Vanderboom, Patrick M.

Abstract Background The diagnosis of monoclonal gammopathies relies on the detection of monoclonal immunoglobulins (M-proteins) in serum or urine. Mass-Fix utilizes matrix-assisted laser desorption ionization time-of-flight (MALDI-TOF) mass spectrometry (MS) to detect and quantify M-proteins. This method employs immunoaffinity enrichment using antibodies against heavy chains (HC) and light chains (LC), followed by MS analysis to determine M-protein isotypes. Mass-Fix has also revealed novel M-protein characteristics, including LC glycosylation and fragmentation, facilitated by measuring the mass of LC. LC glycosylation is as an independent risk factor for disease progression of monoclonal gammopathy of undetermined significance (MGUS), while light chain fragments have been postulated as the origin of amyloid light chain (AL) plaques. Since Mass-Fix enriches intact immunoglobulins before dissociating LCs, it potentially enhances fragment detection. However, the precise nature and clinical significance of these fragments remain to be fully elucidated. Methods Mass-Fix serum results from Mayo Clinic patients tested from September 10, 2018, to October 1, 2024, were reviewed for the presence of M-protein and LC fragments. The frequency and the isotype of fragment LC fragments was determined in the M-protein positive cohort (n=15410). Patients diagnosed with either MGUS (n=6996), AL amyloidosis (n=315), or both (n=32) who had positive M-protein results on Mass-Fix, either prior to or within one month after the diagnosis, were included for a retrospective clinical association study of LC fragments and disease. To validate that these fragments were not artifacts of MS analysis, PAGE gel analysis and Western blots were performed using clinical residual serum from 9 patients: 2 IgG/kappa and 3 IgG/lambda patients with detectable LC fragments and 2 IgG/kappa and 2 IgG/lambda patients without fragments. Samples were purified using antibodies against gamma heavy chains and reduced with TCEP prior to gel electrophoresis and Western blot. Results Of the 15410 patients with monoclonal proteins detected by Mass-Fix, 2896 (18.7%) had detectable LC fragments; kappa fragments in 1533 and lambda fragments in 1363. Most often, the fragments were observed in pairs, with combined molecular weight typically equaled that of the full-length monoclonal LC present in the same sample. LC fragments were observed more frequently among patients diagnosed with AL amyloidosis (118/347=34%) compared to those without the diagnosis (685/6996=10%), with an odds ratio of 4.75 (95% CI, 3.75-6.01). PAGE with Coomassie blue staining revealed bands with sizes representing LC fragments in the five M-protein samples with detectable LC fragments on Mass-Fix, while no such bands observed in those without LC fragments. Western blot using anti-kappa or anti-lambda antibodies confirmed the identity of the bands with higher molecular weight as a fragment of LC in each of the IgG/kappa and IgG/lambda samples. Conclusion Mass-Fix is able to discriminate LC fragments from intact LC based on their sizes. The detection of LC fragments with Western blot without ionization suggests a biological origin rather than analytical artifacts from MS. The clinical association study suggests that LC fragments may have utility in increasing the suspicion of AL amyloidosis in M-protein positive patients with LC fragments, potentially facilitating earlier intervention and improving patient outcomes.

