Polyfunctional Analysis of Human Cytomegalovirus (HCMV)-Specific CD4⁺ and CD8⁺ Memory T-Cells in HCMV-Seropositive Healthy Subjects Following Different Stimuli

Purpose: Following primary human cytomegalovirus (HCMV) infection, both humoral and T-cell-mediated immune responses develop in immunocompetent subjects. However, while antibodies may be measured by different methodologies, the T-cell-mediated response remains to be analyzed in its polyfunctional aspects, in view of defining (following different stimuli) the optimal assay to monitor the HCMV-specific T-cell response in HCMV-seropositive subjects.

Methods: In a group of 30 HCMV-seropositive adults, T-cell response revealed by the HCMV-infected dendritic cell (iDC) stimulus was compared with those given by the HCMV-infected cell lysate (iCL), and by a 34-peptide pool (PP).

Results: All HCMV-seropositive subjects showed presence of both HCMV-specific CD4⁺ and CD8⁺ T-cells in peripheral blood following iDC stimulation. One subject did not respond to PP. As compared to iDC, the number of HCMV-specific stimulated T-cells/μl blood was slightly lower for iCL (P = 0.195) and significantly lower for PP (P = 0.001). Polyfunctional analysis of the T-cell response indicated that the lower number of CD4⁺ T-cells stimulated by iCL was due to the bifunctional (IFN-γ⁺ TNF-α⁺) and CD40L-negative T-cell reduction, while the reduction in specific PP-stimulated CD8⁺ T-cells was attributable to the reduction in tri-(IFN-γ⁺ TNF-α⁺ IL2⁺), bi-(IFN-γ⁺ TNF-α⁺) and mono-(IFN-γ⁺) functional T-cells. In addition, 15/30 (50 %) subjects showed a CD4⁺ cross-response to PP, and 11/30 (37 %) a CD8⁺ cross-response to iCL.

Conclusions: HCMV-specific stimulus given by iDC is not significantly different from that of iCL on CD4⁺ and is significantly superior to that of PP on CD8+ T-cells. However, iCL may contribute significantly to CD8⁺, and PP to CD4⁺ T-cell stimulation.