- Email: [email protected]
Predicting the outcome of hepatitis C virus infection
312
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GASTROENTEROLOGY Vol. 120, No. 1
bilirubin level ⬎ 5 mg/dL, serum creatinine level ⬎ 3 mg/dL, or hepatic encephalopathy beyond grade 1. In fact, baseline values for these parameters in the study population were well below these cutoff criteria, as exemplified by the fact that ⬎80% of the patients had a serum bilirubin level ⬍ 3 mg/dL. It is likely that the stringent selection criteria ensured a generally favorable prognosis for the study population, a conclusion supported by the high 1-year survival rate and significant incidence of spontaneous resolution of ascites observed in the paracentesis cohort. Furthermore, more than three quarter of the patients included in the study had alcoholic liver disease, which has been associated with a more favorable response to TIPS than other causes of cirrhosis (Hepatology 2000;31:864 – 871). It is notable that Ro¨ssle et al. were not only able to successfully deploy a shunt in all but 1 patient (who subsequently underwent a successful implantation 15 months later), but also apparently did not experience any acute complications associated with the procedure. Moreover, patients in the TIPS cohort did not show significant worsening of hepatic encephalopathy compared with the paracentesis group. This surprising observation, which is contrary to previous reports indicating a significant increase in the grade of encephalopathy after TIPS (Semin Liver Dis 1996;16:315–320), may reflect the select nature of the patient population as well as the technical prowess and enormous experience of the investigators. However, even under these nearly ideal circumstances, 1 patient in the TIPS cohort (and 2 additional patients in the paracentesis group who received rescue shunts) did develop debilitating encephalopathy, necessitating subsequent intervention to reduce flow through the shunt. An additional 2 patients who experienced a suboptimal response to TIPS were deemed unable to undergo shunt revision because of concerns about exacerbating overt hepatic encephalopathy. Of note, the issue of cost-effectiveness of TIPS remains to be addressed. Although the investigators show a decrease (albeit nonsignificant) in the number of hospitalization days for the shunt cohort, this potential cost savings must be balanced against the increased expense of the TIPS procedure compared with large-volume paracentesis (N Engl J Med 2000;342:1745–1747). Moreover, even in the best of hands, a high rate of shunt stenosis has been reported ( J Clin Gastroenterol 2000;30:14 –28). In the present study, 38% of patients required one revision of the TIPS and an additional 17% underwent a second procedure over the course of the study. Hence, the frequency and cost associated with monitoring and reestablishing shunt patency must be factored in to any cost analysis. Which patients with refractory ascites should be offered TIPS? Extrapolating from the data, it appears that (1) a proportion of patients improve with large-volume paracentesis alone, (2) mortality rates for TIPS and large volume paracentesis are similar over the first 3– 6 months of treatment, and (3) salvage TIPS in patients who do not respond to large-volume paracentesis is effective. Based on these observations, it can be reasonably argued that all patients with ascites unresponsive to diuretic therapy should initially be managed with large-volume paracentesis over a several month period. In experienced hands, TIPS seems to be a viable and appropriate alternative for those select individuals with preserved renal function, minimal encephalopathy, and low serum bilirubin levels (⬍3 mg/dL) who do not respond to an adequate trial of paracentesis. Obviously, the ensuing development of other complications of cirrhosis for which TIPS has been shown to be effective, such as recurrent variceal hemorrhage or hepatic hydrothorax (Gastrointest Endosc 1998;47:584 –587, JAMA 1995;273:1824 –1830, Semin Liver Dis 1999;19:457– 473), may prompt consideration for earlier intervention. STEPHEN D. ZUCKER, M.D.
