PBMCs are re-suspended in RPMI -10% (or RPMI -0 if RPMI -20% was used to prepare the antigen plates) and should not sit for more than one hour at room temperature. Do not place the cells on ice.
5.22.6. Count ≥300 cells for white blood count and ≥100 cells for viability. Adjust PBMC concentration to 1x106 viable cells/mL for dispensing into culture wells. For Pediatric protocols, some wells may be omitted if not enough PBMCs are obtained; follow guidelines in the protocol or the PIIS.
6. ASSAY SETUP
6.1.1. Thaw antigen/mitogen culture plates at 37°C in an incubator. Label the tissue culture plate with patient identification (PID), date plated, date to be pulsed with isotope and harvested.
6.1.2. Dispense 100μL of the PBMC suspension (106 cells/mL or 100,000 cells per well) into culture wells. Be certain to keep cells suspended, by gentle mixing, while the cells are being dispensed. Cells should be dispensed as soon as possible in order to avoid the medium becoming alkaline. This is day 0. It may be necessary to store LPA plates in bags inside the incubator if lack of humidity is a problem.
7. HARVESTING AND COUNTING
7.1. On the morning of day 6, pulse plates with 25μL/well (1μCi/well) of [H3]TdR.
7.2. After six hours, harvest on glass fiber filters using a cell harvester. If the cell harvester is not in a biohazard hood or splashing during harvesting is a concern, then add 25μL/well of a 5% Triton X-100 detergent solution to inactivate HIV. If harvesting can not be done immediately after the six-hour pulse, plates may be stored at –20°C until harvesting. Do not store plates at –20°C for more than a few days. Do not add Triton X-100 to plates prior to freezing because it causes bubbles during thawing.
7.3. After harvesting, filters are allowed to dry at room temperature on the bench top, punched-out into scintillation vials, or the filter sheets are processed for counting in a betaplate counter. Add scintillation fluid to vials/filters and leave filters in scintillation fluid according to the manufacturer’s directions prior to counting. Count vials/filters on a beta scintillation counter at laboratory-determined settings to measure counts per minute (cpm).
8. CALCULATIONS AND REPORTING OF RESULTS
8.1. LPA data can be expressed and calculated in two different ways following determination of mean values (e.g. from triplicates, quadruplicates); both methods make biological sense. Because the stimulation index (SI) is a ratio, it is greatly influenced by biologically insignificant variations in the low cpm levels of background, unstimulated wells.
8.2. SI = (cpm experimental/ cpm background unstimulated)
8.3. Net counts or cpm = (cpm experimental - cpm background unstimulated)
8.4. For multicenter trials, agreement is slightly better if the SI calculation is used, since the efficiency of counting of different scintillation counters varies. Raw data (cpm) from each culture well shall be entered electronically onto Excel®-based
PBMCs are re-suspended in RPMI -10% (or RPMI -0 if RPMI -20% was used to prepare the antigen plates) and should not sit for more than one hour at room temperature. Do not place the cells on ice.5.22.6. Count ≥300 cells for white blood count and ≥100 cells for viability. Adjust PBMC concentration to 1x106 viable cells/mL for dispensing into culture wells. For Pediatric protocols, some wells may be omitted if not enough PBMCs are obtained; follow guidelines in the protocol or the PIIS.6. ASSAY SETUP6.1.1. Thaw antigen/mitogen culture plates at 37°C in an incubator. Label the tissue culture plate with patient identification (PID), date plated, date to be pulsed with isotope and harvested.6.1.2. Dispense 100μL of the PBMC suspension (106 cells/mL or 100,000 cells per well) into culture wells. Be certain to keep cells suspended, by gentle mixing, while the cells are being dispensed. Cells should be dispensed as soon as possible in order to avoid the medium becoming alkaline. This is day 0. It may be necessary to store LPA plates in bags inside the incubator if lack of humidity is a problem.7. HARVESTING AND COUNTING7.1. On the morning of day 6, pulse plates with 25μL/well (1μCi/well) of [H3]TdR.7.2. After six hours, harvest on glass fiber filters using a cell harvester. If the cell harvester is not in a biohazard hood or splashing during harvesting is a concern, then add 25μL/well of a 5% Triton X-100 detergent solution to inactivate HIV. If harvesting can not be done immediately after the six-hour pulse, plates may be stored at –20°C until harvesting. Do not store plates at –20°C for more than a few days. Do not add Triton X-100 to plates prior to freezing because it causes bubbles during thawing.7.3. After harvesting, filters are allowed to dry at room temperature on the bench top, punched-out into scintillation vials, or the filter sheets are processed for counting in a betaplate counter. Add scintillation fluid to vials/filters and leave filters in scintillation fluid according to the manufacturer’s directions prior to counting. Count vials/filters on a beta scintillation counter at laboratory-determined settings to measure counts per minute (cpm).8. CALCULATIONS AND REPORTING OF RESULTS8.1. LPA data can be expressed and calculated in two different ways following determination of mean values (e.g. from triplicates, quadruplicates); both methods make biological sense. Because the stimulation index (SI) is a ratio, it is greatly influenced by biologically insignificant variations in the low cpm levels of background, unstimulated wells.8.2. SI = (cpm experimental/ cpm background unstimulated)8.3. Net counts or cpm = (cpm experimental - cpm background unstimulated)8.4. For multicenter trials, agreement is slightly better if the SI calculation is used, since the efficiency of counting of different scintillation counters varies. Raw data (cpm) from each culture well shall be entered electronically onto Excel®-based
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