Bridge-to-transplant temporary mechanical circulatory support and risk of allosensitization.

INTRODUCTION: Since the 2018 change in the US adult heart allocation policy, more patients are bridged-to-transplant on temporary mechanical circulatory support (tMCS). Previous studies indicate that durable left ventricular assist devices (LVAD) may lead to allosensitization. The goal of this study was to assess whether tMCS implantation is associated with changes in sensitization. METHODS: We included patients evaluated for heart transplants between 2015 and 2022 who had alloantibody measured before and after MCS implantation. Allosensitization was defined as development of new alloantibodies after tMCS implant. RESULTS: A total of 41 patients received tMCS before transplant. Nine (22.0%) patients developed alloantibodies following tMCS implantation: 3 (12.0%) in the intra-aortic balloon pump group (n = 25), 2 (28.6%) in the microaxial percutaneous LVAD group (n = 7), and 4 (44.4%) in the veno-arterial extra-corporeal membrane oxygenation group (n = 9)-p = .039. Sensitized patients were younger (44.7 ± 11.6 years vs. 54.3 ± 12.5 years, p = .044), were more likely to be sensitized at baseline - 3 of 9 (33.3%) compared to 2 out of 32 (6.3%) (p = .028) and received more transfusions with red blood cells (6 (66.6%) vs. 8 (25%), p = .02) and platelets (6 (66.6%) vs. 5 (15.6%), p = .002). There was no significant difference in tMCS median duration of support (4 [3,15] days vs. 8.5 [5,14.5] days, p = .57). Importantly, out of the 11 patients who received a durable LVAD after tMCS, 5 (45.5%) became sensitized, compared to 4 out of 30 patients (13.3%) who only had tMCS-p = .028. CONCLUSIONS: Our findings suggest that patients bridged-to-transplant with tMCS, without significant blood product transfusions and a subsequent durable LVAD implant, have a low risk of allosensitization. Further studies are needed to confirm our findings and determine whether risk of sensitization varies by type of tMCS and duration of support.

Comparison of Two Clinical Laboratory Assays for Measuring Serum Adalimumab and Antibodies to Adalimumab.

BACKGROUND: Adalimumab is a fully human monoclonal antibody developed against tumor necrosis factor (TNF), used for the treatment of autoimmune and chronic inflammatory diseases. Immunogenicity to this drug may lead to therapeutic failure. Various laboratory assays are used for measuring serum adalimumab and anti-drug antibodies (ADA) to adalimumab, for therapeutic monitoring and evaluation of clinical non-responsiveness. This study compared the performance of 2 clinical assays used by different reference laboratories. METHODS: In total, 120 residual clinical samples were tested at both laboratories. A sandwich ELISA for adalimumab detecting free drug and a bridging ELISA capable of detecting both free and bound ADA were performed at the Mayo Clinic. A functional cell-based reporter gene assay (RGA) was used at ARUP Laboratories for measuring bioactive serum drug concentrations, and neutralizing ADA. RESULTS: Seventy-eight samples had measurable concentrations of adalimumab by both methods and yielded a correlation coefficient r = 0.93, slope = 0.886, and intercept = 0.950. Overall agreement of 92.5% was observed between the assays, with most discrepant drug results being attributed to a higher positivity rate with ELISA (8/9). One outlier positive with RGA and negative with ELISA was confirmed by LC-MS/MS to be attributed to infliximab. Overall agreement of 79.2% was observed between the ADA assays. Differences in ADA results may be due to the bridging ELISA detecting total ADA (free, drug-bound, neutralizing, and non-neutralizing), while RGA detects free, neutralizing ADA only. CONCLUSIONS: Although the assays are fundamentally different, the results show significant concordance between the clinically validated tests performed in different laboratories.

Comparison of Next-Generation Sequencing-Based Human Leukocyte Antigen Typing with Clinical Flow Cytometry and Allele-Specific PCR Melting Assays for HLA-B27 Genotyping.

