1345
their sole indicator of filtration. Also, their figure seems to show creatinine concentrations in only six patients. Rabelink et al offer some explanations for the observed reduction in albuminuria with simvastatin, including an interaction between apolipoprotein B and albumin synthesis. There is no evidence that apolipoprotein B concentration has any effect on hepatic albumin as
synthesis, and reduced glomerular injury is probably a direct benefit of lipid lowering therapy. Glomerular injury may have diminished because of reduced mesangial cell uptake of native or modified low-density lipoprotein, which would otherwise lead to mesangial proliferation.’,’ There may also be reduced lipoproteinglycosaminoglycan binding at the basement membrane,’ or reduced glomerular macrophage activity. The importance of each of these mechanisms is uncertain. Such new data, as Rabelink
et
al
provide,
is welcome. Double-
blind, placebo controlled trials with accurate measurement of GFR are now needed. Only then will the place of lipid lowering nephrotic syndrome be more clearly defined.
Department of Nephrology and Transplantation, Royal Free Hospital, London NW3 2QG, UK
in the
MARK THOMAS JOHN F. MOORHEAD
JR, Kamovsky MJ. Focal and segmental glomerulosclerosis: analogies to atherosclerosis. Kidney Int 1988; 33: 917-24. 2. Frick HM, Elo O, Haapa K, et al. Helsinki heart study, primary prevention trial with gemfibrozil in middle-aged men with dyslipidemia: safety of treatment, changes in risk factors, and incidence of coronary heart disease. N Engl J Med 1987; 317: 1237-45. 3. Lipid Research Clinics Program. The Lipid Research Clinics Coronary Primary Prevention Trial results, I: reduction in incidence of coronary heart disease. JAMA 1984; 251: 351-64. 4. Bauer JH, Brooks CS, Burch RN. Clinical appraisal of creatinine clearance as a measure of glomerular filtration rate. Am J Kidney Dis 1982; 2: 337-46. 5. Shemesh O, Golbetz H, Kriss J, Myers B. Limitations of creatinine as a filtration marker in glomerulopathic patients. Kidney Int 1985; 28: 830-38. 6. Wheeler DC, Persaud JW, Femando R, Sweny P, Varghese Z, Moorhead JF. Effects of low-density lipoproteins on mesangial cell growth and viability in vitro. Nephrol Dial Transplant 1990; 5: 185-91. 7 Moorhead JF, Chan MK, El Nahas M, Varghese Z Lipid nephrotoxicity in chronic progressive glomerular and tubulo-interstitial disease. Lancet 1982; ii 1309-11. 1. Diamond
Specificity of hepatitis C antibody ELISA patients with haemophilia
in
SiR,-Dr McFarlane and colleagues (March 31, p 754) report that from patients with autoimmune chronic active hepatitis may contain a component that gives false-positive results in the Ortho ELISA test for antibodies to hepatitis C virus (HCV)-thus joining others who claim that a reliable, independent confirmatory anti-HCV assay is urgently needed. We have reported1 that 193 (82%) of 236 patients with haemophilia attending this centre had anti-HCV as a consequence of repeated infusions with infectious clotting factor concentrates. The prevalence of anti-HCV was very high in patients with persistently (93%) or intermittently (90%) increased serum transaminase activities. However, antibody was also found in 63% of 81 patients who had had persistently normal transaminase values for ten years. In patients with raised transaminase activities anti-HCV is thought to be a marker for persistent infection with non-A, non-B hepatitis agent but its significance where transaminase activity is consistently normal is less clear, and we wondered if false-positive reactions might occur as a result of the raised IgG levels that often develop as a consequence of repeated clotting factor infusions or HIV infection. The development of a recombinant-based immunoblot assay (RIBA; Chiron, Emeryville, California) has enabled us to investigate the specificity of the anti-HCV ELISA reactions in the 51 patients with serum
normal transaminases. The RIBA detects antibodies directed against three recombinant antigens-namely, the 5-1-1 polypeptide of HCV, which is produced in Escherichia coli clones of HCV as a fusion protein with human superoxide dismutase (SOD); the SOD fusion protein C-100-3 produced by selected yeast clones, which is the antigen present in the ELISA: and the SOD protein itself, which is in the RIBA as control. 20 td of serum is incubated for 4 h at room temperature with these three antigens immobilised in lanes on nitrocellulose strips. The strips are then reacted with goat
anti-human IgG labelled with horseradish peroxidase. Anti-HCV reactions were seen in 47 sera (92%). Of the remaining 4, 1 gave a positive reaction with 5-1-1 antigen only and 1 with C-100-3 antigen only, and 2 gave no reactions at all. This study confirms that the ELISA reactions for anti-HCV that we found in patients with haemophilia and normal transaminase activities, were specific. Further investigations are necessary to establish whether this antibody denotes previous exposure to the
virus
or
chronic infection.