Abstract Background Anti-citrullinated peptide antibodies (ACPA) (tested as anti-cyclic citrullinated peptide [CCP] antibodies) are frequently ordered in the evaluation of patients with suspected rheumatoid arthritis (RA) and considered to be specific biomarkers for RA. The 2010 American College of Rheumatology/European Alliance of Associations for Rheumatology (ACR/EULAR) classification criteria for RA include both ACPA and rheumatoid factor in their scoring system, despite limited standardization of commercially available anti-CCP antibody tests. In an attempt to overcome this limitation, the classification criteria recommends using multiples of the assay-specific upper limit of normal (ULN) to normalize results and standardize classification. This study evaluates the correlation between normalized results from different assays and the concordance in result classification according to the ACR/EULAR criteria. Methods A total of 265 samples with ACPA ordered as part of routine clinical care were tested on four commercial anti-CCP antibody assays, including QUANTA Lite CCP3 IgG ELISA (Werfen) (Negative: <20 Units), QUANTA Flash CCP3 chemiluminescence immunoassay (Werfen) (Negative: <20 Chemiluminescent Units), EUROIMMUN Anti-CCP ELISA (IgG) (EUROIMMUN) (Negative: <=5 Relative Units/mL), and Elecsys anti-CCP electrochemiluminescence immunoassay (Roche) (Negative: <17.0 Units/mL). The QUANTA Lite and EUROIMMUN ELISA were performed on the Agility platform (Dynex), QUANTA Flash was performed on BioFlash platform (Werfen), and Elecsys anti-CCP was performed on Cobas e601 platform (Roche). All testing was performed according to manufacturer’s instructions. Results from each assay were converted to the multiples of assay-specific ULN as the normalized results. Regression analysis was performed, and the coefficient of determination (R²) was calculated to assess the correlation between paired assays. The concordance in result classification across assays was also investigated using both assay specific cut-offs and the ACR/EULAR criteria-defined cut-offs: Negative (<=1xULN), Low positive (>1xULN and <3xULN), High positive (>=3xULN). Results Using assay-specific cut-offs, 63 samples were negative on all assays. 202 samples were positive on at least one assay, of which 79 (39%) were positive across all assays. The overall concordance of qualitative result was 54% ([63+79]/265). After result normalization using multiples of assay-specific ULNs, the highest correlation was observed between the EUROIMMUN ELISA and Elecsys anti-CCP (R²=0.83), despite differences in methodology and manufacturer. The lowest correlation was observed between QUANTA Lite and QUANTA Flash (R²=0.49), even though both are from the same manufacturer although methodologies differ. When applying the criteria-defined cut-offs, 64 samples were negative on all assays. 130 samples were classified as low positive on at least one assay; however, only 3 (2%) samples were classified as low positive across all assays. 103 samples were classified as high positive on at least one assay, of which 54 (52%) were classified as high positive across all assays. With result normalization, the overall concordance in result classification across all assays using the criteria-defined cut-offs were 46% ([64+3+54]/265). Conclusion Despite normalization using multiplies of assay-specific ULN values, the inter-assay correlation remains suboptimal, and the concordance in result classification is limited. These findings suggest that the anti-CCP antibody results from different assays may not be interchangeable even after normalization as recommended by current criteria, potentially impacting disease classification.

Abstract Background Celiac disease (CeD) is a chronic autoimmune disorder that can affect people of any age. Both ingestion of gluten and the presence of human leukocyte antigens (HLA)-DQ2 or DQ8 are required for disease development. In adults, correlation between HLA-DQ2/DQ8 allele combinations and tissue transglutaminase (tTG) antibody positivity has been well described. In comparison, this association in pediatric patients is less defined. In this study, we evaluated the roles of HLA-DQ2 and HLA-DQ8 as predictors of tTG-IgA positivity in a pediatric cohort, aiming to enhance understanding of CeD risk assessment in this diagnostic group. Methods Retrospective data were collected from individuals who underwent CeD diagnostic testing at Mayo Clinic Laboratories between 2011 and 2024; all patients were tested for total IgA, HLA-DQ typing, and tTG-IgA. Total IgA was measured using quantitative nephelometry on the BN™ II System (Siemens); HLA-DQ typing was performed using reverse sequence-specific oligonucleotide (SSO) DNA typing (LABType SSO kits, One Lambda, Thermo). tTG-IgA was tested using an enzyme-linked immunosorbent assay (QUANTA Lite® h-tTG IgA, Werfen Diagnostics). Those with total IgA below the age-specific reference interval were excluded from this analysis. Logistic regression was used to evaluate the association between HLA-DQ haplotypes and tTG-IgA positivity to assess the risk gradient across different HLA-DQ genotypes in children. Results The cohort identified in this study consisted of 115,499 individuals for whom total IgA, HLA-DQ typing and tTG-IgA testing was performed. Within this cohort, 20,676 (17.9%) were pediatric patients (age<=18 at the time of testing). Pediatric patients tested for CeD exhibited a slightly higher prevalence of at least one copy of HLA-DQ2 or DQ8 compared to adults (57.6% vs 55.4%, p<0.001). Additionally, these patients showed significantly higher rates of tTG-IgA positive across all genotypes, particularly those carrying HLA-DQ2.5 or DQ8, with positivity rates 1.2 to 2.3 times higher than in adults (p<=0.01). However, in non-permissive genotypes, the positivity rates were 0.3% (p=0.95), for both populations, indicating comparable specificity. Individuals with homozygous HLA-DQ2.5/DQ2.5 and HLA-DQ2.5/DQ2.2 showed the highest risks for tTG-IgA positivity with ORs of 85.7 (95% CI: 55.1-137.7) and 78.5 (95% CI: 51.3-124.3), respectively. Moderate risk was observed for HLA-DQ2.5/DQ8 with an OR of 49.0 (95% CI: 32.1-77.3), followed by single copy HLA-DQ2.5 (OR=35.0, 95% CI: 24.0-53.4) and homozygous HLA-DQ8/DQ8 (OR=21.7, 95% CI: 11.7-39.4). Although single copies of HLA-DQ2.2 and HLA-DQ8 showed lower risks with ORs of 5.4 and 8.9 (95% CI: 3.2-9.2 and 5.7–13.9), their combination increased the OR to 22.6 (95% CI: 13.0-39.2), similar to homozygous HLA-DQ8. Conclusion This large cohort study demonstrates the predictive value of HLA-DQ genotypes for pediatric CeD seropositivity. Notably, pediatric patients showed slightly higher prevalence and positivity rates compared to adults, particularly among those with homozygous HLA-DQ2.5/DQ2.5 and HLA-DQ2.5/DQ2.2 genotypes, which exhibited the highest risks for tTG-IgA positivity. The findings confirm that HLA-DQ2.5 is the main driver of serology positivity and suggest that HLA-DQ8 also influences serological positivity in pediatric patients, which can enhance targeted screening and potentially inform decisions regarding the necessity of duodenal biopsy.

