Treatment of spontaneous EAE by laquinimod reduces Tfh, B cell aggregates, and disease progression.

OBJECTIVE

To evaluate the influence of oral laquinimod, a candidate multiple sclerosis (MS) treatment, on induction of T follicular helper cells, development of meningeal B cell aggregates, and clinical disease in a spontaneous B cell-dependent MS model.

METHODS

Experimental autoimmune encephalomyelitis (EAE) was induced in C57BL/6 mice by immunization with recombinant myelin oligodendrocyte glycoprotein (rMOG) protein. Spontaneous EAE was evaluated in C57BL/6 MOG p35-55-specific T cell receptor transgenic (2D2) × MOG-specific immunoglobulin (Ig)H-chain knock-in (IgH [Th]) mice. Laquinimod was administered orally. T cell and B cell populations were examined by flow cytometry and immunohistochemistry.

RESULTS

Oral laquinimod treatment (1) reduced CD11cCD4 dendritic cells, (2) inhibited expansion of PD-1CXCR5BCL6 T follicular helper and interleukin (IL)-21-producing activated CD4CD44 T cells, (3) suppressed B cell CD40 expression, (4) diminished formation of FasGL7 germinal center B cells, and (5) inhibited development of MOG-specific IgG. Laquinimod treatment not only prevented rMOG-induced EAE, but also inhibited development of spontaneous EAE and the formation of meningeal B cell aggregates. Disability progression was prevented when laquinimod treatment was initiated after mice developed paralysis. Treatment of spontaneous EAE with laquinimod was also associated with increases in CD4CD25Foxp3 and CD4CD25IL-10 regulatory T cells.

CONCLUSIONS

Our observations that laquinimod modulates myelin antigen-specific B cell immune responses and suppresses both development of meningeal B cell aggregates and disability progression in spontaneous EAE should provide insight regarding the potential application of laquinimod to MS treatment. Results of this investigation demonstrate how the 2D2 × Th spontaneous EAE model can be used successfully for preclinical evaluation of a candidate MS treatment.