1413
1. Robson KJH, Hall
JRS, Jennings MW, et al. A highly conserved amino-acid sequence in thrombospondin, properdin and in proteins from sporozoites and blood stages of a human malaria parasite. Nature 1988; 335: 79-82. 2. Lawler J, Hynes RO. The structure of human thrombospondin, an adhesive glycoprotein with multiple calcium-binding sites and homologies with several different proteins. J Cell Biol 1986, 103: 1635-48. 3. Goundis D, Reid KBN. Properdin, the terminal complement components, thrombospondin and the circumsporozoite protein of malana parasites contain similar sequence motifs. Nature 1988; 335: 82-85. 4. Robson KJH, Hall JRS, Davies LC, Crisanti A, Hill AVS, Wellems TE. Polymorphism of the TRAP gene of Plasmodium falciparum. Proc R Soc Lond [Biol] 1990; 242: 205-16. 5. Good MF, Berzofsky JA, Miller L. The T cell response to the malaria circumsporozoite protein: an immunological approach to vaccine development. Annu Rev Immunol 1988; 6: 663-88. 6. Khusmith S, Charoenvit Y, Kumar S, Sedegah M, Beaudoin RL, Hoffman SL. Protection against malaria by vaccination with sporozoite surface protein 2 plus CS protein. Science 1991; 252: 715-18. 7. Hedstrom RC, Campbell JR, Leef ML, et al. A malaria sporozoite surface antigen distinct from the circumsporozoite protein. Bull WHO 1990; 68: 152-57. 8. Malik A, Egan JE, Houghten RA, Sadoff JC, Hoffman SL. Human cytotoxic T lymphocytes against the Plasmodium falciparum circumsporozoite protein. Proc Natl Acad Sci USA 1991; 88: 3300-04.
Arsenic, selenium, and African
trypanosomiasis SIR,-Melarsoprol is used to treat African trypanosomiasis, despite an associated case fatality rate of 2-10%, because it is usually the only drug available. Eflornithine, a recently introduced alternative, costs about$200 for a 14-day course. Post-arsenical reactive encephalopathy (PARE) has restricted the use of melarsoprol to the final stages of the disease, by which time the patient is usually debilitated and severely malnourished. Dr Hunter and colleagues (May 18, p 956) demonstrate trypanosomal DNA in the brains of fatal cases of PARE and reproduce, in mice, its pathological features by using a drug that does not penetrate the central nervous system. They suggest that "removal of the parasites from all parts of the body except the brain induces a restored immune system to respond vigorously to parasites within the brain". They cite an unpublished observation that subcurative doses of arsenicals also induce PARE whereas
higher doses do not, and now recommend more aggressive treatment-presumably higher doses of melarsoprol. This presupposes that Hurst’s suggestion! that PARE is related to arsenic toxicity is incorrect. Although it is generally thought that PARE has an immunological basis, Hunter’s suggested mechanism not only requires that the patient’s immunosuppression is entirely due to the trypanosomiasis alone but also that immunocompetence is restored, within days, despite persistence of cerebral, trypanosomal infection. The demonstration that the dose of arsenical used is not toxic in normal uninfected animals is an unsafe basis for dismissing potential toxicity in chronically infected animals. The organic arsenicals chelate elements of the sulphur/selenium group. Trypanosomes are very vulnerable to depletion of glutathione in vivo.2Arsenicals are trypanocidal by depriving the protozoa of a unique low-molecular-weight thiol (trypanothione3) that has an even higher affmity for melarsoprol than does glutathione, the low-molecular-weight thiol of most organisms. Indeed, melarsoprol is a condensation product between melarsen oxide and dimercaprol and the latter moiety alleviates some of the basic compound’s effects on the thiols of normal cells. If an infected patient (or laboratory animal) is either sulphur or selenium deficient an organic arsenical is likely to be much more toxic than usual. Severe malnutrition, infection-associated immunosuppression, protozoal infection, and a low sulphur aminoacid intake can all lead to a depletion of tissue glutathione. These conditions, which are frequently present in African trypanosomiasis, will make patients much more vulnerable to arsenic toxicity. I hypothesise that the encephalopathy associated with arsenical treatment arises in patients who have an associated selenium deficiency. Arsenic toxicity can be alleviated by selenium and is In Chinese factory greatly enhanced by selenium deficiency.4- workers, DNA strand breaks caused by arsenic exposure were rapidly reversed by doses of selenium within the range of normal dietary intakes in the westSelenium deficiency is common in the
tropics. Soil chemistry studies and the low selenium/sulphur content of staple foods in the tropics point in this direction as does measurement of blood selenium in patients from Zaire8 and other countries. Furthermore, the clinical conditions associated with glutathione deficiency usually have an associated selenium deficiency. Selenium deficiency, with or without a combined sulphur deficiency, as a basis for individual variation in melarsoprol toxicity would provide an explanation for the higher prevalence of PARE inland and in rural areas than on the African coast (A. H. Fairlamb, personal communication). If my hypothesis is correct, more aggressive therapy, in the absence of nutritional supplementation, would not be appropriate. Melarsoprol is an effective and cheap drug; if the associated morbidity and mortality could be reduced by prior nutritional supplementation the use of this drug could be extended
to
the
earlier
stages
of the
disease.
