IMedical Hypotheses
Monoclonal Antibody Therapy in the Treatment of Reye’s Syndrome S. P. TREON and S. A. BROITMAN Departments of Micmbdogy
and Pathology, Boston University School of Medicine, Boston, MA 02118, USA
Abstract-A role for lipopolysaccharides (endotoxins, LPS) in7 the pathogenesis of Reye’s syndrome (RS) has previously been suggested. Impairment of hepatic LPS clearance can lead to systemic endotoxemia as previous studies by this and other laboratories have suggested for several hepatic disorders including RS. Systemic LPS may mediate many of the clinical findings associated with RS by eliciting monokines such as tumor necrosis factor-alpha, interleukin-1 , interleukin-6, and interleukin-6. Monoclonal antibody therapy directed at LPS, and monokines may represent a novel approach to the treatment of RS.
Introduction Reye’s syndrome (RS) is predominantly a childhood disease which commonly follows a prodromal febrile illness. RS is characterized by protracted vomiting, delirium, stupor, and is often complicated by seizures, coma and death (1, 2). Use of salicylates during a viral febrile illness, which in children commonly includes varicella, and influenza has been implicated in the etiology of RS (1, 2). Case reports have also described RS in adults (3,4, 5). and in the absence of preceding febrile illness (6). RS is characterized histopathologically by a fatty liver secondary to fatty acid accumulation and associated hepatocellular necrosis with evidence of mitochondrial intoxication (1, 2). A presumptive diagnosis of RS is based on clinical grounds including history and presentation, along with supporting liver function tests and plasma ammonia levels suggestive of hepatic insult. Confirmation of RS requires liver biopsy (7). Date received 18 March 1992 Date accqwd 14 May 1992
The etiology of RS remains unknown. A role for endotoxin (lipopolysaccharides, LPS) was suggested by Cooperstock et al (8) who demonstrated systemic endotoxemia in children with RS. Involvement of LPS in the pathogenesis of RS is supported by the work of Kilpatrick et al (9) who showed in a rat model that sublethal doses of LPS plus aspirin (ASA) produce similar biochemical and histopathologic findings as those found in RS patients, Rats administered sublethal doses of LPS showed significantly decreased hepatic energy production secondary to impaired hepatic fatty acid oxidation as reflected by decreased ATP/ADP levels, acetyl-CoA production and ketogenesis. Administration of LPS plus aspirin (ASA) to rats had minimal effects versus LPS alone on hepatic fatty acid oxidation; however, a significant increase in metabolites of odd-chain fatty acid (OCFA) and branched-chain amino acid (BCAA) oxidation pathways was noted (9). ASA administered alone showed
238
MONOCLONAL. ANTIBODY THERAPY IN THE TREATMENT OF REYE’S SYNDROME
minimal effects on hepatic fatty acid oxidation but did result in modest increases in metabolites of GCFA and BCAA oxidation pathways (9). Decreased hepatic acetyl-CoA and ketone levels and increased metabolites of OCFA and BCAA oxidation pathways have also been demonstrated by Corkey et al (10) in human liver biopsy samples taken from RS patients versus controls. Histologically, livers of rats subjected to LPS plus ASA showed microvesicular fat deposition and mitochondriaI swelling similar to liver biopsy samples taken from RS patients. Hepatic clearance of gut derived LPS There exists a large reservoir of LPS in the gut of man due to the presence of gram negative bacteria which constitute the bulk of normal colonic flora. LPS arising from the gut flora readily transit through gut mucosa (11). Supporting the concept that LPS readily cross the gut mucosa. Jacob et al (12) demonstrated portal venous endotoxemia in 33 of 34 patients who underwent abdominal surgery. In contrast, systemic endotoxemia was detected in 4 of these 33 patients, among whom 3 patients had a hepatic disorder, and one a gram negative septicemia. Impairment of hepatic LPS clearance can result in systemic endotoxemia as studies by Copperstock et al (9) involving Reye’s syndrome children have suggested. Systemic endotoxemia has also been demonstrated in other hepatic disorders including acute viral hepatitis (13, 14), and cirrhosis (15, 16, 17). Clearance of LPS by the liver involves Kupffer cells (KC), the tissue fixed macrophages lining the hepatic sinusoids and hepatocytes (18, 19, 20). Initially there is uptake of LPS by KC, then release of a modified LPS which has been altered by loss of carbohydrate (21.22). KC modified LPS is then cleared by hepatocytes (23). These studies provide support for a concept originally set forth by Broitman et al (24) and advanced by Nolan et al (25) which suggested that: 1) portal venous endotoxemia is a normal physiological event, 2) endotoxins are readily cleared by the liver, and 3) impairment of hepatic LPS clearance can result in systemic endotoxemia. which may further potentiate hepatic injury. Reye’s syndrome, lipopolysaccharides and cytokine release The concept that hepatic LPS clearance may represent a ‘detoxification’ process by preventing elicitation of cytokines has been suggested by Treon et al (23). LPS affect biological activities in vivo by stimulating the
