Modulation of murine Lyme borreliosis by interruption of the B7/CD28 T-cell costimulatory pathway

Abstract

Recent studies have implicated cytokines associated with Th2 cells in the genetic resistance to murine Lyme borreliosis. Because the B7/CD28 costimulatory pathway has been shown to influence the differentiation of Th-cell subsets, we investigated the contribution of the B7 molecules CD80 and CD86 to the Th2 cytokine profile and development of arthritis in BALB/c mice infected with Borrelia burgdorferi. Effective blockade of CD86/CD28 interaction was demonstrated by elimination of interleukin 4 (IL-4) and upregulation of gamma interferon (IFN-gamma) responses by B. burgdorferi-specific T cells and by reduction of B. burgdorferi-specific immunoglobulin G. Despite the shift toward a Th1 cytokine pattern, which others have associated with disease susceptibility, the severity of arthritis was unchanged. Moreover, combined CD80/CD86 blockade by using anti-CD80 and anti-CD86 monoclonal antibodies or CTLA-4Ig enhanced IFN-gamma production over that seen with CD86 blockade alone, yet augmentation of this Th1-associated cytokine did not enhance disease. These results demonstrate that IL-4 production by T cells in B. burgdorferi-infected BALB/c mice is dependent upon CD86/CD28 interaction and that this cytokine does not contribute significantly to host resistance to the development of arthritis. In addition, combined CD80/CD86 blockade resulted in preferential expansion of IFN-gamma-producing T cells in B. burgdorferi infection, suggesting that costimulatory pathways other than B7/CD28 may contribute to T-cell activation during continuous antigen stimulation. These studies may provide insight into the role of the B7/CD28 pathway in other infectious and autoimmune diseases in which deviation of Th cell immune responses occurs and antigen is persistently present.

FIG. 1

Enhanced IFN-γ production by LNCs from B. burgdorferi-infected BALB/c mice treated with anti-CD80 and/or anti-CD86 MAb or CTLA-4Ig. (A) BALB/c mice were treated with antibodies to the indicated molecules or with control rat IgG as described in Materials and Methods. Bars represent the mean amount of IFN-γ present in the supernatants of pooled LNCs stimulated with B. burgdorferi lysates, as determined by ELISA, + standard error of the mean. These results are representative of three separate experiments. (B) BALB/c mice were treated with anti-CD80 and anti-CD86 MAbs, rat IgG, CTLA-4Ig, or L6 (control) as described in Materials and Methods. Bars represent the mean amount of IFN-γ produced by LNCs after restimulation with B. burgdorferi lysate, as determined by ELISA, + standard error of the mean. These results are representative of two separate experiments.

FIG. 2

T cells are required for IFN-γ production by LNCs of infected BALB/c mice treated with CTLA-4Ig. LNCs of infected BALB/c mice treated with the indicated reagents were restimulated in vitro after depletion of T cells by antibody- and complement-mediated cell lysis. Control cells were sham treated with antibody and complement. The bars represent the mean amount of IFN-γ produced after 72 h of incubation with B. burgdorferi lysate, as determined by ELISA, + standard error of the mean.

FIG. 3

Treatment of BALB/c mice with anti-CD86 MAb inhibits the development of IL-4-producing T cells. LNCs from mice treated with MAbs as described in the legend to Fig. 1A were stimulated in vitro with B. burgdorferi lysate, and levels of IL-4 were quantitated in supernatants by ELISA. The lower limit of IL-4 detection by this assay was 50 pg/ml. These results are representative of three independent experiments.