Reply. Although we fully agree with most of Dr. Zucker’s statements, we would like to make a few comments. The citation of Colapinto et al. (Can Med Assoc J 1982;196:267– 268) as the first report of TIPS is misleading. Colapinto et al. reported on balloon dilatation of the parenchymal tract without the implantation of a metallic stent. The results were disappointing and investigations therefore discontinued. The first report describing the TIPS implantation in a patient with the use of a metallic stent was published in 1988 (Hepatology 1988;8:1348A). This abstract was followed by a letter (Lancet 1989;2:153) and a full publication (Radiologe 1989;29:406 – 411) by the same group. Dr. Zucker states that stringent selection criteria used in our study ensured a favorable response to TIPS. However, we feel that the exclusion criteria were comparable with most studies investigating paracentesis in patients with cirrhosis. Furthermore, a subgroup analysis, not contained in the published manuscript, showed the same favorable trend toward improved survival in Child–Pugh class C patients treated with TIPS. Thus, in contrast to the conclusions of a study with a smaller number of patients ( J Hepatol 1996;25:135– 144), we consider that TIPS can be beneficial for patients with advanced cirrhosis. Furthermore, patients with marked renal insufficiency were included in the study. These patients responded well to TIPS with an increase of creatinine clearance from 41 ⫾ 27 mL/min at baseline to 61 ⫾ 36 mL/min at 6 months after TIPS. These observations are in line with our previous findings that the extent of renal response to TIPS in patients with cirrhosis is inversely related to the functional renal impairment before TIPS (Hepatology 1998;28: 683– 688). Encephalopathy was not significantly increased in the TIPS compared with the paracentesis group. This in part may be due to the select nature of the patient population as stated by Dr. Zucker, but also partly because of the beneficial effects of TIPS on factors favoring encephalopathy. Factors such as hyponatremia, renal impairment, and electrolyte imbalance improve after the shunt and may compensate for a negative effect of shunting on encephalopathy. The suggestion first to use paracentesis over a period of several months before proceeding to TIPS was deduced from our study. Most of the patients included had refractory ascites for months and had received multiple paracenteses before TIPS. However, if tense ascites recurs very rapidly without identifying an explanation (e.g., spontaneous bacterial peritonitis, portal vein thrombosis), the probability of further response to paracentesis is rather low and, therefore, TIPS implantation may be indicated without further delay. ALEXANDER L. GERBES, M.D. MARTIN RO¨SSLE, M.D.
PREDICTING THE OUTCOME OF HEPATITIS C VIRUS INFECTION Farci P, Shimoda A, Coiana A, Diaz G, Peddis G, Melpolder JC, Strazzera A, Chien DY, Munoz SJ, Balestrieri A, Purcell RH, Alter HJ. The outcome of acute hepatitis C predicted by the evolution of the viral quasispecies. Science 2000;288:339 – 344. Farci et al. examined the relationship between the natural history of hepatitis C virus (HCV) infection and the evolution of quasispecies. Generation of quasispecies (defined as the simultaneous presence of different but closely related viral
January 2001
variants within the same individual) has been proposed to allow the virus to circumvent the immune response, and therefore lead to chronic infection. Serial serum samples were obtained from 12 patients with HCV enrolled in a long-term study of posttransfusion hepatitis (Ann Intern Med 1986;104:488 – 495) who were selected on the basis of their clinical outcome determined during clinical evaluation for up to 20 years. Three patients had fulminant hepatitis, 3 patients had acute self-limited hepatitis (rapid clearance of HCV RNA from the serum within 16 weeks after transfusion), and 6 patients had persistent viremia and progression of hepatitis to chronicity. Using this cohort of 12 patients, the study investigators examined the number of viral variants, genetic distance between the different variants (genetic diversity), and evolution of HCV quasispecies over time. These features were correlated with the level of viral replication, humoral immune response, and clinical outcome. Sequences within the HCV sequences spanning the envelope genes (E1 and E2) both within and outside the hypervariable region 1 (HVR1) were analyzed. In early stages of infection, the genetic diversity and the number of viral variants within the HCV quasispecies did not differ significantly between patients who had resolution of HCV infection and those who developed chronic disease. However, later in the course of infection (i.e., after antibody seroconversion) patients with resolving hepatitis had a decrease in the genetic diversity (of HVR1), whereas those with progressive hepatitis had a marked increase in genetic diversity. The number of viral variants, as assessed by HVR1 sequences, did not correlate with disease outcome, although a slight increase in the number of variants was observed for those with progressive hepatitis. There were significant changes in genetic diversity from the time before antibody conversion to after antibody conversion upon comparing resolving hepatitis (lower genetic diversity) and progressing hepatitis (higher genetic diversity). The investigators also found that the mean number of nonsynonymous nucleotide substitutions per week within HVR1 was significantly higher in progressing hepatitis than in resolving or fulminant hepatitis, whereas the mean number of synonymous nucleotide substitutions per week within HVR1 was similar for all 3 groups. Interestingly, in fulminant hepatitis, there was a higher degree of amino acid conservation both within and outside HVR1, despite a high rate of viral replication and synonymous substitutions. These data suggest that a homogeneous viral population is maintained in fulminant hepatitis. Comment. HCV, a single-stranded RNA virus consisting of 9000 nucleotides, is genetically complex. Many studies have emphasized HCV genetic variability, including HCV quasispecies in several situations ( J Virol 2000;74:805– 811 and 2000;74:661– 668, Hepatology 1999;30:1037–1044). Considerable work has further attempted to correlate this information with meaningful clinical insight about the course of the disease. However, there is limited information on the early evolution of HCV genetic variability; therefore, an important strength of the study by Farci is that it provides information about HCV during the natural history of disease.
