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.