The most widespread Plasmodium species, Plasmodium vivax, poses a significant public health threat. An effective vaccine is needed to reduce global malaria burden. Of the erythrocytic stage vaccine candidates, the 19 kDa fragment of the P. vivax Merozoite Surface Protein 1 (PvMSP119) is one of the most promising. Our group has previously defined several promiscuous T helper epitopes within the PvMSP1 protein, with features that allow them to bind multiple MHC class II alleles. We describe here a P. vivax recombinant modular chimera based on MSP1 (PvRMC-MSP1) that includes defined T cell epitopes genetically fused to PvMSP119. This vaccine candidate preserved structural elements of the native PvMSP119 and elicited cytophilic antibody responses, and CD4+ and CD8+ T cells capable of recognizing PvMSP119. Although CD8+ T cells that recognize blood stage antigens have been reported to control blood infection, CD8+ T cell responses induced by P. falciparum or P. vivax vaccine candidates based on MSP119 have not been reported. To our knowledge, this is the first time a protein based subunit vaccine has been able to induce CD8+ T cell against PvMSP119. The PvRMC-MSP1 protein was also recognized by naturally acquired antibodies from individuals living in malaria endemic areas with an antibody profile associated with protection from infection. These features make PvRMC-MSP1 a promising vaccine candidate.

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Background Entamoeba histolytica, E. dispar and E. moshkovskii are the most frequent species described in human infection where E. histolytica is the only true pathogen. The epidemiology of this infection is complex due to the absence of a routine exam that allows a correct discrimination of the Entamoeba species complex. Therefore, molecular methods appear as the unique epidemiological tool to accomplish the species discrimination. Herein, we conducted a cross-sectional study to determine the frequency of Entamoeba species infections in a group of asymptomatic individuals from a rural area in central Colombia.Methodology/Principal FindingsA total of 181 fecal samples from asymptomatic children under 16 years old from the hamlet La Vírgen, Cundinamarca (Colombia) that voluntarily accepted to participate in the study were collected. The fecal samples were examined by light microscopy and DNA-extracted, subsequently submitted to molecular discrimination of E. dispar/E. histolytica/E. moshkovskii infection based on a multiplex PCR assay targeting the 18S rRNA fragment. To confirm the species description, twenty samples were randomly submitted to DNA sequencing of the aforementioned fragment. By direct microscopic examination, frequency of the complex E. histolytica/E. dispar/E. moshkovskii was 18.8% (34/181). PCR showed a frequency of 49.1% (89/181), discriminated as 23.2% (42/181) that were positive for E. dispar, 25.4% (46/181) for E. moshkovskii and 0.55% (1/ 181) for E. histolytica. Also, mixed infections were detected between E. dispar and E. moshkovskii at 4.42% (8/181) of the samples. Molecular barcoding confirmed the diagnosis depicted by the multiplex PCR assay.Conclusions/SignificanceThis is the first description of E. moshkovskii in Colombia and the second report in South-America to our knowledge. Our results suggest the need to unravel the true epidemiology of Entamoeba infections around the world, including the real pathogenic role that E. moshkovskii may have.

dPlasmodium vivax is the most widespread species of Plasmodium, causing up to 50% of the malaria cases occurring outside subSaharan Africa. An effective vaccine is essential for successful control and potential eradication. A well-characterized vaccine candidate is the circumsporozoite protein (CSP). Preclinical and clinical trials have shown that both antibodies and cellular immune responses have been correlated with protection induced by immunization with CSP. On the basis of our reported approach of developing chimeric Plasmodium yoelii proteins to enhance protective efficacy, we designed PvRMC-CSP, a recombinant chimeric protein based on the P. vivax CSP (PvCSP). In this engineered protein, regions of the PvCSP predicted to contain human T cell epitopes were genetically fused to an immunodominant B cell epitope derived from the N-terminal region I and to repeat sequences representing the two types of PvCSP repeats. The chimeric protein was expressed in soluble form with high yield. As the immune response to PvCSP has been reported to be genetically restricted in the murine model, we tested the immunogenicity of PvRMC-CSP in groups of six inbred strains of mice. PvRMC-CSP was able to induce robust antibody responses in all the mouse strains tested. Synthetic peptides representing the allelic forms of the P. vivax CSP were also recognized to a similar extent regardless of the mouse strain. Furthermore, the immunization regimen induced high frequencies of multifunctional CD4؉ and CD8 ؉ PvRMC-CSP-specific T cells. The depth and breadth of the immune responses elicited suggest that immunization with PvRMC-CSP can circumvent the genetic restriction of the immune response to P. vivax CSP. Interestingly, PvRMC-CSP was also recognized by naturally acquired antibodies from individuals living in areas where malaria is endemic. These features make PvRMC-CSP a promising vaccine candidate for further development. P lasmodium vivax is the most widespread species of Plasmodium, causing up to 50% of the malaria cases occurring outside sub-Saharan Africa, with an estimated 2.48 billion people living in areas with risk of malaria transmission (1-4). Unlike Plasmodium falciparum, P. vivax is able to persist in a latent stage called hypnozoite within infected parenchymal liver cells. Activation of hypnozoites weeks or months after the primary infection leads to new blood stage infections, causing relapses and opportunities for further transmission (5).A vaccine targeting the P. vivax preerythrocytic stages preventing the entry of sporozoites into hepatocytes or inhibiting the liver stage development could block the production of hypnozoites. The most-characterized antigen and one of the few vaccine candidates for P. vivax tested in clinical trials is the circumsporozoite protein (CSP). CSP is an attractive target, since anti-CSP antibodies derived from naturally infected patients or from volunteers exposed to irradiated sporozoites have the ability to inhibit the infection of hepatic cells by sporozoites in vitro (6). Unlike P. ...

Exploitation of the immune system has emerged as an important therapeutic strategy for acute lymphoblastic leukemia (ALL). However, the mechanisms of immune evasion during leukemia progression remain poorly understood. We sought to understand the role of calcineurin in ALL and observed that depletion of calcineurin B (CnB) in leukemia cells dramatically prolongs survival in immunecompetent but not immune-deficient recipients. Immunecompetent recipients were protected from challenge with leukemia if they were first immunized with CnB-deficient leukemia, suggesting robust adaptive immunity. In the bone marrow (BM), recipients of CnB-deficient leukemia harbored expanded T-cell populations as compared with controls. Gene expression analyses of leukemia cells extracted from the BM identified Cn-dependent significant changes in the expression of immunoregulatory genes. Increased secretion of IL12 from CnB-deficient leukemia cells was sufficient to induce T-cell activation ex vivo, an effect that was abolished when IL12 was neutralized. Strikingly, recombinant IL12 prolonged survival of mice challenged with highly aggressive BALL. Moreover, gene expression analyses from children with ALL showed that patients with higher expression of either IL12A or IL12B exhibited prolonged survival. These data suggest that leukemia cells are dependent upon calcineurin for immune evasion by restricting the regulation of proinflammatory genes, particularly IL12. Significance: This report implicates calcineurin as an intracellular signaling molecule responsible for immune evasion during leukemia progression and raises the prospect of reexamining IL12 as a therapeutic in leukemia.