Institute of Internal Medicine, A Bianchi Bonomi Hemophilia and Thrombosis Centre.
University of Milan, 20122 Milan, Italy
MASSIMO COLOMBO MARIA GRAZIA RUMI PIER MANNUCCIO MANNUCCI
1. Rumi MG, Colombo M, Gringeri A, Mannucci PM. High prevalence of antibodies to hepatitis C virus in multitransfused hemophiliacs with normal transaminase levels. Ann Intern Med 1990; 112: 379-80.
Antibody to superoxide dismutase, autoimmune hepatitis, and antibody tests for hepatitis C virus SIR,-Dr McFarlane and colleagues (March 31, p 754) report a high prevalence of antibody to hepatitis C virus (HCV) in patients with autoimmune chronic active hepatitis. They suggest that the Ortho HCV ELISA gave false-positive results. Dr Gray and colleagues (March 10, p 609) also suggest that anti-HCV detected by this assay contains non-specific low-avidity antibodies. In this ELISA a recombinant HCV peptide (C100-3)/superoxide dismutase (SOD) fusion polypeptide is the target antigen.’ Could the antibody in sera from patients with autoimmune chronic active hepatitis be reacting with SOD portion of the fusion polypeptide? We have used
an
ELISA based
on
SOD from bovine
erythrocytes (Sigma Chemical)2 to search for antibody to SOD and found it in all of nine anti-HCV positive patients with autoimmune chronic active hepatitis but in none of ten anti-HCV positive patients with transfusion-related chronic hepatitis (figure). The ELISA absorbance values in the anti-HCV assay correlated well with those in the assay for anti-SOD antibody in all ten patients with autoimmune chronic active hepatitis (p
their sole indicator of filtration. Also, their figure seems to show creatinine concentrations in only six patients. Rabelink et al offer some explanations for the observed reduction in albuminuria with simvastatin, including an interaction between apolipoprotein B and albumin synthesis. There is no evidence that apolipoprotein B concentration has any effect on hepatic albumin as
synthesis, and reduced glomerular injury is probably a direct benefit of lipid lowering therapy. Glomerular injury may have diminished because of reduced mesangial cell uptake of native or modified low-density lipoprotein, which would otherwise lead to mesangial proliferation.’,’ There may also be reduced lipoproteinglycosaminoglycan binding at the basement membrane,’ or reduced glomerular macrophage activity. The importance of each of these mechanisms is uncertain. Such new data, as Rabelink
et
al
provide,
is welcome. Double-
blind, placebo controlled trials with accurate measurement of GFR are now needed. Only then will the place of lipid lowering nephrotic syndrome be more clearly defined.
