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Antibodies to Clp protease in primary biliary cirrhosis: possible role of a mimicking T-cell epitope
Letters to the Editor
tion testing between 1993 and efavirenz treatment (liver function tests have been performed on a three times per year basis between 1993 and 1997). Moreover, HCV RNA had been tested once before the present history in April 1997and was found negative. Because liver function tests were normal and HCV RNA was negative, no liver biopsy was performed at this time, and the patient never received interferon therapy. Therefore. it seems that HCV infection played a limited role in the occurrence of hepatitis following efavirenz treatment in this patient. The possibility of reactivation of HCV infection under antiretroviral therapy has been recently suggested [3], but detection of serum HCV RNA remained negative throughout the course of the hepatitis and no HCV-related abnormalities were found on liver biopsy. Recently, a hypersensitivity syndrome associated with efavirenz therapy has been described in a patient 20 days after starting efavirenz treatment [4]. In our case, symptoms were limited to hepatitis and rash and no lymph node or interstitial pneumonia were observed. The availability of a liver biopsy with eosinophilic in®ltrates in our observation strongly suggests that the clinical picture described here may be a part of more general hypersensitivity syndrome. Of interest, the patient reported having taken twice the
785
dosage of efavirenz during the ®rst 3 days of treatment; additional studies should determine whether efavirenz hepatotoxicity is dose-related. Physicians should be aware of such an adverse effect, especially in patients who develop rash or eosinophilia under efavirenz therapy. Renaud Verdon 1, Mathilde Six 1, Pierre Rousselot 2, Claude Bazin 1 1 Infectious Diseases Unit, University Hospital of Caen, Caen, France, 2Laboratory of Pathology, University Hospital of Caen, Caen, France
References [1] Young SD, Britcher SF, Tran OL, Payne LS, Lumma WC, Lyle TA. L743,726 (DMP-266): a novel, highly potent non-nucleoside inhibitor of the human immunode®ciency virus type 1 reverse transcriptase. Antimicrob Agents Chemother 1995;39:2602±2605. [2] Efavirenz prescribing information. In: ReÂsume des CaracteÂristiques du Produit. Du Pont Pharma Laboratories, Paris, France. [3] John M, Flexman J, French MAH. Hepatitis C virus-associated hepatitis following treatment of HIV-infected patients with HIV protease inhibitors: an immune restauration disease? AIDS 1998;12:2289±2293. [4] Bossi P, Cohn D, Bricaire F, Caumes E. Hypersensitivity syndrome associated with efavirenz therapy. Clin Infect Dis 2000;30:227±228.
Antibodies to Clp protease in primary biliary cirrhosis: possible role of a mimicking T-cell epitope To the Editor: In their recent paper, Mayo et al. [1], show that antibodies to ClpP, the proteolytic component of the ATP-dependent Clp protease of Escherichia coli, are strongly associated with primary biliary cirrhosis (PBC). They also show that such antibodies are found in a small number of apparently healthy elderly subjects, but always in association with antibodies to the E2 subunit of the pyruvate dehydrogenase complex (PDC-E2). These interesting observations are dif®cult to account for since there are no structural similarities between these antigens and the respective antibodies are not cross-reactive. We now wish to propose an explanation for this ®nding, based on help given by auto-reactive T-cells that recognise a peptide of ClpX, the regulatory sub-unit of the Clp protease complex, that is a structural mimic of a dominant T-cell epitope of PDC±E2 (Fig. 1). PDC-E2 is the diagnostic mitochondrial autoantigen for PBC [2]. Its dominant B- and T-cell epitopes have been extensively studied, and both shown to be in the inner lipoyl-binding domain of the subunit [3]. Mayo et al. have identi®ed the B-cell epitope for ClpP, and this shares no obvious homology with PDC-E2. This is in contrast with a number of microbial `mimics' of the PDC-E2 epitopes, which respectively demonstrate antibody and T-cell cross reactivity [4]. Such ®ndings, as well as epidemiological
