A comparative performance evaluation of the VIDAS cytomegalovirus (CMV) interferon-gamma release assay (IGRA) and T-SPOT CMV for measuring CMV-specific T-cell responses in allogeneic hematopoietic stem cell transplant recipients receiving letermovir prophylaxis.

UNLABELLED: Assessment of cytomegalovirus (CMV) cell-mediated immunity (CMV-CMI) using standardized, commercially available interferon-gamma release assays (IGRAs) may improve the clinical management of CMV infection in allogeneic hematopoietic stem cell transplant recipients (allo-HCT). Studies comparing the performance of CMV IGRA assays have been conducted in this setting, revealing frequent discrepancies between assays. Here, we compared the performance of a newly released VIDAS CMV IGRA (bioMérieux) and the T-SPOT. CMV (Oxford Immunotec) was evaluated in a cohort of 85 allo-HCT recipients who received letermovir prophylaxis. A total of 107 whole blood samples were collected at either day +100 (n = 53) or day +180 (n = 54) after allo-HCT and analyzed in parallel. A moderate qualitative agreement between assays was observed (Cohen's kappa coefficient, 0.47; 95% CI, 0.30-0.63). Discrepant results were obtained in 29 specimens, most of which were collected at day +100. A moderate correlation (rho, 0.54; P < 0.001) was observed between T-SPOT pp65-SPC and IFN-γ levels measured by the VIDAS CMV assay, whereas the correlation was weaker for T-SPOT IE-1 SPC and VIDAS IFN-γ levels (rho, 0.32; P < 0.001). The previously described booster effect of CMV DNAemia on the magnitude of CMV-CMI was captured by the VIDAS CMV assay. Neither the qualitative nor the quantitative results obtained with either IGRA predicted protection from CMV DNAemia following LMV discontinuation. While our data support the validity of the VIDAS CMV assay for the assessment of CMV-CMI in allo-HCT, they reinforce the idea that results from commercially available IGRA assays are not interchangeable, particularly in allo-HCT recipients with impaired CMV-CMI reconstitution.

IMPORTANCE

This is the first study comparing a new interferon-gamma release assay (IGRA), the VIDAS cytomegalovirus (CMV), performed on whole blood and based on an enzyme-linked immunofluorescent assay detection technique, with a commercially available ELISpot assay (T-SPOT CMV) for measuring CMV-specific T-cell responses (CMV-CMI). Our cohort included allogeneic hematopoietic stem cell transplant recipients who underwent letermovir prophylaxis. In this clinical setting, tailoring the duration of LMV prophylaxis based on CMV-CMI at the time of drug discontinuation has emerged as a promising application of these assays. Our data revealed substantial qualitative and quantitative differences between the assays, which should be taken into consideration in future observational studies or clinical trials assessing the utility of IGRAs for individualizing LMV prophylaxis duration.