ABSTRACT
BACKGROUND: The lectin from Cratylia argentea (CFL) is able to modulate the immune system response and is thus a potential phytotherapeutic substance. HYPOTHESIS/PURPOSE: In this study, we investigated the role of CFL on control of bacterial infection caused by Listeria monocytogenes, the causative agent of human listeriosis. STUDY DESIGN: Swiss mice were infected with L. monocytogenes and then treated with CFL. METHODS: Adult Swiss mice weighing with 30-40 g were infected intraperitoneally with a bacterial suspension (0.2 ml; 1 × 107 CFU/ml). After 30 min, the mice were treated with CFL intravenously at concentrations of 0.1 or 10 mg/kg. Control mice received phosphate-buffered saline (PBS). The animals were euthanized 24 h after infection. RESULTS: We observed that i.v. administration of CFL to Swiss mice did not cause acute toxicity, and reduced the leukocyte counts in the bloodstream 24 h after infection with virulent L. monocytogenes. There was a reduction in the bacterial burden within peritoneal macrophages after infection in CFL-treated mice. Accordingly, the bacterial counts in the bloodstream, spleen and liver also decreased in comparison with the PBS group. Histological damage in the spleen and liver was lower in mice that received CFL treatment. In vitro antimicrobial assays demonstrated that CFL does not inhibit the growth of L. monocytogenes. The mRNA expression of the anti-inflammatory cytokine IL-10 was enhanced with CFL treatment after infection. CONCLUSION: The lectin from C. argentea (CFL) has immunomodulatory and anti-infective properties of pharmacological interest for control of infectious diseases.