Defining blood processing parameters for optimal detection of cryopreserved antigen-specific responses for HIV...

Area of Science:

• Immunology
• Vaccine Development
• Clinical Trials

Background:

• Interferon-gamma (IFN-gamma) ELISpot and intracellular cytokine staining (ICS) assays are vital for assessing T cell responses in HIV vaccine trials.
• Cryopreserved peripheral blood mononuclear cells (PBMC) are commonly used, but their immunological function can be affected by pre-analytical variables.
• Key variables include anticoagulant type, time to processing, isolation method, and shipping procedures.

Purpose of the Study:

• To investigate the impact of blood collection, processing, and shipping parameters on T cell function in immunological assays.
• To identify critical factors influencing the performance of IFN-gamma ELISpot assays in HIV vaccine clinical trials.

Main Methods:

• Evaluation of various parameters including anticoagulant, time from venipuncture to PBMC isolation/cryopreservation, PBMC isolation techniques, and cold shipping methods.
• Comparison of blood processed within 8 hours versus 24 hours post-venipuncture.
• Assessment of PBMC viability, cell recovery, and IFN-gamma T cell frequencies using ELISpot assay.

Main Results:

• The time from venipuncture to cryopreservation emerged as the most critical parameter affecting T cell assay performance.
• Processing blood at 24 hours post-venipuncture, compared to within 8 hours, resulted in an approximate 8% decrease in PBMC viability.
• Significant losses were observed in cell recovery (approximately 32%) and IFN-gamma T cell frequencies (36-56%) when processing was delayed.

Conclusions:

• Cryopreservation of PBMC should ideally occur within 8 hours of venipuncture to ensure optimal immunological assay performance.
• This finding highlights the importance of timely specimen processing for maintaining T cell function in clinical trials.
• Strict adherence to this processing window is essential for selecting and monitoring clinical sites with adequate laboratory capacity.