antibodies Are Not Associated with Increased Risk for Kidney Graft Failure

Background Complement-fixing antibodies against donor HLA are considered a contraindication for kidney transplant. A modification of the IgG single-antigen bead (SAB) assay allows detection of anti-HLA antibodies that bind C3d. Because early humoral graft rejection is considered to be complement mediated, this SAB-based technique may provide a valuable tool in the pretransplant risk stratification of kidney transplant recipients.Methods Previously, we established that pretransplant donor-specific anti-HLA antibodies (DSAs) are associated with increased risk for long-term graft failure in complement-dependent cytotoxicity crossmatch-negative transplants. In this study, we further characterized the DSA-positive serum samples using the C3d SAB assay.Results Among 567 pretransplant DSA-positive serum samples, 97 (17%) contained at least one C3d-fixing DSA, whereas 470 (83%) had non-C3d-fixing DSA. At 10 years after transplant, patients with C3d-fixing antibodies had a death-censored, covariate-adjusted graft survival of 60%, whereas patients with non-C3d-fixing DSA had a graft survival of 64% (hazard ratio, 1.02; 95% confidence interval, 0.70 to 1.48 for C3d-fixing DSA compared with non-C3d-fixing DSA; P=0.93). Patients without DSA had a 10-year graft survival of 78%.Conclusions The C3d-fixing ability of pretransplant DSA is not associated with increased risk for graft failure.

CD21 and CD19 deficiency: Two defects in the same complex leading to different disease modalities

PURPOSE

Deficiencies in CD19 and CD81 (forming the CD19-complex with CD21 and CD225) cause a severe clinical phenotype. One CD21 deficient patient has been described. We present a second CD21 deficient patient, with a mild clinical phenotype and compared the immunobiological characteristics of CD21 and CD19 deficiency.

METHODS

CD21 deficiency was characterized by flowcytometric immunophenotyping and sequencing. Real-time PCR, in vitro stimulation and next generation sequencing were used to characterize B-cell responses and affinity maturation in CD21(-/-) and CD19(-/-) B cells.

RESULTS

A compound heterozygous mutation in CD21 caused CD21 deficiency. CD21(-/-) B cells responded normally to in vitro stimulation and AID was transcribed. Affinity maturation was less affected by CD21 than by CD19 deficiency.

CONCLUSIONS

Both CD21 and CD19 deficiencies cause hypogammaglobulinemia and reduced memory B cells. CD19 deficiency causes a more severe clinical phenotype. B-cell characteristics reflect this, both after in vitro stimulation as in affinity maturation.

Human plasmacytoid dendritic cells phagocytose, process, and present exogenous particulate antigen

Plasmacytoid dendritic cells (pDCs) play a major role in shaping both innate and adaptive immune responses, mainly via their production of large amounts of type I IFNs. pDCs are considered to primarily present endogenous Ags and are thought not to participate in the uptake and presentation of Ags from the extracellular environment, in contrast to their myeloid counterparts, which efficiently endocytose extracellular particulates. In this study, we show that human pDCs are able to phagocytose and process particulate forms of Ag entrapped in poly(lactic-coglycolic acid) microparticles. Furthermore, pDCs were also able to sense TLR ligands (TLR-Ls) incorporated in these particles, resulting in rapid pDC activation and high IFN-alpha secretion. Combining a tetanus toxoid peptide and TLR-Ls (CpG C and R848) in these microparticles resulted in efficient pDC activation and concomitant Ag-specific T cell stimulation. Moreover, particulate Ag was phagocytosed and presented more efficiently than soluble Ag, indicating that microparticles can be exploited to facilitate efficient delivery of antigenic cargo and immunostimulatory molecules to pDCs. Together, our results show that in addition to their potency to stimulate innate immunity, pDCs can polarize adaptive immune responses against exogenous particulate Ag. These results may have important consequences for the development of new immunotherapeutic strategies exploiting Ag and TLR-Ls encapsulated in microparticles to target APC subsets.

