Review in translational hematology
`
`New approaches for preventing and treating chronic graft-versus-host disease
`Stephanie J. Lee
`
`Despite improvements in the practice of
`allogeneic hematopoietic stem cell trans-
`plantation (HCT) over the last 25 years,
`chronic graft-versus-host disease (GVHD)
`remains a substantial problem with little
`change in the incidence, morbidity, and
`mortality of this complication.
`In fact,
`with increased use of peripheral blood,
`Introduction
`
`transplantation of older patients, and less
`immediate transplantation-related mortal-
`ity, the prevalence of chronic GVHD may
`increase. One of the difficulties in combat-
`ing chronic GVHD is a lack of understand-
`ing about the pathophysiology of the syn-
`drome. Inherent difficulties in conducting
`human clinical trials also contribute to
`
`the lack of meaningful progress. This
`review covers potential new approaches
`to the prevention and treatment of chronic
`GVHD. (Blood. 2005;105:4200-4206)
`
`© 2005 by The American Society of Hematology
`
`Chronic graft-versus-host disease (GVHD) is the most serious and
`common long-term complication of allogeneic hematopoietic stem
`cell transplantation (HCT), occurring in 20% to 70% of people
`surviving more than 100 days.1,2 Approximately half of affected
`people have 3 or more involved organs, and treatment typically
`requires immunosuppressive medications for a median of 1 to 3
`years. Because of higher treatment-related (nonrelapse) mortality,
`chronic GVHD remains the major cause of late death despite its
`association with a lower relapse rate.3,4 In addition, secondary
`malignancies are more common in people with chronic GVHD,
`particularly of commonly involved tissues such as mouth and skin,
`suggesting that chronic inflammation, prolonged exposure to
`immunosuppressive medications, or immune dysregulation facili-
`tates the development of new cancers.5 Finally, the functional
`consequences of chronic GVHD organ involvement are major
`determinants of the health and quality of life of survivors.6,7
`Despite the well-recognized adverse effects of chronic GVHD on
`the long-term success of allogeneic transplantation, its pathophysi-
`ology is poorly understood, and management strategies beyond
`systemic corticosteroids have not been established.
`While there are some lessons that can be translated from basic
`and clinical studies of acute GVHD, several lines of evidence
`suggest that chronic GVHD is not simply a continuation of acute
`GVHD, and that separate approaches will be required for its
`prevention and management. First, except for T-cell depletion and
`use of umbilical cord blood, the major innovations that have
`improved acute GVHD rates do not seem to have affected chronic
`GVHD incidence. Second, while there is significant overlap
`between the organs involved in acute and chronic GVHD, the
`distribution of affected organs in chronic GVHD is much broader.
`Fully evolved chronic GVHD is largely an inflammatory and
`fibrotic process, while acute GVHD is more likely to reflect
`apoptosis and necrosis. Although traditionally the boundary be-
`tween acute and chronic GVHD has been set at 100 days after
`transplantation, more recent definitions hinge on different clinical
`manifestations rather than time of onset. Third, while acute GVHD
`
`is highly associated with subsequent chronic GVHD, approxi-
`mately 25% to 35% of chronic GVHD is de novo without any
`preceding acute manifestations, while 20% to 30% of people who
`had acute GVHD do not go on to develop chronic GVHD later.
`This paper will review current beliefs about the pathophysiol-
`ogy of chronic GVHD and discuss the evidence for emerging
`approaches to prevent or
`treat
`this complication. Readers
`interested in reviews focusing on clinical management are referred
`to other sources.8-10
`
`Rodent models
`
`Both human and murine studies will be reviewed throughout this
`article, although it is important to recognize the similarities and
`differences between the 2 species. In mice, chronic GVHD
`manifestations are highly dependent on the age of the mice, the
`strain combinations selected, the number and type of donor cells
`injected, and the preparative regimen. In contrast to humans, mice
`are not given pharmacologic prophylaxis against GVHD or treat-
`ment for GVHD.
