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BackgroundWe report the detailed development of biomarkers to predict the clinical outcome under dengue infection. Transcriptional signatures from purified peripheral blood mononuclear cells were derived from whole-genome gene-expression microarray data, validated by quantitative PCR and tested in independent samples.Methodology/Principal FindingsThe study was performed on patients of a well-characterized dengue cohort from Recife, Brazil. The samples analyzed were collected prospectively from acute febrile dengue patients who evolved with different degrees of disease severity: classic dengue fever or dengue hemorrhagic fever (DHF) samples were compared with similar samples from other non-dengue febrile illnesses. The DHF samples were collected 2–3 days before the presentation of the plasma leakage symptoms. Differentially-expressed genes were selected by univariate statistical tests as well as multivariate classification techniques. The results showed that at early stages of dengue infection, the genes involved in effector mechanisms of innate immune response presented a weaker activation on patients who later developed hemorrhagic fever, whereas the genes involved in apoptosis were expressed in higher levels.Conclusions/SignificanceSome of the gene expression signatures displayed estimated accuracy rates of more than 95%, indicating that expression profiling with these signatures may provide a useful means of DHF prognosis at early stages of infection.

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Primers targeting the gene encoding the small subunit rRNA were designed to amplify DNA from Schistosoma mansoni with high specificity. Three PCR systems were developed: conventional PCR, two-step nested PCR (NPCR) and single-tube nested PCR (STNPCR). The limits of detection of parasite DNA for the conventional PCR, NPCR and STNPCR were 10 pg, 0.1 fg and 1 fg, respectively. The assays were highly specific for S. mansoni and did not recognise DNA from closely related non-schistosome trematodes. Using pools of Biomphalaria molluscs, PCR, NPCR and STNPCR were positive in 6/16 (37.5%), 15/16 (93.8%) and 13/16 (81.3%) of the tested samples, respectively, whereas the observation of cercariae shedding after exposure to light was able to detect S. mansoni infection in 6/16 (37.5%) of the pools. Thus, the molecular detection systems had a higher level of sensitivity than standard screening of intermediate hosts by cercarial shedding when DNA was purified from pools of snails collected from endemic areas. These PCR protocols have potential to be used as tools for monitoring of schistosome transmission.

The detection of specific DNA sequences by polymerase chain reaction (PCR) Key words: polymerase chain reaction -molecular diagnosis -schistosomiasis -transmission -snail -Schistosoma Schistosomiasis is a disease transmitted by fresh water snails. It affects more than 200 million people worldwide and is endemic in 74 countries, with more than 80% of infected persons living in Africa. In Brazil, Schistosoma mansoni is the only causative species of schistosomiasis, and there are three species of intermediate hosts: Biomphalaria glabrata, B. straminea, and B. tenagophila. Adult S. mansoni live in the bloodstream. Their eggs pass out of the host with the faeces. In contact with water, free-swimming miracidia emerge from the egg and penetrate the soft tissues of the snail host. Within the snails, miracidia immediately differentiate into sporocysts and, as they migrate through the snail tissues, give rise to cercariae. Cercariae are shed from the snails and are infective to humans by direct penetration of the skin. Thus, molecular approaches can be used to detect DNA of different life cycle stages of S. mansoni by analyzing different biological samples: feces, snail tissues, and infested water bodies, resulting in diagnosis of vertebrate and invertebrate host infections, and identification of transmission sites.The detection of specific DNA sequences by polymerase chain reaction (PCR) has proved extremely valuable for the analysis of genetic disorders and the diagnosis of a variety of infectious disease pathogens (Leal et al.