Department of Immunology, Landspitali, The National University Hospital of Iceland, Reykjavik, Iceland.
J Infect Dis. 2012 Feb 1;205(3):422-30. doi: 10.1093/infdis/jir750. Epub 2011 Dec 7.
Repeated immunizations with polysaccharide (PS) vaccines cause hyporesponsiveness through undefined mechanisms. We assessed the effects of a PS booster on immune responses, frequency, and survival of PS-specific B-cell subpopulations in spleen and bone marrow.
Neonatal mice were primed with meningococcus serotype C (MenC) conjugate MenC-CRM(197)+CpG1826, boosted with MenC-CRM(197), MenC-PS, or saline; subsequently, bromodeoxyuridine (BrdU) was injected daily intraperitoneally. MenC-PS-specific cells were labeled with fluorescent MenC-PS and phenotyped by flow cytometry.
After MenC-PS booster, proliferating (BrdU(+)) MenC-PS-specific naive B cells (CD138(-)/B220(+); P = .0003) and plasma cells (CD138(+)/B220(-); P = .0002) in spleen were fewer than after saline booster. BrdU(+) MenC-PS-specific plasma cells were also reduced in bone marrow (P = .0308). Compared to saline, MenC-PS booster reduced BrdU(+) IgG(+) MenC-PS-specific B cells in spleen (P = .0002). Twelve hours after the MenC-PS booster, an increased frequency of apoptotic (AnnexinV(+)) MenC-PS-specific B cells in spleen was observed compared with MenC-CRM(197) (P = .0286) or saline (P = .001) boosters.
We demonstrated that the MenC-PS booster significantly reduced the frequency of newly activated MenC-PS-specific B cells-mostly switched IgG(+) memory cells-by driving them into apoptosis. It shows directly that apoptosis of PS-specific memory cells is the cause of PS-induced hyporesponsiveness. These results should be taken into account prior to consideration of the use of PS vaccines.
多糖（PS）疫苗的重复免疫会通过未知机制引起低反应性。我们评估了 PS 佐剂对免疫反应、频率以及脾和骨髓中 PS 特异性 B 细胞亚群存活的影响。
新生小鼠用脑膜炎球菌 C 型（MenC）结合物 MenC-CRM(197)+CpG1826 进行初始免疫，用 MenC-CRM(197)、MenC-PS 或生理盐水进行加强免疫；随后，每天经腹腔注射溴脱氧尿苷（BrdU）。用荧光标记的 MenC-PS 标记 MenC-PS 特异性细胞，并通过流式细胞术进行表型分析。
在 MenC-PS 加强免疫后，脾中增殖的（BrdU(+)）MenC-PS 特异性幼稚 B 细胞（CD138(-)/B220(+)；P =.0003）和浆细胞（CD138(+)/B220(-)；P =.0002）少于生理盐水加强免疫。骨髓中 BrdU(+) MenC-PS 特异性浆细胞也减少（P =.0308）。与生理盐水相比，MenC-PS 加强免疫减少了脾中 BrdU(+) IgG(+) MenC-PS 特异性 B 细胞（P =.0002）。在 MenC-PS 加强免疫后 12 小时，与 MenC-CRM(197)（P =.0286）或生理盐水（P =.001）加强免疫相比，脾中凋亡（AnnexinV(+)）的 MenC-PS 特异性 B 细胞频率增加。
我们证明，MenC-PS 佐剂通过诱导其凋亡，显著降低了新激活的 MenC-PS 特异性 B 细胞（主要是转换的 IgG(+)记忆细胞）的频率。这直接表明 PS 特异性记忆细胞的凋亡是 PS 引起低反应性的原因。在考虑使用 PS 疫苗之前，应考虑这些结果。
