Background: Cytomegalovirus (CMV) is a common viral infection, with sero-prevalence in Australia around 60%. In immunocompromised patients, it can lead to serious disease. CMV functional assays provide more in-depth information regarding CMV control by the immune system, supplementing CMV serology and viral load. We developed a fit for purpose CMV specific T cell functional flow cytometry assay that has been incorporated into our routine clinical work.

Objectives: Establish whether there is reduced CMV specific T cell response using our CMV flow cytometry-based assay in CMV seropositive immunocompromised participants.

Methods: CMV T cell functional assay

Whole blood samples were incubated for 48 hours with tube 1) Negative control (no stimulus), tube 2) Positive control (polyclonal T cell activator), and tube 3) CMV pp65 peptide pool. Samples were analysed with T cell activation markers for CD4+ T cells (CD4+ CD25+ CD134+) and CD8+ T cells (CD8+ CD25+CD137+) using flow cytometry.

Participants recruitment and analysis

This study was conducted as a cross-sectional study. We recruited 52 healthy participants to establish the reference range for polyclonal T cell and CMV specific T cell response. We also recruited 82 immunocompromised participants. For the final analysis, we reviewed the CMV seropositive participants with immunodeficiency secondary to immunosuppression use (n=32). We also collected relevant CMV serology, IgG, IgA, IgM, lymphocyte subsets, and relevant clinical notes were reviewed.

Results: A reference range was established for the polyclonal T cell response and CMV specific T cell response using healthy controls. For the secondary immunodeficiency due to immunosuppression cohort (n=32), the majority were on T cell dominant immunosuppression, with methotrexate or mycophenolate in combination with other immunosuppression the most common. The most common autoimmune disease in this cohort was SLE (15.6%). Seven participants (21.9%) had current CMV viraemia or disease. Nine participants with a positive polyclonal response did not have a detected CMV T cell response, indicating an impaired CMV specific T cell immunity.

Conclusions: This study has demonstrated the feasibility of a novel CMV T cell flow cytometry functional assay in a cohort of immunocompromised participants. We envisage that this assay has the potential to contribute to clinical decision-making for CMV prophylaxis and/or treatment.

REFERENCES: NIL.

Acknowledgments: NIL.

Disclosure of Interests: None declared.