Immunization with a P53 synthetic long peptide vaccine induces P53-specific immune responses in ovarian cancer patients, a phase II trial

The prognosis of ovarian cancer, the primary cause of death from gynecological malignancies, has only modestly improved over the last decades. Immunotherapy is one of the new treatment modalities explored for this disease. To investigate safety, tolerability, immunogenicity and obtain an impression of clinical activity of a p53 synthetic long peptide (p53-SLP) vaccine, twenty patients with recurrent elevation of CA-125 were included, eighteen of whom were immunized 4 times with 10 overlapping p53-SLP in Montanide ISA51. The first 5 patients were extensively monitored for toxicity, but showed no > or = grade 3 toxicity, thus accrual was continued. Overall, toxicity was limited to grade 1 and 2, mostly locoregional, inflammatory reactions. IFN-gamma producing p53-specific T-cell responses were induced in all patients who received all 4 immunizations as measured by IFN-gamma ELISPOT. An IFN-gamma secretion assay showed that vaccine-induced p53-specific T-cells were CD4(+), produced both Th1 and Th2 cytokines as analyzed by cytokine bead array. Notably, Th2 cytokines dominated the p53-specific response. P53-specific T-cells were present in a biopsy of the last immunization site of at least 9/17 (53%) patients, reflecting the migratory capacity of p53-specific T-cells. As best clinical response, stable disease evaluated by CA-125 levels and CT-scans, was observed in 2/20 (10%) patients, but no relationship was found with vaccine-induced immunity. This study shows that the p53-SLP vaccine is safe, well tolerated and induces p53-specific T-cell responses in ovarian cancer patients. Upcoming trials will focus on improving T helper-1 polarization and clinical efficacy.

Viral vector-based prime-boost immunization regimens: a possible involvement of T-cell competition

Vaccination with recombinant viral vectors may be impeded by preexisting vector-specific immunity or by vector-specific immunity induced during the priming immunization. It is assumed that virus-neutralizing antibodies represent the principal effector mechanism of vector-specific immunity, while killing of infected cells by vector-specific cytotoxic T lymphocytes (CTLs) has also been suggested. Using recombinant Semliki Forest virus (rSFV) expressing E6E7 antigen from human papillomavirus, we demonstrate that secondary immune responses against E6E7 are neither affected by vector-specific antibodies nor by CTL-mediated killing of infected cells. Instead, the presence of the antigen during the prime immunization appeared to be the main determinant for the boosting efficacy. After priming with rSFVeE6,7, a homologous booster stimulated the primed E6E7-specific CTL response and induced long-lasting memory. Passively transferred SFV-neutralizing antibodies did not inhibit E6E7-specific CTL responses, although transgene expression was strongly reduced under these conditions. Conversely, in mice primed with irrelevant rSFV, induction of E6E7-specific CTLs was inhibited presumably due to vector-specific responses induced by the priming immunization. When during the priming with irrelevant rSFV, E7-protein was co-administered, the inhibitory effect of vector-specific immunity was abolished. These results suggest that, apart from vector-specific antibodies or killing of infected cells, T-cell competition may be involved in determining the efficacy of viral vector-based prime-boost immunization regimens.

Serum Cytokine Profiling as a Diagnostic and Prognostic Tool in Ovarian Cancer: A Potential Role for Interleukin 7

PURPOSE

To evaluate if serum cytokine levels could be used as diagnostic or prognostic markers in ovarian cancer.

EXPERIMENTAL DESIGN

A cytokine bead array was done to simultaneously analyze 14 cytokines in the sera of 187 ovarian cancer patients with complete clinicopathologic data and follow-up, 45 patients with benign ovarian tumors, and 50 healthy controls. Serum levels of the well-known serum tumor marker CA-125 were routinely measured in all patients.

RESULTS

Serum levels of CA-125, interleukin 6 (IL-6), IL-7, and IL-10 were elevated in ovarian cancer patients compared with patients with benign ovarian tumors. Analyzing the cytokines in combination with CA-125 showed that a combination of IL-7 and CA-125 serum levels could accurately predict 69% of the ovarian cancer patients, without falsely classifying patients with benign pelvic mass. The cytokines IL-6, IL-7, IL-8, IL-10, monocyte chemotactic protein-1 (MCP-1), and IP-10 and CA-125 were associated with disease-free and overall survival in univariate analysis. In multivariate analysis, IL-7 and IP-10 were independent predictors of overall survival, although after inclusion of the clinicopathologic parameters, only stage and residual disease remained as independent predictors of survival.

CONCLUSIONS

IL-7 levels were found to be strongly associated with ovarian cancer and could be used in combination with CA-125 to distinguish between malignant and benign ovarian tumors.