`Murine chronic GVHD can be induced by transplantation
`across class I, class II, or minor histocompatibility antigen barriers
`using irradiation-based regimens. Clinically, these models produce
`late weight loss, lymphoid atrophy, and lymphocyte infiltration of
`affected organs. Fibrosis of the skin, liver, lung, and exocrine
`glands is seen.11 Autoreactive T helper (Th) clones can be
`isolated.12 One minor mismatch model mimics human scleroderma
`with skin and lung fibrosis, a process that can be blocked by
`anti–transforming growth factor ␤ (TGF-␤) antibody treatment.13
`Another murine model mimics systemic lupus erythematosis
`with splenomegaly, B-cell expansion, autoantibodies, and glomeru-
`lonephritis. This syndrome is induced by transplantation of parental
`(P1) cells into F1 (P1 crossed with P2) nonirradiated recipients in
`strain combinations with inherent or induced deficiencies in donor
`CD8⫹ T cells. Th2 cells secreting interleukin-4 (IL-4), IL-6, and
`
`From the Department of Medical Oncology, Dana-Farber Cancer Institute,
`Boston, MA.
`
`Supported in part by P01 HL070149 from the National Heart, Lung, and Blood
`Institute.
`
`Submitted October 22, 2004; accepted February 2, 2005. Prepublished online as
`Blood First Edition Paper, February 8, 2005; DOI 10.1182/blood-2004-10-4023.
`
`Reprints: Stephanie Lee, Dana-Farber Cancer Institute, Boston, MA 02115; e-
`mail: stephanie_lee@dfci.harvard.edu.
`
`© 2005 by The American Society of Hematology
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`This material may be protected by Copyright law (Title 17 U.S. Code)
`
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`NEW APPROACHES TO CHRONIC GVHD
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`4201
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`IL-10 appear responsible for clinical manifestations. Notably,
`transplantation from the other parental (P2) strain often results in
`an acute GVHD syndrome unless CD8⫹ T cells are depleted.14
`Administration of cytokines (IL-12, IL-18), costimulatory block-
`ade (4-1BB, cytotoxic T-lymphocyte antigen 4 [CTLA-4], induc-
`ible costimulator [ICOS], CD2815,16), and chemokine antagonists
`(CC chemokine receptor 7 [CCR7])17 can interfere with develop-
`ment of the chronic syndrome. However, the relevance of this
`model has been questioned, as splenomegaly and glomerulonephri-
`tis are not components of human chronic GVHD. Also, most
`human transplantation occurs between major histocompatibility
`complex (MHC)–matched individuals using some form of recipient
`conditioning.
`As with humans, some chronic GVHD manifestations are seen
`in nontransplant situations. The tight skin (TSK) mouse contains a
`partially duplicated fibrillin-1 gene that results in lung, heart, and
`skin lesions and an antibody profile akin to human scleroderma.18
`Transgenic mice with tumor necrosis factor ␣ (TNF-␣) expressed
`in keratinocytes under the keratin-14 promoter have skin fibrosis
`and evidence of cachexia.19 While these models show some
`resemblance to chronic GVHD, their relevance to the human
`syndrome following HCT is questionable.
`
`Human pathophysiology
`
`In humans, chronic GVHD is exceedingly rare after autologous or
`syngeneic transplantation despite similar preparatory regimens. In
`the allogeneic setting, the onset of chronic GVHD is usually
`delayed until 4 to 6 months after transplantation, rarely appearing
`before day ⫹80 and with less than 5% of cases developing after 1
`year. These observations suggest that alloreactivity is a key
`requirement, and that the processes leading to chronic GVHD
`either have a long latency or they exert their effects slowly on
`target tissues.
`The current understanding of human chronic GVHD etiology
`starts with pathogenic donor T cells that expand in response to
`alloantigens or autoantigens unchecked by normal
`thymic or
`peripheral mechanisms of deletion. Critical donor or recipient
`tolerance-promoting cells may be absent. These pathologic T cells
`then attack target tissue directly through cytolytic attack, secretion
`of inflammatory and fibrosing cytokines, or promotion of B-cell
`activation and autoantibody production. Tissue damage leads to
`fibrosis and dysfunction. Chronic GVHD or its treatment leads to
`death from organ failure or infection. Thus, prevention and
`treatment of chronic GVHD has focused on interrupting this
`process through elimination or inhibition of pathogenic T cells,
`induction of tolerance, cytokine therapy, elimination of B cells, or
`modulating effects on local tissues.
