Performance of new pp65-IGRA for the quantification of HCMV specific CD4 + T cell response in healthy subjects and in solid organ transplant recipients

Dalila Mele¹Federica Zavaglio¹Federica Bergami¹Giuditta Comolli¹Irene Cassaniti^1,2Daniele Lilleri^1*Fausto Baldanti^1,2

• ¹Department of Microbiology and Virology, San Matteo Hospital Foundation (IRCCS), Pavia, Lombardy, Italy
• ²Department of Clinical-Surgical, Diagnostic and Pediatric Sciences, University of Pavia, Pavia, Lombardy, Italy

Immune control of HCMV replication is critical in bone marrow and solid organ transplant recipients, where uncontrolled replication can lead to high mortality. Current commercial immune monitoring tools have several limitations, such as lack of appropriate test cut-off values and the inability to characterise antigen-specific T cells. The main aim of our study was to develop a new Interferon (IFN)-γ release assays (IGRA), easy to use, to quantify and characterise the HCMV-specific T cell response (pp65-IGRA). Secondary analyses included an evaluation of the performance of pp65-IGRA to assess whether its specificity and sensitivity were equal to or greater than those of the intracellular cytokine staining (ICS) and ELISpot assays. In the study were enrolled 76 immunocompetent donors and 9 solid organ transplant recipients. Blood samples or PBMC were stimulated with HCMV pp65-Recombinant Protein or with a complete pool of overlapping pp65 peptides. IFN-γ production was analysed by ELISA, ELISpot assays and flow cytometry. For each assay, appropriate cut-off values were calculated. Our data demonstrate the suitability of pp65-IGRA for the quantification of HCMV-specific CD4 + T-cell responses and may support its use in routine clinical practice to improve the management of immunocompromised patients.