239
release of a wide array of monokines including tumor necrosis factor-alpha (TNF-a), interleukin-1 (IL-l), interleukin-6 (IL-6) and interleukin-8 (IL-Q (2&29). Many effects of experimental or pathologically induced endotoxemia can be mimicked by infusion with TNF-a, IL-l, IL-6 and IL-8 (3&35). TNF-a, though, may be the principal mediator of the LPS response since passive transfer of anti-TNF-a antibodies protects animals exposed to lethal doses of LPS (36,37). TNF-a may also serve as a principal mediator of the LPS response since it can induce the release of other monokines thus potentiating their primary induction by LPS. IL-l and IL-6, whose in vivo effects are similar to TNF-a, are released by fibroblasts and endothelial cells in response to TNF-a (31, 34). Impairment of normal hepatic clearance of LPS may contribute to a systemic monokinemia as a consequence of LPS stimulation of peripheral monocytes and macrophages. Indeed, elevated systemic TNF-a and interleukin-1 levels were shown by Corkey et al (38) in RS patients, but not in control subjects or patients recovering from RS. Systemic TNF-aemia occurs in patients with other hepatic disorders including acute viral hepatitis (14). alcoholic hepatitis (39,40), and fulminant hepatic failure (41). Elevated IL-1 and IL-6 serum levels were shown in alcoholic hepatitis patients (39) and elevated IL-l release was seen in fulminant hepatic failure patients (41). Induction of systemic monokines in cases of Reye’s syndrome may be potentiated by ASA use, which is well known to block the production of prostaglandin E2 (PGE2), and inhibitor of TNF-a release by monocytes and macrophages (42,43). In a study by Martich et al (44). healthy subjects infused with LPS showed four fold higher levels of TNF-a, IL-l, IL-6. and IL-8 if LPS was coadminsitered with ibuprofen. Monokines and the pathogenesis of Reye’s syndrome A role for monokines in the pathogenesis of RS has been suggested previously by Larrick et al (45) and Kilpatrick et al (9). Constitutional symptoms of viral illness such as fever, chills, fatigue, anorexia, and malaise which often precede development of RS can in fact be induced by TNF-a (46, 47, 48). TNF-a is also hepatotoxic (49, 50) and mediates elevations in serum SGPT and SGOT levels (48) which is seen in RS patients. Interestingly, TNF-a may lead to alterations in fatty acid oxidation resulting in decreased ketogenesis, acetyl-CoA production, and ATP/ADP levels by inhibiting electron transfer in mitochondria (51). Decreased ATP production could in tum effect ureagenesis by the liver resulting in hyperammone-
240 mia (9). Elevated plasma fatty acids which constitute a hallmark of RS are also dramatically increased in cachectic tumor bearing rats, and have been attributed to the effects of TNF-a (52). Rats infused with TNF-a also show elevations in plasma free fatty acid (53). Interestingly, increased BCAA production typical of RS patients may reflect increased BCAA transferase activity which is elevated in muscle tissue of cachectic rats, and also attributed to the effects of TNF-a (52). A role for monokines in the progression of encephalopathy in RS patients may also be possible following their induction by systemic LPS (53). Cooperstock et al (8) first raised this possibility with the finding that levels of LPS in children with RS correlated well with electroencephalographic (EEG) abnormalities in this group (rzO.63). In support of the correlation of systemic LPS levels and encephalopathy are the studies of Bigatello et al (15) who showed that cirrhotic patients with hepatic encephalopathy had higher systemic LPS levels than ‘control cirrhotic’ patients deemed well-compensated. LPS levels were also higher in those patients with encephalopathy who were in deep coma (Child grade 3-4) versus those patients in light coma (Child grade l-2). Cirrhotic patients in the encephalopathy group who eventually died also showed higher LPS levels than patients who survived. LPS are known to mediate monokine release by