Solid-organ transplant recipients can maintain peripheral immunity for up to 6 months after SARS-CoV-2 infection—especially with greater clinical severity—reports a pre-proof paper in Kidney International.
The researchers evaluated serologic and functional T-cell and B-cell immune memory against major immunogenic SARS-CoV-2 antigens. The cross-sectional study included two groups of COVID-19 convalescent patients: 53 solid-organ transplant recipients (38 kidney recipients) and 49 immunocompetent patients.
In both groups, patients were classified as having severe COVID-19, requiring hospitalization and supplemental oxygen; mild COVID-19, not requiring hospitalization; or asymptomatic infection. Immunologic assessments included SARS-CoV-2-specific serologic memory and immunoglobulin G (IgG)-producing memory B cells and SARS-CoV-2-reactive cytokine-producing memory T cells.
At a median follow-up of 199 days, memory responses in different immune compartments were similar for organ transplant recipients and immunocompetent patients. However, responses varied by COVID-19 severity: seroconversion rates for IgG antibodies to spike protein were 97.6% for patients with severe COVID-19, 80.5% for those with mild disease, and 42.1% for those with asymptomatic infection. For nucleoprotein antibodies, seroconversion rates were 92.7%, 75.6%, and 47.4%, respectively.
Similar ranges were found for IgG-producing memory B cells: severe infection, 84.0%; mild infection, 75.0%; and asymptomatic infection, 35.7%; for interferon-γ-producing T cells: 82.5%, 86.9%, and 31.6%, respectively. Regardless of COVID-19 severity, patients with longer times since solid-organ transplantation were more likely to have detectable long-lasting immune memory.
The study provides new data on long-term adaptive immune memory after SARS-CoV-2 infection in solid-organ transplant recipients. The findings show “robust humoral and cellular immune memory” lasting beyond 6 months, similar to that seen in immunocompetent patients.
Responses are driven mainly by the clinical severity of COVID-19, perhaps reflecting the level of viral antigen exposure. The researchers add, “[L]ong-lasting adaptive immunity seems to be challenged to some extent by chronic immunosuppression, especially among those more recently transplanted” [Favà A, et al. A comprehensive assessment of long-term SARS-CoV-2-specific adaptive immune memory in convalescent COVID-19 solid organ transplant recipients. Kidney Int, published online ahead of print February 3, 2022. doi: 10.1016/j.kint.2021.12.029; https://www.kidney-international.org/article/S0085-2538(22)00029-1/fulltext].