Differential Cytokine Gene Expression According to Outcome in a Hamster Model of Leptospirosis

Abstract

BackgroundParameters predicting the evolution of leptospirosis would be useful for clinicians, as well as to better understand severe leptospirosis, but are scarce and rarely validated. Because severe leptospirosis includes septic shock, similarities with predictors evidenced for sepsis and septic shock were studied in a hamster model.Methodology/Principal FindingsUsing an LD50 model of leptospirosis in hamsters, we first determined that 3 days post-infection was a time-point that allowed studying the regulation of immune gene expression and represented the onset of the clinical signs of the disease. In the absence of tools to assess serum concentrations of immune effectors in hamsters, we determined mRNA levels of various immune genes, especially cytokines, together with leptospiraemia at this particular time-point. We found differential expression of both pro- and anti-inflammatory mediators, with significantly higher expression levels of tumor necrosis factor α, interleukin 1α, cyclo-oxygenase 2 and interleukin 10 genes in nonsurvivors compared to survivors. Higher leptospiraemia was also observed in nonsurvivors. Lastly, we demonstrated the relevance of these results by comparing their respective expression levels using a LD100 model or an isogenic high-passage nonvirulent variant.Conclusions/SignificanceUp-regulated gene expression of both pro- and anti-inflammatory immune effectors in hamsters with fatal outcome in an LD50 model of leptospirosis, together with a higher Leptospira burden, suggest that these gene expression levels could be predictors of adverse outcome in leptospirosis.

Gene Expression Profiles of Immune Mediators and Histopathological Findings in Animal Models of Leptospirosis: Comparison between Susceptible Hamsters and Resistant Mice

“…Opposite this, the anti-inflammatory IL-10, though upregulated, was induced later or maintained at lower levels in hamsters than in mice, a finding consistent with previous reports in hamster blood or kidneys (21,55,56). In contrast, a rapid and higher induction of IL-10 gene expression was observed in mouse tissues, except the liver.…”

“…The expression of target genes was assessed using RT-qPCR, and the effect of EMJH medium was first evaluated. Considering that target genes are induced when a 2-fold change in mRNA levels is observed between samples and control (55), the injection of the EMJH medium alone induced the expression of several genes in blood and tissues at 3 h p.i. but not at later time points (data not shown).…”

“…Five-to 6-week-old healthy mice and hamsters were i.p. injected with virulent L. interrogans serovar Icterohaemorrhagiae strain Verdun at the LD 100 (2 ϫ 10 8 bacteria), previously determined in hamster (55), in 500 to 600 l EMJH medium. Animals were stocked in individual cages at room temperature with sawdust bedding, fed their routine food, and watered with a bottle of sterile water during the experimentations.…”

“…Indeed, we have previously shown an increase in expression of several inflammatory mediators, such as cyclo-oxygenase-2 (COX-2), IFN-␥, IL-1␣, IL-4, IL-6, IL-10, IL12p40, and TNF-␣, in the blood of hamsters infected with a 50% lethal dose (LD 50 ) of virulent Leptospira interrogans serovar Icterohaemorrhagiae strain Verdun (55). The comparison between surviving and nonsurviving animals evidenced significant differences in COX-2, IL-1␣, IL-10, and TNF-␣ mRNA levels at 3 days postinfection (p.i.…”

Eyedrop Inoculation Causes Sublethal Leptospirosis in Mice

“…Humans are accidental hosts that acquire leptospirosis via contact with infected urine shed by dogs, pigs, cattle, and rodents or through contact with contaminated soil and water during daily activities, like washing, fishing, and swimming, or during recreational activities (5)(6)(7). The outcome of the disease is greatly influenced by the pathogen serovar and the host's age and species (8)(9)(10)(11). The ensuing immune response and inflammation may lead to bacterial clearance, limited bacterial colonization of a few target organs, or the induction of sepsis as the host succumbs to infection and dies (12).…”