Latex proteins downregulate inflammation and restores blood-coagulation homeostasis in acute Salmonella infection

BACKGROUND: Calotropis procera latex protein fraction (LP) was previously shown to protect animals from septic shock. Further investigations showed that LP modulate nitric oxide and cytokines levels. OBJECTIVES: To evaluate whether the protective effects of LP, against lethal bacterial infection, is observed in its subfractions (LP(PII) and LP(PIII)). METHODS: Subfractions (5 and 10 mg/kg) were tested by i.p. administration, 24 h before challenging with lethal injection (i.p.) of Salmonella Typhimurium. LP(PIII) (5 mg/kg) which showed higher survival rate was assayed to evaluate bacterial clearance, histopathology, leukocyte recruitment, plasma coagulation time, cytokines and NO levels. FINDINGS: LP(PIII) protected 70% of animals of death. The animals given LP(PIII) exhibited reduced bacterial load in blood and peritoneal fluid after 24 h compared to the control. LP(PIII) promoted macrophage infiltration in spleen and liver. LP(PIII) restored the coagulation time of infected animals, increased IL-10 and reduced NO in blood. MAIN CONCLUSIONS: LP(PIII) recruited macrophages to the target organs of bacterial infection. This addressed inflammatory stimulus seems to reduce bacterial colonisation in spleen and liver, down regulate bacterial spread and contribute to avoid septic shock.