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

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 I (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.