`
`Approaches to chronic GVHD prevention
`
`Choice of donor, graft source, and GVHD prophylaxis
`
`Clinical studies have identified many recipient, donor, and trans-
`plant factors associated with higher rates of chronic GVHD.
`Children experience lower rates of chronic GVHD, but the major
`risk factors for, organ manifestations in, and clinical impact on
`affected children appear similar.2 Many recipient risk factors
`associated with increased chronic GVHD are not modifiable, and
`include older age, certain diagnoses (eg, chronic myeloid leukemia,
`
`aplastic anemia), and lack of an HLA-matched donor. Other
`modifiable factors are associated with lower rates of chronic
`GVHD, and although causality is not proved, avoidance of
`high-risk factors may decrease the risk of clinically significant
`chronic GVHD. Assuming multiple HLA-matched donors are
`available, then selection of a younger related donor, use of bone
`marrow rather than peripheral blood,20 and limitation of CD34⫹21
`and T-cell dose infused may minimize the risk of chronic GVHD.
`Two reports suggest that chronic GVHD is also more likely to be
`extensive and difficult to treat in recipients of related and unrelated
`peripheral blood compared with bone marrow.1,22 Comment on the
`incidence and clinical manifestations of chronic GVHD after
`nonmyeloablative or reduced-intensity conditioning regimens awaits
`more definitive reports. If the recipient is male, then avoidance of a
`female donor, especially someone multiparous, may decrease the
`risk of chronic GVHD.23 Donor ABO compatibility and cytomega-
`lovirus (CMV) seronegativity have also been associated with lower
`risks of chronic GVHD. While umbilical cord blood is currently a
`graft source of last resort in adults, it appears to be associated with
`lower rates of chronic GVHD.24
`As most HCT procedures use HLA-matched donors, so-called
`“minor” histocompatibility antigens (mHAs) must contribute to the
`pathophysiology of acute and chronic GVHD. Minor antigens are
`polymorphic proteins encoded in the genome that are degraded and
`presented to T cells in the context of HLA,
`thus inducing
`MHC-restricted immune responses. Conceivably,
`identification
`and avoidance of important minor mismatches could prevent both
`acute and chronic GVHD. In human transplantation, studies of
`predictors of acute GVHD have primarily focused on mHA-1 and
`mHA-2, expressed solely on hematopoietically derived cells (includ-
`ing dendritic and Langerhans cells) and presented in the context of
`HLA-A*0201. Other antigens are broadly expressed on tissues:
`mHA-3 is presented by HLA-A*0101, while mHA-8 is presented
`by HLA-A*0201 and HLA-A*0202. However, none of these
`mHAs has been associated with chronic GVHD.25,26
`An increased risk of chronic GVHD has long been recognized
`when a male recipient receives a graft from a female donor,
`particularly one who may have been alloimmunized by pregnancy
`or transfusion.27 The best explanation for this clinical observation
`is that mHAs encoded on the Y chromosome can elicit responses
`from female donors in male recipients.28 In a murine skin explant
`model, female cytotoxic T lymphocytes (CTLs) specific for the
`H-Y antigens found in males caused severe changes consistent with
`acute GVHD when exposed to male but not female skin.29
`
`Prevention of acute GVHD
`
`Acute GVHD is a major predictor of chronic GVHD, and 70% to
`80% of people with grades II to IV acute GVHD develop chronic
`GVHD.30 The nature of the observed association is highly contro-
`versial, and at least 4 explanations have been offered. Chronic
`GVHD has been suggested to be a later manifestation of alloreac-
`tive acute GVHD, a result of tissue damage (particularly thymus)
`caused by acute GVHD,31 a result of treatment (particularly
`steroids) for acute GVHD,32 or an epiphenomenon that is associ-
`ated with but not etiologically linked to acute GVHD. These
`distinctions are important because interfering with the development
`of acute GVHD may prevent chronic GVHD if any of the first 3
`mechanisms is operative, but would not affect chronic GVHD
`incidence if the last were true. In fact, some successful attempts to
`decrease acute GVHD may have actually increased chronic GVHD
`rates. Two reports have suggested that exposure to steroids as
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`prophylaxis for acute GVHD tends to increase the rate of subse-
`quent chronic GVHD.32,33
`Some attention has recently focused on the role of recipient
`and donor APCs in prevention of acute GVHD while preserving
`graft-versus-tumor effects. Shlomchik et al34 reported murine
`studies in which recipient antigen-presenting cells are critical
`for initiation of acute GVHD by donor CD8 cells. Human
`reports also suggest that APCs may be important. In patients
`with myeloid malignancies undergoing haplotype-mismatched
`and killer immunoglobulin-like receptor (KIR) mismatched
`transplantations, decreased rates of acute GVHD, decreased
`relapse rates, and higher overall survival in patients were reported.