SELECTED SUMMARIES
313
Perhaps the most important implication of this study is its suggestion that the outcome of acute hepatitis C may be determined during the acute phase of HCV infection. This conclusion fits reasonably well with the widely held postulate that HCV evades the host immune response by mutation in immune epitopes. Indeed, the investigators report that in resolving hepatitis there was a monophyletic population, whereas in progressive hepatitis, there was a tendency to form clusters over time, suggesting the emergence of more diverse populations in this group, implying that diversity is good for the virus and bad for the host. Does this study prove that outcome of acute HCV infection may be determined in the early phase of infection? The answer is probably not, because only small numbers of patients were studied. Indeed, larger numbers of patients with various types of HCV exposure will have to be observed prospectively. Nonetheless, the study raises a critical putative hypothesis for the mechanism of persistent HCV infection. The study raises another important issue concerning acute infection with HCV. How does the body normally clear HCV? If viral clearance correlates with a reduction in viral genotypic diversity, in patients who are unable to clear the virus, the possibility of an inadequate host response (i.e., which would pressure the virus into greater genetic diversity) is raised. Alternatively, in patients who clear the virus, a highly effective immune system would be predicted to eradicate all but the most abundant variants. Further, a potent immune response would be predicted to eradicate a surviving (genetically simple) final variant. Farci et al. provide substantial evidence that the putative envelope 2 region containing the HVR1 region of HCV is most prone to mutation during evolution of infection. This finding is consistent with the observation that interferon ␣ therapy was shown to cause mutations in the HVR1 region in 9 of 9 patients examined, compared with only 2 of 9 patients with mutations in nonstructural areas ( J Virol 1998;72:4288 – 4296). The implication is that the acute infections, as well as interferon ␣, somehow exert pressure on the virus, perhaps by stimulation of the immune system. A critical question concerning this study is whether the data in transfusion-associated HCV infection as studied by Farci et al. can be extrapolated to other forms of infection. Remote HCV infection is most commonly associated with transfusion, whereas recent infection is currently most commonly caused by illegal drug use (Am J Med 1999;107:2S–9S). Given differences in the clinical course of HCV infection after transfusion compared with other forms of exposure, it is reasonable to speculate that there may be differences in the biology of quasispecies generation and genetic diversity after diverse forms of HCV exposure. One of the most important questions concerning this study is whether this new information can be translated to the clinic. Given the postulate that the outcome of acute hepatitis C may be predicted by the evolution of genetic variability during the acute phase of HCV infection, the relevant question becomes: could such knowledge be used in the clinic to predict who will clear the virus and who will go on to develop severe disease? Implicit in the answer to this question is the notion that those who might be predicted to have an aggressive course should have some sort of intervention. Addressing this issue then leads to further questions. First, by the time it is known which patients exhibit genetic diversity, is it too late for therapy to have an improved outcome? Would patients with increased numbers of HCV variants, early in their course, be more or less responsive to therapy? Can response rates be predicted based on genetic diversity of HCV? Farci et al. have clearly provided an important and interesting view of
314
SELECTED SUMMARIES
GASTROENTEROLOGY Vol. 120, No. 1
the natural history of HCV infection, but more work is required to address the resulting important translational questions. DON C. ROCKEY, M.D.