BACKGROUND: Due to the strong association between ankylosing spondylitis and Human Leukocyte Antigen (HLA)-B27, accurate identification of HLA-B27 is important in the diagnosis of patients with suspected spondyloarthritides. For this study, we compared a high-resolution HLA-B typing method to the clinical flow cytometry and allele-specific PCR melting assays to determine clinical benefits of high-resolution testing. METHODS: Residual clinical samples submitted for HLA-B27 testing by flow cytometry were tested by single-locus HLA-B genotyping using next-generation sequencing (NGS), and PCR with melting curve analysis, currently used as a reflex test for indeterminate flow cytometry results. RESULTS: Fifty out of the 51 samples (98%) positive by flow cytometry confirmed as HLA-B27 positive by PCR melting assay and by NGS. The sample that did not confirm was genotyped as HLA-B*07:02. All the samples negative by flow cytometry were confirmed as HLA-B27 negative by both PCR melting assay and NGS. For the group that was indeterminate by flow cytometry, 84.5% (n = 49) typed as positive for HLA-B27, while 15.5% (n = 9) were negative for HLA-B27 but positive for HLA-B*07:02. NGS was the only method able to distinguish between pathogenic and nonpathogenic HLA-B27 variants, in contrast to the flow cytometry or the PCR melting assays. CONCLUSIONS: Single-locus NGS is superior to flow cytometry and PCR melting assay for the unambiguous identification of HLA-B27 variants, and uniquely able to distinguish between pathogenic and nonpathogenic B27 alleles. Due to its high accuracy, it may be a feasible superior alternative to flow cytometry and traditional molecular methods for clinical HLA-B27 testing.

Development of Label-Free Immunoassays as Novel Solutions for the Measurement of Monoclonal Antibody Drugs and Antidrug Antibodies.

BACKGROUND: Immunoassays based on label-free technologies (label-free immunoassay [LFIA]) offer an innovative approach to clinical diagnostics and demonstrate great promise for therapeutic drug monitoring (TDM) of monoclonal antibody (mAb) drugs. An LFIA measures immunocomplex formation in real time and allows for quantification on initial binding rate, which facilitates fast measurement within a few minutes. METHODS: Based on thin-film interferometry (TFI) technology, open-access LFIAs were developed for the quantification of the mAb drugs adalimumab (ADL) and infliximab (IFX) and for the detection of the antidrug antibodies (ADAs) to the mAb drugs (ADL-ADAs and IFX-ADAs). RESULTS: The LFIAs for active mAb drugs (ADL and IFX) and for ADAs (ADL-ADAs and IFX-ADAs) were validated. The analytical measurement range (AMR) for both ADL and IFX was from 2 to 100 µg/mL. The AMR for ADL-ADAs was from 5 to 100 µg/mL and for IFX-ADAs was 10 to 100 µg/mL. In the comparison of LFIAs and reporter gene assays, the correlation coefficient was 0.972 for the quantification of ADL and 0.940 for the quantification of IFX. The concordance rate was 90% for the detection of ADL-ADAs and 76% for the detection of IFX-ADAs. CONCLUSIONS: The LFIAs for active mAb drugs and ADAs were appropriate for the TDM of ADL and IFX. The TFI technology has unique advantages compared with other technologies used for the measurement of mAb drugs. Label-free technologies, especially those allowing for open-access LFIAs, have great potential for clinical diagnostics.

Clinical utility of next generation sequencing based HLA typing for disease association and pharmacogenetic testing.

HLA associations have been linked to many diseases and are important for risk assessment of drug hypersensitivity reactions. The increasing number of HLA alleles discovered generated a list of ambiguities that cannot be resolved with the current clinical assays, which commonly include sequence-specific oligonucleotide probe (SSOP) genotyping, and real-time PCR with melting curve analysis. HLA typing by next-generation sequencing (NGS) has recently been adopted by clinical laboratories for transplantation testing, as it provides unambiguous and cost-effective HLA typing. The goal of this study was to evaluate the feasibility of using NGS-based HLA-B and DQ genotyping for clinical HLA disease association testing, and provide direct comparison with the currently used clinical tests, including SSOP genotyping, and real-time PCR with melting curve analysis. While the real-time PCR method is easy and inexpensive to perform, ambiguities are rapidly increasing as more and more HLA alleles are discovered. SSOP genotyping identifies the alleles present but limitations include ambiguities and underreporting less common alleles. Our data show that HLA typing by NGS is superior to the existing clinical methods for identifying HLA alleles associated with disease or drug hypersensitivity, and offers a viable approach for high volume clinical diagnostic laboratories.

