Targeting Macrophages with Microspheres Containing Cytokine-Neutralizing Antibodies Prevents Lethality in Gram-Negative Peritonitis

Abstract

Macrophages release proinflammatory cytokines in response to infection that play a critical role in the pathophysiology of septic shock. We propose that targeting cytokine-neutralizing antibodies using albumin microspheres to macrophages will be more beneficial than the soluble form in reducing mortality related to peritonitis. In this study, we compared the distribution pattern of microspheres in infected and noninfected animals, evaluated the amount of microsphere taken up by peritoneal macrophages in vitro, and compared the efficacy of soluble and microsphere forms of cytokine-neutralizing antibodies in preventing lethality caused by Escherichia coli-induced peritonitis. The results indicate that twice the amount of microspheres accumulates near the site of infection (the peritoneal cavity), and 70% of the microspheres exposed to peritoneal macrophages were phagocytosed in 1 h. Treatment with the microsphere form of cytokine-neutralizing antibodies was more efficacious than using the soluble form in preventing lethality induced by E. coli. Immediate treatment was more efficacious than delayed treatment in the absence of gentamicin, whereas immediate and delayed treatment were equally efficacious in the presence of gentamicin. The combination of microspheres containing neutralizing antibodies to tumor necrosis factor-alpha (TNF-alpha) and interleukin-1beta (IL-1beta) protected 100% of the animals, whereas either one alone protected only 60%-90% of the animals from lethality caused by E. coli-induced peritonitis. In conclusion, the microsphere form of neutralizing antibodies to TNF-alpha IL-1beta may be an effective therapeutic agent in the treatment of septic shock caused by peritonitis.

Microspheres Containing Neutralizing Antibodies to Tumor Necrosis Factor-α and Interleukin-1β Protect Rats fromStaphylococcus aureus-Induced Peritonitis

“…In surviving animals, IL-1 concentrations were elevated to 200-839 pg/ml at 24 h. The levels of both TNF and IL-1 were quantitatively similar to levels in a previous study by our group in which peritonitis was introduced into rats in a similar fashion with E. coli. (30) Comparison of TNF levels among the groups was difficult because of the high mortality rates in all groups except for the antibiotic and microsphere treatment group. However, cytokine levels were significantly lower in this group, which correlated with ultimate survival.…”

“…(25,26) In a previous study, we found that using a combination of microencapsulated TNF and IL-1 NA resulted in a higher survival in experimental peritonitis than using TNF or IL-1 NA alone. (30) It is the purpose of this investigation to determine if microencapsulated NA to TNF and IL-1 are effective in a compartmentalized model of infection with the gram-positive organism, S. aureus. Microencapsulated NA dramatically increased survival in this model, confirming the improved effectiveness of targeting the macrophage with cytokine NA in peritonitis.…”

Cytokine Responses in Secondary Peritonitis

“…In the context of secondary peritonitis, experimental and clinical reports have shown that increased levels of IL-1-b correlate significantly with the disease severity. Local treatment with antibodies against IL-1-b has shown a 90%-decrease of the lethality in models of septic shock [45]. Furthermore, systemic effects of IL-1-b not only induce activation of leukocytes in distant organs but might play a role in the metabolic response of the host.…”

“…Anti-TNF-a monoclonal (or polyclonal) antibodies administered intravenously have failed in the attempt of attenuating the severity of secondary peritonitis; they decrease the production of associated inflammatory cytokines but do not improve animal survival [92] or glucose dyshemostasis [93]. But recent experimental designs in which albumin microspheres of anti-TNF-a antibodies were administered in association with anti-IL-1 antibodies showed a 100% prevention of lethality if concomitantly treated with gentamycin [94]. Furthermore, as sepsis and peritonitis are main factors of delayed healing, anti-TNF-a therapy was demonstrated to increase the strength of incisional repair (anastomoses or abdominal wall) up to control levels, reversing the adverse effects of peritonitis and sepsis [95].…”

“…Furthermore, as sepsis and peritonitis are main factors of delayed healing, anti-TNF-a therapy was demonstrated to increase the strength of incisional repair (anastomoses or abdominal wall) up to control levels, reversing the adverse effects of peritonitis and sepsis [95]. As described above, anti-IL-1 antibody therapy has only demonstrated a clear efficacy in addition to anti-TNF-a antibody therapy [94]. Anti-IL-8 therapies had demonstrated some protective effects, reducing up to 40% the neutrophil influx to inflamed peritoneal surface.…”