A recombinant tumor necrosis factor-alpha p80 receptor:Fc fusion protein decreases circulating bioactive tumor necrosis factor-alpha but not lung injury or mortality during immunosuppression-related gram-negative bacteremia.
OBJECTIVE
During gram-negative bacteremia (GNB), tumor necrosis factor-alpha (TNF-alpha) is a critical early mediator of host defense, whose overexpression can initiate acute lung injury, multiple organ failure, and death. In this study we evaluated the ability of a chimeric fusion protein containing two extracellular domains of the human p80 TNF-alpha receptor and the Fc region of human IgG1 (TNFR:Fc) to reduce circulating TNF-alpha, and to ameliorate organ injury and improve survival in a rodent model of GNB during immunosuppression-related neutropenia.


METHODS
Conscious catheterized male rats (n = 37) with stable cyclophosphamide-induced neutropenia were infected intravenously (i.v.) with 5 x 10(9) live Escherichia coli (EC, serotype O55:B5) ending at t = 0. All animals received antibiotics (penicillin/ amikacin sulfate) at t = 0.5 and t = 8 hours, and 0.9% sodium chloride (normal saline solution (NS), 1 mL/h) from t = 0 to 8 hours. Subgroups were post-treated at t = 0.5 hours with a 1.0 mL i.v. dose of TNFR:Fc (60, 600, or 1,200 micrograms; Immunex), 600 micrograms of human IgG1-kappa or IgG1-lambda (Sigma), or NS alone (controls). A separate TNFR:Fc pretreatment subgroup received 600 micrograms/rat of the fusion protein 5 minutes before starting EC infusion. Hemodynamics were monitored continuously through t = 24 hours, and arterial samples were collected at baseline and at t = 1.5, 4.5, 8, and 24 hours after EC were analyzed for blood gases, quantitative culture, serum endotoxin, bioactive and antigenic TNF-alpha, and formed elements. Postmortem tissues were examined for histopathologic changes.


RESULTS
Compared with antibiotic-treated and fluid-supported controls, TNFR:Fc dose-dependently reduced bioactive but not antigenic TNF-alpha without altering bacterial clearance, serum endotoxin, or 24-hour survival. Of note, 600 micrograms of IgG1-kappa or IgG1-lambda attenuated peak bioactive TNF-alpha to a similar degree as 1,200 micrograms TNFR:Fc, and also significantly reduced serum endotoxin levels. Nevertheless, by t = 8 hours all bacteremic rats were hypothermic with tachypnea-related hypocarbia and hyperoxemia and were thrombocytopenic. At death, all subgroups showed similar hepatic glycogen depletion and pulmonary congestion with perivascular edema and alveolar hemorrhage.


CONCLUSIONS
Although TNFR:Fc and its idiotypic control IgG1 reduced circulating bioactive TNF-alpha, neither treatment prevented progression of lethal shock with attendant organ injury in this conscious, antibiotic-treated and fluid-resuscitated model of immunosuppression-related GNB.
Lechner
A J
AJ
Department of Pharmacological and Physiological Science, Saint Louis University School of Medicine, MO 63104-1028, USA.
Johanns
C A
CA
Matuschak
G M
GM
D000818:Animals; D015703:Antigens, CD / Q000276:immunology*; D016470:Bacteremia / Q000276:immunology / Q000628:therapy*; D004195:Disease Models, Animal; D004353:Drug Evaluation, Preclinical; D004927:Escherichia coli Infections / Q000276:immunology / Q000628:therapy*; D007074:Immunoglobulin G / Q000276:immunology*; D008297:Male; D009503:Neutropenia / Q000150:complications; D051381:Rats; D017207:Rats, Sprague-Dawley; D017452:Receptors, IgG / Q000276:immunology*; D018124:Receptors, Tumor Necrosis Factor / Q000276:immunology*; D047889:Receptors, Tumor Necrosis Factor, Type II; D011993:Recombinant Fusion Proteins / Q000627:therapeutic use*; D012128:Respiratory Distress Syndrome / Q000382:microbiology; D016019:Survival Analysis; D014409:Tumor Necrosis Factor-alpha / Q000187:drug effects*
D015703:Antigens, CD; D007074:Immunoglobulin G; D017452:Receptors, IgG; D018124:Receptors, Tumor Necrosis Factor; D047889:Receptors, Tumor Necrosis Factor, Type II; D011993:Recombinant Fusion Proteins; D014409:Tumor Necrosis Factor-alpha