Evaluation of Mass Cytometry in the Clinical Laboratory.

BACKGROUND: Mass cytometry can differentiate more channels than conventional flow cytometry. However, for clinical use, standardization and agreement with well-established methods is paramount. We compared mass cytometry to standard clinical flow cytometry. METHODS: Mass and flow cytometry were performed in parallel on peripheral blood samples from 25 healthy individuals. Antibody staining was performed on the same samples at the same time, and analyzed for granulocyte, monocyte, lymphocyte, T, B, NK, CD4 and CD8 percentages. Validation parameters included comparison to flow cytometry, inter- and intra-assay precision and establishment of reference intervals. RESULTS: There was a positive correlation between mass and flow cytometry for the eight populations studied (R2 between 0.26 and 0.97). Slopes of the best-fit lines varied from 0.50 to 1.21 (fluorescence/mass). No significant differences in variance were found (F-test, P > 0.05). However, paired t-tests were significantly different for four of the eight markers (granulocytes, NK cells, T cells and CD4 cells), resulting in different reference intervals. Signal intensities were correlated for monocytes, lymphocytes, T, CD4 and CD8 cells (R2 = 0.41-0.57). The mass cytometry intra-assay precisions were 0.7-8.5% and inter-assay precisions 1.5-13.8%. CONCLUSION: Mass and flow cytometry evaluations of whole blood for major cell populations correlate with similar precision and signal intensity. However, for clinical use, separate reference interval studies are required. Cell population identification should rely on gating strategies that take advantage of the characteristics offered by each method. © 2019 International Clinical Cytometry Society.

Inductively coupled plasma mass spectrometry assay for quantification of free infliximab in serum.

TNF antagonists such as infliximab are effective for the treatment of several inflammatory and autoimmune diseases. Recent clinical studies have advocated the importance of measuring trough infliximab levels to guide treatment decisions. We have developed a novel assay for measuring serum free infliximab levels using inductively coupled plasma-mass spectrometry (ICP-MS). The method involves the incubation of patient serum in wells coated with recombinant TNF, followed by detection with lanthanide-labeled monoclonal anti-human IgG1 and ICP-MS analysis. Full method validation was performed and results for clinical samples tested with the new method were compared with those obtained from a capture ELISA and a cell-based assay. Validation of the ICP-MS assay revealed a lower limit of detection of 0.4 µg/mL in serum. The linear range of quantitation was 1-50 µg/mL. The within-run and between-run precision had a coefficient of variation (CV) of <10%, and the accuracy of the assay had a CV of <15%. In serum samples, the ICP-MS method was devoid of analytical interferences by high levels of hemoglobin, bilirubin and triglycerides. Serum sample results from 123 drug-naïve donors revealed a test cutoff at 0.5 µg/mL. Test results from clinical samples obtained by the ICP-MS method showed strong correlation with both the ELISA and cell-based assay. The ICP-MS methodology presented in this study is a robust method for measuring TNF antagonist serum levels, which makes it well suited for therapeutic drug monitoring in the clinical laboratory.

Implications of Monoclonal Antibody Therapeutics Use for Clinical Laboratory Testing.

BACKGROUND: Monoclonal antibody therapeutics (MATs) represent a rapidly expanding class of biological drugs used to treat a variety of diseases. The widespread use of MATs increasingly affects clinical laboratory medicine. CONTENT: This review provides an overview of MATs currently approved for clinical use in the US, starting from basic biology of antibodies to the engineering, pharmacokinetic and pharmacodynamic properties, nomenclature, and production of MATs. Immunogenicity and the production of antidrug antibodies (ADAs) play a major role in loss of therapeutic response and the development of treatment failure to certain MATs. Laboratory-based monitoring for MATs and detection of ADAs represent emerging needs for optimizing the use of MATs to achieve the best outcomes at affordable cost. In addition, the increased use of MATs affects clinical laboratory testing by interference of MATs with clinical laboratory tests across different areas of laboratory medicine, including histocompatibility, blood bank, and monoclonal protein testing. SUMMARY: The number of MATs is rapidly growing each year to address previously unmet clinical needs. Laboratory monitoring of MATs and detecting ADAs represent expanding areas of laboratory testing. Test-based strategies allow for treatment optimization at the level of the individual patient, thus providing a personalized medicine approach. In addition, clinical laboratories must be aware that the increasing use of MATs affects laboratory testing and be ready to implement methods to eliminate or mitigate interference with clinical tests.