considerations, lend support to microbial infection as having a role in the pathogenesis of the disease [4±6]. In connection with such studies we have shown [7] that 54% of a group of PBC patients showed reactivity against one or more of a panel of E. coli peptides that are functionally unrelated to, but share some sequence similarity with human mitochondrial PDC-E2213±227 (that peptide itself, KLSEGDLLAEIETDK, showed reactivity in 96% of the patients). However, in this study [7] there was one E. coli peptide that was a very strong ªmimicº of the PDC peptide but only reacted with sera of 2% of the PBC subjects. That peptide is KASEGELLAQVEPED, (identities in bold, conservative substitutions in italic), representing residues 280-294 of ClpX, the regulatory, ATP-binding sub-unit of the E. coli Clp complex. The Clp protease is a high relative molecular mass (approximately 70 000) ATP-dependent complex found in the cytoplasm of E. coli. The proteolytic subunit, ClpP, is present in 14 copies, assembled as a hollow, solid-walled cylinder, composed of two 7-fold symmetric rings stacked back-to-back [8]. Hexamers of the regulatory subunit, ClpX are attached at one or both ends of this structure [8]. These various observations lead us to suggest an explanation for the otherwise curious ®nding of disease-speci®c antibodies recognising a dominant epitope with no similarity to PDC-E2, notwithstanding that such antibodies are
786
Letters to the Editor
Fig. 1. The P subunit of the Clp complex of E. coli is recognised by a speci®c antibody present on the surface of a B lymphocyte (1). The complex is internalised (2), processed and a peptide of the X subunit is inserted in an HLA class II molecule and presented to a CD4 helper T lymphocyte possessing the appropriate T cell receptor (TCR) (3). The helper T lymphocyte releases soluble mediators such as IL4 (4) stimulating B lymphocyte proliferation and release of anti-P speci®c antibodies (5). Of note is the fact that the peptide recognised by the helper T lymphocyte shares striking similarity with the primary biliary cirrhosis (PBC) ± speci®c PDC-E2 immunodominant epitope (inset). In our hypothesis, it is the cross-reactivity between these two antigenic determinants at the helper T cell level that accounts for the PBC-speci®c antimicrobial response (P subunit of Clp complex of E. coli) described in the paper by Mayo et al. [1].
also found in a set of healthy subjects who also have antiE2 antibodies. The suggestion is that, during infection, Bcells with receptors recognising a repetitive, exposed sequence of ClpP on the Clp complex of E. coli, internalise the complex, and degrade it to release and present a peptide of the ClpX component of the complex (Fig. 1). This HLA associated peptide will be recognised by autoreactive Tcells because of molecular mimicry with a T-cell epitope of PDC-E2, thus stimulating the production of the antiClpP antibodies observed by Mayo et al. [1]. Minimal reactivity was observed against the homologous human ClpP, and it is interesting to note that although human and E. coli ClpX are highly homologous, there is little similarity between the E2-mimicking peptide of E. coli ClpX and the human protein or between human ClpX and PDC-E2. The kind of scenario proposed in this case is analogous to what is commonly seen in immune reactions to viral infections [9]. If correct in the case of antibodies to ClpP, it may also give insight into other ®ndings in PBC, such as the occurrence of various, disease-speci®c anti-nuclear antibo-
dies, where again the antigens have no obvious relationship to PDC-E2. Harold Baum 1, Dimitrios-Petrou Bogdanos 2, Diego Vergani 2 1 Division of Life Sciences, King's College, London, UK, 2 Immunology Group, Institute of Hepatology, University College London Medical School, 69±75 Chenies Mews, London WC1E 6HX, UK
References [1] Mayo I, Arizti P, Pares A, Oliva J, Doforno RA, de Sagarra MR, et al. Antibodies against the COOH-terminal region of E. coli ClpP protease in patients with primary biliary cirrhosis. J Hepatol 2000;33:528±536. [2] Bassendine MF, Jones DE, Yeaman SJ. Biochemistry and autoimmune response to the 2-oxoacid dehydrogenase complexes in primary biliary cirrhosis. Semin Liver Dis 1997;17:49±60. [3] Gershwin ME, Ansan AA, Mackay IR, Nakanuma Y, Nishio A, Rowley MJ, Coppel RL. Primary biliary cirrhosis: an orchestrated immune response against epithelial cells. Immunol Rev. 2000;174:210±225.
