Comprehensive Immune Profiling of a Kidney Transplant Recipient With Peri-Operative SARS-CoV-2 Infection: A Case Report.

To date there is limited data on the immune profile and outcomes of solid organ transplant recipients who encounter COVID-19 infection early post-transplant. Here we present a unique case where the kidney recipient's transplant surgery coincided with a positive SARS-CoV-2 test and the patient subsequently developed symptomatic COVID-19 perioperatively. We performed comprehensive immunological monitoring of cellular, proteomic, and serological changes during the first 4 critical months post-infection. We showed that continuation of basiliximab induction and maintenance of triple immunosuppression did not significantly impair the host's ability to mount a robust immune response against symptomatic COVID-19 infection diagnosed within the first week post-transplant.

Aptamer-based enrichment of TDP-43 from human cells and tissues with quantification by HPLC-MS/MS.

BACKGROUND: There is great interest in detecting, characterizing and quantifying transactive response DNA binding protein of 43 kDa (TDP-43), and its post-translational modifications, due to its association with frontotemporal dementia (FTD) and amyotrophic lateral sclerosis. Unfortunately, detailed analysis of TDP-43 in human biological matrices by immunometric methods has been hindered by the relatively low abundance of TDP-43 and poor antibody reagent specificity. NEW METHOD: With the goal of developing a selective and multiplex method for characterizing TDP-43, we previously developed a high-performance liquid chromatography tandem mass spectrometry (HPLC-MS/MS) assay for relative quantification of TDP-43 in human brain tissue and cells. To improve analytical sensitivity and to perform absolute quantification, we coupled a novel RNA-based aptamer enrichment workflow (and inclusion of a stable isotope-labeled standard) to HPLC-MS/MS. RESULTS: The TDP-43 aptamer-enrichment-HPLC-MS/MS assay was linear from 0.37 to 2.55nmol/L, a range suitable for analysis of both human cells and brain tissue homogenates, and had a total CV of 14.8%. Quantitative TDP-43 peptide profiles were developed for cases of FTD with TDP-43 pathology and cases with no neurodegenerative pathology. COMPARISON WITH EXISTING METHODS: Compared to immunoenrichment, aptamer-enrichment yielded cleaner recoveries of TDP-43. The aptamer-enrichment-HPLC-MS/MS method, compared to our previous method without enrichment, increased analytical sensitivity by 8.7-fold and 11.8-fold for endogenous TDP-43 in human cells and brain tissue, respectively. Critically, inclusion of the aptamer enrichment step improved sequence resolution and enabled identification of TDP-43 C-terminal fragments. CONCLUSIONS: The aptamer-enrichment-HPLC-MS/MS method enabled highly selective quantification, enhanced sequence coverage and structural characterization of endogenous TDP-43.

Detection and characterization of TDP-43 in human cells and tissues by multiple reaction monitoring mass spectrometry.

Transactive response DNA-binding protein 43 kDa (TDP-43) is a highly conserved and widely expressed protein in human tissues that regulates nucleic acid processing. In frontotemporal dementia and amyotrophic lateral sclerosis, however, TDP-43 forms insoluble aggregates in central nervous tissues. These pathological deposits of TDP-43 have been primarily studied by ligand binding, namely western blot analysis, and, thus, methods with greater structural resolution are needed to aid in our understanding of the pathological processes associated with TDP-43 misfolding and aggregation. Toward this goal, we have developed a selective and multiplex method for the detection and characterization of TDP-43 using liquid chromatography tandem mass spectrometry. As proof-of-concept, the method was applied to the detection and characterization of TDP-43 in human cell lines and human brain tissue.