In
the
immunocompromised, anorexic, nutritionally deficient host there may be no therapeutic window between the dose of arsenical that will kill the parasite and the dose that will kill the host. Department of Medicine and Therapeutics, University of Aberdeen, Aberdeen AB9 2ZD, UK
MICHAEL H. N. GOLDEN
1. Hurst EW. The lesions
produced in the central nervous system by certain organic arsenical compounds. J Pathol Bacteriol 1959; 77: 523-34. 2. Arrick BA, Griffith OW, Cerami A. Inhibition of glutathione synthesis as a chemotherapeutic strategy for trypanosomiasis. J Exp Med 1981; 153: 720-25. 3. Hunter KJ, Strobos CA, Fairlamb AH. The interaction of trypanocidal drugs with polyamine and trypanothione metabolism. Biochem Soc Trans 1990; 18: 1094-96. 4. Sweins A. Protective effect of selenium against arsenic-induced chromosomal damage in cultured human lymphocytes. Hereditas 1983; 98: 249-52. 5. Levander OA. Metabolic interrelationships between arsenic and selenium. Environ Health Perspect 1977; 19: 159-64. 6. Muth OH, Whanger PD, Weswig PH, Oldfield JE. Occurrence of myopathy in lambs and ewes fed added arsenic in a selenium-deficient ration. Am J Vet Res 1971; 32: 1621-23 7. Hu GG. Investigation of protective effect of selenium on genetic materials among workers exposed to arsenic. Chung Hua Yu Fang I Hsueh Tsa Chih 1989; 23: 286-88. 8. Fondu P, Hariga Muller C, Mozes N, Neve J, Van Steirteghem A, Mandelbaum IM. Protein-energy malnutrition and anemia in Kivu. Am J Clin Nutr 1978; 31: 46-56.
