COVID‐19 vaccine humoral response in frequent platelet donors with plateletpheresis‐associated lymphopenia

Abstract

Background: Plateletpheresis involves platelet separation and collection from whole blood while other blood cells are returned to the donor. Because platelets are replaced faster than red blood cells, as many as 24 donations can be done annually. However, some frequent apheresis platelet donors (>20 donations annually) display severe plateletpheresis-associated lymphopenia; in particular, CD4 + T but not B cell numbers are decreased. COVID-19 vaccination thereby provides a model to assess whether lymphopenic platelet donors present compromised humoral immune responses. Study Design and Methods: We assessed vaccine responses following 2 doses of COVID-19 vaccination in a cohort of 43 plateletpheresis donors with a range of pre-vaccination CD4 + T cell counts (76-1537 cells/μl). In addition to baseline T cell measurements, antibody binding assays to full-length Spike and the Receptor Binding Domain (RBD) were performed pre-and post-vaccination. Furthermore, pseudo-particle neutralization and antibody-dependent cellular cytotoxicity assays were conducted to measure antibody functionality. Results: Participants were stratified into two groups: <400 CD4/μl (n = 27) and ≥ 400 CD4/μl (n = 16). Following the first dose, 79% seroconverted within the <400 CD4/μl group compared to 87% in the ≥400 CD4/μl group; all donors were seropositive post-second dose with significant increases in antibody levels. Importantly differences in CD4 + T cell levels minimally impacted neutralization, Spike recognition, and IgG Fc-mediated effector functions.Discussion: Overall, our results indicate that lymphopenic plateletpheresis donors do not exhibit significant immune dysfunction; they have retained the T and B cell functionality necessary for potent antibody responses after vaccination.

Risk factors for T‐cell lymphopenia in frequent platelet donors: The BEST collaborative study

“…Two recent studies examined immunologic responses to vaccination in frequent platelet donors. In a study of 43 frequent platelet donors collected using an LRS chamber, Laumaea et al 14 found that seroresponses to COVID‐19 mRNA vaccination were essentially identical among donors with CD4 + T‐cell counts below 400/μL versus those with counts at or above 400/μL. Desjardin et al 15 evaluated seroresponses to a quadrivalent Neisseria meningitidis vaccine in 102 vaccine‐naïve frequent platelet donors collected using an LRS chamber.…”

Duties to donors

“…In one, COVID-19 MRNA vaccine responses were similar for donors with CD4+ T-cell counts both above and below 400 cells/μL. 9 In the other, a group of frequent donors, some 34% of whom had CD4+ T-cell counts <350 cells/μL, had, nonetheless, normal responses to meningococcal conjugate vaccine. 10 While it is encouraging that there is some evidence that lymphopenic study subjects are not at risk for morbidity or impaired immune response, Kaufman et al appropriately remind the reader that volunteers must be in good health to be accepted as apheresis platelet donors.…”

“…In a study reporting on the duration of apheresis‐associated lymphopenia, Rahmani et al commented that lymphopenia in their group of frequent donors who had not given for a year “is not harmful.” 8 As reassurance for those concerned about lymphopenia and an impaired immune response, the BEST group cited two recent vaccination studies. In one, COVID‐19 MRNA vaccine responses were similar for donors with CD4+ T‐cell counts both above and below 400 cells/μL 9 . In the other, a group of frequent donors, some 34% of whom had CD4+ T‐cell counts <350 cells/μL, had, nonetheless, normal responses to meningococcal conjugate vaccine 10…”

“…For some donors this information might be especially beneficial. In the study by Laumaea et al 9 that revealed appropriate humoral immune response to COVID‐19 vaccine in lymphopenic platelepheresis donors, the investigators included comment about the importance of donors learning about their lymphopenia, lest that finding put them at unnecessary risk of invasive investigations of low counts.…”