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Rituximab Immunotherapy in Pemphigus: Therapeutic Effects Beyond B-Cell Depletion

2008; Elsevier BV; Volume: 128; Issue: 12 Linguagem: Inglês

10.1038/jid.2008.330

1523-1747

Giovanna Zambruno, Luca Borradori,

Coagulation, Bradykinin, Polyphosphates, and Angioedema

The anti-CD20 mAb rituximab, first approved for use in B-cell malignancies, is increasingly used to treat a variety of autoimmune diseases. Two studies in this issue investigate the effects of rituximab in pemphigus. Rituximab induces not only a depletion of all B cells and a decline of antidesmoglein autoantibodies but also a decrease in desmoglein-specific T cells. Furthermore, B-cell populations recovered after treatment were modified. These novel aspects may contribute to the clinical responses observed in patients. The anti-CD20 mAb rituximab, first approved for use in B-cell malignancies, is increasingly used to treat a variety of autoimmune diseases. Two studies in this issue investigate the effects of rituximab in pemphigus. Rituximab induces not only a depletion of all B cells and a decline of antidesmoglein autoantibodies but also a decrease in desmoglein-specific T cells. Furthermore, B-cell populations recovered after treatment were modified. These novel aspects may contribute to the clinical responses observed in patients. Rituximab is a potent B-cell-depleting chimeric anti-CD20 mAb first approved in 1997 for use in relapsed or refractory low-grade follicular B-cell lymphoma. Since then, it has become a major therapeutic agent in the management of several B-cell malignancies. In parallel, there has been a growing interest in exploiting the B-cell-depleting effect of rituximab in treating autoimmune conditions in which autoantibodies (autoAb) are thought to play a pathogenetic role. The 75 trials currently listed in the National Institutes of Health registry (http://www.clinicaltrials.govin this field. Since 2006, rituximab has been approved for the treatment of active rheumatoid arthritis not responding to tumor necrosis factor blockers (Edwards and Cambridge, 2006Edwards J.C. Cambridge G. B-cell targeting in rheumatoid arthritis and other autoimmune diseases.Nat Rev Immunol. 2006; 6: 394-403Crossref PubMed Scopus (387) Google Scholar; Kessel et al., 2008Kessel A. Rosner I. Toubi E. Rituximab: beyond simple B cell depletion.Clin Rev Allergy Immunol. 2008; 34: 70-79Crossref Scopus (49) Google Scholar). Furthermore, this chimeric antibody has been increasingly used off-label in a variety of autoimmune diseases, including systemic lupus erythematosus, Sjögren's syndrome, idiopathic thrombocytopenic purpura, acquired hemophilia, autoimmune hemolytic anemia, HCV mixed cryoglobulinemia, Wegener's granulomatosis, autoantibody-associated neuropathies, myasthenia gravis, dermatomyositis/polymyositis, and multiple sclerosis, as well as in autoimmune blistering skin diseases (Edwards and Cambridge, 2006Edwards J.C. Cambridge G. B-cell targeting in rheumatoid arthritis and other autoimmune diseases.Nat Rev Immunol. 2006; 6: 394-403Crossref PubMed Scopus (387) Google Scholar; Kessel et al., 2008Kessel A. Rosner I. Toubi E. Rituximab: beyond simple B cell depletion.Clin Rev Allergy Immunol. 2008; 34: 70-79Crossref Scopus (49) Google Scholar; Sailler, 2008Sailler L. Rituximab off label use for difficult-to-treat auto-immune diseases: reappraisal of benefits and risks.Clin Rev Allergy Immunol. 2008; 34: 103-110Crossref PubMed Scopus (36) Google Scholar). CD20 is a transmembrane glycoprotein specifically expressed on B cells and regulated during differentiation. It is first expressed on the cell surface during the transition from pre-B to immature cell in the bone marrow, is maintained on mature naive, activated, and memory cells present in blood and in secondary lymphoid organs, and is lost upon plasma cell differentiation (Edwards and Cambridge, 2006Edwards J.C. Cambridge G. B-cell targeting in rheumatoid arthritis and other autoimmune diseases.Nat Rev Immunol. 