Targeting B and T Lymphocyte Attenuator Regulates Lupus Disease Development in NZB/W Mice

The co-inhibitory receptor B and T Lymphocyte Attenuator (BTLA) negatively regulates B and T cell activation. We have previously shown an altered BTLA expression by regulatory T cells and an impaired capacity of BTLA to inhibit CD4⁺ T cell activation in lupus patients. In this study, we analyzed BTLA expression and function in the NZB/W lupus-mouse model and examined the therapeutic potential of BTLA targeting.

BTLA expression and function were analyzed in young (10-12-week-old) and old-diseased NZB/W mice (>35-week-old with proteinuria) in comparison to age-related BALB/W control mice. 20-22 weeks old NZB/W mice (n=10) were injected i.p with 3 mg/kg, twice a week for ten weeks, with the anti-BTLA antibody 6F7 or its isotype control.

In old-diseased NZB/W mice, BTLA expression is slightly modified in B cell subsets whereas CD4⁺ T cells display impaired BTLA functionality. Administration of the 6F7 anti-BTLA antibody into 20-22 week-old NZB/W mice resulted in a delayed onset of proteinuria (p<0.01), limited kidney damages (p<0.05) and an increased survival rate (p<0.01) compared to isotype-treated mice. This beneficial effect was associated with a decrease in circulating B cell and spleen follicular B cell numbers. Regarding its mode of action, we demonstrated that the 6F7 antibody is not a depleting antibody and does not block HVEM binding to BTLA, but instead induces BTLA down modulation and exhibits in vivo agonist activity.

Overall, our data confirm the involvement of BTLA in lupus pathogenesis and provide the first evidence that BTLA is a potential therapeutic target for the treatment of lupus.