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Elucidation of pathways regulating parasite cell death is believed to contribute to identification of novel therapeutic targets for protozoan diseases, and in this context, apoptosis-like cell death has been reported in different groups of protozoa, in which metacaspases seem to play a role. In the genus Plasmodium, apoptotic markers have been detected in P. falciparum and P. berghei, and no study focusing on P. vivax cell death has been reported so far. In the present study, we investigated the susceptibility of P. vivax to undergo apoptotic cell death after incubating mature trophozoites with the classical apoptosis inducer staurosporine. As assessed by flow cytometry assays, staurosporine inhibited parasite intraerythrocytic development, which was accompanied by a decrease in cell viability, evidenced by reduced plasmodial mitochondrial activity. However, typical signs of apoptosis, such as DNA fragmentation, chromatin condensation, and nuclear segregation, were not detected in the parasites induced to cell death, and no significant alteration in metacaspase gene expression (PvMCA1) was observed under cell death stimulus. Interestingly, dying parasites positively modulated cell death (eryptosis) of host erythrocytes, which was marked by externalization of phosphatidylserine and cell shrinkage. Our study shows for the time that P. vivax blood stages may not be susceptible to apoptosis-like processes, while they could trigger eryptosis of parasitized cells by undergoing cell death. Further studies are required to elucidate the cellular machinery involved in cell death of P. vivax parasites as well as in the modulation of host cell death. [ABSTRACT FROM AUTHOR]

Hepatitis C is a public health problem worldwide, affecting chronically about 71 million people, or 1% of the world population. The early detection of infection in clinical practice routine and blood donors is still important, being necessary for the development of new specific, sensitive, reliable tests that can improve the screening of HCV infection. Flow cytometry beads assay opens the possibility to detect multiple antigens, decrease cross-reactivity, increase in the sensitivity, with low sample volumes. Here, we describe proof-of-concept of a method for anti-Core and anti-NS5a detection using magnetic beads and flow cytometry. The immunoassay presented 93.33% sensitivity and 100% specificity for rCore magnetic beads (MgBs), and 93.33% sensitivity and 96.67% specificity for rctNS5a MgBs. The accuracy values for the tests using rCore and rctNS5a MgBs were 96.67% and 95%, respectively. The results of the ROC curve were 0.97 and 0.99 for rCore and rctNS5a MgBs, respectively. Therefore, we concluded that the method presented here for the detection of anti-HCV antibodies using magnetic beads analyzed by flow cytometry showed promising results, achieving satisfactory sensitivity and specificity values, with future potential to be an alternative method for screening anti-HCV antibodies in blood banks and blood centers. [ABSTRACT FROM AUTHOR]

Background: Immunoassays for Plasmodium detection are, presently, most frequently based on monoclonal antibodies (MAbs); Polyclonal antibodies (PAbs), which are cheaper to develop and manufacture, are much less frequently used. In the present study we describe a sandwich ELISA assay which is capable of detecting P. vivax Lactate Dehydrogenase (LDH) in clinical blood samples, without cross reacting with those infected with P. falciparum.Methods: Two recombinant proteins were produced from different regions of the P. vivax LDH gene. Two sandwich ELISA assay were then designed: One which uses mouse anti-LDH 1-43aa PAbs as primary antibodies ("Test 1") and another which uses anti-LDH 35-305aa PAbs ("Test 2") as the primary antibodies. Rabbit anti-LDH 1-43aa PAbs were used as capture antibodies in both ELISA assays. Blood samples taken from P. vivax and P. falciparum infected patients (confirmed by light microscopy) were analysed using both tests.Results: "Test 2" performed better at detecting microscopy-positive blood samples when compared to "Test 1", identifying 131 of 154 positive samples (85%); 85 positives (55%) were identified using "test 1". "Test 1" produced one false positive sample (from the 20 malaria-free control) blood samples; "test 2" produced none. Kappa coefficient analysis of the results produced a value of 0.267 when microscope-positive blood smears were compared with "test 1", but 0.734 when microscope-positive blood smears were compared with the results from "test 2". Positive predictive value (PPV) and negative predictive value (NPV) were observed to be 98% and 22% respectively, for "Test 1", and 99% and 45%, for "test 2". No cross reactivity was detected with P. falciparum positive blood samples (n = 15) with either test assay.Conclusion: Both tests detected P. vivax infected blood and showed no evidence of cross-reacting with P. falciparum. Further studies will need to be conducted to establish the full potential of this technique for malaria diagnostics. As well as representing a promising new cost-effective novel technique for P. vivax diagnosis and research, the method for developing this assay also highlights the potential for PAb-based strategies for diagnostics in general. [ABSTRACT FROM AUTHOR]

The spores of Bacillus subtilis have already been proposed for different biotechnological and immunological applications; however, there is an increasing need for the development of methodologies that improve the detection of antigens immobilized on the surface of spores together with their quantification. Flow cytometry-based analyses have been previously proposed as fast, reliable, and specific approaches for detecting labeled cells of B. subtilis. Herein, we propose the use of flow cytometry to evaluate the display efficiency of a fluorescent antibody (FA) on the surface of the spore and quantify the number of spores using counting beads. For this, we used ethidium bromide as a DNA marker and an allophycocyanin (APC)-labeled antibody, which was coupled to the spores, as a surface marker. The quantification of spores was performed using counting beads since this technique demonstrates high accuracy in the detection of cells. The labeled spores were analyzed using a flow cytometer, which confirmed the coupling. As a result, it was demonstrated that DNA labeling improved the accuracy of quantification by flow cytometry, for the detection of germinated spores. It was observed that ethidium bromide was not able to label dormant spores; however, this technique provides a more precise determination of the number of spores with fluorescent protein coupled to their surface, thus helping in the development of studies that focus on the use of spores as a biotechnological platform in different applications.