The Role of Human Leukocyte Antigen in Celiac Disease Diagnostics.

Celiac disease is an autoimmune disease affecting the small intestine, triggered by gluten sensitization in genetically susceptible individuals worldwide. Celiac disease development is strongly linked to the presence of HLA-DQ2 and/or DQ8, which present the immunogenic gluten peptides and trigger the immune response leading to pathogenesis. Because of the variability of clinical symptoms, the disease is often underdiagnosed. Intestinal biopsy and the presence of antibodies to deamidated gliadin and tissue transglutaminase are recommended diagnostic tools. Genetic testing for HLA DQ2 and DQ8 can be used to rule out disease in at-risk populations.

Development and validation of a targeted affinity-enrichment and LC-MS/MS proteomics approach for the therapeutic monitoring of adalimumab.

BACKGROUND: The anti-tumor necrosis factor alpha (TNFα) therapeutic monoclonal antibodies (mAbs), such as adalimumab, are widely used in the treatment of rheumatoid arthritis, inflammatory bowel diseases, and other auto-immune diseases. The administration of adalimumab can elicit the immune responses from some patients, resulting in the formation of anti-drug antibodies (ADAbs). The ADAbs can diminish the therapeutic effects of adalimumab by neutralizing the TNFα binding site or increasing its clearance from circulation. METHODS: To effectively monitor the therapeutic concentrations of adalimumab, we developed and validated a targeted quantitative proteomic assay to determine the circulating concentrations of adalimumab. Since drug effects can be attenuated by ADAbs, the method adopted an affinity-enrichment step to selectively quantify the bioavailable forms of adalimumab in patient serum samples. RESULTS: The performance of the LC-MS/MS based assay provides the analytical measuring range and precisions applicable for the therapeutic monitoring of adalimumab. It also provides comparable results to a cell-based activity assay when evaluating patient samples with different concentrations of adalimumab. CONCLUSION: Our assay can quantify both sub-therapeutic and therapeutic concentrations of bioavailable adalimumab in patient serum samples. This assay design provides an alternative to isotope-labeled peptides approach currently adopted in targeted proteomics methods.

Comparison of Clinical Laboratory Assays for Measuring Serum Infliximab and Antibodies to Infliximab.

BACKGROUND: Infliximab (IFX) is a chimeric monoclonal antibody targeting tumor necrosis factor-α, used for the management of autoimmune and inflammatory diseases. Immunogenicity to this protein drug may lead to therapeutic failure. Laboratory testing for serum IFX and antidrug antibodies (ADAs) is available for the evaluation of clinical nonresponsiveness. The purpose of this study was to compare the performance of testing methodologies used by 2 clinical reference laboratories for the quantification of IFX and detection of ADAs. METHODS: Deidentified serum samples submitted for clinical testing were selected (n = 120) and tested at both sites. A trypsin-based LC-MS/MS assay for IFX and a bridging electrochemiluminescent immunoassay (ECLIA) for ADAs (Mayo Clinic) and a functional cell-based reporter gene assay (RGA) to measure both bioactive drug concentrations and neutralizing ADAs (ARUP Laboratories) were compared. RESULTS: In all, 105 samples had measurable concentrations of IFX by both methods and yielded a correlation coefficient (r) = 0.917, slope = 1.028, and intercept = -0.377. One outlier measured <1.0 µg/mL by LC-MS/MS and 37 µg/mL by RGA, which was confirmed to be attributed to the presence of adalimumab. Regarding detection of ADAs, 81 of 120 samples were negative by ECLIA and RGA, whereas 30 of 120 were positive by both methods, resulting in an overall 92.5% agreement. CONCLUSION: Although there are substantial methodological differences in the assays used for detecting IFX and ADAs, results show significant concordance between the clinically validated methodologies performed in different laboratories.