PROKINETICS REDUCE BACTERIAL TRANSLOCATION IN CIRRHOSIS: WILL SWEEPING THE GUT KEEP THE FLUID CLEAN? Pe´rez-Pa´ramo M, Mun˜oz J, Albillos A, Freile I, Portero F, Santos M, Ortiz-Berrocal J (Divisions of Nuclear Medicine, Gastroenterology, Microbiology, and Experimental Surgery, Clı´nica Puerta de Hierro; and Division of Gastroenterology, Hospital Ramo´n y Cajal, Madrid, Spain). Effect of propranolol on the factors promoting bacterial translocation in cirrhotic rats with ascites. Hepatology 2000;31:43– 48. Pardo A, Bartoli R, Lorenzo-Zu´uˆiga V, Planas R, Viuˆado B, Riba J, Cabre´ E, Santos J, Luque T, Ausina V, Gassull M (Departments of Gastroenterology, Microbiology, and Nuclear Medicine, Hospital Universitari Germans Trias I Pujol, Badalona, Spain). Effect of cisapride on intestinal bacterial overgrowth and bacterial translocation in cirrhosis. Hepatology 2000;31: 858 – 863. Bacterial translocation, the phenomenon by which viable microorganisms from the intestinal lumen migrate to mesenteric lymph nodes (MLNs) and other extraintestinal sites, has been postulated as one of the main mechanisms in the pathogenesis of spontaneous bacterial peritonitis (SBP) and other spontaneous infections in cirrhosis. Bacterial translocation is facilitated by intestinal bacterial overgrowth (BO) that in turn is facilitated by disorders in intestinal motility. The present studies show that BO and bacterial translocation can be decreased in cirrhosis by accelerating intestinal transit, either with propranolol (Hepatology 2000;31:43– 48) or with cisapride (Hepatology 2000;31:858 – 863). Pe´rez-Pa´ramo et al. used rats with CCl4-induced cirrhosis and ascites. In the first part of the study, they assessed BO (by aerobic culture of ileal content), intestinal transit time (by determination of the geometric center ratio of orally administered 51Cr), and intestinal permeability (by the urinary excretion of 99mTc-diethylenetriaminepentaacetic acid) and related them to the presence or absence of bacterial translocation (defined as positive MLN bacteriologic culture). Bacterial translocation was present in 48% (14/29) cirrhotic rats and in none of 20 controls. BO was significantly more frequent in animals with bacterial translocation (13/14 or 93%) than in those without translocation (7/15 or 47%) and was related to a delayed intestinal transit time. Of 9 cirrhotic rats without BO, only 1 (11%) had positive MLN cultures. Intestinal permeability was significantly increased in cirrhotic animals, particularly in those with bacterial translocation. Although bacterial translocation occurred in 13 of 15 (87%) rats that had both BO and increased intestinal permeability, it occurred in 0 of 6 animals with increased intestinal permeability alone, in 0 of 5 with BO alone, and in 1 of 3 (33%) rats in which both
factors were absent. In the second part of the study, a 2-week course of propranolol was administered to 13 cirrhotic rats and results were compared with 12 placebo-treated animals. Propranolol-treated animals had a significantly shorter intestinal transit time and lower rates of BO and bacterial translocation. Bacterial translocation was absent in the 15 animals (11 propranolol-treated, 4 placebo-treated) that had no evidence of BO. Although the rate of SBP was lower in propranolol-treated animals (8%), it was not significantly different from placebotreated rats (33%). In the first part of their study, Pardo et al. studied the effect of a 7-day course of cisapride on BO (by bacteriologic analysis of jejunal content) and on bacterial translocation (defined as the presence of viable enteric organisms in MLNs) in rats with CCl4-induced cirrhosis and ascites. Cisapride significantly reduced BO in cirrhotic rats, and although bacterial translocation did not occur in any of the 15 cisapride-treated animals, it was present in 40% (6/15) of the untreated rats. Translocation occurred in only 1/20 (5%) cirrhotic rats without BO. Bacterial peritonitis was present in only 1 untreated animal (not significantly different from treated animals). In the second part of the study, jejunal fluid was obtained from 46 cirrhotic patients; BO was detected in 23 of them, 10 caused by gram-negative organisms. Orocecal transit time (time between ingestion of an isotope and increase of activity in the cecal area) significantly decreased after cisapride therapy, which was associated with elimination of BO in 4 of 5 patients. Both studies concluded that propranolol, cisapride, or other prokinetic agents may be useful in preventing bacterial translocation and may therefore be useful in preventing spontaneous infections in cirrhosis. Comment. Bacterial translocation, BO, and alterations in intestinal motility have all been shown to be more frequent in cirrhosis, particularly in animals or patients with the most severe liver disease. Although there is evidence of an association between bacterial translocation and SBP, it is still unclear whether the relationship is causal or circumstantial. Evidence in favor of the gut as the source of bacteria in SBP supports a causal relationship. Organisms isolated from ascites of patients with SBP are predominantly of enteric origin, and selective