Background: Patients with primary antibody deficiencies, such as Common Variable Immunodeficiency (CVID), have some problems to assess immune response after coronavirus disease (COVID) vaccination. Cutaneous delayed-type hypersensitivity (DTH) has the potential to be used as a useful, simple, and cheaper tool to assess T-cell (T lymphocyte) function.
Methods: Seventeen patients with CVID, a rare disease, received two doses of the mRNA-based Pfizer-BioNTech COVID-19 vaccine. Humoral Immune Response (HIR) was determined by measuring specific immunoglobulin G (IgG) antibodies, and Cellular Immune Response (CIR) was evaluated using an ex vivo interferon-gamma release assay (IGRA) and in vivo by DTH skin test.
Results: Two weeks after the second dose of the vaccine, 12 out of 17 CVID patients have high optical density (OD) ratios of specific anti-spike protein (S) IgG whereas five patients were negative or low. Ex vivo CIR was considered positive in 14 out of 17 S1-stimulated patients. Unspecific stimulation was positive in all 17 patients showing no T-cell defect. A positive DTH skin test was observed in 16 CVID patients. The only patient with negative DTH also had negative ex vivo CIR.
Conclusions: The use of DTH to evaluate CIR was validated with an optimal correlation with the ex vivo CIR. The CIR after vaccination in patients with antibody deficiencies seems to have high precision and more sensitivity to antibodies-based methods in CVID.
Clinical implications: There is a remarkable correlation between cutaneous DTH and ex vivo IGRA after COVID vaccination. A COVID-specific skin DTH test could be implemented in large populations.
Capsule summary: Cutaneous delayed-type hypersensitivity has the potential to be used as a useful, simple, and cheaper tool to assess T-cell functioning.
Keywords: COVID vaccination; Common Variable Immunodeficiency (CVID); DTH; SARS-CoV-2; T-cell response; antibody deficiency; rare disease; skin test.