Aflatoxin biomarkers SIR,-Professor Ross and colleagues (April 18, p 943) provide the first epidemiological evidence of an interaction at the individual level between hepatitis B persistence and aflatoxin exposure, by use of a urinary marker of exposure. The result is surprising, not because there is an interaction, but rather because the urinary aflatoxin method used can detect a risk of such magnitude. The urinary excretion of aflatoxin metabolites and adducts is very rapid and hence is dependent on the consumption of aflatoxin in the preceding 24 h.l Consequently a single measurement is unlikely to accurately indicate the long-term exposure of an individual to this carcinogen. The finding that it can demonstrate such a large statistical interaction with hepatitis B is therefore surprising. Perhaps the single measurement does indeed reflect this long-term exposure-ie, some individuals have consistently high exposure to aflatoxin and some the reverse. However, studies in the wet season in The Gambia have failed to demonstrate this happening in children.2 It seems more likely that there is considerable misclassification of individuals with the single urine sample for long-term exposure, and therefore the true interaction would be even larger than that described. As Ross et al point out, the use of the assay for aflatoxin/serum-albumin adducts would provide a longer term measure of exposure and should improve exposure classification. A second issue raised is the interval between exposure measurement and diagnosis of cancer. The major advantage of cohort studies is that the aflatoxin measurement is made before cancer develops, so that there is no question of the tumour affecting diet and/or hepatic metabolism. It would therefore be important to know the interval, at the individual level, between the urinary sampling and the diagnosis to allow some assessment of this potential bias. Chronic liver disease, including cirrhosis, often
1414
underlies hepatocellular carcinoma and might alone affect metabolism of aflatoxin, so it would be useful to know how many subjects had evidence of such disease at recruitment and diagnosis. In addition, aflatoxin/albumin-bound adduct values were higher in children positive for hepatitis B surface antigen than in non-infected or surface antigen negative infected controls in The Gambia,2 and the cytochrome P450 enzymes in the liver implicated in aflatoxin metabolism were higher in a small group of hepatitis B infected individuals.3,4 Thus hepatitis B infection could determine the exposure marker. As more cases accrue in the cohort, a detailed study of the various urinary metabolites, which reflect either activation or detoxification of aflatoxin, may be informative in this respect. Ross et al do not address the biological mechanism behind the observed statistical interaction but it is important in planning intervention strategy. They conclude that reduction of aflatoxin exposure might provide some form of cancer prevention in the short term while hepatitis B vaccinated children become mature. This conclusion assumes, however, that the aflatoxin exposure is acting after establishment of the hepatitis B carrier state and at a late stage of liver carcinogenesis. Other possibilities exist-for example, exposure to the mutagenic effects of aflatoxin in the perinatal period2,s before hepatitis infection could be of especial importance. Alternatively, aflatoxin may act as an immunosuppressant,6 allowing establishment of the hepatitis B carrier state. Intervention to reduce exposure to this widespread dietary toxin is important in relation to diseases other than cancer, and it is likely to offer the only means of finally determining causality with respect to hepatocellular carcinoma. Now that the necessary means to assess the efficacy of intervention are available, in particular the aflatoxin/serum-albumin adduct assay, the time is ripe to initiate such studies. Department of Epidemiology, London School of Hygiene and Tropical Medicine
A.
International Agency for Research Lyon, France
C. P. WILD
on
J. HALL
Cancer,
1. Wild CP, Hudson GJ, Sabbioni G, et al. Dietary intake of aflatoxins and the level of albumin-bound aflatoxin in peripheral blood in The Gambia, West Africa. Cancer Epidemiol Biomarkers Prev 1992; 1: 229-34. 2. Allen SJ, Wild CP, Wheeler JG, et al. Aflatoxin exposure, malaria and hepatitis B infection in rural Gambian children. Trans R Soc Trop Med (in press). 3. Geubel AP, Pauwels S, Buchet JP, Dumont E, Dive C. Increased cyt P-450 dependent function in health HBsAg carriers. Pharmac Ther 1987; 33: 193-96. 4. Shimada T, Guengench FP. Evidence for cytochrome P450NE, the nifedipine oxidase, being the principal enzyme involved in the bioacavation of aflatoxins in human liver. Proc Natl Acad Sci USA 1989; 86: 46265. 5. Wild CP, Rasheed FN, Jawla MFB, Hall AJ, Jansen LAM, Montesano R. In utero exposure to aflatoxin in West Africa. Lancet 1991; 337: 1602 6. Peir AC, McLoughlin ME. Mycotoxic suppression of immunity. In: Lacey J, ed. Trichothecenes and other mycotoxins. Chichester: John Wiley & Sons, 1985: 507-19.