intestinal decontamination by the use of oral nonabsorbable antibiotics has been shown to decrease the development of SBP. Additionally, cirrhotic rats with positive ascites cultures have concurrent positive MLN cultures, often with the same organism. In fact, a study that performed DNA typing of isolated organisms showed an identity rate of 80% in 5 cases in which bacteria were isolated from both MLNs and ascites ( J Hepatol 1998;28:307–313). Pe´rez-Pa´ramo et al. suggests that for bacterial translocation to occur, both BO and an increased intestinal permeability must be present; however, they also show that the elimination of BO alone, without changes in intestinal permeability, leads to a decrease in bacterial translocation. This suggests that bacterial translocation occurs more as a result of BO than from a loss of intestinal barrier function, a concept that is supported by experiments performed in rats fed an elemental diet (Am J Surg 1991;161:300 –304). BO has been shown to be more prevalent in cirrhotic patients than in healthy controls, particularly those with more severe liver disease (Dig Dis Sci 1995;40:1252–1256) and those with a prior history of
SELECTED SUMMARIES
GASTROENTEROLOGY Vol. 120, No. 1
bilirubin level ⬎ 5 mg/dL, serum creatinine level ⬎ 3 mg/dL, or hepatic encephalopathy beyond grade 1. In fact, baseline values for these parameters in the study population were well below these cutoff criteria, as exemplified by the fact that ⬎80% of the patients had a serum bilirubin level ⬍ 3 mg/dL. It is likely that the stringent selection criteria ensured a generally favorable prognosis for the study population, a conclusion supported by the high 1-year survival rate and significant incidence of spontaneous resolution of ascites observed in the paracentesis cohort. Furthermore, more than three quarter of the patients included in the study had alcoholic liver disease, which has been associated with a more favorable response to TIPS than other causes of cirrhosis (Hepatology 2000;31:864 – 871). It is notable that Ro¨ssle et al. were not only able to successfully deploy a shunt in all but 1 patient (who subsequently underwent a successful implantation 15 months later), but also apparently did not experience any acute complications associated with the procedure. Moreover, patients in the TIPS cohort did not show significant worsening of hepatic encephalopathy compared with the paracentesis group. This surprising observation, which is contrary to previous reports indicating a significant increase in the grade of encephalopathy after TIPS (Semin Liver Dis 1996;16:315–320), may reflect the select nature of the patient population as well as the technical prowess and enormous experience of the investigators. However, even under these nearly ideal circumstances, 1 patient in the TIPS cohort (and 2 additional patients in the paracentesis group who received rescue shunts) did develop debilitating encephalopathy, necessitating subsequent intervention to reduce flow through the shunt. An additional 2 patients who experienced a suboptimal response to TIPS were deemed unable to undergo shunt revision because of concerns about exacerbating overt hepatic encephalopathy. Of note, the issue of cost-effectiveness of TIPS remains to be addressed. Although the investigators show a decrease (albeit nonsignificant) in the number of hospitalization days for the shunt cohort, this potential cost savings must be balanced against the increased expense of the TIPS procedure compared with large-volume paracentesis (N Engl J Med 2000;342:1745–1747). Moreover, even in the best of hands, a high rate of shunt stenosis has been reported ( J Clin Gastroenterol 2000;30:14 –28). In the present study, 38% of patients required one revision of the TIPS and an additional 17% underwent a second procedure over the course of the study. Hence, the frequency and cost associated with monitoring and reestablishing shunt patency must be factored in to any cost analysis. Which patients with refractory ascites should be offered TIPS? Extrapolating from the data, it appears that (1) a proportion of patients improve with large-volume paracentesis alone, (2) mortality rates for TIPS and large volume paracentesis are similar over the first 3– 6 months of treatment, and (3) salvage TIPS in patients who do not respond to large-volume paracentesis is effective. Based on these observations, it can be reasonably argued that all patients with ascites unresponsive to diuretic therapy should initially be managed with large-volume paracentesis over a several month period. In experienced hands, TIPS seems to be a viable and appropriate alternative for those select individuals with preserved renal function, minimal encephalopathy, and low serum bilirubin levels (⬍3 mg/dL) who do not respond to an adequate trial of paracentesis. Obviously, the ensuing development of other complications of cirrhosis for which TIPS has been shown to be effective, such as recurrent variceal hemorrhage or hepatic hydrothorax (Gastrointest Endosc 1998;47:584 –587, JAMA 1995;273:1824 –1830, Semin Liver Dis 1999;19:457– 473), may prompt consideration for earlier intervention. STEPHEN D. ZUCKER, M.D.