monocytes and macrophages (37-49), but their ability to stimulate monokine release by astorcytes has raised interest in their ability to mediate neurotoxic effects (54, 55). TNF-a is cytotoxic to oligodendrocytes (56) and may mediate myelin sheath disruption in RS patients (57). Such a mechanism for TNF-a mediated encephalopathy has been advanced by Liebennan et al (55) for New Castle’s disease wherein TNF-a is released by astrocytes in response to a neurotropic paramyxovirus; TNF-a then may mediate oligodendrocyte killing and demyelination in this disease. TNF-a is also known to mediate decreased neuronal sodium conductance which may contribute to EEG abnormalities seen in patients with RS (58). Interestingly, the role of TNF-a in mediating progressive encephalopathy (PE) has not been limited to RS, but also implicated in PE of malaria (59) and acquired immunodeficiency syndrome (AIDS) in children (60). A role for IL-1 in mediating encephalopathy has also been suggested by Miller et al (61). IL-l, like TNF-a is also produced by astrocytes in response to LPS (55). Unlike TNF-a, IL-1 can enhance gammaaminobutyric alpha acid (GABAA) receptor function which may lead to increased somnogenic and motor
MEDICAL HyBYl-HESEs
depressant effects and contribute to encephalopathic changes in RS patients (61). A novel approach to the therapy of Reye’s syndrome The above studies suggest a role for LPS induced monokines in mediating many of the clinical findings associated with RS. At present, therapy for acute viral hepatitis is supportive (1). A novel approach to treating RS might be targeted at suppressing systemic endotoxemia and with this, the induction of monokine release. Such a treatment plan could involve use of centoxin (Centocor) which utilizes the HA-IA human monoclonal IgM antibody directed against the Lipid A domain of LPS (62). This therapy has been effectively used in treating patients with sepsis and gram negative bacteremia (62). Additionally, treatment for RS might also be aimed at systemic monokine release by use of neutralizing monoclonal antibodies. Use of anti-TNF-a monoclonal antibody in conjunction with centoxin may offer a more effective combination in treating combined endotoxemia and monokinemia seen in RS patients. This, upon consideration that certain monokines like TNF-a can stimulate the release of other monokines with similar in vivo effects (31, 34). In addition, TNF-a is also capable of auto-propagatory release by inducing its own release by monocytes and macrophages (63). Hence a strategy using a combination treatment with monoclonal antibodies aimed at LPS and TNF-a may be more effective at suppressing primary as well as secondary monokine release in RS patients. Acknowledgements The authors are grateful to the Mehos. Grunebaum. and Culpqper Foundations for generous fellowship support, and the National Institutes of Health for an Oncobiology Training Grant, T32-CA9423, in support of studies which made this work possible. The authors also wish IO thank Joel Bass, MD, Department of Pediatrics. Metrowest Medical Center, Framingham MA for his review of this manuscript.
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242 47. Spriggs D R. Sherman M L, Michie H. Arthur K A et al. Recombinant human tumor necnwis factor administered as a 24hour iv infusion. A phase I and pharmacological study. JNCI 80: 1039-1044, 1988. 48. Lenk H. Tmeberger S. Muller LJ, Ebert J et al. Phase II clinical trial of highdose recombinant human tumor necrosis factor. Cancer Chem Phatm 24: 391-2, 1989. 49. Creavm P J. Bremter D E, Cowens J W. Huben R P et al. A phase I clinical trial of recombiit human NmOT necrosis factor given daily for five days. Cancer Chem Pharm 23: 186-191, 1989. 50. McClain C J. Manuscrip in preparation. 51. Lancaster J R, Laster S M, Gooding L R. Inhibition of target cell mitochondrial electron transfer by tumor necrosis factor. Febs Letters 248: 169-174. 1989. 52. Siddiqui R A, Williams J E The regulation of fatty acid and branchedahain amino acid oxidation in cancer cache&c rats: a proposed role for a cytokine, eicosanoid, and hormone trilogy. Biochem Med Metab Biol 42: 71-86. 1989. 53. Grunfeld C. Verdier J A, Neese R. Moser A H et al. Mechanisms by which tmror necrosis factor stimulates hepatic fatty acid synthesis in vivo. J Lipid Res 29: 1327-1335, 1988. 54. Chung I Y, Benveniste E N. Tumor Necrosis Factor-a production by astrocytes: Induction by lipopolysaccharide, IFN-y, and IL-lb. J Imm 144: 2999-3007, 1990. 55. Lieberman A P, Pitha PM. Shin H S, Shin M L. Production of tumor necrosis factor and other cytokines by astrocytes stim-
