The effect of splenectomy on the levels of PCV-13-induced memory B- and T cells.

AIM: Splenectomised patients are associated with lifelong risk of fatal overwhelming post-splenectomy infection (OPSI), which is mostly caused by Streptococcus pneumoniae. Today OPSI cases can still be reported even in patients with appropriate vaccination. In our study, the levels of vaccine-specific memory B- and T cells were compared between control and splenectomised patients to enlighten the underlying reason.

MATERIALS AND METHODS: Five healthy and 14 post-traumatic splenectomised individuals were vaccinated with 13-valent pneumococcal conjugate vaccine (PCV-13) followed by 23-valent pneumococcal polysaccharide vaccine (PPV-23). The levels of memory B- and T cells were compared by ELISPOT analysis.

RESULTS: Splenectomised patients generated reduced levels of memory IgG B cells in response to PCV-13 vaccination, while the memory IFN-γ T-cell levels were undetectable in asplenic patients. This was despite the detection of vaccine-induced memory T-cell levels in control patients, which were analysed simultaneously following the same experimental protocol.

CONCLUSION: Our results suggest that spleen is important, but not essential, for survival and/or generation of memory IgG B cells. In contrast, it seems to be indispensable for PCV-13-specific memory TH 1-cell levels. Studies enhancing the levels of vaccine-induced memory cells and further enlightening the immune responses in asplenic individuals are required to develop more effective vaccination strategies against OPSI.