Mechanism of Action of Combined Short-Term CTLA4Ig and Anti-CD40 Ligand in Murine Systemic Lupus Erythematosus

Abstract

Short-term combination therapy with the costimulatory antagonists CTLA4Ig and anti-CD40 ligand induces prolonged suppression of disease onset in New Zealand Black/New Zealand White F1 systemic lupus erythematosus-prone mice. To determine the mechanism for this effect, 20- to 22-wk-old New Zealand Black/New Zealand White F1 mice were treated with six doses each of CTLA4Ig and anti-CD40 ligand Ab over 2 wk. Combination-treated mice, but not mice treated with either agent alone, had prolonged survival and the production of pathogenic IgG anti-dsDNA Ab was suppressed. Twenty weeks after completion of treatment the frequency of activated B cells producing anti-dsDNA Ab was decreased, and the abnormal transition of T cells from the naive to the memory compartment was blocked. Combination treatment partially suppressed class switching and decreased the frequency of somatic mutations in the VHBW-16 gene, which is expressed by pathogenic anti-DNA Abs. Treated mice were still able to respond to the hapten oxazolone when it was given 8 wk after treatment initiation, and they mounted a somatically mutated IgG anti-oxazolone response that was noncross-reactive with dsDNA. Fifty to 60% of previously treated mice, but only 14% of previously untreated mice, responded within 2–3 wk to a second course of therapy given at the onset of fixed proteinuria and remained well for a further 3–4 mo. Although this treatment had no immediate effect on serum anti-dsDNA Abs or on the abnormal T cell activation observed in sick mice, 25% of treated mice lived for >18 mo compared with 5% of untreated controls. These results suggest that the effect of costimulatory blockade in remission induction must be mediated by a different mechanism than is demonstrated in the disease prevention studies.

Mechanism of Action of Transmembrane Activator and Calcium Modulator Ligand Interactor-Ig in Murine Systemic Lupus Erythematosus

“…In preventive studies neither CTLA4-Ig, anti-CD40L, nor the combination of the two agents induced either a change in serum levels of Ig or a decrease in titers of IgM anti-DNA Abs, even in young mice (17,20,31). In contrast, these treatments inhibited class switching and somatic mutation and appeared to alter selection of autoreactive V region genes, consistent with their effect on delivery of T cell help to B cells (37).…”

“…Mice were bled at weekly intervals, and anti-Ox Abs were measured by ELISA as previously described (19). Mice were challenged with 50 g of Ox by skin paint 4 -6 wk later, and spleens were harvested for ELISPOT analysis as previously described (20) 3 days after boosting. To determine whether TACI-Ig interfered with established memory B cells in treated mice, 10 NZB/W F 1 mice, aged 14 wk, were immunized with 750 g of Ox.…”

“…Hybridomas were screened for anti-Ox or anti-dsDNA activity, and positive hybridomas were isotyped as previously described (20).…”

Targeting CD40L: a Promising Therapeutic Approach

“…It has been postulated that CTLA4Ig and anti-CD40L MAb treatment may act synergistically to block antiapoptotic signals and, hence, facilitate apoptosis of B cells during early B-cell activation. This treatment did not cause long-term global immunosuppression (66).…”

The Effect of BAFF Inhibition on Autoreactive B-Cell Selection in Murine Systemic Lupus Erythematosus

“…Our data underscore the complexity of regulation of the autoreactive B-cell repertoire by BAFF and may help to explain the heterogeneity of responses observed after BAFF inhibition in humans. Quantitation of autoantibodies to Cardiolipin and dsDna Serial enzyme-linked immunosorbent assays (ELISAs) of serum for antibodies to CL and dsDNA were performed as previously described (22,24,25).…”