Reply. Although we fully agree with most of Dr. Zucker’s statements, we would like to make a few comments. The citation of Colapinto et al. (Can Med Assoc J 1982;196:267– 268) as the first report of TIPS is misleading. Colapinto et al. reported on balloon dilatation of the parenchymal tract without the implantation of a metallic stent. The results were disappointing and investigations therefore discontinued. The first report describing the TIPS implantation in a patient with the use of a metallic stent was published in 1988 (Hepatology 1988;8:1348A). This abstract was followed by a letter (Lancet 1989;2:153) and a full publication (Radiologe 1989;29:406 – 411) by the same group. Dr. Zucker states that stringent selection criteria used in our study ensured a favorable response to TIPS. However, we feel that the exclusion criteria were comparable with most studies investigating paracentesis in patients with cirrhosis. Furthermore, a subgroup analysis, not contained in the published manuscript, showed the same favorable trend toward improved survival in Child–Pugh class C patients treated with TIPS. Thus, in contrast to the conclusions of a study with a smaller number of patients ( J Hepatol 1996;25:135– 144), we consider that TIPS can be beneficial for patients with advanced cirrhosis. Furthermore, patients with marked renal insufficiency were included in the study. These patients responded well to TIPS with an increase of creatinine clearance from 41 ⫾ 27 mL/min at baseline to 61 ⫾ 36 mL/min at 6 months after TIPS. These observations are in line with our previous findings that the extent of renal response to TIPS in patients with cirrhosis is inversely related to the functional renal impairment before TIPS (Hepatology 1998;28: 683– 688). Encephalopathy was not significantly increased in the TIPS compared with the paracentesis group. This in part may be due to the select nature of the patient population as stated by Dr. Zucker, but also partly because of the beneficial effects of TIPS on factors favoring encephalopathy. Factors such as hyponatremia, renal impairment, and electrolyte imbalance improve after the shunt and may compensate for a negative effect of shunting on encephalopathy. The suggestion first to use paracentesis over a period of several months before proceeding to TIPS was deduced from our study. Most of the patients included had refractory ascites for months and had received multiple paracenteses before TIPS. However, if tense ascites recurs very rapidly without identifying an explanation (e.g., spontaneous bacterial peritonitis, portal vein thrombosis), the probability of further response to paracentesis is rather low and, therefore, TIPS implantation may be indicated without further delay. ALEXANDER L. GERBES, M.D. MARTIN RO¨SSLE, M.D.
PREDICTING THE OUTCOME OF HEPATITIS C VIRUS INFECTION Farci P, Shimoda A, Coiana A, Diaz G, Peddis G, Melpolder JC, Strazzera A, Chien DY, Munoz SJ, Balestrieri A, Purcell RH, Alter HJ. The outcome of acute hepatitis C predicted by the evolution of the viral quasispecies. Science 2000;288:339 – 344. Farci et al. examined the relationship between the natural history of hepatitis C virus (HCV) infection and the evolution of quasispecies. Generation of quasispecies (defined as the simultaneous presence of different but closely related viral
January 2001
variants within the same individual) has been proposed to allow the virus to circumvent the immune response, and therefore lead to chronic infection. Serial serum samples were obtained from 12 patients with HCV enrolled in a long-term study of posttransfusion hepatitis (Ann Intern Med 1986;104:488 – 495) who were selected on the basis of their clinical outcome determined during clinical evaluation for up to 20 years. Three patients had fulminant hepatitis, 3 patients had acute self-limited hepatitis (rapid clearance of HCV RNA from the serum within 16 weeks after transfusion), and 6 patients had persistent viremia and progression of hepatitis to chronicity. Using this cohort of 12 patients, the study investigators examined the number of viral variants, genetic distance between the different variants (genetic diversity), and evolution of HCV quasispecies over time. These features were correlated with the level of viral replication, humoral immune response, and clinical outcome. Sequences within the HCV sequences spanning the envelope genes (E1 and E2) both within and outside the hypervariable region 1 (HVR1) were analyzed. In early stages of infection, the genetic diversity and the number of viral variants within the HCV quasispecies did not differ significantly between patients who had resolution of HCV infection and those who developed chronic disease. However, later in the course of infection (i.e., after antibody seroconversion) patients with resolving hepatitis had a decrease in the genetic diversity (of HVR1), whereas those with progressive hepatitis had a marked increase in genetic diversity. The number of viral variants, as assessed by HVR1 sequences, did not correlate with disease outcome, although a slight increase in the number of variants was observed for those with progressive hepatitis. There were significant changes in genetic diversity from the time before antibody conversion to after antibody conversion upon comparing resolving hepatitis (lower genetic diversity) and progressing hepatitis (higher genetic diversity). The investigators also found that the mean number of nonsynonymous nucleotide substitutions per week within HVR1 was significantly higher in progressing hepatitis than in resolving or fulminant hepatitis, whereas the mean number of synonymous nucleotide substitutions per week within HVR1 was similar for all 3 groups. Interestingly, in fulminant hepatitis, there was a higher degree of amino acid conservation both within and outside HVR1, despite a high rate of viral replication and synonymous substitutions. These data suggest that a homogeneous viral population is maintained in fulminant hepatitis. Comment. HCV, a single-stranded RNA virus consisting of 9000 nucleotides, is genetically complex. Many studies have emphasized HCV genetic variability, including HCV quasispecies in several situations ( J Virol 2000;74:805– 811 and 2000;74:661– 668, Hepatology 1999;30:1037–1044). Considerable work has further attempted to correlate this information with meaningful clinical insight about the course of the disease. However, there is limited information on the early evolution of HCV genetic variability; therefore, an important strength of the study by Farci is that it provides information about HCV during the natural history of disease.