Abstract Background Multiple sclerosis (MS) is an immune-mediated central nervous system (CNS) demyelinating disease which is diagnosed based on CNS lesions' spatial and temporal dissemination. The 2017 revised McDonald Criteria include cerebrospinal fluid (CSF) specific oligoclonal bands (OCBs) to indicate dissemination in time, but their assessment is labor-intensive and requires a paired serum sample. Kappa immunoglobulin free light chain in CSF (KCSF) has emerged as a more sensitive but less specific MS biomarker, measured from a single CSF sample. Our institution's MS testing panel uses KCSF initially to rule out MS, with reflex to OCB for positive confirmation if KCSF is borderline positive (≥0.06 mg/dL). However, manual correlation of laboratory and clinical data hinders the direct comparison of the diagnostic performance between these markers. Herein we report a retrospective assessment of KCSF and OCB diagnostic performance using automated chart review. Methods Between January 1st, 2021 and December 31st, 2022, there were 1,237 patients with simultaneously measured OCB and KCSF. CSF-specific OCBs were measured by separating CSF and serum proteins using an agarose isoelectric focusing gel with a pH gradient from 3-10 (Sebia). After transfer to nitrocellulose paper, antisera were applied to visualize IgG specific bands and quantify CSF-specific OCBs. KCSF was quantitated using nephelometry by applying free light chain antisera (Binding Site) to CSF samples using a Siemens BNII analyzer. An automated chart review process utilizing keyword matching was implemented to identify patients with MS. An initial filter phase required presence of the term “multiple sclerosis”, while a second required the presence of any of the following terms: “primary progressive,” “secondary progressive,” “relapsing remitting,” “progressive relapsing,” or “tumefactive” to identify patients with diagnosed MS. The automated method’s performance was then compared to a manual chart review of 200 randomly selected patients. Subsequently, the automated process was used to determine the MS diagnosis status of all 1,237 patients. Results Of the 200 manually reviewed patients, 44 MS diagnoses were found. The automated process correctly identified 41 of these with a resulting sensitivity and specificity of 93.18% and 95.51%, respectively. Applied to the entire cohort, the automated review identified 275 MS diagnoses. For the entire cohort, the area under the curve (AUC) for the receiver operating characteristic (ROC) curves for OCB and KCSF were 0.824 (95% confidence interval: 0.794, 0.854) and 0.808 (0.777, 0.839) respectively. Our institution’s diagnostic cutoff of ≥2 for OCB yielded a sensitivity and specificity of 74.2% (68.3%, 79.1%) and 84.9% (73.8%, 89.5%), respectively. The best combination for sensitivity and specificity for KCSF with the Youden index yielded a cutoff ≥0.0654 mg/dL (sensitivity of 79.6% [73.1%, 84.0%] and specificity of 72.4% [62.8%, 76.8%]), which is similar to previous publications. This supports the use of automated chart review and suggests the KCSF cutoff has been stable over time. Conclusions KCSF exhibits comparable MS diagnostic performance to OCB yet only requires one CSF sample and can be measured rapidly. When validated, mining unstructured data allows for test performance characterization in large patient cohorts without the need for manual chart review.

