Evaluation of the Blood Stabilizers TransFix™ and Cyto-Chex®BCT for Low-Cost CD4 T-Cell Methodologies

Extending flow cytometry sample stability by freezing lysed whole blood for clinical monitoring of Treg

Aim: A major challenge for flow cytometry assays supporting clinical trials is postcollection sample stability. Here we present an approach that could mitigate the stability issue while preserving sample integrity and cellular markers, especially when enumerating rare populations such as Tregs. Materials & methods: Stability was evaluated using whole blood stored at room temperature and lysed whole blood stored at -80°C. Results: Freezing of lysed whole blood preserved sample integrity and prolonged sample stability for Treg percentage, absolute cell count and median fluorescent intensity values to 11 versus 3 days at room temperature storage. Conclusion: Frozen storage of lysed whole blood can extend sample stability, improve data quality and facilitate sample batch processing during clinical study sample analysis.

Guidelines for the use of flow cytometry and cell sorting in immunological studies (second edition)

These guidelines are a consensus work of a considerable number of members of the immunology and flow cytometry community. They provide the theory and key practical aspects of flow cytometry enabling immunologists to avoid the common errors that often undermine immunological data. Notably, there are comprehensive sections of all major immune cell types with helpful Tables detailing phenotypes in murine and human cells. The latest flow cytometry techniques and applications are also described, featuring examples of the data that can be generated and, importantly, how the data can be analysed. Furthermore, there are sections detailing tips, tricks and pitfalls to avoid, all written and peer-reviewed by leading experts in the field, making this an essential research companion.

Interlaboratory comparison of the TransFix®/EDTA Vacuum Blood Collection tube with the 5 mL Cyto-Chex® BCT

BACKGROUND

An interlaboratory study was performed to compare the performance of the 3 mL TransFix®/EDTA Vacuum Blood Collection Tube (TVT), with the 5 mL Cyto-Chex® BCT tube (BCT). Both devices are intended for collection and storage of whole blood specimens for immunophenotyping of leukocytes by flow cytometry for up to 14 days.

METHODS

One site in the United States and two in the United Kingdom tested samples from 10 HIV positive patients and four healthy subjects for a total of 42 samples. From each subject, three blood samples were collected: a BD 4 mL K₃ EDTA Vacutainer (Vacutainer), a TVT, and a BCT. At all sites, samples were analyzed on a BD FACS Canto II flow cytometer for a full lymphocyte subset count within 6 h of collection (all devices) and on Day 11 and Day 15 (TVT and BCT only). Data obtained from the Vacutainer were used as the control data set with which TVT and BCT data were statistically compared.

RESULTS AND CONCLUSIONS

Statistical concordance was demonstrated for both devices in relation to cell absolute count recovery. For cell marker signal, both devices exhibited a significant decrease in mean fluorescence intensity (MFI) for the detection of lymphocyte subsets and their target markers. There was a marked increase in autofluorescence observed for BCT stabilized lymphocytes whereas values for the TVTs were comparable to the control. There were eight instances of statistical equivalence between the level of antibody autofluorescence observed in the control tube and the TVT across both patient cohorts, versus two for the BCT. © 2018 International Clinical Cytometry Society.

Effect of PF-00547659 on Central Nervous System Immune Surveillance and Circulating β7+ T Cells in Crohn's Disease: Report of the TOSCA Study

BACKGROUND AND AIMS

Progressive multifocal leukoencephalopathy [PML], a brain infection associated with anti-integrin drugs that inhibit lymphocyte translocation from bloodstream to tissue, can be fatal. Decreased central nervous system [CNS] immune surveillance leading to this infection has been reported in patients with multiple sclerosis or Crohn's disease treated with anti-integrin antibody natalizumab. PF-00547659 is an investigational human monoclonal antibody for inflammatory bowel disease, targeted against α4β7-mucosal addressin cell-adhesion molecule-1 [the integrin ligand selectively expressed in the gut]. We hypothesised that this selective agent would not affect central nervous system immune surveillance.

METHODS

Cerebrospinal fluid from five healthy volunteers, and from 10 patients with Crohn's disease previously treated with immunosuppressants, was evaluated to assess the feasibility of the study. Subsequently, 39 patients with active Crohn's disease and previous immunosuppression were evaluated over 12 weeks of PF-00547659-induction therapy. We measured total lymphocytes, T cell subsets in cerebrospinal fluid, and circulating β7+ memory cells. Disease activity was assessed using the Harvey-Bradshaw Index.

RESULTS

Patients treated with PF-00547659 had no reduction of cerebrospinal fluid lymphocytes, T-lymphocyte subsets, or CD4:CD8 ratio, whereas circulating β7+ memory cells increased significantly. A total of 28/35 [80%] patients had a clinical response and 27/34 [79%] had disease remission. Treatment-related adverse events, none serious, were reported in 23/49 [47%] patients.