Letters to the Editor [4] Joplin R. Thoughts on the infectious aetiology of primary biliary cirrhosis. In: Manns MP, Paumgartner G, Leuschner U, editors. Falk Symposium 114, Immunology and Liver, Dordrecht: Kluwer Academic Publishers, 2000. pp. 268±278. [5] Burroughs AK, Butler P, Sternberg MJ, Baum H. Molecular mimicry in liver disease. Nature 1992;358:377±378. [6] Haydon GH, Neuberger J. PBC: an infectious disease? Gut 2000;47:586±588. [7] Bogdanos DP, Grasso A, Okamoto M, Butler P, Williams R, Baum H,
787
et al. Double reactivity to E. coli/pyruvate dehydrogenase complex-E2 characterises primary biliary cirrhosis. J Hepatol 2000;32(Suppl 2): 39. [8] Wang J, Hartling JA, Flanagan JM. The structure of ClpP at 2.3 A resolution suggests a model for ATP-dependent proteolysis. Cell 1997;91:447±456. [9] Liang B, Mamula MJ. Molecular mimicry and the role of B lymphocytes in the processing of autoantigens. Cell Mol Life Sci 2000;57:561±568.
Ursodeoxycholic acid for primary biliary cirrhosis: lesson for the future? To the Editor: A `rebuttal' of the results of a meta-analysis [1] and a systematic review [2] published in 1999 has appeared in an Editorial in Journal of Hepatology [3]. The two independently performed meta-analyses ± one performed as a traditional meta-analysis [1] and one as a Cochrane Hepato±Biliary systematic review [2] based on a published protocol [4] ± have demonstrated that there is no statistically signi®cant evidence supporting that ursodeoxycholic acid (UDCA) bene®cially affects the rate of mortality and/or liver transplantation in patients with primary biliary cirrhosis (PBC) compared to placebo/no intervention. The Editorial on the subject [3] disregards the negative ®nding of the recently published Pares et al. trial [5] on the issue and claims that the results of the meta-analyses are biased. To this we have the following comments: First, it has been demonstrated that the results obtained in individual patients data (IPD) meta-analyses are the same as in meta-analyses based on aggregate data from the same trials ([6] unpublished observations). IPD are not easily available, and therefore most IPD-meta-analyses will be based only on a fraction of the evidence. Consequently IPD-meta-analysis may be misleading because of trial selection bias. Thus IPD meta-analyses should call for a cautious conservative interpretation [7]. Second, the Editorial [3] presents a meta-analysis based on only ®ve of the 16 trials that have been performed [2]. This may imply a marked trial selection bias and thus be highly misleading [7]. Third, it is not surprising that different quality scores lead to different quality assessment of randomised clinical trials [8]. However, in the Goulis et al. meta-analysis [1] as well as in the systematic review [2], including all identi®ed trials on the issue, both the low quality trials and the high quality trials were unable to demonstrate any statistically signi®cant effect of UDCA versus placebo/no intervention on PBC mortality. These analyses [1,2] are suf®ciently strong to contradict the combined analyses using a biased selection of the evidence base as presented by Poupon et al. [9]. Fourth, the claim by the Editorial [3] that `it is well estab-
lished that meta-analysis is inferior to actual data obtained from larger trials' is not supported by the work of Le Lorier et al. [10], who found that agreement between metaanalyses and large clinical trials was fair. We do not contest that UDCA affects certain biochemical tests, including serum bilirubin levels, and possibly liver histology of PBC patients [3]. However, these outcomes are weak surrogates for what the patients really want, i.e., improved survival and quality of life [11]. Therefore, we disagree [1,2] with the conclusion of the Editorial that UDCA affects mortality or the combined outcome measure of mortality and liver transplantation [3]. This lack of effect on mortality is supported by the recent ®ndings