Abstract Background Celiac disease (CeD) is a chronic autoimmune disorder triggered by the ingestion of gluten in persons with the genetic risk factors human leukocyte antigens (HLA)-DQ2 and DQ8. Diagnostic evaluation of patients with suspected CeD often includes serology tests for tissue transglutaminase (tTG) antibodies. While the presence of HLA-DQ2 or DQ8 is required for the initiation and development of CeD, the genetic risk associated with the various alleles is not equivalent. Previous studies in patients with normal total IgA demonstrated the risk gradients of various HLA-DQ2 and DQ8 heterodimers in CeD. However, the impact of both gene variants in IgA deficient patients has not been investigated. In this study, HLA-DQ2 and HLA-DQ8 as risk factors for tTG-IgG positivity in IgA deficient patients were evaluated. Methods Retrospective data was collected from a cohort of individuals (n=3,515) with IgA concentrations below the age-dependent reference interval with suspicion for CeD who were tested for HLA-DQ genotyping and tTG-IgG (reference interval < 6 U/mL) at Mayo Clinic Laboratories. Total IgA was measured using quantitative nephelometry (Siemens BN™ II System); HLA typing was performed using the reverse SSO DNA typing assay (LABType SSO kits). tTG-IgG was determined by enzyme-linked immunosorbent assay (QUANTA Lite R h-tTG, Werfen Diagnostics) on the Dynex Agility System. The prevalence and frequency distribution of HLA-DQ2 and DQ8 haplotypes were determined and the odds ratio (OR) was calculated to evaluate the risk gradient for tTG-IgG positivity based on different HLA-DQ variants. Results Among IgA deficient patients, 58% (n=2,041) expressed HLA-DQ2 or DQ8 haplotypes. Relative to patients without permissive alleles, patients homozygous for HLA-DQ2.5 exhibited a significantly increased risk for tTG-IgG positivity (OR = 10.98, 95% CI: 6.56-18.18, p < 0.001) while those homozygous for HLA-DQ2.2 and DQ8 did not (DQ2.2/DQ2.2_OR = 0.72, 95% CI: 0.04-3.44, p = 0.75; DQ8/DQ8_OR = 0.96, 95% CI: 0.05-4.64, p = 0.97). Patients heterozygous for HLA-DQ2.5 (DQ2.5/x) displayed a lower odds ratio relative to homozygous patients (OR = 3.31, 95% CI: 2.29-4.82, p < 0.001); however, the risk for tTG-IgG positivity increased in the presence of HLA-DQ2.2 (DQ2.5/DQ2.2_OR = 7.59, 95% CI: 4.48-12.65, p < 0.001) or HLA-DQ8 (DQ2.5/DQ8_OR = 6.26, 95% CI: 3.55-10.73, p < 0.001) alleles. Conversely, in the absence of HLA-DQ2.5, HLA-DQ2.2 heterozygotes (DQ2.2/x_OR = 2.80, 95% CI: 1.77-4.39, p < 0.001) and HLA-DQ8 heterozygotes (DQ8/x_OR = 0.99, 95% CI: 0.52-1.77, p = 0.99) displayed lower correlations with tTG-IgG positivity, suggesting a potential risk elevation for tTG-IgG positivity is associated with the combination of DQ2.5 and DQ2.2 or DQ8. Conclusions Our study indicates the risk gradient of HLA-DQ genes in IgA deficient patients. Overall, compared to patients without HLA-DQ2 or DQ8 haplotypes, the homozygous HLA-DQ2.5 genotype had the highest correlation with tTG-IgG positivity, followed by HLA-DQ2.5/DQ2.2 and HLA-DQ2.5/DQ8 heterodimers. The results suggest that HLA-DQ2.2 or HLA-DQ8 alone does not confer risk, but when in the presence of HLA-DQ2.5 these alleles may increase the risk for tTG-IgG positivity. Results from this study shed light on the risk of CeD in patients with IgA deficiency.

AbstractBackgroundPrecursor plasma cell disorders such as monoclonal gammopathy of undetermined significance (MGUS) always precede the development of active malignancies such as multiple myeloma (MM). There is a need for novel biomarkers to identify those patients with such precursor plasma cell disorders who rapidly progress to MM. Plasma‐derived extracellular vesicles (EVs) may serve as a reservoir of potential biomarkers that can shed light on the pathogenesis and disease biology of MM.MethodsThis study isolated small EVs (SEVs) and large EVs (LEVs) from the platelet‐poor peripheral blood plasma of MGUS (n = 9) and MM (n = 12) patients using the size exclusion chromatography‐based method and evaluated their proteome using a label‐free proteomics workflow.ResultsIn total, 2055 proteins were identified in SEVs, while 2794 proteins were identified in LEVs. The transferrin receptor (or CD71) protein was upregulated in both populations of EVs derived from MM patients compared to MGUS patients and was of prognostic significance. Similarly, three isoforms of serum amyloid A (SAA) protein, SAA1, SAA2, and SAA4, were also highly upregulated in SEVs within MM patients relative to MGUS patients. Finally, CD40 expression was also higher in the LEVs derived from MM patients than in MGUS patients.ConclusionsThis study demonstrates the feasibility of successfully isolating both SEVs and LEVs from the peripheral blood of patients with plasma cell disorders and quantifying protein biomarkers within these EVs that could be of prognostic and diagnostic interest.