Peripheral intravenous nutrition SIR,-We would respond to the comments made by Mr Khawaja and Mr McCullagh (April 18, p 996) on our Jan 11report (p 101). The aim of our study was to compare the fine-bore silicone catheter, which was shown to be associated with a low incidence of thrombophlebitis by Kohldart and Smith,l with a short Teflon cannula that is used in many centres for the administration of intravenous nutrition (IVN). The feed infused in our study was nutritionally complete for most surgical patients. One investigator inserted all cannulae and catheters into one of the veins in the proximal third of the forearm. We found veins in this site easy to cannulate and we had no difficulty in fixation of lines with the technique we described. Our results showed that most patients who received IVN through a fine-bore silicone catheter were free of complications. We did not find any significant difference in the incidence of thrombophlebitis between males and females in the Teflon cannula group, hence for brevity this was not reported; the incidence of thrombophlebitis in the fine-bore silicone group was too low to allow analysis of subsets. Recording of headache was not the point of the protocol, and it did not emerge as a major difficulty.
The data cited in our paper are correct as presented and as reported by Khawaja et all at the 13th congress of the European Society of Parenteral and Enteral Nutrition; however, we apologise for misquoting the reference. Although we agree that the statistical points made by Khawaja and McCullagh may be technically correct, there was such a large difference between the two groups in our study that the application of alternative statistical analyses would have little impact upon our
conclusions. In view of these results we now use peripheral IVN in most of our
patients. Academic Unit of Surgery, University of Leeds, General Infirmary, Leeds LS1 3EX, UK
MICHAEL J. MCMAHON MANMOHAN MADAN DAVID J. ALEXANDER
1. Kohldart SR, Smith RC. Fine bore silicone for perpheral intravenous nutrition in J adults. Br Med 1989; 29: 1380-81 2. Khawaja HT, Weaver PC. Peripheral total intravenous nutrition: a feasibility study. J Parenteral Enteral Nutr 1989; 13: 10S.
Endotoxin
antibody for sepsis in infants
SIR,-Dr Lorijn (April 11, p 930) rejects Dr Nadel and colleagues’ (March 14, p 678) concerns about potential adverse enhancement of cytokine production in patients receiving monoclonal antibody to endotoxin (HA-IA, Centoxin). We have investigated patients with confirmed and strongly-suspected gramnegative bacteraemia, both before and after treatment with HA-IA, sampling every 2 hours for endotoxin, tumour necrosis factor, and interleukin-6 (IL-6) for 24 hours. We have shown that production of IL-6 is not suppressed completely, and indeed was increased above pre-infusion concentrations in three of eight patients. These patients died, despite aggressive medical and surgical intervention. Of the five survivors, four showed serially decreasing IL-6; the fifth had normal values throughout the study. Although we do not disagree with Lorijn’s explanation for the complement receptor-mediated binding of immune complexes in vitro, we feel that there are insufficient data to allow extrapolation of these findings in vivo. The cytokine cascade is very complex, and little is known about the genetic mechanisms controlling individual patient response in the sepsis syndrome, or about how these mechanisms are modified by therapeutic strategies, such as monoclonal antibodies. We have noted that tumour necrosis factor (TNF) was only sporadically detected in our patients. This may indicate the nature of secretion of this cytokine or true suppression of its production. TNF suppression would be expected to be associated with inhibition of IL-6, but this does not seem to be a consistent finding in our studies. Proper control populations cannot be obtained since all patients in our units with or strongly suspected of having gram-negative infection receive IgM monoclonal antibody. We feel that individual differences in clinical response to this agent are a real possibility. Our in-vivo work is supported by similar observations in the mononuclear cell system in vitro. Department of Surgery, Institute of Clinical Science, Belfast BT12 6BJ, UK
G. DAMIAN MAGEE M. ISLA HALLIDAY BRIAN J. ROWLANDS
SIR,-Dr Lorijn says that Dr Nadel and colleagues’ suggestion that the monoclonal endotoxin antibody (HA-1A) could induce the release of inflammatory mediators is unfounded and inconsistent with what we know of the mechanism of action of HA-1A. We have investigated the spontaneous and endotoxin-induced release in vitro of interleukin-6 (IL-6) and tumour necrosis factor-alpha (TNF) in whole blood from acutely ill patients in intensive care. Samples were placed in endotoxin-free lithium heparin. Part of the sample was separated immediately and plasma IL-6 and TNF concentrations were measured (To) with a bioassay for IL-62 and an ELISA3for TNF. These concentrations were again measured in plasma separated after incubation of blood at
1. Robson KJH, Hall