Structure-guided development of a high-affinity human Programmed Cell Death-1: Implications for tumor immunotherapy.

Programmed Cell Death-1 (PD-1) is an inhibitory immune receptor, which plays critical roles in T cell co-inhibition and exhaustion upon binding to its ligands PD-L1 and PD-L2. We report the crystal structure of the human PD-1 ectodomain and the mapping of the PD-1 binding interface. Mutagenesis studies confirmed the crystallographic interface, and resulted in mutant PD-1 receptors with altered affinity and ligand-specificity. In particular, a high-affinity mutant PD-1 (HA PD-1) exhibited 45 and 30-fold increase in binding to PD-L1 and PD-L2, respectively, due to slower dissociation rates. This mutant (A132L) was used to engineer a soluble chimeric Ig fusion protein for cell-based and in vivo studies. HA PD-1 Ig showed enhanced binding to human dendritic cells, and increased T cell proliferation and cytokine production in a mixed lymphocyte reaction (MLR) assay. Moreover, in an experimental model of murine Lewis lung carcinoma, HA PD-1 Ig treatment synergized with radiation therapy to decrease local and metastatic tumor burden, as well as in the establishment of immunological memory responses. Our studies highlight the value of structural considerations in guiding the design of a high-affinity chimeric PD-1 Ig fusion protein with robust immune modulatory properties, and underscore the power of combination therapies to selectively manipulate the PD-1 pathway for tumor immunotherapy.

Immunogenicity Assessment of Tumor Necrosis Factor Antagonists in the Clinical Laboratory.

BACKGROUND: Tumor necrosis factor (TNF) antagonists are increasingly used for the treatment of inflammatory and autoimmune diseases. Immunogenicity of these drugs poses therapeutic challenges such as therapeutic failure and adverse effects in a number of patients. Evaluation of clinical nonresponsiveness includes laboratory testing for drug concentrations and detecting the presence of antidrug antibodies. CONTENT: This review provides an overview of the immunogenicity of TNF antagonists and testing methodologies currently available for measuring antidrug antibody response, which decreases treatment efficacy and may result in therapeutic failure. This review summarizes methodologies such as binding assays, including ELISA and HPLC-based homogenous mobility shift assay, as well as functional cell-based assays such as reporter gene assay. Furthermore, based on the laboratory findings of testing for antidrug antibody response, as well as serum drug concentrations, an algorithm is provided for interpretation, based on the current available literature and guidelines, which may aid in determining optimal therapy after treatment failure. SUMMARY: Laboratory testing methodologies for measuring serum concentrations of TNF inhibitors and antidrug antibodies are clinically available. These methods provide an evidence-based, personalized approach for the workup of patients showing treatment failure, which saves time and resources, and contributes to improved patient care.

Clinical laboratory application of a reporter-gene assay for measurement of functional activity and neutralizing antibody response to infliximab.

BACKGROUND: TNF-α antagonists such as infliximab are effective for the treatment of inflammatory bowel disease and other inflammatory and autoimmune diseases. Development of an immune response and subsequent neutralizing antibodies against these protein-based drugs is a major impediment that contributes to therapeutic failure, or adverse effects such as hypersensitivity reactions. As opposed to empirical dose-escalation strategies, rational and cost-effective evaluation of clinical non-responsiveness includes measurement of serum drug levels, and detection of drug-specific antibodies. We present the validation and 2-y experience using a functional, cell-based reporter gene assay (RGA) developed for measuring the biological activity and antibody response to serum infliximab. METHODS: The RGA was used to test 4699 clinical specimens from patients suspected of therapeutic failure. In contrast to binding assays, which detect an overall antibody response, the RGA specifically detects those antibodies that have drug-neutralizing function, and thus, poses higher risk for therapeutic failure. RESULTS: The RGA presented here is currently the only functional clinical test available to measure serum infliximab activity and neutralizing antibodies. CONCLUSIONS: Due to its accuracy and precision, and suitability for high-throughput testing, this robust platform can be applied to any TNF-α antagonist, providing an invaluable tool for the clinical management of patients with treatment failure.

Autoimmune NMDA receptor encephalitis.