2006; 6: 394-403Crossref PubMed Scopus (387) Google Scholar; Kessel et al., 2008Kessel A. Rosner I. Toubi E. Rituximab: beyond simple B cell depletion.Clin Rev Allergy Immunol. 2008; 34: 70-79Crossref Scopus (49) Google Scholar). Thus, rituximab treatment spares long-lived plasma cells that are resident in the bone marrow and represent the major source of serum antibodies. Rituximab has proven remarkably potent in eradicating both malignant and normal B cells, because a single course usually leads to depletion of B cells from peripheral blood for 6–12 months (Edwards and Cambridge, 2006Edwards J.C. Cambridge G. B-cell targeting in rheumatoid arthritis and other autoimmune diseases.Nat Rev Immunol. 2006; 6: 394-403Crossref PubMed Scopus (387) Google Scholar; Kessel et al., 2008Kessel A. Rosner I. Toubi E. Rituximab: beyond simple B cell depletion.Clin Rev Allergy Immunol. 2008; 34: 70-79Crossref Scopus (49) Google Scholar). In addition, there is evidence that the removal of B cells also occurs in secondary lymphoid tissues, although with slower kinetics (Edwards and Cambridge, 2006Edwards J.C. Cambridge G. B-cell targeting in rheumatoid arthritis and other autoimmune diseases.Nat Rev Immunol. 2006; 6: 394-403Crossref PubMed Scopus (387) Google Scholar; Kessel et al., 2008Kessel A. Rosner I. Toubi E. Rituximab: beyond simple B cell depletion.Clin Rev Allergy Immunol. 2008; 34: 70-79Crossref Scopus (49) Google Scholar; Yanaba et al., 2008Yanaba K. Bouaziz J.D. Matsushita T. Magro C.M. St Clair E.W. Tedder T.F. B-lymphocyte contributions to human autoimmune diseases.Immunol Rev. 2008; 223: 284-299Crossref PubMed Scopus (262) Google Scholar). The efficacy of rituximab is probably the result of a combination of factors: CD20 is expressed at high levels on B cells and does not become internalized or shed from the plasma membrane following mAb treatment, allowing for prolonged persistence of the bound mAb on the cell surface. Different mechanisms have been implicated in rituximab-mediated B-cell depletion, such as antibody-dependent cell-mediated cytotoxicity (ADCC), complement-dependent cytotoxicity, and direct triggering of apoptosis (Glennie et al., 2007Glennie M.J. French R.R. Cragg M.S. Taylor R.P. Mechanisms of killing by anti-CD20 monoclonal antibodies.Mol Immunol. 2007; 44: 3823-3837Crossref PubMed Scopus (418) Google Scholar). The role of ADCC is supported by experiments in mouse models and by human data that indicate a correlation between FcgRIIIA polymorphisms and the extent of B-cell depletion by rituximab (Glennie et al., 2007Glennie M.J. French R.R. Cragg M.S. Taylor R.P. Mechanisms of killing by anti-CD20 monoclonal antibodies.Mol Immunol. 2007; 44: 3823-3837Crossref PubMed Scopus (418) Google Scholar; Yanaba et al., 2008Yanaba K. Bouaziz J.D. Matsushita T. Magro C.M. St Clair E.W. Tedder T.F. B-lymphocyte contributions to human autoimmune diseases.Immunol Rev. 2008; 223: 284-299Crossref PubMed Scopus (262) Google Scholar). In ADCC, the interaction between mAb Fc and FcgRs expressed on effector cells, such as natural killer cells, macrophages, or neutrophils, drives the killing of mAb-coated target cells. Pemphigus is a life-threatening autoimmune blistering disorder of the skin and mucosae associated with autoAb directed against desmoglein (Dsg)-1 and Dsg3, two transmembrane components of desmosomes, which are cell–cell adhesion complexes (Stanley and Amagai, 2006Stanley J.R. Amagai M. Pemphigus, bullous impetigo, and the staphylococcal scalded-skin syndrome.N Engl J Med. 2006; 355: 1800-1810Crossref PubMed Scopus (329) Google Scholar). AutoAb production in pemphigus is polyclonal, and the autoAb belong mainly to the IgG4 and IgG1 subclasses. Two major forms of the disease—pemphigus vulgaris (PV) and pemphigus foliaceus (PF)—are