of a longterm follow-up randomised trial [12]. We therefore also disagree with the recommendation [3] that future efforts should focus on improving the ef®cacy of UDCA. On the contrary, in our opinion, it is now time to focus the attention on development of more effective interventions in this disease, evaluated in large trials of high methodological quality. Christian Gluud 1, Erik Christensen 2 The Copenhagen Trial Unit, Centre for Clinical Intervention Research, Copenhagen University Hospital, H:S Rigshospitalet,Copenhagen, Denmark 2 Clinic of Internal Medicine I, Bispebjerg University Hospital,Copenhagen, Denmark
1
References [1] Goulis J, Leandro G, Burroughs AK. Randomised controlled trials of ursodeoxycholic-acid therapy for primary biliary cirrhosis. Lancet 1999;354:1053±1060. [2] Gluud C, Christensen F. Ursodeoxycholic acid (UDCA) in primary biliary cirrhosis (PBC) ± a Cochrane Hepato±Biliary Systematic Review. J Hepatol 1999;30:83A [Abstract]. [3] Poupon RE. Ursodeoxycholic acid for primary biliary cirrhosis: lessons from the past ± issues for the future. J Hepatol 2000;32:685± 688. [4] Gluud C, Christensen E. Ursodeoxycholic acid for primary biliary cirrhosis. (Protocol for a Cochrane Review), The Cochrane Library, Issue 3. Oxford: Update Software, 1999. [5] The UDCA-Cooperative Group from the Spanish Association of the Study of the Liver, Pares A, Caballerla L, RodeÂs J, Bruguera M,
tion testing between 1993 and efavirenz treatment (liver function tests have been performed on a three times per year basis between 1993 and 1997). Moreover, HCV RNA had been tested once before the present history in April 1997and was found negative. Because liver function tests were normal and HCV RNA was negative, no liver biopsy was performed at this time, and the patient never received interferon therapy. Therefore. it seems that HCV infection played a limited role in the occurrence of hepatitis following efavirenz treatment in this patient. The possibility of reactivation of HCV infection under antiretroviral therapy has been recently suggested [3], but detection of serum HCV RNA remained negative throughout the course of the hepatitis and no HCV-related abnormalities were found on liver biopsy. Recently, a hypersensitivity syndrome associated with efavirenz therapy has been described in a patient 20 days after starting efavirenz treatment [4]. In our case, symptoms were limited to hepatitis and rash and no lymph node or interstitial pneumonia were observed. The availability of a liver biopsy with eosinophilic in®ltrates in our observation strongly suggests that the clinical picture described here may be a part of more general hypersensitivity syndrome. Of interest, the patient reported having taken twice the
785
dosage of efavirenz during the ®rst 3 days of treatment; additional studies should determine whether efavirenz hepatotoxicity is dose-related. Physicians should be aware of such an adverse effect, especially in patients who develop rash or eosinophilia under efavirenz therapy. Renaud Verdon 1, Mathilde Six 1, Pierre Rousselot 2, Claude Bazin 1 1 Infectious Diseases Unit, University Hospital of Caen, Caen, France, 2Laboratory of Pathology, University Hospital of Caen, Caen, France
References [1] Young SD, Britcher SF, Tran OL, Payne LS, Lumma WC, Lyle TA. L743,726 (DMP-266): a novel, highly potent non-nucleoside inhibitor of the human immunode®ciency virus type 1 reverse transcriptase. Antimicrob Agents Chemother 1995;39:2602±2605. [2] Efavirenz prescribing information. In: ReÂsume des CaracteÂristiques du Produit. Du Pont Pharma Laboratories, Paris, France. [3] John M, Flexman J, French MAH. Hepatitis C virus-associated hepatitis following treatment of HIV-infected patients with HIV protease inhibitors: an immune restauration disease? AIDS 1998;12:2289±2293. [4] Bossi P, Cohn D, Bricaire F, Caumes E. Hypersensitivity syndrome associated with efavirenz therapy. Clin Infect Dis 2000;30:227±228.
