(517) Characterization of the B1 Cell Repertoire in Sickle Cell Disease Pre- and Post-Pneumococcal Vaccination

Introduction/Rationale: Rationale: Patients with sickle cell disease (SCD) are 600 times more susceptible to S. pneumoniae infections than the general population. This increased risk is mainly attributed to the absence of a functional spleen in SCD patients. However, those with SCD remain more susceptible than those without a functional spleen for reasons unrelated to SCD. Although vaccination has helped counteract this increased risk, pneumococcal infection remains a significant threat to patients with SCD. CD5+B1a cells produce natural antibodies that provide immediate protection against pneumococcal infections, whereas CD5-B1b cells produce protective adaptive antibodies in response to pneumococcal vaccination.

Methods:

Methods: We examined the peritoneal and splenic CD5+B1a and CD5-B1b cell repertoires pre- and post-vaccination with Pneumovax23 (PPSV23) in mice with sickle cell disease (Townes model) and compared them with healthy controls. PPSV23 is a native vaccine that covers 23 pneumococcal serotypes and elicits a T-cell-independent response. CD5+B1a and CD5-B1b cells were single-cell sorted from mice with SCD and healthy controls (wild type) pre- and 14 days post-PPSV23 vaccination. The variable heavy chain (IgM) was amplified by PCR and sequenced.

Results:

Results: Single-cell BCR repertoire analysis demonstrated significant differences in VH use (notably VH11 and VH12) and the number of N-region additions (more N-additions pre- and post-vaccination in SCD mice) between wild-type and SCD mice. In mice with SCD, B1 cells over-utilized different identical CDR-H3 sequences compared to wild-type mice.

Conclusion:

Conclusion: Our results revealed significant differences in the pre- and post-PPSV23 vaccination repertoire of B1 cells in SCD mice compared to healthy mice, offering insights into the effectiveness of pneumococcal vaccination in SCD. These results provide a rationale for optimizing vaccine strategies and developing targeted immunotherapies to enhance immune protection in patients with SCD.