Abstract Objectives Recent work has demonstrated that automated fluorescence flow cytometry (FLC) is a potential alternative for the detection and quantification of Plasmodium parasites. The objective of this study was to apply this novel FLC method to detect and quantify Babesia parasites in venous blood and compare results to light microscopy and polymerase chain reaction methods. Methods An automated hematology/malaria analyzer (XN-31; Sysmex) was used to detect and quantify B microti–infected red blood cells from residual venous blood samples (n = 250: Babesia positive, n = 170; Babesia negative, n = 80). As no instrument software currently exists for Babesia, qualitative and quantitative machine learning (ML) algorithms were developed to facilitate analysis. Results Performance of the ML models was verified against the XN-31 software using P falciparum–infected samples. When applied to Babesia-infected samples, the qualitative ML model demonstrated an area under the curve (AUC) of 0.956 (sensitivity, 95.9%; specificity, 83.3%) relative to polymerase chain reaction. For valid scattergrams, the qualitive model achieved an AUC of 1.0 (sensitivity and specificity, 100%), while the quantitative model demonstrated an AUC of 0.986 (sensitivity, 94.4%; specificity, 100%). Conclusions This investigation demonstrates that Babesia parasites can be detected and quantified directly from venous blood using FLC. Although promising, opportunities remain to improve the general applicability of the method.

Abstract Background: Precursor plasma cell disorders such as monoclonal gammopathy of undetermined significance (MGUS) always precede the development of active malignancies such as multiple myeloma (MM). There is a need for novel biomarkers to identify those patients with such precursor plasma cell disorders who rapidly progress to MM. Plasma-derived extracellular vesicles (EVs) may serve as a reservoir of potential biomarkers that can shed light on the pathogenesis and disease biology in MM. Methods: This study isolated small EVs (SEVs) and large EVs (LEVs) from the platelet-poor peripheral blood plasma of MGUS (n=9) and MM (n=12) patients using the size exclusion chromatography (SEC)-based method and evaluated their proteome using a label-free proteomics workflow. Results: In total, 2,055 proteins were identified in SEVs, while 2,794 proteins were identified in LEVs. The transferrin receptor (TFRC or CD71) protein was upregulated in both populations of EVs derived from MM patients compared to MGUS patients and was of prognostic significance. Similarly, three isoforms of serum amyloid A (SAA) protein, SAA1, SAA2, and SAA4, were also highly upregulated in SEVs within MM patients relative to MGUS patients. Finally, CD40 expression was also higher within the LEVs derived from MM patients than MGUS patients. Conclusions: This study demonstrates the feasibility of successfully isolating both SEVs and LEVs from the peripheral blood of patients with plasma cell disorders and quantifying protein biomarkers within these EVs that could be of prognostic and diagnostic interest.

Aging and many illnesses and injuries impair skeletal muscle mass and function, but the molecular mechanisms are not well understood. To better understand the mechanisms, we generated and studied transgenic mice with skeletal muscle–specific expression of growth arrest and DNA damage inducible α (GADD45A), a signaling protein whose expression in skeletal muscle rises during aging and a wide range of illnesses and injuries. We found that GADD45A induced several cellular changes that are characteristic of skeletal muscle atrophy, including a reduction in skeletal muscle mitochondria and oxidative capacity, selective atrophy of glycolytic muscle fibers, and paradoxical expression of oxidative myosin heavy chains despite mitochondrial loss. These cellular changes were at least partly mediated by MAP kinase kinase kinase 4, a protein kinase that is directly activated by GADD45A. By inducing these changes, GADD45A decreased the mass of muscles that are enriched in glycolytic fibers, and it impaired strength, specific force, and endurance exercise capacity. Furthermore, as predicted by data from mouse models, we found that GADD45A expression in skeletal muscle was associated with muscle weakness in humans. Collectively, these findings identify GADD45A as a mediator of mitochondrial loss, atrophy, and weakness in mouse skeletal muscle and a potential target for muscle weakness in humans.