JRS, Jennings MW, et al. A highly conserved amino-acid sequence in thrombospondin, properdin and in proteins from sporozoites and blood stages of a human malaria parasite. Nature 1988; 335: 79-82. 2. Lawler J, Hynes RO. The structure of human thrombospondin, an adhesive glycoprotein with multiple calcium-binding sites and homologies with several different proteins. J Cell Biol 1986, 103: 1635-48. 3. Goundis D, Reid KBN. Properdin, the terminal complement components, thrombospondin and the circumsporozoite protein of malana parasites contain similar sequence motifs. Nature 1988; 335: 82-85. 4. Robson KJH, Hall JRS, Davies LC, Crisanti A, Hill AVS, Wellems TE. Polymorphism of the TRAP gene of Plasmodium falciparum. Proc R Soc Lond [Biol] 1990; 242: 205-16. 5. Good MF, Berzofsky JA, Miller L. The T cell response to the malaria circumsporozoite protein: an immunological approach to vaccine development. Annu Rev Immunol 1988; 6: 663-88. 6. Khusmith S, Charoenvit Y, Kumar S, Sedegah M, Beaudoin RL, Hoffman SL. Protection against malaria by vaccination with sporozoite surface protein 2 plus CS protein. Science 1991; 252: 715-18. 7. Hedstrom RC, Campbell JR, Leef ML, et al. A malaria sporozoite surface antigen distinct from the circumsporozoite protein. Bull WHO 1990; 68: 152-57. 8. Malik A, Egan JE, Houghten RA, Sadoff JC, Hoffman SL. Human cytotoxic T lymphocytes against the Plasmodium falciparum circumsporozoite protein. Proc Natl Acad Sci USA 1991; 88: 3300-04.
Arsenic, selenium, and African
trypanosomiasis SIR,-Melarsoprol is used to treat African trypanosomiasis, despite an associated case fatality rate of 2-10%, because it is usually the only drug available. Eflornithine, a recently introduced alternative, costs about$200 for a 14-day course. Post-arsenical reactive encephalopathy (PARE) has restricted the use of melarsoprol to the final stages of the disease, by which time the patient is usually debilitated and severely malnourished. Dr Hunter and colleagues (May 18, p 956) demonstrate trypanosomal DNA in the brains of fatal cases of PARE and reproduce, in mice, its pathological features by using a drug that does not penetrate the central nervous system. They suggest that "removal of the parasites from all parts of the body except the brain induces a restored immune system to respond vigorously to parasites within the brain". They cite an unpublished observation that subcurative doses of arsenicals also induce PARE whereas
higher doses do not, and now recommend more aggressive treatment-presumably higher doses of melarsoprol. This presupposes that Hurst’s suggestion! that PARE is related to arsenic toxicity is incorrect. Although it is generally thought that PARE has an immunological basis, Hunter’s suggested mechanism not only requires that the patient’s immunosuppression is entirely due to the trypanosomiasis alone but also that immunocompetence is restored, within days, despite persistence of cerebral, trypanosomal infection. The demonstration that the dose of arsenical used is not toxic in normal uninfected animals is an unsafe basis for dismissing potential toxicity in chronically infected animals. The organic arsenicals chelate elements of the sulphur/selenium group. Trypanosomes are very vulnerable to depletion of glutathione in vivo.2Arsenicals are trypanocidal by depriving the protozoa of a unique low-molecular-weight thiol (trypanothione3) that has an even higher affmity for melarsoprol than does glutathione, the low-molecular-weight thiol of most organisms. Indeed, melarsoprol is a condensation product between melarsen oxide and dimercaprol and the latter moiety alleviates some of the basic compound’s effects on the thiols of normal cells. If an infected patient (or laboratory animal) is either sulphur or selenium deficient an organic arsenical is likely to be much more toxic than usual. Severe malnutrition, infection-associated immunosuppression, protozoal infection, and a low sulphur aminoacid intake can all lead to a depletion of tissue glutathione. These conditions, which are frequently present in African trypanosomiasis, will make patients much more vulnerable to arsenic toxicity. I hypothesise that the encephalopathy associated with arsenical treatment arises in patients who have an associated selenium deficiency. Arsenic toxicity can be alleviated by selenium and is In Chinese factory greatly enhanced by selenium deficiency.4- workers, DNA strand breaks caused by arsenic exposure were rapidly reversed by doses of selenium within the range of normal dietary intakes in the westSelenium deficiency is common in the
tropics. Soil chemistry studies and the low selenium/sulphur content of staple foods in the tropics point in this direction as does measurement of blood selenium in patients from Zaire8 and other countries. Furthermore, the clinical conditions associated with glutathione deficiency usually have an associated selenium deficiency. Selenium deficiency, with or without a combined sulphur deficiency, as a basis for individual variation in melarsoprol toxicity would provide an explanation for the higher prevalence of PARE inland and in rural areas than on the African coast (A. H. Fairlamb, personal communication). If my hypothesis is correct, more aggressive therapy, in the absence of nutritional supplementation, would not be appropriate. Melarsoprol is an effective and cheap drug; if the associated morbidity and mortality could be reduced by prior nutritional supplementation the use of this drug could be extended
to
the
earlier
stages
of the
disease.