`Chronic GVHD rates were not reported. The proposed mechanism
`of action is elimination of host APCs (decreasing acute GVHD) and
`host tumor cells (decreasing relapse rate) by uninhibited donor
`natural killer (NK) cells.35 This interpretation was supported by a
`similar study in unrelated donor transplantation that
`included
`anti–thymocyte globulin (ATG) for GVHD prophylaxis. KIR
`mismatching was associated with better survival and marginally
`lower rates of acute GVHD, although rates of chronic GVHD were
`comparable.36 Studies in other populations have disputed these
`findings or identified other important NK factors; however, chronic
`GVHD rates are not mentioned.37,38 A second approach to depletion
`of host APCs uses extracorporeal photopheresis (ECP) prior to
`infusion of donor stem cells. In a small series, Chan et al39 reported
`lower rates of extensive chronic GVHD, especially when donor
`dendritic cell (DC) chimerism is achieved by day 100.
`Two other studies looked at donor APCs, specifically plasmacy-
`toid DC2 cells. Clark et al40 reported that people with chronic
`GVHD had normal numbers of donor-derived plasmacytoid DC2s
`in their blood compared with reduced numbers in posttransplanta-
`tion controls without chronic GVHD. In contrast, Waller et al41
`reported that patients receiving bone marrow grafts with higher
`numbers of CD3⫺CD4bright, presumably DC2 cells, had a lower
`incidence of chronic GVHD. A better understanding of the role of
`APCs in chronic GVHD awaits additional studies.
`
`Chronic GVHD prophylaxis
`
`Attempts to prevent chronic GVHD through prolonged use of
`immunosuppressive medications or addition of other agents have
`been unsuccessful. Based on observational reports that extended
`calcineurin inhibitor treatment may have decreased the incidence
`of chronic GVHD,42 a randomized trial by the Seattle group
`compared 6 months versus 24 months of cyclosporine in patients
`with prior acute GVHD or evidence of subclinical chronic GVHD
`on skin biopsy. No statistically significant difference was seen in
`rates of clinical extensive chronic GVHD.43 Chao et al44 studied
`thalidomide beginning 80 days after transplantation in a random-
`ized, double-blinded, placebo-controlled study and found a higher
`rate of chronic GVHD and mortality in patients receiving active
`drug. Ringden et al45 treated a small number of patients with grade I
`or higher acute GVHD with steroids until 6 months after transplan-
`tation in an attempt to prevent chronic GVHD. They abandoned
`this approach when a higher than expected incidence of severe
`chronic GVHD was noted.