distinguished. Ample data support the pathogenetic role of Dsg autoAb in PV and PF. Specific examples include the following: (i) serum levels of anti-Dsg1 and anti-Dsg3 antibodies in patients generally correlate with disease activity, (ii) passive transfer of purified IgG from PV and PF sera in neonatal mice results in the induction of pemphigus-like features, (iii) inactivation of the Dsg3 gene in mice results in a mucosal-dominant PV-like phenotype, and (iv) immunization of Dsg3 knockout mice with murine Dsg3 and adoptive transfer of the immune splenocytes into Rag2−/− immunodeficient mice result in persistent anti-Dsg3 autoAb production and a PV-like disease phenotype. In vitro and in vivo findings also indicate that autoreactive CD4+ T cells are involved in the pathogenesis of PV and PF, most likely by controlling the activation of specific B lymphocytes and possibly by inducing local inflammation (Hertl et al., 2006Hertl M. Eming R. Veldman C. T cell control in autoimmune bullous disorders.J Clin Invest. 2006; 116: 1159-1166Crossref PubMed Scopus (138) Google Scholar). Intriguingly, a subset of Dsg3-reactive T cells with regulatory functions has recently been identified, raising the possibility that this disease may be dependent on the fine balance between helper and suppressor T cells. In view of the key role played by autoAb in PV and PF, over the past few years rituximab has been used in cases of severe pemphigus resistant to conventional immunosuppressive therapies and alternative therapeutic approaches, such as high-dose intravenous Ig. Four independent, nonrandomized, prospective studies (Ahmed et al., 2006Ahmed A.R. Spigelman Z. Cavacini L.A. Posner M.R. Treatment of pemphigus vulgaris with rituximab and intravenous immune globulin.N Engl J Med. 2006; 355: 1772-1779Crossref PubMed Scopus (406) Google Scholar; Joly et al., 2007Joly P. Mouquet H. Roujeau J.C. D'Incan M. Gilbert D. Jacquot S. et al.A single cycle of rituximab for the treatment of severe pemphigus.N Engl J Med. 2007; 357: 545-552Crossref PubMed Scopus (366) Google Scholar; Cianchini et al., 2007Cianchini G. Corona R. Frezzolini A. Ruffelli M. Didona B. Puddu P. Treatment of severe pemphigus with rituximab: report of 12 cases and review of the literature.Arch Dermatol. 2007; 143: 1033-1038Crossref PubMed Scopus (130) Google Scholar), including that by Eming et al. (Eming et al., 2008Eming R. Nagel A. Wolff-Franke S. Podstawa E. Debus D. Hertl M. Rituximab exerts a dual effect in pemphigus vulgaris.J Invest Dermatol. 2008; 128: 2850-2858Abstract Full Text Full Text PDF PubMed Scopus (145) Google Scholar, this issue) have been published to date. These studies demonstrate that rituximab, in most cases administered in an adjuvant setting, led to complete remission in the large majority of PV and PF patients with refractory disease, with frequently sustained clinical benefits. In particular, a previous report (Joly et al., 2007Joly P. Mouquet H. Roujeau J.C. D'Incan M. Gilbert D. Jacquot S. et al.A single cycle of rituximab for the treatment of severe pemphigus.N Engl J Med. 2007; 357: 545-552Crossref PubMed Scopus (366) Google Scholar) on the clinical outcomes of the patients analyzed by Mouquet et al. (Mouquet et al., 2008Mouquet H. Musette P. Gougeon M.-L. Jacquot S. Lemercier B. Lim A. et al.B-cell depletion immunotherapy in pemphigus: effects on cellular and humoral immune responses.J Invest Dermatol. 