Anti-N-methyl-d-aspartate receptor (anti-NMDAR) encephalitis is a treatable autoimmune disease of the central nervous system (CNS) with prominent neurologic and psychiatric features at disease onset. The disease is associated with the production of autoantibodies to NMDAR, a protein involved in memory function and synaptic plasticity. Affected patients develop a multistage progressive illness with symptoms ranging from memory deficits, seizures and psychosis, to potentially lethal catatonia, and autonomic and breathing instability. The outcome can be much improved with accurate diagnosis and early treatment using adequate immunosuppressive therapy. However, since the neurological and psychiatric symptoms as well as the clinical examination results can be non-specific, the disease is probably under-recognized. Reliable and accurate clinical testing for the identification of NMDAR autoantibodies is crucial for diagnosis, timely treatment selection, and monitoring. Recently, a cell-based indirect immunofluorescent antibody test for the detection of IgG antibodies to NMDAR has become available for diagnostic use. This review highlights the progress and challenges of laboratory testing in the evaluation and management anti-NMDAR encephalitis, and perspectives for the future.

Human cancer immunotherapy with antibodies to the PD-1 and PD-L1 pathway.

The programmed death 1 (PD-1) receptor and its ligands programmed death ligand 1 (PD-L1) and PD-L2, members of the CD28 and B7 families, play critical roles in T cell coinhibition and exhaustion. Overexpression of PD-L1 and PD-1 on tumor cells and tumor-infiltrating lymphocytes, respectively, correlates with poor disease outcome in some human cancers. Monoclonal antibodies (mAbs) blockading the PD-1/PD-L1 pathway have been developed for cancer immunotherapy via enhancing T cell functions. Clinical trials with mAbs to PD-1 and PD-L1 have shown impressive response rates in patients, particularly for melanoma, non-small-cell lung cancer (NSCLC), renal cell carcinoma (RCC), and bladder cancer. Further studies are needed to dissect the mechanisms of variable response rate, to identify biomarkers for clinical response, to develop small-molecule inhibitors, and to combine these treatments with other therapies.

Tissue-expressed B7-H1 critically controls intestinal inflammation.

B7-H1 (PD-L1) on immune cells plays an important role in T cell coinhibition by binding its receptor PD-1. Here, we show that both human and mouse intestinal epithelium express B7-H1 and that B7-H1-deficient mice are highly susceptible to dextran sodium sulfate (DSS)- or trinitrobenzenesulfonic acid (TNBS)-induced gut injury. B7-H1 deficiency during intestinal inflammation leads to high mortality and morbidity, which are associated with severe pathological manifestations in the colon, including loss of epithelial integrity and overgrowth of commensal bacteria. Results from bone marrow chimeric and knockout mice show that B7-H1 expressed on intestinal parenchyma, but not on hematopoietic cells, controls intestinal inflammation in an adaptive immunity-independent fashion. Finally, we demonstrate that B7-H1 dampened intestinal inflammation by inhibiting tumor necrosis factor α (TNF-α) production and by stimulating interleukin 22 secretion from CD11c(+)CD11b(+) lamina propria cells. Thus, our data uncover a mechanism through which intestinal tissue-expressed B7-H1 functions as an essential ligand for innate immune cells to prevent gut inflammation.

A single subset of dendritic cells controls the cytokine bias of natural killer T cell responses to diverse glycolipid antigens.

Many hematopoietic cell types express CD1d and are capable of presenting glycolipid antigens to invariant natural killer T cells (iNKT cells). However, the question of which cells are the principal presenters of glycolipid antigens in vivo remains controversial, and it has been suggested that this might vary depending on the structure of a particular glycolipid antigen. Here we have shown that a single type of cell, the CD8α(+) DEC-205(+) dendritic cell, was mainly responsible for capturing and presenting a variety of different glycolipid antigens, including multiple forms of α-galactosylceramide that stimulate widely divergent cytokine responses. After glycolipid presentation, these dendritic cells rapidly altered their expression of various costimulatory and coinhibitory molecules in a manner that was dependent on the structure of the antigen. These findings show flexibility in the outcome of two-way communication between CD8α(+) dendritic cells and iNKT cells, providing a mechanism for biasing toward either proinflammatory or anti-inflammatory responses.