`
`Preemptive treatment of minimal chronic GVHD
`
`A provocative study that attempted to avert clinical chronic GVHD
`by preemptive treatment of subclinical chronic GVHD noted that
`
`most (70%) went on to develop chronic GVHD, and that the relapse
`rate was higher in patients who underwent
`transplantation in
`relapse who did not develop chronic GVHD.46
`Eosinophilia is associated with Th2 allergic disorders and may
`precede the diagnosis of clinical chronic GVHD, leading at least
`one pediatric center to start treatment when eosinophilia alone is
`noted after transplantation. No long-term results of this strategy
`were reported.47
`
`New approaches to treatment
`
`More than 20 years ago, corticosteroid therapy was shown to
`improve survival in patients with chronic GVHD compared with no
`therapy.48 However, extended corticosteroid therapy has well-
`known, long-term adverse effects, and alternative treatments are
`generally unsatisfactory.49 Other reviews concisely summarize data
`on primary and salvage therapies currently available to treat
`chronic GVHD, so this information will not be reviewed here.
`Instead, potential new approaches to control of chronic GVHD are
`emphasized. Two ongoing randomized, double-blinded multicenter
`studies of hydroxychloroquine or mycophenolate mofetil added to
`standard corticosteroid initial treatment seek to improve initial
`therapy (A. L. Gilman, University of North Carolina at Chapel Hill,
`and P. J. Martin, Fred Hutchinson Cancer Research Center, oral
`communication, July 2004).
`
`Elimination or inhibition of pathogenic T cells
`through pharmacologic therapy
`
`Pharmacologic inhibition of T cells forms the backbone of modern
`chronic GVHD therapy. In human cutaneous chronic GVHD, most
`infiltrating lymphocytes are CD8⫹,50,51 although one recent report
`suggests that alloreactive CD4⫹ infiltrating cells are also important
`and pre-exist in the donor.52 Newer agents under study include
`mycophenolate mofetil,53 sirolimus,54 daclizumab,55 pentostatin,56
`and alemtuzumab. When pharmacologic therapy is stopped, be-
`tween 10% to 25% of patients flare and require reinstitution of
`systemic treatment.57 Optimally, novel methods of T-cell inhibition
`would target specifically the T cells responsible for chronic GVHD
`while sparing other cells that could provide protective immunity.
`For example, given the relative lymphopenia with fewer recent
`thymic emigrants (as measured by T-cell receptor excision circle
`levels) and a relative deficit of central memory populations
`(CD45⫺CCR7⫹, precursor effector cells) noted in chronic GVHD,
`preservation of any nonpathologic T cells might help decrease
`serious infections.31,58,59
`In humans, OX-40 (CD134, a member of TNF receptor
`superfamily responsible for costimulation) expressing CD4⫹ cells
`are reportedly associated with onset of chronic GVHD and
`decreased response to initial therapy.60 If OX-40 is a marker of cells
`involved in chronic GVHD, then targeting these cells or their
`interactions at the onset of chronic GVHD may be therapeutic. In
`mice, antibody to the OX-40 ligand (OX-40L) decreases acute
`GVHD, but to this point, human trials have not been conducted.
`
`Inhibition of pathogenic T cells through cellular therapy
`
`Cellular approaches to inhibiting T cells have recently focused on
`so called T regulatory cells (Tregs), a small subset of T cells that can
`suppress proliferation and function of T effector cells, particularly
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`of the Th1 class.61 Tregs are activated in an antigen-specific
`manner, perhaps with involvement of IL-10, TGF-␤, and immature
`dendritic cells, causing them to express high levels of CD25⫹ (IL-2
`receptor alpha chain) constitutively.53 They are unresponsive to
`mitogens, express CTLA-4, and are able to block production of
`IL-2 and interferon ␥ (IFN-␥) by effector T cells in a manner that
`relies on cell-to-cell contact. Most reports suggest
`that Tregs
`function in an antigen-nonspecific manner as tested in vitro,
`although at least one report suggested that they may be antigen
`specific in vivo.62 Tregs may also have inhibitory effects on APCs,
`and their high expression of CCR4 and CCR8 suggests aberrant
`trafficking.53 Recently, a distinction has been made between
`“natural” Tregs, important in preventing autoimmune responses to
`continually expressed antigens in the noninflammatory setting, and
`“adaptive” Tregs, which are important in developing tolerance to