In
the
immunocompromised, anorexic, nutritionally deficient host there may be no therapeutic window between the dose of arsenical that will kill the parasite and the dose that will kill the host. Department of Medicine and Therapeutics, University of Aberdeen, Aberdeen AB9 2ZD, UK
MICHAEL H. N. GOLDEN
1. Hurst EW. The lesions
produced in the central nervous system by certain organic arsenical compounds. J Pathol Bacteriol 1959; 77: 523-34. 2. Arrick BA, Griffith OW, Cerami A. Inhibition of glutathione synthesis as a chemotherapeutic strategy for trypanosomiasis. J Exp Med 1981; 153: 720-25. 3. Hunter KJ, Strobos CA, Fairlamb AH. The interaction of trypanocidal drugs with polyamine and trypanothione metabolism. Biochem Soc Trans 1990; 18: 1094-96. 4. Sweins A. Protective effect of selenium against arsenic-induced chromosomal damage in cultured human lymphocytes. Hereditas 1983; 98: 249-52. 5. Levander OA. Metabolic interrelationships between arsenic and selenium. Environ Health Perspect 1977; 19: 159-64. 6. Muth OH, Whanger PD, Weswig PH, Oldfield JE. Occurrence of myopathy in lambs and ewes fed added arsenic in a selenium-deficient ration. Am J Vet Res 1971; 32: 1621-23 7. Hu GG. Investigation of protective effect of selenium on genetic materials among workers exposed to arsenic. Chung Hua Yu Fang I Hsueh Tsa Chih 1989; 23: 286-88. 8. Fondu P, Hariga Muller C, Mozes N, Neve J, Van Steirteghem A, Mandelbaum IM. Protein-energy malnutrition and anemia in Kivu. Am J Clin Nutr 1978; 31: 46-56.