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dated with iipopolysaccharide or a neurotropic virus. PNAS 86: 6348-6352. 1989. 56. Sehnaj K. Raine C S, Farooq M, Norton W T et al. Cytokine. cytotoxicity against oligodendrocytes. Apcptosis induced by lymphctoxin. J Imm 147: 1522-1529. 1991. 57. Blisard K S. Davis L E. Neuropathologic findings in Reye syndrome. J Child Neur 6: 414t, 1991. 58,. Sawada M. Hara N. Mamo T. Analysis of a decreased Na+ conductance by tumor necrosis factor in identified neurons of Aplysia kurodai. J Nemo Res 28: 46ti73, 1991. 59. Clark I A, Chaudhri G. Cowden W B. Roles of Nmour necrosis factor in the ilhtess and pathology of malaria. Trans Royal Sot Trop Med Hyg 83: 436-440. 1989. 60. Mintz M, Rapport R. Oleske J M, Connor E M et al. Elevated serum levels of tumor necrosis factor are associated with progressive encephalopathy in children with acquired immunodeficiency syndrome. Am J Dis Child 143: 771-774, 1989. 61. Miller L G. Galnem W R. Dunlau K. Dinarello C A et al. Interlcukin-1 augments gamma-am&butyric acid A receptor function in brain. Mol Pharm 39: 105-108. 1991. 62. Ziegler E J. Fisher C J. Sprung C L, Straube R C et al. Treatment of Gram-negative bacteremia and septic shock with HA-IA human monoclonal antibody against endotoxin. NEJM 324: 429-436. 1991. 63. Philip R, Epstein L B. Tumour necrosis factor as immunomodulator and mediator of monocyte toxicity induced by itself, y-interferon and interleukin-1. Nature 323: 86-89. 1986.
Monoclonal Antibody Therapy in the Treatment of Reye’s Syndrome S. P. TREON and S. A. BROITMAN Departments of Micmbdogy
and Pathology, Boston University School of Medicine, Boston, MA 02118, USA
Abstract-A role for lipopolysaccharides (endotoxins, LPS) in7 the pathogenesis of Reye’s syndrome (RS) has previously been suggested. Impairment of hepatic LPS clearance can lead to systemic endotoxemia as previous studies by this and other laboratories have suggested for several hepatic disorders including RS. Systemic LPS may mediate many of the clinical findings associated with RS by eliciting monokines such as tumor necrosis factor-alpha, interleukin-1 , interleukin-6, and interleukin-6. Monoclonal antibody therapy directed at LPS, and monokines may represent a novel approach to the treatment of RS.
Introduction Reye’s syndrome (RS) is predominantly a childhood disease which commonly follows a prodromal febrile illness. RS is characterized by protracted vomiting, delirium, stupor, and is often complicated by seizures, coma and death (1, 2). Use of salicylates during a viral febrile illness, which in children commonly includes varicella, and influenza has been implicated in the etiology of RS (1, 2). Case reports have also described RS in adults (3,4, 5). and in the absence of preceding febrile illness (6). RS is characterized histopathologically by a fatty liver secondary to fatty acid accumulation and associated hepatocellular necrosis with evidence of mitochondrial intoxication (1, 2). A presumptive diagnosis of RS is based on clinical grounds including history and presentation, along with supporting liver function tests and plasma ammonia levels suggestive of hepatic insult. Confirmation of RS requires liver biopsy (7). Date received 18 March 1992 Date accqwd 14 May 1992
The etiology of RS remains unknown. A role for endotoxin (lipopolysaccharides, LPS) was suggested by Cooperstock et al (8) who demonstrated systemic endotoxemia in children with RS. Involvement of LPS in the pathogenesis of RS is supported by the work of Kilpatrick et al (9) who showed in a rat model that sublethal doses of LPS plus aspirin (ASA) produce similar biochemical and histopathologic findings as those found in RS patients, Rats administered sublethal doses of LPS showed significantly decreased hepatic energy production secondary to impaired hepatic fatty acid oxidation as reflected by decreased ATP/ADP levels, acetyl-CoA production and ketogenesis. Administration of LPS plus aspirin (ASA) to rats had minimal effects versus LPS alone on hepatic fatty acid oxidation; however, a significant increase in metabolites of odd-chain fatty acid (OCFA) and branched-chain amino acid (BCAA) oxidation pathways was noted (9). ASA administered alone showed
238
MONOCLONAL. ANTIBODY THERAPY IN THE TREATMENT OF REYE’S SYNDROME