`foreign antigens and quelling inflammatory processes.63
`In murine models, infusion of CD4⫹CD25⫹ T cells is able to
`prevent acute GVHD while graft-versus-tumor is maintained.64,65
`Removal of CD4⫹CD25⫹ T cells from the graft or blockade by
`CD25⫹ antibodies worsened acute GVHD.66 Another model sug-
`gested that chronic GVHD incidence and severity is higher in the
`absence of recipient CD4⫹CD25⫹ cells, and that repletion with
`recipient or host Tregs is protective.11 These murine observations
`led to the hypothesis that human chronic GVHD results from a low
`Treg population, and that expansion ex vivo and replacement could
`help control chronic GVHD. However, a small study of 17 patients
`with chronic GVHD showed higher numbers of CD4⫹CD25⫹ cells
`in people with chronic GVHD but lower CD62 ligand (CD62L)
`expression compared with people without chronic GVHD, al-
`though absolute numbers and functionality were similar to con-
`trols.67 A more recent study of people considered to have allogeneic
`or autologous chronic GVHD quantified Foxp3 expression as a
`marker of Tregs and suggested that they may indeed be deficient.68
`Thus,
`it remains controversial whether Tregs are involved in
`chronic GVHD, and further studies are warranted.
`
`Interventions to induce tolerance
`
`It is not clear when donor tolerance to the recipient is established.
`Possibilities include before engraftment due to lack of critical
`donor-recipient differences, early after transplantation due to
`deletion or tolerization of donor T cells, or in an ongoing process
`later after transplantation. The role of immunosuppressive medica-
`tions in promoting or interfering with tolerance development is
`unknown. Anecdotal reports of exacerbation or induction of
`chronic GVHD with sun exposure, sunburns, and infections
`suggest that a state of apparent tolerance can be broken by aberrant
`antigen presentation or inflammatory states.
`Improvement of thymic function has the potential both to
`improve protection against pathogens and decrease autoimmunity,
`either by increasing the thymus’ ability to delete autoreactive cells
`or by fostering development of natural Tregs. Loss of thymic
`function in older patients may explain the higher observed rates of
`chronic GVHD compared with children. IL-7 is produced by
`stromal cells in the thymus and bone marrow and plays a critical
`role in T- and B-cell development. In children, posttransplantation
`IL-7 levels inversely correlate with the absolute lymphocyte
`number.69 The effects of exogenous IL-7 have been tested on
`human thymic cultures or human stem cells injected into immunoin-
`competent mice, showing that T-cell production can be increased.70,71
`
`Other approaches to T-cell tolerization rely on immunomodu-
`lation, such as might be provided by extracorporeal photophere-
`sis (ECP). Subjects who responded to ECP were more likely to
`have a clonal T-cell population, although these populations were
`found equally in people with and without chronic GVHD.72
`Approximately 5% of mononuclear cells undergo apoptosis
`after ECP, and these degrading cells may cause autoimmuniza-
`tion and an increased production of IL-10 and IL-1 receptor
`antagonist (IL-1Ra).73 Clinical responses are typically delayed
`until 2 to 3 months of therapy.
`tolerance
`There are several reports of oral and intranasal
`induced in murine models. In a minor mismatch chronic GVHD
`model, recipients fed recipient splenocyte proteins for 11 days after
`transplantation developed less fibrosis, less organ inflammation,
`and higher levels of IL-10.74 In a parent into F1 acute GVHD
`model, tolerance was induced by posttransplantation oral adminis-
`tration of recipient splenocytes.75 The intranasal route has been
`used to tolerize female mice to male HY peptides, resulting in
`acceptance of male skin grafts and bone marrow cells that are
`rejected in controls.76 The mechanism of oral tolerance is hypoth-
`esized to be induction of a regulatory T cell of Th3 phenotype that
`secretes high amounts of TGF-␤.77
`
`Cytokine therapy
`
`Cytokines secreted by T cells, APCs, and damaged target tissues
`may contribute to chronic GVHD. T-cell cytokines are generally
`classified as Th1-type (IL-2, IFN-␥) and Th2-type (IL-4, IL-5,
`IL-10, IL-13).78 APCs and damaged target
`tissue can secrete
`TNF-␣ and IL-1. While animal studies have demonstrated the
`importance of cytokine availability to chronic GVHD develop-
`ment, documentation in human systems has been less convincing.