2008; 128: 2859-2869Abstract Full Text Full Text PDF PubMed Scopus (101) Google Scholar, this issue) demonstrated that 18 of 21 (86%) patients with severe PV or PF had complete remissions 3 months after a single cycle of four weekly infusions of rituximab, administered in association with corticosteroids in most of the patients (Joly et al., 2007Joly P. Mouquet H. Roujeau J.C. D'Incan M. Gilbert D. Jacquot S. et al.A single cycle of rituximab for the treatment of severe pemphigus.N Engl J Med. 2007; 357: 545-552Crossref PubMed Scopus (366) Google Scholar). Disease relapse was observed in 9 of 21 patients after a mean of 19 months, and, after a mean follow-up of 36 months, 18 (86%) patients were free of disease, including 8 (38%) who were not receiving corticosteroids (Joly et al., 2007Joly P. Mouquet H. Roujeau J.C. D'Incan M. Gilbert D. Jacquot S. et al.A single cycle of rituximab for the treatment of severe pemphigus.N Engl J Med. 2007; 357: 545-552Crossref PubMed Scopus (366) Google Scholar; Mouquet et al., 2008Mouquet H. Musette P. Gougeon M.-L. Jacquot S. Lemercier B. Lim A. et al.B-cell depletion immunotherapy in pemphigus: effects on cellular and humoral immune responses.J Invest Dermatol. 2008; 128: 2859-2869Abstract Full Text Full Text PDF PubMed Scopus (101) Google Scholar). Eming et al. also describe a significant improvement in all 11 PV patients treated with a single cycle of rituximab in association with corticosteroids and immunosuppressive drugs. Thus, the efficacy of rituximab in pemphigus is impressive. However, the mechanisms by which this is achieved are not well understood. The studies by Mouquet et al. and Eming et al. now provide further insight into this relevant issue. These authors confirm that in almost all treated pemphigus patients, complete CD19+ B-cell depletion occurred, lasting up to 12 months. Furthermore, total serum IgG levels and the levels of antipneumococcal capsular polysaccharide and tetanus toxoid antibodies remained unchanged, whereas only IgM levels decreased (Mouquet et al.). These findings are in line with published data obtained in both lymphoproliferative and autoimmune diseases (Looney et al., 2008Looney R.J. Srinivasan R. Calabrese L.H. The effects of rituximab on immunocompetency in patients with autoimmune disease.Arthritis Rheum. 2008; 58: 5-14Crossref PubMed Scopus (74) Google Scholar). The observation that total serum IgG and protective antibody levels are not affected by a single course of rituximab is consistent with the fact that long-lived plasma cells resident in bone marrow are CD20 negative and are therefore spared from the chimeric antibody. In contrast, both studies document a selective role of rituximab-induced B-cell depletion in decreasing autoAb levels. These findings imply that the pathogenetic antibodies are produced by an ongoing immune response that is continually fueled by specific B cells stimulated by antigen and possibly antigen-specific T cells. In particular, both groups demonstrate the following: (i) significantly decreased levels of anti-Dsg autoAb in most treated patients undergoing clinical improvement and (ii) increasing titers of anti-Dsg antibodies in relapsing patients. Again, these findings are in line with data in autoimmune diseases such as rheumatoid arthritis, in which clinical improvement and relapse correlate with the decrease and subsequent increase in autoAb levels in the majority of treated patients (Edwards and Cambridge, 2006Edwards J.C. Cambridge G. B-cell targeting in rheumatoid arthritis and other autoimmune diseases.Nat Rev Immunol. 2006; 6: 394-403Crossref PubMed Scopus (387) Google Scholar). The correlation between clinical response and decreasing autoAb titers seems to be even more marked in diseases characterized by pathogenetic autoantibodies, such as idiopathic thrombotic thrombocytopenic purpura and acquired hemophilia (Barnett et al., 2008Barnett B. Kruse-Jarres R. Leissinger C.A. Current management of acquired factor VIII inhibitors.Curr Opin Hematol. 2008; 15: 451-455Crossref PubMed Scopus (20) Google Scholar; Sadler, 2008Sadler J.E. Von Willebrand factor, ADAMTS13, and thrombotic thrombocytopenic purpura.Blood. 