Department of Nephrology and Transplantation, Royal Free Hospital, London NW3 2QG, UK
in the
MARK THOMAS JOHN F. MOORHEAD
JR, Kamovsky MJ. Focal and segmental glomerulosclerosis: analogies to atherosclerosis. Kidney Int 1988; 33: 917-24. 2. Frick HM, Elo O, Haapa K, et al. Helsinki heart study, primary prevention trial with gemfibrozil in middle-aged men with dyslipidemia: safety of treatment, changes in risk factors, and incidence of coronary heart disease. N Engl J Med 1987; 317: 1237-45. 3. Lipid Research Clinics Program. The Lipid Research Clinics Coronary Primary Prevention Trial results, I: reduction in incidence of coronary heart disease. JAMA 1984; 251: 351-64. 4. Bauer JH, Brooks CS, Burch RN. Clinical appraisal of creatinine clearance as a measure of glomerular filtration rate. Am J Kidney Dis 1982; 2: 337-46. 5. Shemesh O, Golbetz H, Kriss J, Myers B. Limitations of creatinine as a filtration marker in glomerulopathic patients. Kidney Int 1985; 28: 830-38. 6. Wheeler DC, Persaud JW, Femando R, Sweny P, Varghese Z, Moorhead JF. Effects of low-density lipoproteins on mesangial cell growth and viability in vitro. Nephrol Dial Transplant 1990; 5: 185-91. 7 Moorhead JF, Chan MK, El Nahas M, Varghese Z Lipid nephrotoxicity in chronic progressive glomerular and tubulo-interstitial disease. Lancet 1982; ii 1309-11. 1. Diamond
Specificity of hepatitis C antibody ELISA patients with haemophilia
in
SiR,-Dr McFarlane and colleagues (March 31, p 754) report that from patients with autoimmune chronic active hepatitis may contain a component that gives false-positive results in the Ortho ELISA test for antibodies to hepatitis C virus (HCV)-thus joining others who claim that a reliable, independent confirmatory anti-HCV assay is urgently needed. We have reported1 that 193 (82%) of 236 patients with haemophilia attending this centre had anti-HCV as a consequence of repeated infusions with infectious clotting factor concentrates. The prevalence of anti-HCV was very high in patients with persistently (93%) or intermittently (90%) increased serum transaminase activities. However, antibody was also found in 63% of 81 patients who had had persistently normal transaminase values for ten years. In patients with raised transaminase activities anti-HCV is thought to be a marker for persistent infection with non-A, non-B hepatitis agent but its significance where transaminase activity is consistently normal is less clear, and we wondered if false-positive reactions might occur as a result of the raised IgG levels that often develop as a consequence of repeated clotting factor infusions or HIV infection. The development of a recombinant-based immunoblot assay (RIBA; Chiron, Emeryville, California) has enabled us to investigate the specificity of the anti-HCV ELISA reactions in the 51 patients with serum
normal transaminases. The RIBA detects antibodies directed against three recombinant antigens-namely, the 5-1-1 polypeptide of HCV, which is produced in Escherichia coli clones of HCV as a fusion protein with human superoxide dismutase (SOD); the SOD fusion protein C-100-3 produced by selected yeast clones, which is the antigen present in the ELISA: and the SOD protein itself, which is in the RIBA as control. 20 td of serum is incubated for 4 h at room temperature with these three antigens immobilised in lanes on nitrocellulose strips. The strips are then reacted with goat
anti-human IgG labelled with horseradish peroxidase. Anti-HCV reactions were seen in 47 sera (92%). Of the remaining 4, 1 gave a positive reaction with 5-1-1 antigen only and 1 with C-100-3 antigen only, and 2 gave no reactions at all. This study confirms that the ELISA reactions for anti-HCV that we found in patients with haemophilia and normal transaminase activities, were specific. Further investigations are necessary to establish whether this antibody denotes previous exposure to the
virus
or
chronic infection.
Institute of Internal Medicine, A Bianchi Bonomi Hemophilia and Thrombosis Centre.
University of Milan, 20122 Milan, Italy
MASSIMO COLOMBO MARIA GRAZIA RUMI PIER MANNUCCIO MANNUCCI
1. Rumi MG, Colombo M, Gringeri A, Mannucci PM. High prevalence of antibodies to hepatitis C virus in multitransfused hemophiliacs with normal transaminase levels. Ann Intern Med 1990; 112: 379-80.
Antibody to superoxide dismutase, autoimmune hepatitis, and antibody tests for hepatitis C virus SIR,-Dr McFarlane and colleagues (March 31, p 754) report a high prevalence of antibody to hepatitis C virus (HCV) in patients with autoimmune chronic active hepatitis. They suggest that the Ortho HCV ELISA gave false-positive results. Dr Gray and colleagues (March 10, p 609) also suggest that anti-HCV detected by this assay contains non-specific low-avidity antibodies. In this ELISA a recombinant HCV peptide (C100-3)/superoxide dismutase (SOD) fusion polypeptide is the target antigen.’ Could the antibody in sera from patients with autoimmune chronic active hepatitis be reacting with SOD portion of the fusion polypeptide? We have used
an
ELISA based
on
SOD from bovine
erythrocytes (Sigma Chemical)2 to search for antibody to SOD and found it in all of nine anti-HCV positive patients with autoimmune chronic active hepatitis but in none of ten anti-HCV positive patients with transfusion-related chronic hepatitis (figure). The ELISA absorbance values in the anti-HCV assay correlated well with those in the assay for anti-SOD antibody in all ten patients with autoimmune chronic active hepatitis (p
