Objective: This study tried to determine whether administration of antilipopolysaccharide (LPS) murine monoclonal antibody (mAb) 2A3 to mice was associated with (1) protective capacity during experimental gram-negative bacterial sepsis, and (2) inhibition of tumor necrosis factor alpha (TNF-alpha) secretion in the systemic circulation and at the tissue level during experimental infection.
Design: Mice received an initial intravenous injection of either saline or 100 micrograms of anti-LPS mAb 2A3, and 1 hour later underwent intraperitoneal inoculation of viable Escherichia coli 0111:B4. Mortality was assessed daily for 7 days. Separate groups of mice were treated similarly and plasma TNF-alpha concentrations were determined from blood samples obtained at 1, 3, 6, 10, and 16 hours after infection by enzyme-linked immunosorbent assay. Concurrently, splenocytes harvested from animals 3, 10, and 16 hours after infection were incubated in culture ex vivo and supernatant TNF-alpha levels were determined.
Results: Pretreatment with anti-LPS mAb 2A3 prior to an intraperitoneal challenge of live E coli 0111:B4 was associated with the following: (1) significant protective capacity (100% vs 0% mortality, P < .001); (2) inhibition of plasma TNF-alpha levels 16 hours after infection (1257 +/- 323 pg/mL vs 292 +/- 254 pg/mL, P < .001); and (3) abrogation of TNF-alpha secretion derived from splenic macrophages isolated 16 hours after bacterial challenge (229 +/- 12 pg/mL vs 107 +/- 48 pg/mL, P < .05).
Conclusions: These results strongly support the contention that inhibition of LPS-induced TNF-alpha secretion at both the tissue and systemic levels is a key mechanism by which anti-LPS mAbs provide protection during gram-negative bacterial peritonitis. We believe that in vivo monitoring of macrophage cytokine secretion will be critical for elucidating the precise role of a variety of mediators in the pathogenesis of gram-negative bacterial sepsis.