Development of an automated capillary nano-immunoassay-Simple Western assay-to quantify total TDP43 protein in human platelet samples.

Frontotemporal lobar degeneration syndrome is the second cause of young-onset dementia. Unfortunately, reliable biomarkers are currently lacking for the diagnosis of this disease. As TDP43 protein is one of the proteins pathologically involved in frontotemporal lobar degeneration, many studies have been performed to assess TDP43 protein diagnostic performances. Mixed results were obtained using cerebrospinal fluid and plasma samples so far. The aim of the study was to develop an automated capillary nano-immunoassay-Simple Western assay-to detect and quantify TDP43 protein simultaneously in human blood-based samples. Simple Western assay was developed with two different cell lysates used as positive controls and was compared to Western blot. TDP43 protein profiles in plasma samples were disappointing, as they were discordant to our positive controls. On the contrary, similar TDP43 patterns were obtained between platelet samples and cell lysates using both assays. Simple Western assay provided good quantitative performances in platelet samples: a linearity of signals could be observed (r2 = 0.994), associated to a within-run variability at 5.7%. Preliminary results based on a cohort of patients suffering from frontotemporal lobar degeneration showed large inter-individual variations superior to Simple Western's analytical variability. Simple Western assay seems to be suitable for detecting and quantifying TDP43 protein in platelet samples, providing a potential candidate biomarker in this disease. Further confirmation studies should now be performed on larger cohorts of patients to assess diagnostic performances of TDP43 protein in platelet samples.