SC-45 Comparing T-Spot and in-house IGRA for assessing SARS-CoV-2-specific cell-mediated immunity

• Published in: Sexually transmitted infections Vol. 100; no. Suppl 1; pp. A115 - A116
• Main Authors: Benedetti, L, Ferrari, L, Ruggiero, A, Braccialarghe, N, Piermatteo, L, Sarmati, L, Geretti, AM, Iannetta, M
• Format: Journal Article
• Language: English
• Published: London BMJ Publishing Group Ltd 01.06.2024; BMJ Publishing Group LTD
• Subjects: Antiretroviral drugs; HIV; Human immunodeficiency virus; Medical personnel; Peptides; Severe acute respiratory syndrome coronavirus 2; Short Communication; Vaccines
• ISSN: 1368-4973; 1472-3263
• DOI: 10.1136/sextrans-ICAR-2024.105

BackgroundDifferent approaches can be used to assess SARS-CoV-2-specific cell-mediated immunity (CMI) as a tool to improve COVID-19 prevention and care in immunocompromised patients, such as people living with HIV. Here we compare our in-house interferon (IFN)-γ release assay (IGRA) with a commercial T-spot assay (Oxford Immunotec).Materials and Methods Whole blood samples were collected from adults with HIV and healthcare workers. For the IGRA, blood was stimulated overnight with partially overlapping peptides covering the Spike (S) and Nucleocapsid (N) proteins of SARS-CoV-2 in two separate assays. IFN-γ production in supernatants was assessed with the ELLA platform, offering automated and highly sensitive quantification. For the T-spot assay, PBMCs were isolated and stimulated with partially overlapping peptides covering S and N proteins. Antigen specific IFN-γ producing T-cells were counted in an elispot reader; the positivity cutoff was the formation of ≥8 spots. Both methods included negative (NS) and positive (PHA) controls. The assay turn-around time was 24 hours for IGRA and 48 hours for T-spot (including PBMC isolation). The two assays were evaluated in ROC analyses and by the Spearman’s correlation test.ResultsWe enrolled 24 participants with HIV (15 males and 9 females) with a median age of 57 years (IQR 42–61), median nadir CD4 count of 124 cells/µL (32–420), median current CD4 count of 705 cells/µL (404–967), and median CD4/CD8 ratio of 0.9 (0.5–1.4); all were on antiretroviral treatment and 20/24 (83%) had HIV-RNA <50 copies/mL. All were vaccinated with the BNT162b2 vaccine; 1/24 (4%) received 2 doses; 17/24 (70%) 3 doses and 6/24 (25%) 4 doses; 10/24 (42%) had received a prior diagnosis of SARS-CoV-2 infection. Median time from last vaccination or documented infection was 18 months (IQR 14–22). Five vaccinated (three BNT162b2 vaccine doses) healthcare workers (1 male and 4 females) with a median age of 35 years (33–43) were also enrolled. The number of spots in T-spot assay correlated with the level of IFN-γ production in the IGRA (Spearman’s rho 0.65 [p<0.001] for S and Spearman’s rho 0.6 [p<0.001] for N, respectively) (figure 1). ROC analysis confirmed the association between the two tests (S: area 0.8, p=0.007; N: area 0.9, p=0.004). Applying the Youden’s J method, two cutoffs for the IGRA were identified, whereby IFN-γ levels >89 pg/mL and >69 pg/mL after S and N stimulation, respectively, were associated with a positive T-spot result (figure 1).ConclusionsOur study demonstrated a strong association between our in-house IGRA and the T-spot assay for measuring SARS-CoV-2 specific CMI, with comparable performance in healthy subjects and people living with HIV. The ultrasensitive detection of IFN-γ production in supernatants with the ELLA platform, coupled with the accessibility and rapidity of the assay, enhances the relevance of IGRA for the routine assessment of SARS-CoV-2-specific CMI.Abstract SC-45 Figure 1IFN-γ production after S and N peptide stimulation in the two tests correlates