Antibodies to Clp protease in primary biliary cirrhosis: possible role of a mimicking T-cell epitope To the Editor: In their recent paper, Mayo et al. [1], show that antibodies to ClpP, the proteolytic component of the ATP-dependent Clp protease of Escherichia coli, are strongly associated with primary biliary cirrhosis (PBC). They also show that such antibodies are found in a small number of apparently healthy elderly subjects, but always in association with antibodies to the E2 subunit of the pyruvate dehydrogenase complex (PDC-E2). These interesting observations are dif®cult to account for since there are no structural similarities between these antigens and the respective antibodies are not cross-reactive. We now wish to propose an explanation for this ®nding, based on help given by auto-reactive T-cells that recognise a peptide of ClpX, the regulatory sub-unit of the Clp protease complex, that is a structural mimic of a dominant T-cell epitope of PDC±E2 (Fig. 1). PDC-E2 is the diagnostic mitochondrial autoantigen for PBC [2]. Its dominant B- and T-cell epitopes have been extensively studied, and both shown to be in the inner lipoyl-binding domain of the subunit [3]. Mayo et al. have identi®ed the B-cell epitope for ClpP, and this shares no obvious homology with PDC-E2. This is in contrast with a number of microbial `mimics' of the PDC-E2 epitopes, which respectively demonstrate antibody and T-cell cross reactivity [4]. Such ®ndings, as well as epidemiological
considerations, lend support to microbial infection as having a role in the pathogenesis of the disease [4±6]. In connection with such studies we have shown [7] that 54% of a group of PBC patients showed reactivity against one or more of a panel of E. coli peptides that are functionally unrelated to, but share some sequence similarity with human mitochondrial PDC-E2213±227 (that peptide itself, KLSEGDLLAEIETDK, showed reactivity in 96% of the patients). However, in this study [7] there was one E. coli peptide that was a very strong ªmimicº of the PDC peptide but only reacted with sera of 2% of the PBC subjects. That peptide is KASEGELLAQVEPED, (identities in bold, conservative substitutions in italic), representing residues 280-294 of ClpX, the regulatory, ATP-binding sub-unit of the E. coli Clp complex. The Clp protease is a high relative molecular mass (approximately 70 000) ATP-dependent complex found in the cytoplasm of E. coli. The proteolytic subunit, ClpP, is present in 14 copies, assembled as a hollow, solid-walled cylinder, composed of two 7-fold symmetric rings stacked back-to-back [8]. Hexamers of the regulatory subunit, ClpX are attached at one or both ends of this structure [8]. These various observations lead us to suggest an explanation for the otherwise curious ®nding of disease-speci®c antibodies recognising a dominant epitope with no similarity to PDC-E2, notwithstanding that such antibodies are
786
Letters to the Editor
Fig. 1. The P subunit of the Clp complex of E. coli is recognised by a speci®c antibody present on the surface of a B lymphocyte (1). The complex is internalised (2), processed and a peptide of the X subunit is inserted in an HLA class II molecule and presented to a CD4 helper T lymphocyte possessing the appropriate T cell receptor (TCR) (3). The helper T lymphocyte releases soluble mediators such as IL4 (4) stimulating B lymphocyte proliferation and release of anti-P speci®c antibodies (5). Of note is the fact that the peptide recognised by the helper T lymphocyte shares striking similarity with the primary biliary cirrhosis (PBC) ± speci®c PDC-E2 immunodominant epitope (inset). In our hypothesis, it is the cross-reactivity between these two antigenic determinants at the helper T cell level that accounts for the PBC-speci®c antimicrobial response (P subunit of Clp complex of E. coli) described in the paper by Mayo et al. [1].