Aflatoxin biomarkers SIR,-Professor Ross and colleagues (April 18, p 943) provide the first epidemiological evidence of an interaction at the individual level between hepatitis B persistence and aflatoxin exposure, by use of a urinary marker of exposure. The result is surprising, not because there is an interaction, but rather because the urinary aflatoxin method used can detect a risk of such magnitude. The urinary excretion of aflatoxin metabolites and adducts is very rapid and hence is dependent on the consumption of aflatoxin in the preceding 24 h.l Consequently a single measurement is unlikely to accurately indicate the long-term exposure of an individual to this carcinogen. The finding that it can demonstrate such a large statistical interaction with hepatitis B is therefore surprising. Perhaps the single measurement does indeed reflect this long-term exposure-ie, some individuals have consistently high exposure to aflatoxin and some the reverse. However, studies in the wet season in The Gambia have failed to demonstrate this happening in children.2 It seems more likely that there is considerable misclassification of individuals with the single urine sample for long-term exposure, and therefore the true interaction would be even larger than that described. As Ross et al point out, the use of the assay for aflatoxin/serum-albumin adducts would provide a longer term measure of exposure and should improve exposure classification. A second issue raised is the interval between exposure measurement and diagnosis of cancer. The major advantage of cohort studies is that the aflatoxin measurement is made before cancer develops, so that there is no question of the tumour affecting diet and/or hepatic metabolism. It would therefore be important to know the interval, at the individual level, between the urinary sampling and the diagnosis to allow some assessment of this potential bias. Chronic liver disease, including cirrhosis, often
1414
underlies hepatocellular carcinoma and might alone affect metabolism of aflatoxin, so it would be useful to know how many subjects had evidence of such disease at recruitment and diagnosis. In addition, aflatoxin/albumin-bound adduct values were higher in children positive for hepatitis B surface antigen than in non-infected or surface antigen negative infected controls in The Gambia,2 and the cytochrome P450 enzymes in the liver implicated in aflatoxin metabolism were higher in a small group of hepatitis B infected individuals.3,4 Thus hepatitis B infection could determine the exposure marker. As more cases accrue in the cohort, a detailed study of the various urinary metabolites, which reflect either activation or detoxification of aflatoxin, may be informative in this respect. Ross et al do not address the biological mechanism behind the observed statistical interaction but it is important in planning intervention strategy. They conclude that reduction of aflatoxin exposure might provide some form of cancer prevention in the short term while hepatitis B vaccinated children become mature. This conclusion assumes, however, that the aflatoxin exposure is acting after establishment of the hepatitis B carrier state and at a late stage of liver carcinogenesis. Other possibilities exist-for example, exposure to the mutagenic effects of aflatoxin in the perinatal period2,s before hepatitis infection could be of especial importance. Alternatively, aflatoxin may act as an immunosuppressant,6 allowing establishment of the hepatitis B carrier state. Intervention to reduce exposure to this widespread dietary toxin is important in relation to diseases other than cancer, and it is likely to offer the only means of finally determining causality with respect to hepatocellular carcinoma. Now that the necessary means to assess the efficacy of intervention are available, in particular the aflatoxin/serum-albumin adduct assay, the time is ripe to initiate such studies. Department of Epidemiology, London School of Hygiene and Tropical Medicine
A.
International Agency for Research Lyon, France
C. P. WILD
on
J. HALL
Cancer,
1. Wild CP, Hudson GJ, Sabbioni G, et al. Dietary intake of aflatoxins and the level of albumin-bound aflatoxin in peripheral blood in The Gambia, West Africa. Cancer Epidemiol Biomarkers Prev 1992; 1: 229-34. 2. Allen SJ, Wild CP, Wheeler JG, et al. Aflatoxin exposure, malaria and hepatitis B infection in rural Gambian children. Trans R Soc Trop Med (in press). 3. Geubel AP, Pauwels S, Buchet JP, Dumont E, Dive C. Increased cyt P-450 dependent function in health HBsAg carriers. Pharmac Ther 1987; 33: 193-96. 4. Shimada T, Guengench FP. Evidence for cytochrome P450NE, the nifedipine oxidase, being the principal enzyme involved in the bioacavation of aflatoxins in human liver. Proc Natl Acad Sci USA 1989; 86: 46265. 5. Wild CP, Rasheed FN, Jawla MFB, Hall AJ, Jansen LAM, Montesano R. In utero exposure to aflatoxin in West Africa. Lancet 1991; 337: 1602 6. Peir AC, McLoughlin ME. Mycotoxic suppression of immunity. In: Lacey J, ed. Trichothecenes and other mycotoxins. Chichester: John Wiley & Sons, 1985: 507-19.
