Agonistic αCD40 Ab’s have been shown to be potent immune adjuvants for both cell- and humoral-mediated immunity. While enhancing short-lived humoral immunity, the administration of a CD40 agonist during thymus-dependent immune responses ablates germinal center formation, prematurely terminates the humoral immune response, blocks the generation of B cell memory, and prevents the generation of long-lived bone marrow plasma cells. Interestingly, some of these effects of heightened CD40 engagement could be mimicked by enhancing the magnitude of antigen-specific T cell help. Taken together, these studies demonstrate that as the magnitude of CD40 signaling intensifies, the fate of antigen-reactive B cells can be dramatically altered. These are the first studies to describe the multifaceted function of CD40 in determining the fate of antigen-reactive B cells and provide novel insights into how CD40 agonists can short-circuit humoral immunity.
Loren D. Erickson, Brigit G. Durell, Laura A. Vogel, Brian P. O’Connor, Marilia Cascalho, Teruhito Yasui, Hitoshi Kikutani, Randolph J. Noelle
Glatiramer acetate (GA; Copaxone) is a random copolymer of glutamic acid, lysine, alanine, and tyrosine that is used therapeutically in patients with multiple sclerosis (MS). To investigate the mechanism of the drug’s immunomodulatory effect, we used immunophenotypic approaches to characterize the precise nature of GA-induced T cell responses. We demonstrate here that healthy individuals and untreated MS patients exhibit prominent T cell proliferative responses to GA. However, these responses are different in distinct subsets of T cells. Whereas GA-induced CD4+ T cell responses are comparable in healthy individuals and MS patients, CD8+ T cell responses are significantly lower in untreated MS patients. Treatment with GA results in upregulation of these CD8+ responses with restoration to levels observed in healthy individuals. Both CD4+ and CD8+ GA-specific responses are HLA-restricted. GA therapy also induces a change in the cytokine profile of GA-specific CD4+ and CD8+ T cells. This study provides the first direct immunophenotypic evidence, to our knowledge, of GA-specific CD8+ T cell responses and their upregulation during the course of therapy, which may suggest a role for these responses in the immunomodulatory effects of the drug.
Nitin J. Karandikar, Michael P. Crawford, Xiao Yan, Robert B. Ratts, Jason M. Brenchley, David R. Ambrozak, Amy E. Lovett-Racke, Elliot M. Frohman, Peter Stastny, Daniel C. Douek, Richard A. Koup, Michael K. Racke
Treatment of advanced, poorly immunogenic tumors in animal models, considered the closest simulation available thus far for conditions observed in cancer patients, remains a major challenge for cancer immunotherapy. We reported previously that established tumors in mice receiving an agonistic mAb to the T cell costimulatory molecule 4-1BB (CD137) regress due to enhanced tumor antigen–specific cytotoxic T lymphocyte responses. In this study, we demonstrate that several poorly immunogenic tumors, including C3 tumor, TC-1 lung carcinoma, and B16-F10 melanoma, once established as solid tumors or metastases, are refractory to treatment by anti–4-1BB mAb. We provide evidence that immunological ignorance, rather than anergy or deletion, of tumor antigen–specific CTLs during the progressive growth of tumors prevents costimulation by anti–4-1BB mAb. Breaking CTL ignorance by immunization with a tumor antigen–derived peptide, although insufficient to stimulate a curative CTL response, is necessary for anti–4-1BB mAb to induce a CTL response leading to the regression of established tumors. Our results suggest a new approach for immunotherapy of human cancers.
Ryan A. Wilcox, Dallas B. Flies, Gefeng Zhu, Aaron J. Johnson, Koji Tamada, Andrei I. Chapoval, Scott E. Strome, Larry R. Pease, Lieping Chen
Primary HIV-1 infection causes extensive immune activation, during which CD4+ T cell activation supports massive HIV-1 production. We tested the safety and the immune-modulating effects of combining cyclosporin A (CsA) treatment with highly active antiretroviral therapy (HAART) during primary HIV-1 infection. Nine adults with primary HIV-1 infection were treated with CsA along with HAART. At week 8, all patients discontinued CsA but maintained HAART. Viral replication was suppressed to a comparable extent in the CsA + HAART cohort and in 29 control patients whose primary infection was treated with HAART alone. CsA restored normal CD4+ T cell levels, both in terms of percentage and absolute numbers. The increase in CD4+ T cells was apparent within a week and persisted throughout the study period. CsA was not detrimental to virus-specific CD8+ or CD4+ T cell responses. At week 48, the proportion of IFN-γ–secreting CD4+ and CD4+CCR7– T cells was significantly higher in the CsA + HAART cohort than in the HAART-alone cohort. In conclusion, rapid shutdown of T cell activation in the early phases of primary HIV-1 infection can have long-term beneficial effects and establish a more favorable immunologic set-point. Appropriate, immune-based therapeutic interventions may represent a valuable complement to HAART for treating HIV infection.
G. Paolo Rizzardi, Alexandre Harari, Brunella Capiluppi, Giuseppe Tambussi, Kim Ellefsen, Donatella Ciuffreda, Patrick Champagne, Pierre-Alexandre Bart, Jean-Philippe Chave, Adriano Lazzarin, Giuseppe Pantaleo
Ab-mediated mechanisms have been considered the major causes of glomerulonephritis (GN). However, recent studies suggest that T cells may be more important in mediating GN. To investigate the effects of antigen-specific CD4+ T cells, we generated Th1 cell lines specific for this antigen from rats that had been immunized with a recombinant form of the glomerular basement membrane (GBM) antigen, Col4α3NC1. Upon the transfer of in vitro–activated T cell lines to pertussis toxin-primed, naive syngeneic rats, the recipients developed severe proteinuria/albuminuria, which plateaued after ∼35 days. Although no IgG binding to GBM or C3 deposition could be detected by immunofluorescence, five out of eleven rats exhibited severe GN, as judged by the formation of characteristic crescent-shaped lesions in the glomerluli, whereas the others exhibited modest GN. Thus Col4α3NC1-specific T cells directly initiated glomerular injury in the recipients. One notable difference from GN induced by active immunization was a T cell infiltration in the renal interstitium, which affected some tubules. We therefore injected fluorescence-labeled Col4α3NC1-specific into naive rats, and we found that they were enriched 4.5-fold in the kidney cortex relative to nonspecific control T cells 24 hours later. Many of the T cells were located in the Bowman’s space and had a flattened shape, suggesting that the primary target for the T cells was in or adjacent to the Bowman’s capsule.
Jean Wu, John Hicks, Jason Borillo, William F. Glass II, Ya-Huan Lou