Immunogenicity of quadrivalent meningococcal conjugate vaccine in frequent platelet donors

Frequent plateletpheresis is associated with severe lymphopenia of uncertain clinical significance. We assessed the functional impact of frequent platelet donations and associated lymphopenia on the response to neoantigens. We conducted a prospective study of 102 platelet donors (HIV uninfected) who were naive to meningococcal vaccination recruited at Brigham and Women's Hospital. One dose of quadrivalent meningococcal conjugate vaccine was administered. Seroresponse was defined as a fourfold increase of serum bactericidal antibody titers and seroprotection was defined as postvaccination titers of ≥1:8, for each of the 4 vaccine antigens (A, C, W, and Y). Mean age of participants was 61 years, 69% were male, and medial number of platelet donations in prior year was 14 (interquartile range, 4-20). Frequent platelet donors had a low CD4 count (14% with ≤200/μL and 34% with ≤350/μL). Seroresponse rates varied from 68% for serogroup Y to 86% for serogroup A and were higher for participants with baseline titers of <1:8. Postvaccination seroprotection rates varied from 76% for serogroup Y to 96% for serogroup A. After adjustments for age, sex, and frequent donations, lower total lymphocyte or lower CD4 counts were not associated with lower responses. These data suggest no impairment by plateletpheresis-associated lymphopenia on response to these neoantigens. This trial was registered at www.clinicaltrials.gov as #NCT04224311.

996. CD4+ T-Cell Lymphopenia Associated with Frequent Plateletpheresis in Healthy Donors

Background

Frequent plateletpheresis using the Time Accel leukoreduction system chamber may result in lymphopenia in healthy donors, with increased donation in the previous year associated with CD4+ T-cell count of less than 200 cells/µL. However, this finding has not been replicated and the clinical significance of plateletpheresis-associated lymphopenia remains unclear.

Methods

A prospective observational study of healthy plateletpheresis donors aged 18 or older who donated at least once in the previous 365 days was conducted at the Kraft Blood Center at Brigham and Women’s Hospital/Dana Farber Cancer Institute, where the Time Accel system is used exclusively. Blood was drawn immediately before plateletpheresis or at least 2 weeks after the last donation to assess for total lymphocyte and CD4+ T-cell counts.

Results

A total of 86 participants were enrolled: 23 had 1-5 donations, 36 had 6-19 donations, and 27 had 20-24 donations within the previous 365 days (Figure 1). For the low-, medium-, and high-frequency donation groups, the median age was 53 years (IQR 43-64), 61 years (IQR 53-68), and 61 years (IQR 55-65), respectively. The median total lymphocyte count was 1.5 (IQR 1.3-1.9), 1.2 (IQR 0.9-1.5), 0.8 (IQR 0.6-0.9) 10³ cells/µL, and the median CD4+ T-cell count was 648 (IQR 531-843), 525 (IQR 348-698), and 220 (IQR 184-347) cells/µL. CD4+ T-cell counts were < 200 cells/µL in 0/23 (0%), 3/36 (8%), and 9/27 (33%) participants across the three groups. Total lymphocyte and CD4+ T-cell counts were inversely correlated with the number of platelet donations in the prior 365 days, R² = 0.384 (Fig 2) and 0.402 (Fig 3) respectively.

Conclusion

Frequent plateletpheresis using Time Accel leukoreduction system chamber is associated with CD4+ T-cell lymphopenia, with counts below 200 cells/µL seen in one third of those who donated 20-24 times in the previous year. Vaccine immunogenicity studies are ongoing to evaluate the clinical significance of this finding.

Disclosures

Stephen R. Walsh, MDCM, Janssen Vaccines (Scientific Research Study Investigator)Regeneron (Scientific Research Study Investigator)Sanofi Pasteur (Scientific Research Study Investigator)