Peripheral intravenous nutrition SIR,-We would respond to the comments made by Mr Khawaja and Mr McCullagh (April 18, p 996) on our Jan 11report (p 101). The aim of our study was to compare the fine-bore silicone catheter, which was shown to be associated with a low incidence of thrombophlebitis by Kohldart and Smith,l with a short Teflon cannula that is used in many centres for the administration of intravenous nutrition (IVN). The feed infused in our study was nutritionally complete for most surgical patients. One investigator inserted all cannulae and catheters into one of the veins in the proximal third of the forearm. We found veins in this site easy to cannulate and we had no difficulty in fixation of lines with the technique we described. Our results showed that most patients who received IVN through a fine-bore silicone catheter were free of complications. We did not find any significant difference in the incidence of thrombophlebitis between males and females in the Teflon cannula group, hence for brevity this was not reported; the incidence of thrombophlebitis in the fine-bore silicone group was too low to allow analysis of subsets. Recording of headache was not the point of the protocol, and it did not emerge as a major difficulty.
The data cited in our paper are correct as presented and as reported by Khawaja et all at the 13th congress of the European Society of Parenteral and Enteral Nutrition; however, we apologise for misquoting the reference. Although we agree that the statistical points made by Khawaja and McCullagh may be technically correct, there was such a large difference between the two groups in our study that the application of alternative statistical analyses would have little impact upon our
conclusions. In view of these results we now use peripheral IVN in most of our
patients. Academic Unit of Surgery, University of Leeds, General Infirmary, Leeds LS1 3EX, UK
MICHAEL J. MCMAHON MANMOHAN MADAN DAVID J. ALEXANDER
1. Kohldart SR, Smith RC. Fine bore silicone for perpheral intravenous nutrition in J adults. Br Med 1989; 29: 1380-81 2. Khawaja HT, Weaver PC. Peripheral total intravenous nutrition: a feasibility study. J Parenteral Enteral Nutr 1989; 13: 10S.
Endotoxin
antibody for sepsis in infants
SIR,-Dr Lorijn (April 11, p 930) rejects Dr Nadel and colleagues’ (March 14, p 678) concerns about potential adverse enhancement of cytokine production in patients receiving monoclonal antibody to endotoxin (HA-IA, Centoxin). We have investigated patients with confirmed and strongly-suspected gramnegative bacteraemia, both before and after treatment with HA-IA, sampling every 2 hours for endotoxin, tumour necrosis factor, and interleukin-6 (IL-6) for 24 hours. We have shown that production of IL-6 is not suppressed completely, and indeed was increased above pre-infusion concentrations in three of eight patients. These patients died, despite aggressive medical and surgical intervention. Of the five survivors, four showed serially decreasing IL-6; the fifth had normal values throughout the study. Although we do not disagree with Lorijn’s explanation for the complement receptor-mediated binding of immune complexes in vitro, we feel that there are insufficient data to allow extrapolation of these findings in vivo. The cytokine cascade is very complex, and little is known about the genetic mechanisms controlling individual patient response in the sepsis syndrome, or about how these mechanisms are modified by therapeutic strategies, such as monoclonal antibodies. We have noted that tumour necrosis factor (TNF) was only sporadically detected in our patients. This may indicate the nature of secretion of this cytokine or true suppression of its production. TNF suppression would be expected to be associated with inhibition of IL-6, but this does not seem to be a consistent finding in our studies. Proper control populations cannot be obtained since all patients in our units with or strongly suspected of having gram-negative infection receive IgM monoclonal antibody. We feel that individual differences in clinical response to this agent are a real possibility. Our in-vivo work is supported by similar observations in the mononuclear cell system in vitro. Department of Surgery, Institute of Clinical Science, Belfast BT12 6BJ, UK
G. DAMIAN MAGEE M. ISLA HALLIDAY BRIAN J. ROWLANDS
SIR,-Dr Lorijn says that Dr Nadel and colleagues’ suggestion that the monoclonal endotoxin antibody (HA-1A) could induce the release of inflammatory mediators is unfounded and inconsistent with what we know of the mechanism of action of HA-1A. We have investigated the spontaneous and endotoxin-induced release in vitro of interleukin-6 (IL-6) and tumour necrosis factor-alpha (TNF) in whole blood from acutely ill patients in intensive care. Samples were placed in endotoxin-free lithium heparin. Part of the sample was separated immediately and plasma IL-6 and TNF concentrations were measured (To) with a bioassay for IL-62 and an ELISA3for TNF. These concentrations were again measured in plasma separated after incubation of blood at