also found in a set of healthy subjects who also have antiE2 antibodies. The suggestion is that, during infection, Bcells with receptors recognising a repetitive, exposed sequence of ClpP on the Clp complex of E. coli, internalise the complex, and degrade it to release and present a peptide of the ClpX component of the complex (Fig. 1). This HLA associated peptide will be recognised by autoreactive Tcells because of molecular mimicry with a T-cell epitope of PDC-E2, thus stimulating the production of the antiClpP antibodies observed by Mayo et al. [1]. Minimal reactivity was observed against the homologous human ClpP, and it is interesting to note that although human and E. coli ClpX are highly homologous, there is little similarity between the E2-mimicking peptide of E. coli ClpX and the human protein or between human ClpX and PDC-E2. The kind of scenario proposed in this case is analogous to what is commonly seen in immune reactions to viral infections [9]. If correct in the case of antibodies to ClpP, it may also give insight into other ®ndings in PBC, such as the occurrence of various, disease-speci®c anti-nuclear antibo-
dies, where again the antigens have no obvious relationship to PDC-E2. Harold Baum 1, Dimitrios-Petrou Bogdanos 2, Diego Vergani 2 1 Division of Life Sciences, King's College, London, UK, 2 Immunology Group, Institute of Hepatology, University College London Medical School, 69±75 Chenies Mews, London WC1E 6HX, UK
References [1] Mayo I, Arizti P, Pares A, Oliva J, Doforno RA, de Sagarra MR, et al. Antibodies against the COOH-terminal region of E. coli ClpP protease in patients with primary biliary cirrhosis. J Hepatol 2000;33:528±536. [2] Bassendine MF, Jones DE, Yeaman SJ. Biochemistry and autoimmune response to the 2-oxoacid dehydrogenase complexes in primary biliary cirrhosis. Semin Liver Dis 1997;17:49±60. [3] Gershwin ME, Ansan AA, Mackay IR, Nakanuma Y, Nishio A, Rowley MJ, Coppel RL. Primary biliary cirrhosis: an orchestrated immune response against epithelial cells. Immunol Rev. 2000;174:210±225.
Letters to the Editor [4] Joplin R. Thoughts on the infectious aetiology of primary biliary cirrhosis. In: Manns MP, Paumgartner G, Leuschner U, editors. Falk Symposium 114, Immunology and Liver, Dordrecht: Kluwer Academic Publishers, 2000. pp. 268±278. [5] Burroughs AK, Butler P, Sternberg MJ, Baum H. Molecular mimicry in liver disease. Nature 1992;358:377±378. [6] Haydon GH, Neuberger J. PBC: an infectious disease? Gut 2000;47:586±588. [7] Bogdanos DP, Grasso A, Okamoto M, Butler P, Williams R, Baum H,
787
et al. Double reactivity to E. coli/pyruvate dehydrogenase complex-E2 characterises primary biliary cirrhosis. J Hepatol 2000;32(Suppl 2): 39. [8] Wang J, Hartling JA, Flanagan JM. The structure of ClpP at 2.3 A resolution suggests a model for ATP-dependent proteolysis. Cell 1997;91:447±456. [9] Liang B, Mamula MJ. Molecular mimicry and the role of B lymphocytes in the processing of autoantigens. Cell Mol Life Sci 2000;57:561±568.