minimal effects on hepatic fatty acid oxidation but did result in modest increases in metabolites of GCFA and BCAA oxidation pathways (9). Decreased hepatic acetyl-CoA and ketone levels and increased metabolites of OCFA and BCAA oxidation pathways have also been demonstrated by Corkey et al (10) in human liver biopsy samples taken from RS patients versus controls. Histologically, livers of rats subjected to LPS plus ASA showed microvesicular fat deposition and mitochondriaI swelling similar to liver biopsy samples taken from RS patients. Hepatic clearance of gut derived LPS There exists a large reservoir of LPS in the gut of man due to the presence of gram negative bacteria which constitute the bulk of normal colonic flora. LPS arising from the gut flora readily transit through gut mucosa (11). Supporting the concept that LPS readily cross the gut mucosa. Jacob et al (12) demonstrated portal venous endotoxemia in 33 of 34 patients who underwent abdominal surgery. In contrast, systemic endotoxemia was detected in 4 of these 33 patients, among whom 3 patients had a hepatic disorder, and one a gram negative septicemia. Impairment of hepatic LPS clearance can result in systemic endotoxemia as studies by Copperstock et al (9) involving Reye’s syndrome children have suggested. Systemic endotoxemia has also been demonstrated in other hepatic disorders including acute viral hepatitis (13, 14), and cirrhosis (15, 16, 17). Clearance of LPS by the liver involves Kupffer cells (KC), the tissue fixed macrophages lining the hepatic sinusoids and hepatocytes (18, 19, 20). Initially there is uptake of LPS by KC, then release of a modified LPS which has been altered by loss of carbohydrate (21.22). KC modified LPS is then cleared by hepatocytes (23). These studies provide support for a concept originally set forth by Broitman et al (24) and advanced by Nolan et al (25) which suggested that: 1) portal venous endotoxemia is a normal physiological event, 2) endotoxins are readily cleared by the liver, and 3) impairment of hepatic LPS clearance can result in systemic endotoxemia. which may further potentiate hepatic injury. Reye’s syndrome, lipopolysaccharides and cytokine release The concept that hepatic LPS clearance may represent a ‘detoxification’ process by preventing elicitation of cytokines has been suggested by Treon et al (23). LPS affect biological activities in vivo by stimulating the
239
release of a wide array of monokines including tumor necrosis factor-alpha (TNF-a), interleukin-1 (IL-l), interleukin-6 (IL-6) and interleukin-8 (IL-Q (2&29). Many effects of experimental or pathologically induced endotoxemia can be mimicked by infusion with TNF-a, IL-l, IL-6 and IL-8 (3&35). TNF-a, though, may be the principal mediator of the LPS response since passive transfer of anti-TNF-a antibodies protects animals exposed to lethal doses of LPS (36,37). TNF-a may also serve as a principal mediator of the LPS response since it can induce the release of other monokines thus potentiating their primary induction by LPS. IL-l and IL-6, whose in vivo effects are similar to TNF-a, are released by fibroblasts and endothelial cells in response to TNF-a (31, 34). Impairment of normal hepatic clearance of LPS may contribute to a systemic monokinemia as a consequence of LPS stimulation of peripheral monocytes and macrophages. Indeed, elevated systemic TNF-a and interleukin-1 levels were shown by Corkey et al (38) in RS patients, but not in control subjects or patients recovering from RS. Systemic TNF-aemia occurs in patients with other hepatic disorders including acute viral hepatitis (14). alcoholic hepatitis (39,40), and fulminant hepatic failure (41). Elevated IL-1 and IL-6 serum levels were shown in alcoholic hepatitis patients (39) and elevated IL-l release was seen in fulminant hepatic failure patients (41). Induction of systemic monokines in cases of Reye’s syndrome may be potentiated by ASA use, which is well known to block the production of prostaglandin E2 (PGE2), and inhibitor of TNF-a release by monocytes and macrophages (42,43). In a study by Martich et al (44). healthy subjects infused with LPS showed four fold higher levels of TNF-a, IL-l, IL-6. and IL-8 if LPS was coadminsitered with ibuprofen. Monokines and the pathogenesis of Reye’s syndrome A role for monokines in the pathogenesis of RS has been suggested previously by Larrick et al (45) and Kilpatrick et al (9). Constitutional symptoms of viral illness such as fever, chills, fatigue, anorexia, and malaise which often precede development of RS can in fact be induced by TNF-a (46, 47, 48). TNF-a is also hepatotoxic (49, 50) and mediates elevations in serum SGPT and SGOT levels (48) which is seen in RS patients. Interestingly, TNF-a may lead to alterations in fatty acid oxidation resulting in decreased ketogenesis, acetyl-CoA production, and ATP/ADP levels by inhibiting electron transfer in mitochondria (51). Decreased ATP production could in tum effect ureagenesis by the liver resulting in hyperammone-
