Dosage and timing of anti-TNF-alpha antibody treatment determine its effect of resistance to sepsis after injury.

Antibody against tumor necrosis factor-alpha (TNF-alpha) has improved survival in certain models of sepsis, but it remains unproven in clinical studies. In most of the successful animal studies, efficacy has been shown in previously healthy animals subjected to a septic challenge. Patients at risk for sepsis, however, may be ill for some time before the sepsis supervenes. This situation has been described as a "two-hit" model of critical illness. We have developed an animal burn-sepsis model which conforms to this "two-hit" concept. We have quantified macrophage TNF-alpha production at different times after the burn (first "hit") and determined the effect of neutralizing antibody against TNF-alpha during this period on survival after subsequent sepsis (second "hit"). The objective of this study was to determine the role of TNF-alpha and the effect of neutralizing antibody against TNF-alpha in a burn-sepsis model. Animals were subjected to a full thickness burn or sham burn. In vitro TNF-alpha production from cultured lipopolysaccharide-stimulated splenic adherent cells was determined at various time points thereafter by enzyme-linked immunosorbent assay. Separate animals were treated with neutralizing antibody against TNF-alpha at different time points after the thermal injury, and survival was determined after septic challenge (cecal ligation and puncture) on Day 10 after the burn. TNF-alpha production from adherent splenocytes was not elevated in the early days after thermal injury, but was significantly enhanced from Day 6 onward compared with sham-burned animals. Nine percent of the burned mice survived septic challenge compared with 69% of the sham-burned control mice (P < 0.001). Therapy with anti-TNF antibody at 1 x 10(4) neutralizing units (n.u.) kg-1 markedly improved outcome if given when TNF-alpha production was elevated at Day 7 after the burn (survival, 36%; P = 0.01) but did not improve survival when administered at Days 0 or 4 or at the time of the septic challenge (Day 10). High doses of antibody (3.2 x 10(5) n.u.kg-1) were not beneficial and may have been detrimental. These results show that neutralizing antibody against TNF-alpha may reduce the susceptibility to infection seen after thermal injury, but the timing of administration of the antibody and the dose of antibody used are critical to the outcome. This should be considered when neutralizing antibody against TNF is used in the clinical setting.