The Yale IACUC strictly adheres to all Federal and State regulations, including the Animal Welfare Act, those specified by Public Health Support, and the US Department of Agriculture, and uses the as a guide for all those animal studies. Study Design We performed active surveillance at an infectious disease hospital in Salvador, Brazil, to identify patients with suspected leptospirosis between April 2013 and September 2013 with the goal of discovering markers associated with case fatalities. S vs C. (D) Scatter plot of log2 fold-change of significant transcripts for deceased (D) vs Cinobufagin S (red) overlaid with those shared with S vs C (black). Zero indicates no change, while negative numbers indicate the transcripts for survivors in D vs S or at the convalescent time point (C) were elevated relative to deceased patients or acute phase, respectively.(TIF) ppat.1005943.s001.tif (1.0M) GUID:?27C206D1-9CBF-4C65-9B47-27BA77D121EA S2 Fig: Determining model fitness for experimental variables associated with death. In order to assess the linearity of features and goodness of model fit (blue lines), we plotted the observed values of variables associated with death (x-axis) as an outcome for confirmed leptospirosis cases versus the predictive probability of death (y-axis) within a 95% confidence interval (dotted or solid black lines). Modeling is usually described in the Supplemental Methods.(TIF) ppat.1005943.s002.tif (444K) GUID:?94AB49CA-F956-4EAF-95BC-66F8E562DF34 S3 Fig: Cathelicidin (LL-37) protects hamsters from lethal infection. (A) Survival in hamsters pre-treated with 1 mg/kg of cathelicidin (LL-37) (n = 14) was significantly greater than ddH2O-treated controls (n = 14) following lethal challenge with 100 (genome equivalents per mL of whole blood) in 14 infected hamsters were significantly lower at 4 (= 0.010), 6 (= 0.004), and 8 days (= 0.0006) post-infection in LL-37-treated hamsters relative to 14 ddH2O-treated controls. Shown are medians IQR. An ** signifies a = 0.0004) and lower anti-antibody titers (= 0.02) at the time of hospitalization, independent of the duration of illness. Low serum cathelicidin and RANTES levels during acute illness were impartial risk factors for higher bacterial loads (= 0.005) and death (= 0.04), respectively. To investigate the mechanism of cathelicidin in patients surviving acute disease, we administered LL-37, the active peptide of cathelicidin, in a hamster model of lethal leptospirosis and found it significantly decreased bacterial loads and increased survival. Our findings indicate that this host immune response plays a central role in severe leptospirosis disease progression. While drawn from a limited study size, significant conclusions include that poor clinical outcomes are associated with high systemic bacterial loads, and a decreased antibody response. Furthermore, our data identified a key role for the antimicrobial peptide, cathelicidin, in mounting an effective bactericidal response against the pathogen, which represents a valuable new therapeutic approach for leptospirosis. Author Summary Leptospirosis causes over one million cases and nearly 60,000 deaths annually. Infection with the spirochetal bacterium results in a spectrum of symptoms, ranging from moderate febrile illness to life-threatening pulmonary hemorrhage syndrome and acute Cinobufagin kidney injury. Despite leptospirosis being a leading cause of zoonotic morbidity worldwide, little is known about the human immune response to infections, and less about the pathogenic mechanisms resulting in severe disease outcomes. Here, we used a systems biology approach to discover transcripts and immunoprofiles associated with case fatality. We identified new risk factors for high bacterial loads and fatal leptospirosis, including the antimicrobial peptide, cathelicidin, which we validated in an animal model. Cathelicidin therefore represents a potential novel treatment for severe cases of leptospirosis. TGFA Introduction Pathogenic cause life-threatening disease, primarily in the worlds most impoverished populations [1]. Cinobufagin Leptospirosis is considered the most widespread zoonotic disease due to the large number of wild and domestic mammalian reservoirs [2] and causes an estimated 1.03 million infections and 59,000 deaths globally per year [3, 4]. In Brazil alone, epidemic outbreaks of leptospirosis in urban slum communities during seasonal periods of heavy rainfall account for more than 10,000 reported cases each year [5, 6]. Despite its widespread importance, development of a vaccine has been hampered by genetic and antigenic diversity in pathogenic excreted in the urine of reservoir hosts. During a systemic contamination, clinical manifestations can range from a self-limiting febrile illness to Weils disease, the classic severe form with jaundice, acute renal failure and bleeding, or severe pulmonary hemorrhage syndrome (LPHS) [1, 7, 8]. Notably, case fatality rates from Weils disease and LPHS are >10% and 50%, respectively [7, 8, 9, 10]. At present, the factors contributing to disease progression and poor clinical outcomes in patients with leptospirosis are poorly understood. No studies to date have found associations between genetic differences in and poor disease outcomes, suggesting other factors drive disease severity [11, 12]. The infecting inoculum dose may also affect patient outcomes, but these have been intrinsically difficult to measure and evaluate. Alternatively, differences in host factors, such as the immune response to bacteria, are known to contribute in general to the development.