2008; 112: 11-18Crossref PubMed Scopus (408) Google Scholar). Rituximab efficacy in pemphigus is impressive. Rituximab efficacy in pemphigus is impressive. Intriguingly, Mouquet et al. also highlight the fact that individual clinical responses following rituximab immunotherapy in pemphigus do not always correlate with changes in autoAb titers. The authors report that a minority of rituximab-treated PV patients in complete remission had persistently high autoAb titers or showed a re-increase of anti-Dsg3 autoAb over time. In these patients, clinical remission might relate to a modification of targeted epitope profile. In fact, sera from PV patients in complete remission with persistently high anti-Dsg3 levels no longer recognized the pathogenic N-terminal epitopes (EC1 and EC2) of Dgs3 that were targeted during the active phase of the disease. These data should be confirmed by further analyses, including the assessment of the autoAb pathogenicity in these patients. As for rituximab, its varying effect on autoAb levels in pemphigus could reflect the persistence of CD20 plasma cells with heterogeneous life spans, with short-lived plasma cells accounting for a significant proportion of the autoAb production. With their long-term follow-up, Mouquet et al. clearly demonstrate that, in the majority of patients, autoAb production remains at low levels well after B-lymphocyte recovery. It is interesting to note that, similar to what is described in rheumatoid arthritis, B cells that repopulate the peripheral blood after rituximab treatment are enriched in naive B cells (CD19+, CD27−), with their immature (CD5+, CD38high) phenotype, which has been considered an indicator of an origin in the recovering bone marrow (Edwards and Cambridge, 2006Edwards J.C. Cambridge G. B-cell targeting in rheumatoid arthritis and other autoimmune diseases.Nat Rev Immunol. 2006; 6: 394-403Crossref PubMed Scopus (387) Google Scholar). Another intriguing finding of Mouquet et al. is the disappearance of the oligoclonal peaks detected in some immunoglobulin IgM and IgG VH families before treatment and the reconstitution of a polyclonal profile following rituximab. This reconstituted polyclonal B-cell population could play a relevant role in the long-lasting remissions observed in a significant proportion of patients. It will be interesting to determine whether the memory phenotype B cells that appear after rituximab retain all the specificities present before treatment, including reactivities against vaccines and common viruses. Over the past few years, several studies have provided evidence that rituximab-induced B-cell depletion can be associated in different autoimmune diseases with modifications of the T-cell compartment, such as subset alterations, changes in the activation state, and induction of cells with regulatory properties (Kessel et al., 2008Kessel A. Rosner I. Toubi E. Rituximab: beyond simple B cell depletion.Clin Rev Allergy Immunol. 2008; 34: 70-79Crossref Scopus (49) Google Scholar; Liossis and Sfikakis, 2008Liossis S.N. Sfikakis P.P. Rituxiamb-induced B cell depletion in autoimmune diseases: potential effects on T cells.Clin Immunol. 2008; 127: 280-285Crossref PubMed Scopus (108) Google Scholar). Immunophenotypic analyses of the T cells performed in both the study by Eming et al. and the one by Mouquet et al. indicate that rituximab in pemphigus does not significantly affect major T-cell subset numbers or phenotypes. However, Eming et al. studied for the first time the frequency of circulating autoreactive Dsg3-specific CD4+ T helper (Th)-1 and Th2 cells using a magnetic activation cell-sorting cytokine secretion assay. They report a significant reduction in IFN-γ-secreting T cells (Th1) and Dsg3-specific IL-4-secreting T cells (Th2). Such changes were already detectable 1 month following rituximab administration, and they lasted for 12 and 6 months, respectively. In addition, the frequency of both Th1 and Th2 cells remained low in patients with sustained CR, whereas it increased at 6 to 12 months in the three relapsing patients. Thus, Dsg3-specific Th1 and Th2 frequency decreases