CONCLUSIONS

In patients with active Crohn's disease, natalizumab therapy increases the risk for PML, and the increased risk is thought to be associated with iatrogenic leukopenia within the CNS. PML under PF-00547659 may be a lesser concern, as this agent did not reduce lymphocytes or T cell subsets in the cerebrospinal fluid.

Implementation of highly sophisticated flow cytometry assays in multicenter clinical studies: considerations and guidance

Flow cytometry is increasingly becoming an important technology for biomarkers used in drug discovery and development. Within clinical development flow cytometry is used for the determination of PD biomarkers, disease or efficacy biomarkers or patient stratification biomarkers. Significant differences exist between flow cytometry methodology and other widely used technologies measuring soluble biomarkers including ligand binding and mass spectrometry. These differences include the very heavy reliance on aspects of sample processing techniques as well as sample stabilization to ensure viable samples. These differences also require exploration of new approaches and wider discussion regarding method validation requirements. This paper provides a review of the current challenges, solutions, regulatory environment and recommendations for the application of flow cytometry to measure biomarkers in clinical development.

Multisite evaluation of point of care CD4 testing in Papua New Guinea

Laboratory-based CD4 monitoring of HIV patients presents challenges in resource limited settings (RLS) including frequent machine breakdown, poor engineering support and limited cold chain and specimen transport logistics. This study assessed the performance of two CD4 tests designed for use in RLS; the Dynal assay and the Alere PIMA test (PIMA). Accuracy of Dynal and PIMA using venous blood was assessed in a centralised laboratory by comparison to BD FACSCount (BD FACS). Dynal had a mean bias of −50.35 cells/µl (r² = 0.973, p<0.0001, n = 101) and PIMA −22.43 cells/µl (r² = 0.964, p<0.0001, n = 139) compared to BD FACS. Similar results were observed for PIMA operated by clinicians in one urban (n = 117) and two rural clinics (n = 98). Using internal control beads, PIMA precision was 10.34% CV (low bead mean 214.24 cells/µl) and 8.29% (high bead mean 920.73 cells/µl) and similar %CV results were observed external quality assurance (EQA) and replicate patient samples. Dynal did not perform using EQA and no internal controls are supplied by the manufacturer, however duplicate testing of samples resulted in r² = 0.961, p<0.0001, mean bias = −1.44 cells/µl. Using the cut-off of 350 cells/µl compared to BD FACS, PIMA had a sensitivity of 88.85% and specificity of 98.71% and Dynal 88.61% and 100%. A total of 0.44% (2/452) of patient samples were misclassified as “no treat” and 7.30% (33/452) “treat” using PIMA whereas with Dynal 8.91% (9/101) as “treat” and 0% as “no treat”. In our setting PIMA was found to be accurate, precise and user-friendly in both laboratory and clinic settings. Dynal performed well in initial centralized laboratory evaluation, however lacks requisite quality control measures, and was technically more difficult to use, making it less suitable for use at lower tiered laboratories.

Gene expression profiling of immunomagnetically separated cells directly from stabilized whole blood for multicenter clinical trials

Background

Clinically useful biomarkers for patient stratification and monitoring of disease progression and drug response are in big demand in drug development and for addressing potential safety concerns. Many diseases influence the frequency and phenotype of cells found in the peripheral blood and the transcriptome of blood cells. Changes in cell type composition influence whole blood gene expression analysis results and thus the discovery of true transcript level changes remains a challenge. We propose a robust and reproducible procedure, which includes whole transcriptome gene expression profiling of major subsets of immune cell cells directly sorted from whole blood.

Methods

Target cells were enriched using magnetic microbeads and an autoMACS® Pro Separator (Miltenyi Biotec). Flow cytometric analysis for purity was performed before and after magnetic cell sorting. Total RNA was hybridized on HGU133 Plus 2.0 expression microarrays (Affymetrix, USA). CEL files signal intensity values were condensed using RMA and a custom CDF file (EntrezGene-based).

Results

Positive selection by use of MACS® Technology coupled to transcriptomics was assessed for eight different peripheral blood cell types, CD14+ monocytes, CD3+, CD4+, or CD8+ T cells, CD15+ granulocytes, CD19+ B cells, CD56+ NK cells, and CD45+ pan leukocytes. RNA quality from enriched cells was above a RIN of eight. GeneChip analysis confirmed cell type specific transcriptome profiles. Storing whole blood collected in an EDTA Vacutainer® tube at 4°C followed by MACS does not activate sorted cells. Gene expression analysis supports cell enrichment measurements by MACS.

Conclusions

The proposed workflow generates reproducible cell-type specific transcriptome data which can be translated to clinical settings and used to identify clinically relevant gene expression biomarkers from whole blood samples. This procedure enables the integration of transcriptomics of relevant immune cell subsets sorted directly from whole blood in clinical trial protocols.