`Human studies in chronic GVHD have focused on circulating
`cytokine levels (IL-10, TGF-␤1), tissue cytokine expression (IL-2,
`IFN-␥, IL-4, IL-5, IL-10, IL-1␣, TNF-␣, platelet-derived growth
`factor [PDGF], TGF-␤), and donor or recipient cytokine polymor-
`phisms (IFN-␥, IL-6, IL-10, IL-1␣, IL-1␤, IL-1Ra, TNF-␣, TNF-
`␤). To date, only cytokine blockade (TNF-␣) has advanced to
`human trials for treatment of chronic GVHD.
`Studies with limited numbers of patients suggest that circulating
`IL-10 levels are lower in people with chronic GVHD, while IL-1␤,
`IL-6, TNF-␣, and TGF-␤1 levels are higher.79,80 A small study
`suggested that in vitro mononuclear cell IL-10 secretion after
`stimulation was lower in patients with chronic GVHD, while use of
`IL-10 blocking antibodies increased IFN-␥ secretion.81 This con-
`trasts with the murine parent into F1 studies in which high IL-10 is
`associated with chronic GVHD and IL-10 antibodies can block
`chronic GVHD manifestations. Of note, any human trials of
`exogenous IL-10 supplementation will have to be undertaken
`carefully as observational studies in human transplant and nontrans-
`plant settings document an association between higher serum IL-10
`levels, greater severity of septic shock, and fatal outcome.82-84
`Ochs et al30 used reverse-transcription–polymerase chain reac-
`tion (RT-PCR) to study transcription of cytokines in a limited
`number of skin biopsies from people with active chronic GVHD,
`people without active chronic GVHD, and healthy controls.
`Although IFN-␥ transcript levels were elevated in people with
`active chronic GVHD, the other cytokine levels studied were not
`different (IL-1␣, TNF-␣, IL-2, IL-4, IL-5, IL-10, PDGF, TGF-␤).
`Certain donor and recipient cytokine polymorphisms have been
`associated with chronic GVHD, but results are conflicting. In
`contrast with the findings of studies measuring circulating IL-10
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`levels, polymorphisms of IL-10 associated with higher donor85 or
`recipient86 IL-10 production were associated with chronic GVHD.
`Two recipient IL-1␣ polymorphisms were associated with chronic
`GVHD, although one polymorphism is associated with increased
`IL-1␣ while the other, with decreased IL-1␣ production.87 In
`another study, neither recipient IL-10 nor IL-1 polymorphisms
`were associated with chronic GVHD.88 Recipient IL-1Ra polymor-
`phisms associated with lower production of IL-1Ra, and thus
`perhaps more biologic activity of IL-1 were also associated with
`chronic GVHD.86
`Recipient IL-6 polymorphisms have been associated with
`chronic GVHD in 2 reports,89,90 though these studies failed to find
`an association with other donor or recipient polymorphisms
`(TNF-␣, TNF-␤, IL-1, IL-10, IFN-␥). A study by Stark et al90
`identified an association between chronic GVHD and donor
`homozygosity for the 196R allele of the TNF type II receptor
`(TNFRII), associated with decreased TNFRII levels and thus
`increased functional levels of TNF. Eternacept, a recombinant
`soluble TNF inhibitor, has reported activity in 10 steroid-refractory
`patients with chronic GVHD.91 Another TNF inhibitor, infliximab,
`has been associated with invasive fungal infections when used to
`treat steroid-refractory acute GVHD, and there are no reports of its
`use in chronic GVHD.