rapidly after rituximab and seems to parallel disease activity and autoAb levels. The effect on Dsg3-reactive CD4+ T cells appears, at least in part, to be specifically related to rituximab administration, because systemic corticosteroids and immunosuppressive adjuvants had no significant effect on the overall frequency of Dsg3-specific Th1 and Th2 cells. However, it cannot be excluded that the concomitant use of rituximab and immunosuppressive treatments has a synergistic effect on humoral and cellular immune responses, including autoreactive CD4+ T cells, in treated patients. The findings by Eming et al., 2008Eming R. Nagel A. Wolff-Franke S. Podstawa E. Debus D. Hertl M. Rituximab exerts a dual effect in pemphigus vulgaris.J Invest Dermatol. 2008; 128: 2850-2858Abstract Full Text Full Text PDF PubMed Scopus (145) Google Scholar are in agreement with those of a recent report demonstrating that B-cell depletion by anti-CD20 inhibits autoreactive T-cell activation in two animal models of autoimmune diseases: collagen-induced arthritis and type 1 diabetes (Bouaziz et al., 2007Bouaziz J.D. Yanaba K. Venturi G.M. Wang Y. Tisch R.M. Poe J.C. et al.Therapeutic B cell depletion impairs adaptive and autoreactive CD4+ T cell activation in mice.Proc Natl Acad Sci USA. 2007; 104: 20878-20883Crossref PubMed Scopus (250) Google Scholar). In particular, in collagen-induced arthritis, autoantigen-specific CD4+ T-cell proliferation in response to autoantigen challenge was inhibited following B-cell depletion. Overall, Eming et al. indicate that rituximab indirectly decreases the frequency of autoreactive CD4+ T cells via depletion of B cells as critical antigen-presenting cells. Although the crucial role of reciprocal T-cell–B-cell interactions in systemic autoimmune diseases is increasingly recognized (Shlomchik, 2008Shlomchik M.J. Sites and stages of autoreactive B cell activation and regulation.Immunity. 2008; 28: 18-28Abstract Full Text Full Text PDF PubMed Scopus (226) Google Scholar), almost no data are available regarding the function of autoreactive B cells as antigen-presenting cells for Dsg3-specific T cells in PV. In conclusion, the studies of Mouquet et al. (Mouquet et al., 2008Mouquet H. Musette P. Gougeon M.-L. Jacquot S. Lemercier B. Lim A. et al.B-cell depletion immunotherapy in pemphigus: effects on cellular and humoral immune responses.J Invest Dermatol. 2008; 128: 2859-2869Abstract Full Text Full Text PDF PubMed Scopus (101) Google Scholar) and Eming et al. (Eming et al., 2008Eming R. Nagel A. Wolff-Franke S. Podstawa E. Debus D. Hertl M. Rituximab exerts a dual effect in pemphigus vulgaris.J Invest Dermatol. 2008; 128: 2850-2858Abstract Full Text Full Text PDF PubMed Scopus (145) Google Scholar) give an overall picture of immunodynamics following immunotherapy with rituximab in pemphigus and open new directions of investigations regarding the mechanisms of action of this drug. This knowledge is relevant not only for a delineation of the optimal administration modalities for rituximab and to guide the choice of novel therapeutic approaches in pemphigus but ultimately also for a better comprehension of disease pathogenesis. Overall, it is expected and anticipated that the increasing use of novel therapies in autoimmune disorders—whether directly targeted B-cell therapies, including other biologicals targeting CD20 or CD22, or therapies indirectly modulating B cells, such as blockers of the B-cell survival factor BAFF/BLyS—will greatly contribute to a better understanding of B-cell–T-cell interplay and thus of inflammatory and autoimmune disorders in general (Dörner and Burmester, 2008Dörner T. Burmester G.R. New approaches of B-cell-directed therapy: beyond rituximab.Curr Opin Rheumatol. 2008; 20: 263-268Crossref PubMed Scopus (81) Google Scholar). The authors state no conflict of interest. This work was supported in part by EC grant HEALTH-F2-2008-200515.