B cells treated with CTB-p210 acquire a regulatory phenotype in vitro and reduce atherosclerosis in apolipoprotein E deficient mice

Objective: Intranasal immunization with a fusion protein of the ApoB100-derived peptide p210 and the cholera toxin B subunit (CTB-p210) has previously been shown to induce mucosal tolerance and reduce atherosclerosis development, but the exact mode of action remains to be elucidated. Recent studies have indicated an important role for B cells in mucosal tolerance, in particular by induction of regulatory B (Bregs) and T cells (Tregs). In this study, we aimed to investigate if transfer of B cells pulsed with CTB-p210 can protect against atherosclerosis. Method and results: First, we studied if CTB-p210 can induce Bregs and Tregs in vitro. After pulsing B cells from Apob^tm2Sgyldlr^−/− or Apoe^−/− mice with CTB-p210 for 1 h and co-culturing them with naïve T cells for 48 h, we observed increased expression of membrane bound TGFβ/latency-associated peptide (mTGFβ/LAP) on B cells and an increased proportion of CD25^hiFoxP3⁺ Tregs. Adoptive transfer of B cells pulsed with CTB-p210 into high-fat diet-fed Apoe^−/− mice at 8, 10 and 12 weeks of age, reduced the plaque area in the aorta at 20 weeks of age as compared with control-treated (CTB-pOVA treated B cells or PBS) mice. Moreover, mice receiving p210-CTB treated B cells had increased levels of anti-p210 IgG antibodies. Conclusion: Our observations suggest that CTB-p210 pulsed B cells acquire a regulatory phenotype and induce Tregs in vitro. Adoptive transfer of CTB-p210, but not control-treated, B cells into Apoe^−/− mice decreased atherosclerosis development.