240 mia (9). Elevated plasma fatty acids which constitute a hallmark of RS are also dramatically increased in cachectic tumor bearing rats, and have been attributed to the effects of TNF-a (52). Rats infused with TNF-a also show elevations in plasma free fatty acid (53). Interestingly, increased BCAA production typical of RS patients may reflect increased BCAA transferase activity which is elevated in muscle tissue of cachectic rats, and also attributed to the effects of TNF-a (52). A role for monokines in the progression of encephalopathy in RS patients may also be possible following their induction by systemic LPS (53). Cooperstock et al (8) first raised this possibility with the finding that levels of LPS in children with RS correlated well with electroencephalographic (EEG) abnormalities in this group (rzO.63). In support of the correlation of systemic LPS levels and encephalopathy are the studies of Bigatello et al (15) who showed that cirrhotic patients with hepatic encephalopathy had higher systemic LPS levels than ‘control cirrhotic’ patients deemed well-compensated. LPS levels were also higher in those patients with encephalopathy who were in deep coma (Child grade 3-4) versus those patients in light coma (Child grade l-2). Cirrhotic patients in the encephalopathy group who eventually died also showed higher LPS levels than patients who survived. LPS are known to mediate monokine release by monocytes and macrophages (37-49), but their ability to stimulate monokine release by astorcytes has raised interest in their ability to mediate neurotoxic effects (54, 55). TNF-a is cytotoxic to oligodendrocytes (56) and may mediate myelin sheath disruption in RS patients (57). Such a mechanism for TNF-a mediated encephalopathy has been advanced by Liebennan et al (55) for New Castle’s disease wherein TNF-a is released by astrocytes in response to a neurotropic paramyxovirus; TNF-a then may mediate oligodendrocyte killing and demyelination in this disease. TNF-a is also known to mediate decreased neuronal sodium conductance which may contribute to EEG abnormalities seen in patients with RS (58). Interestingly, the role of TNF-a in mediating progressive encephalopathy (PE) has not been limited to RS, but also implicated in PE of malaria (59) and acquired immunodeficiency syndrome (AIDS) in children (60). A role for IL-1 in mediating encephalopathy has also been suggested by Miller et al (61). IL-l, like TNF-a is also produced by astrocytes in response to LPS (55). Unlike TNF-a, IL-1 can enhance gammaaminobutyric alpha acid (GABAA) receptor function which may lead to increased somnogenic and motor
MEDICAL HyBYl-HESEs
depressant effects and contribute to encephalopathic changes in RS patients (61). A novel approach to the therapy of Reye’s syndrome The above studies suggest a role for LPS induced monokines in mediating many of the clinical findings associated with RS. At present, therapy for acute viral hepatitis is supportive (1). A novel approach to treating RS might be targeted at suppressing systemic endotoxemia and with this, the induction of monokine release. Such a treatment plan could involve use of centoxin (Centocor) which utilizes the HA-IA human monoclonal IgM antibody directed against the Lipid A domain of LPS (62). This therapy has been effectively used in treating patients with sepsis and gram negative bacteremia (62). Additionally, treatment for RS might also be aimed at systemic monokine release by use of neutralizing monoclonal antibodies. Use of anti-TNF-a monoclonal antibody in conjunction with centoxin may offer a more effective combination in treating combined endotoxemia and monokinemia seen in RS patients. This, upon consideration that certain monokines like TNF-a can stimulate the release of other monokines with similar in vivo effects (31, 34). In addition, TNF-a is also capable of auto-propagatory release by inducing its own release by monocytes and macrophages (63). Hence a strategy using a combination treatment with monoclonal antibodies aimed at LPS and TNF-a may be more effective at suppressing primary as well as secondary monokine release in RS patients. Acknowledgements The authors are grateful to the Mehos. Grunebaum. and Culpqper Foundations for generous fellowship support, and the National Institutes of Health for an Oncobiology Training Grant, T32-CA9423, in support of studies which made this work possible. The authors also wish IO thank Joel Bass, MD, Department of Pediatrics. Metrowest Medical Center, Framingham MA for his review of this manuscript.
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