Ursodeoxycholic acid for primary biliary cirrhosis: lesson for the future? To the Editor: A `rebuttal' of the results of a meta-analysis [1] and a systematic review [2] published in 1999 has appeared in an Editorial in Journal of Hepatology [3]. The two independently performed meta-analyses ± one performed as a traditional meta-analysis [1] and one as a Cochrane Hepato±Biliary systematic review [2] based on a published protocol [4] ± have demonstrated that there is no statistically signi®cant evidence supporting that ursodeoxycholic acid (UDCA) bene®cially affects the rate of mortality and/or liver transplantation in patients with primary biliary cirrhosis (PBC) compared to placebo/no intervention. The Editorial on the subject [3] disregards the negative ®nding of the recently published Pares et al. trial [5] on the issue and claims that the results of the meta-analyses are biased. To this we have the following comments: First, it has been demonstrated that the results obtained in individual patients data (IPD) meta-analyses are the same as in meta-analyses based on aggregate data from the same trials ([6] unpublished observations). IPD are not easily available, and therefore most IPD-meta-analyses will be based only on a fraction of the evidence. Consequently IPD-meta-analysis may be misleading because of trial selection bias. Thus IPD meta-analyses should call for a cautious conservative interpretation [7]. Second, the Editorial [3] presents a meta-analysis based on only ®ve of the 16 trials that have been performed [2]. This may imply a marked trial selection bias and thus be highly misleading [7]. Third, it is not surprising that different quality scores lead to different quality assessment of randomised clinical trials [8]. However, in the Goulis et al. meta-analysis [1] as well as in the systematic review [2], including all identi®ed trials on the issue, both the low quality trials and the high quality trials were unable to demonstrate any statistically signi®cant effect of UDCA versus placebo/no intervention on PBC mortality. These analyses [1,2] are suf®ciently strong to contradict the combined analyses using a biased selection of the evidence base as presented by Poupon et al. [9]. Fourth, the claim by the Editorial [3] that `it is well estab-
lished that meta-analysis is inferior to actual data obtained from larger trials' is not supported by the work of Le Lorier et al. [10], who found that agreement between metaanalyses and large clinical trials was fair. We do not contest that UDCA affects certain biochemical tests, including serum bilirubin levels, and possibly liver histology of PBC patients [3]. However, these outcomes are weak surrogates for what the patients really want, i.e., improved survival and quality of life [11]. Therefore, we disagree [1,2] with the conclusion of the Editorial that UDCA affects mortality or the combined outcome measure of mortality and liver transplantation [3]. This lack of effect on mortality is supported by the recent ®ndings of a longterm follow-up randomised trial [12]. We therefore also disagree with the recommendation [3] that future efforts should focus on improving the ef®cacy of UDCA. On the contrary, in our opinion, it is now time to focus the attention on development of more effective interventions in this disease, evaluated in large trials of high methodological quality. Christian Gluud 1, Erik Christensen 2 The Copenhagen Trial Unit, Centre for Clinical Intervention Research, Copenhagen University Hospital, H:S Rigshospitalet,Copenhagen, Denmark 2 Clinic of Internal Medicine I, Bispebjerg University Hospital,Copenhagen, Denmark
1
References [1] Goulis J, Leandro G, Burroughs AK. Randomised controlled trials of ursodeoxycholic-acid therapy for primary biliary cirrhosis. Lancet 1999;354:1053±1060. [2] Gluud C, Christensen F. Ursodeoxycholic acid (UDCA) in primary biliary cirrhosis (PBC) ± a Cochrane Hepato±Biliary Systematic Review. J Hepatol 1999;30:83A [Abstract]. [3] Poupon RE. Ursodeoxycholic acid for primary biliary cirrhosis: lessons from the past ± issues for the future. J Hepatol 2000;32:685± 688. [4] Gluud C, Christensen E. Ursodeoxycholic acid for primary biliary cirrhosis. (Protocol for a Cochrane Review), The Cochrane Library, Issue 3. Oxford: Update Software, 1999. [5] The UDCA-Cooperative Group from the Spanish Association of the Study of the Liver, Pares A, Caballerla L, RodeÂs J, Bruguera M,