TABLE 1.
Cell-mediated immunity assays to detect cytomegalovirus-specific T cell immunity
| CMV-CMI assay type | Method | Equipment requirement | Commercial test available (manufacturer)b | Cutoff value for positivity | Clinical scenario in organ transplantation (selected references) | Available interventional studies (reference)a |
|---|---|---|---|---|---|---|
| ELISA | Enzyme-linked immunosorbent assay (ELISA)-based IFN-gamma release assay, capable of detecting CD8+ T cell response after peptide stimulation | ELISA plate reader | QuantiFERON-CMV (Qiagen Inc.)c | 0.2 IU/mL | Pre-transplant risk stratification (14, 29, 33, 35–37); adjunct to pre-emptive monitoring (26, 31); assessment at time of discontinuation of prophylaxis (18–22, 28, 38) | Several (14, 21, 25–27, 30) |
| ELISpot | Highly sensitive immunoassay that measures the frequency of both CD4+ and CD8+ T cells producing IFN-gamma in response to CMV-specific peptides or whole proteins | ELISpot reader | T.Spot.CMV (Oxford Diagnostics); laboratory-developed test in the United StatesT-Track (Lophius Bioscience/Mikrogen GmBH)c | 20–40 spot forming units after stimulation with either IE-1 or pp65 | Pretransplant risk stratification (29, 32, 39, 40); adjunct to pre-emptive monitoring (15, 41, 42); assessment at time of discontinuation of prophylaxis (6, 43) | Few interventional studies (32) |
| Intracellular cytokine staining | Intracellular cytokine staining for IFN-gamma using flow cytometry; whole blood or isolated PBMCs are stimulated with CMV peptides or CMV lysate and stained with monoclonal antibody against IFN-gamma; other cytokine markers can now be tested at the same time; provides quantitative and qualitative assessment | Flow cytometer and intracellular and extracellular markers | CMV Insight T cell immunity testing (Eurofins Viracor); laboratory-developed test in the United States | >0.2% for the commercial assay (multiple research assays) | Pretransplant risk stratification (34, 44, 45); pre-emptive monitoring (46–48); assessment at time of discontinuation of prophylaxis (49, 50) | None |
| MHC multimer staining | Whole-blood assay that directly stains peptide-specific T cells using peptide-conjugated MHC class I tetramers or pentamers | CMVC8 (Mayo Clinic Laboratories) | None established | Observational studies for posttransplant monitoring and risk assessment (51) | None |
a
Interventional study denotes a prospective study where CMV-CMI is used in clinical decision-making.
b
Laboratory Developed Test in the United States describe the test that they follow.
c
CE-marked in Europe, Conformité Européenne Mark (French) - declaration that the product meets regulatory body statndards and is licensed for use in Europe.