SELECTED SUMMARIES
313
Perhaps the most important implication of this study is its suggestion that the outcome of acute hepatitis C may be determined during the acute phase of HCV infection. This conclusion fits reasonably well with the widely held postulate that HCV evades the host immune response by mutation in immune epitopes. Indeed, the investigators report that in resolving hepatitis there was a monophyletic population, whereas in progressive hepatitis, there was a tendency to form clusters over time, suggesting the emergence of more diverse populations in this group, implying that diversity is good for the virus and bad for the host. Does this study prove that outcome of acute HCV infection may be determined in the early phase of infection? The answer is probably not, because only small numbers of patients were studied. Indeed, larger numbers of patients with various types of HCV exposure will have to be observed prospectively. Nonetheless, the study raises a critical putative hypothesis for the mechanism of persistent HCV infection. The study raises another important issue concerning acute infection with HCV. How does the body normally clear HCV? If viral clearance correlates with a reduction in viral genotypic diversity, in patients who are unable to clear the virus, the possibility of an inadequate host response (i.e., which would pressure the virus into greater genetic diversity) is raised. Alternatively, in patients who clear the virus, a highly effective immune system would be predicted to eradicate all but the most abundant variants. Further, a potent immune response would be predicted to eradicate a surviving (genetically simple) final variant. Farci et al. provide substantial evidence that the putative envelope 2 region containing the HVR1 region of HCV is most prone to mutation during evolution of infection. This finding is consistent with the observation that interferon ␣ therapy was shown to cause mutations in the HVR1 region in 9 of 9 patients examined, compared with only 2 of 9 patients with mutations in nonstructural areas ( J Virol 1998;72:4288 – 4296). The implication is that the acute infections, as well as interferon ␣, somehow exert pressure on the virus, perhaps by stimulation of the immune system. A critical question concerning this study is whether the data in transfusion-associated HCV infection as studied by Farci et al. can be extrapolated to other forms of infection. Remote HCV infection is most commonly associated with transfusion, whereas recent infection is currently most commonly caused by illegal drug use (Am J Med 1999;107:2S–9S). Given differences in the clinical course of HCV infection after transfusion compared with other forms of exposure, it is reasonable to speculate that there may be differences in the biology of quasispecies generation and genetic diversity after diverse forms of HCV exposure. One of the most important questions concerning this study is whether this new information can be translated to the clinic. Given the postulate that the outcome of acute hepatitis C may be predicted by the evolution of genetic variability during the acute phase of HCV infection, the relevant question becomes: could such knowledge be used in the clinic to predict who will clear the virus and who will go on to develop severe disease? Implicit in the answer to this question is the notion that those who might be predicted to have an aggressive course should have some sort of intervention. Addressing this issue then leads to further questions. First, by the time it is known which patients exhibit genetic diversity, is it too late for therapy to have an improved outcome? Would patients with increased numbers of HCV variants, early in their course, be more or less responsive to therapy? Can response rates be predicted based on genetic diversity of HCV? Farci et al. have clearly provided an important and interesting view of
314
SELECTED SUMMARIES
GASTROENTEROLOGY Vol. 120, No. 1
the natural history of HCV infection, but more work is required to address the resulting important translational questions. DON C. ROCKEY, M.D.
