Assay Validated for CMV-Specific Immunity

Protection against CMV infection or reactivation is normally assured by both the innate and adaptive arms of the immune system.

Uncontrolled cytomegalovirus (CMV) replication in immunocompromised solid-organ transplant recipients is a clinically relevant issue and an indication of impaired CMV-specific cell-mediated immunity (CMI). Assessment of CMV-specific immunity may be beneficial to identify patients at increased risk of viral complications, possibly allowing personalized adjustment of antiviral and immunosuppressive therapies.

Physicians at the University Medical Center Regensburg and their colleagues recruited 124 hemodialysis patients of any gender and race aged at least 18 years. Lithium heparinized whole blood was collected during routine withdrawal, prior to the start of the dialysis session. Anti-CMV serological testing was performed using fully automated anti-CMV immunoglobulin M (IgM) and IgG tests on the BEP III system. CMV IgG-serology was used as primary reference measurement procedure, used as the gold standard method.

Peripheral blood mononuclear cells (PBMCs) were isolated and stimulated individually with T-activated CMV-specific immediate-early 1 (aIE-1) and phosphoprotein pp65 (app65) proteins for 19 hours at 37 °C and the T-Track CMV assay was performed. Interferon gamma (IFN-γ) ELISpot assays were performed and IFN-γ-specific spot-forming cells (SFC) were enumerated on a Bioreader 5000 Pro-Eα.

The scientists reported that positive T-Track CMV results were obtained in 60/67 (90%) of CMV-seropositive hemodialysis patients. In comparison, 73% (45/62) and 77% (40/52) positive agreement with CMV serology was achieved using two other methods. Positive T-Track CMV responses in CMV-seropositive patients were dominated by pp65-reactive cells in 58/67 (87%), while IE-1-responsive cells contributed to an improved (87% to 90%) positive agreement of T-Track CMV with CMV serology. Notably, T-Track CMV was able to detect IE-1-reactive cells in blood samples of patients with a negative CMV serology, suggesting either a previous exposure to CMV that yielded a cellular but no humoral immune response, or TCR cross-reactivity with foreign antigens, both suggesting a possible protective immunity against CMV in these patients.

The authors concluded that T-Track CMV is a highly sensitive assay, enabling the functional assessment of CMV-responsive cells in hemodialysis patients prior to renal transplantation. T-Track CMV represents a valuable immune monitoring tool to identify candidate transplant recipients potentially at increased risk for CMV-related clinical complications. The study was published on March 7, 2017, in the journal BMC Immunology.