`
`Eliminate B cells
`
`Circulating autoantibodies and polyclonal hypergammaglobuline-
`mia were noted in the earliest reports of human chronic GVHD,92
`but more recent studies show hypogammaglobulinemia and fewer
`precursor and mature B cells.58,93 Nevertheless,
`the similarity
`between many autoimmune diseases associated with autoantibod-
`ies and the clinical manifestations of chronic GVHD has always
`been intriguing. Patients with CMV infection may have anti-CD13
`antibodies, which recognize normal structures in skin.94 Patients
`with sclerodermatous chronic GVHD are more likely to have
`immunoglobulin G (IgG) antibodies to nuclear proteins (95%), but
`these antibodies are also common in patients without chronic
`GVHD.95 Miklos et al96 have found antibody responses to H-Y
`antigens in male recipients with female donors, and these antibod-
`ies were associated with development of chronic GVHD.
`Rituximab is a chimeric murine-human CD20⫹ antibody that
`has reported activity in treating chronic GVHD and other autoim-
`mune diseases. Two case series suggest
`that
`transient B-cell
`depletion can improve clinical manifestations of chronic GVHD
`with durable responses.97,98
`
`Minimize effects on target tissues
`
`Even if the systemic causes of chronic GVHD cannot be controlled,
`treatments aimed at target tissues may still minimize morbidity and
`improve functionality. One of the major debilitating tissue re-
`sponses is fibrosis. Halofuginone has been given topically or
`systemically to inhibit TGF-␤–induced collagen ␣1 gene overex-
`pression. Halofuginone inhibits smad3 phosphorylation, particu-
`larly in fibroblasts induced to oversecrete collagen by activation
`with TGF-␤ or activating mutations, via a mechanism that relies on
`protein synthesis.99 If applied topically, halofuginone is not ab-
`sorbed and effects are reversible after 3 months. In a rat model of
`liver fibrosis, halofuginone was able to reverse fibrosis.100 In
`human and murine studies, normal collagen production was
`unaffected. Despite great interest in studying halofuginone for
`
`sclerodermatous chronic GVHD, this drug is not yet available for
`studies of chronic GVHD in the United States.
`Excess collagen deposition may also be combated through
`physical rehabilitation, similar to the treatment of burn victims and
`people with scleroderma, many of whom also suffer from excess
`collagen deposition. Aggressive heat therapy, massage, and passive
`range-of-motion exercises can help maintain function until the
`sclerotic process can be controlled.101 To date, there are no studies
`specifically evaluating rehabilitative methods in people with
`chronic GVHD.
`Ursodeoxycholic acid has reportedly improved the biochemical
`profile of patients with hepatic chronic GVHD. As a less hydropho-
`bic acid, ursodeoxycholic acid replaces the human bile acids and
`may result in less cholestatic damage. It may also cause decreased
`expression of HLA class I molecules on hepatocytes. However, this
`medication is very expensive and in one study of patients with
`chronic GVHD, biochemical improvements were lost upon discon-
`tinuation of the drug. In primary biliary sclerosis, ursodeoxycholic
`acid has improved liver function tests but not changed the natural
`history of the disease.102 No long-term studies of this drug in
`chronic GVHD have been reported.
`Biedermann et al103 studied skin biopsies in a small number of
`people with acute, chronic, or no GVHD after allogeneic transplan-
`tation, and found fewer microvessels and higher levels of von
`Willebrand factor in people with chronic GVHD. They hypothesize
`that endothelial damage happens first, followed by fibrosis akin to
`what happens in solid organ rejection. Thus, methods to prevent
`endothelial damage may have efficacy in chronic GVHD preven-
`tion or treatment.
`Topical immunosuppressives such as corticosteroids and cal-
`cineurin inhibitors can improve local symptoms in the eyes, mouth,
`skin, and vaginal area. Small series report efficacy for autologous
`serum eyedrops in Sjo¨gren syndrome and UVB laser for lichen
`planus. As new approaches to local therapy are developed for
`autoimmune diseases, rapid translation and testing in the chronic
`GVHD population seems warranted.
`
`Summary
`
`A better understanding of chronic GVHD and discovery of ways to
`prevent or control this complication without compromising disease-
`free survival stand as major barriers to the success of allogeneic
`transplantation. Far too many people