PROKINETICS REDUCE BACTERIAL TRANSLOCATION IN CIRRHOSIS: WILL SWEEPING THE GUT KEEP THE FLUID CLEAN? Pe´rez-Pa´ramo M, Mun˜oz J, Albillos A, Freile I, Portero F, Santos M, Ortiz-Berrocal J (Divisions of Nuclear Medicine, Gastroenterology, Microbiology, and Experimental Surgery, Clı´nica Puerta de Hierro; and Division of Gastroenterology, Hospital Ramo´n y Cajal, Madrid, Spain). Effect of propranolol on the factors promoting bacterial translocation in cirrhotic rats with ascites. Hepatology 2000;31:43– 48. Pardo A, Bartoli R, Lorenzo-Zu´uˆiga V, Planas R, Viuˆado B, Riba J, Cabre´ E, Santos J, Luque T, Ausina V, Gassull M (Departments of Gastroenterology, Microbiology, and Nuclear Medicine, Hospital Universitari Germans Trias I Pujol, Badalona, Spain). Effect of cisapride on intestinal bacterial overgrowth and bacterial translocation in cirrhosis. Hepatology 2000;31: 858 – 863. Bacterial translocation, the phenomenon by which viable microorganisms from the intestinal lumen migrate to mesenteric lymph nodes (MLNs) and other extraintestinal sites, has been postulated as one of the main mechanisms in the pathogenesis of spontaneous bacterial peritonitis (SBP) and other spontaneous infections in cirrhosis. Bacterial translocation is facilitated by intestinal bacterial overgrowth (BO) that in turn is facilitated by disorders in intestinal motility. The present studies show that BO and bacterial translocation can be decreased in cirrhosis by accelerating intestinal transit, either with propranolol (Hepatology 2000;31:43– 48) or with cisapride (Hepatology 2000;31:858 – 863). Pe´rez-Pa´ramo et al. used rats with CCl4-induced cirrhosis and ascites. In the first part of the study, they assessed BO (by aerobic culture of ileal content), intestinal transit time (by determination of the geometric center ratio of orally administered 51Cr), and intestinal permeability (by the urinary excretion of 99mTc-diethylenetriaminepentaacetic acid) and related them to the presence or absence of bacterial translocation (defined as positive MLN bacteriologic culture). Bacterial translocation was present in 48% (14/29) cirrhotic rats and in none of 20 controls. BO was significantly more frequent in animals with bacterial translocation (13/14 or 93%) than in those without translocation (7/15 or 47%) and was related to a delayed intestinal transit time. Of 9 cirrhotic rats without BO, only 1 (11%) had positive MLN cultures. Intestinal permeability was significantly increased in cirrhotic animals, particularly in those with bacterial translocation. Although bacterial translocation occurred in 13 of 15 (87%) rats that had both BO and increased intestinal permeability, it occurred in 0 of 6 animals with increased intestinal permeability alone, in 0 of 5 with BO alone, and in 1 of 3 (33%) rats in which both
factors were absent. In the second part of the study, a 2-week course of propranolol was administered to 13 cirrhotic rats and results were compared with 12 placebo-treated animals. Propranolol-treated animals had a significantly shorter intestinal transit time and lower rates of BO and bacterial translocation. Bacterial translocation was absent in the 15 animals (11 propranolol-treated, 4 placebo-treated) that had no evidence of BO. Although the rate of SBP was lower in propranolol-treated animals (8%), it was not significantly different from placebotreated rats (33%). In the first part of their study, Pardo et al. studied the effect of a 7-day course of cisapride on BO (by bacteriologic analysis of jejunal content) and on bacterial translocation (defined as the presence of viable enteric organisms in MLNs) in rats with CCl4-induced cirrhosis and ascites. Cisapride significantly reduced BO in cirrhotic rats, and although bacterial translocation did not occur in any of the 15 cisapride-treated animals, it was present in 40% (6/15) of the untreated rats. Translocation occurred in only 1/20 (5%) cirrhotic rats without BO. Bacterial peritonitis was present in only 1 untreated animal (not significantly different from treated animals). In the second part of the study, jejunal fluid was obtained from 46 cirrhotic patients; BO was detected in 23 of them, 10 caused by gram-negative organisms. Orocecal transit time (time between ingestion of an isotope and increase of activity in the cecal area) significantly decreased after cisapride therapy, which was associated with elimination of BO in 4 of 5 patients. Both studies concluded that propranolol, cisapride, or other prokinetic agents may be useful in preventing bacterial translocation and may therefore be useful in preventing spontaneous infections in cirrhosis. Comment. Bacterial translocation, BO, and alterations in intestinal motility have all been shown to be more frequent in cirrhosis, particularly in animals or patients with the most severe liver disease. Although there is evidence of an association between bacterial translocation and SBP, it is still unclear whether the relationship is causal or circumstantial. Evidence in favor of the gut as the source of bacteria in SBP supports a causal relationship. Organisms isolated from ascites of patients with SBP are predominantly of enteric origin, and selective intestinal decontamination by the use of oral nonabsorbable antibiotics has been shown to decrease the development of SBP. Additionally, cirrhotic rats with positive ascites cultures have concurrent positive MLN cultures, often with the same organism. In fact, a study that performed DNA typing of isolated organisms showed an identity rate of 80% in 5 cases in which bacteria were isolated from both MLNs and ascites ( J Hepatol 1998;28:307–313). Pe´rez-Pa´ramo et al. suggests that for bacterial translocation to occur, both BO and an increased intestinal permeability must be present; however, they also show that the elimination of BO alone, without changes in intestinal permeability, leads to a decrease in bacterial translocation. This suggests that bacterial translocation occurs more as a result of BO than from a loss of intestinal barrier function, a concept that is supported by experiments performed in rats fed an elemental diet (Am J Surg 1991;161:300 –304). BO has been shown to be more prevalent in cirrhotic patients than in healthy controls, particularly those with more severe liver disease (Dig Dis Sci 1995;40:1252–1256) and those with a prior history of