Publications by authors named "Miranda S Oakley"

15 Publications

  • Page 1 of 1

CD47 blockade reduces the pathologic features of experimental cerebral malaria and promotes survival of hosts with infection.

Proc Natl Acad Sci U S A 2021 Mar;118(11)

Institute for Stem Cell Biology and Regenerative Medicine, Stanford University School of Medicine, Stanford, CA 94305;

CD47 is an antiphagocytic "don't eat me" signal that inhibits programmed cell removal of self. As red blood cells (RBCs) age they lose CD47 expression and become susceptible to programmed cell removal by macrophages. CD47 mice infected with , which exhibits an age-based preference for young RBCs, were previously demonstrated to be highly resistant to malaria infection. Our study sought to test the therapeutic benefit of CD47 blockade on ameliorating the clinical syndromes of experimental cerebral malaria (ECM), using the ANKA () murine model. In vitro we tested the effect of anti-CD47 mAb on infected RBC phagocytosis and found that anti-CD47 treatment significantly increased clearance of -infected RBCs. Infection of C57BL/6 mice with is lethal and mice succumb to the clinical syndromes of CM between days 6 and 10 postinfection. Strikingly, treatment with anti-CD47 resulted in increased survival during the cerebral phase of infection. Anti-CD47-treated mice had increased lymphocyte counts in the peripheral blood and increased circulating levels of IFN-γ, TNF-α, and IL-22. Despite increased circulating levels of inflammatory cytokines, anti-CD47-treated mice had reduced pathological features in the brain. Survival of ECM in anti-CD47-treated mice was correlated with reduced cellular accumulation in the cerebral vasculature, improved blood-brain barrier integrity, and reduced cytotoxic activity of infiltrating CD8 T cells. These results demonstrate the therapeutic benefit of anti-CD47 to reduce morbidity in a lethal model of ECM, which may have implications for preventing mortality in young African children who are the highest casualties of CM.
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http://dx.doi.org/10.1073/pnas.1907653118DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7980459PMC
March 2021

Transcriptome analysis based detection of Plasmodium falciparum development in Anopheles stephensi mosquitoes.

Sci Rep 2018 08 1;8(1):11568. Epub 2018 Aug 1.

Laboratory of Emerging Pathogens, Division of Emerging and Transfusion Transmitted Diseases, Office of Blood Research and Review, Center for Biologics Evaluation and Research, Food and Drug Administration, Silver Spring, MD, USA.

The Plasmodium life cycle within the mosquito involves the gamete, zygote, motile ookinete, and the oocyst stage that supports sporogony and sporozoite formation. We mapped the P. falciparum transcriptome as the parasite progresses through the oocyst stage of development on days 2, 4, 6, and 8 post-P. falciparum infectious blood meal. Through these genomic studies, we identified 212 novel transmission stage biomarkers including genes that are developmentally expressed at a single time point and genes that are pan-developmentally expressed at all four time points in P. falciparum oocysts. Validation of a small subset of genes at the transcriptional and translational level resulted in identification of a signature of genes/proteins that can detect parasites within the mosquito as early as day 2 post-infectious blood meal and can be used to distinguish early versus late stage P. falciparum oocyst development in the mosquito. Currently, circumsporozoite protein (CSP), which is detectable only after day 7 post-infection, is the only marker used for detection of P. falciparum infection in mosquitoes. Our results open the prospect to develop a non-CSP based detection assay for assessment of P. falciparum infection in mosquitoes and evaluate the effect of intervention measures on malaria transmission in an endemic setting.
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http://dx.doi.org/10.1038/s41598-018-29969-4DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6070505PMC
August 2018

TCRβ-expressing macrophages induced by a pathogenic murine malaria correlate with parasite burden and enhanced phagocytic activity.

PLoS One 2018 25;13(7):e0201043. Epub 2018 Jul 25.

Division of Emerging and Transfusion Transmitted Diseases, Office of Blood Research and Review, Center for Biologics Evaluation and Research, Food and Drug Administration, Silver Spring, MD, United States of America.

Macrophages express a wide array of invariant receptors that facilitate host defense and mediate pathogenesis during pathogen invasion. We report on a novel population of CD11bhighCD14+F4/80+ macrophages that express TCRβ. This population expands dramatically during a Plasmodium berghei ANKA infection and sequesters in the brain during experimental cerebral malaria. Importantly, measurement of TCRβ transcript and protein levels in macrophages in wildtype versus nude and Rag1 knockout mice establishes that the observed expression is not a consequence of passive receptor expression due to phagocytosis or trogocytosis of peripheral T cells or nonspecific antibody staining to an Fc receptor or cross reactive epitope. We also demonstrate that TCRβ on brain sequestered macrophages undergoes productive gene rearrangements and shows preferential Vβ usage. Remarkably, there is a significant correlation in the proportion of macrophages that express TCRβ and peripheral parasitemia. In addition, presence of TCRβ on the macrophage also correlates with a significant increase (1.9 fold) in the phagocytosis of parasitized erythrocytes. By transcriptional profiling, we identify a novel set of genes and pathways that associate with TCRβ expression by the macrophage. Expansion of TCRβ-expressing macrophages points towards a convergence of the innate and adaptive immune responses where both arms of the immune system cooperate to modulate the host response to malaria and possibly other infections.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0201043PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6059462PMC
January 2019

TCRβ Combinatorial Immunoreceptor Expression by Neutrophils Correlates with Parasite Burden and Enhanced Phagocytosis during a Plasmodium berghei ANKA Malaria Infection.

Infect Immun 2018 07 21;86(7). Epub 2018 Jun 21.

Laboratory of Mucosal Pathogens and Cellular Immunology, Division of Bacterial, Parasitic, and Allergenic Products, Office of Vaccine Research and Review, Food and Drug Administration, Silver Spring, Maryland, USA

Recent studies have demonstrated that a subpopulation of neutrophils express the TCRαβ combinatorial immunoreceptor in humans and mice. Here, we report that a ANKA murine malaria infection induces expansion of TCRβ expressing CD11b Ly6G neutrophils in the spleen during the early phase of infection. Measurement of TCRβ transcript and protein levels of neutrophils in wild-type versus nude and knockout mice establishes that the observed expression is not a consequence of nonspecific antibody staining or passive receptor expression due to phagocytosis or trogocytosis of peripheral T cells. Remarkably, on day 3 postinfection, we observed a highly significant correlation between the proportion of neutrophils that express TCRβ and peripheral blood parasite burden. In addition, TCRβ neutrophils phagocytose parasitized erythrocytes with 4-fold greater efficiency than TCRβ neutrophils. Together these results signify that TCR expression by the neutrophil plays an important role in the regulation of parasite burden by enhancing the phagocytic capacity of the neutrophil.
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http://dx.doi.org/10.1128/IAI.00899-17DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6013678PMC
July 2018

A Novel Gametocyte Biomarker for Superior Molecular Detection of the Plasmodium falciparum Infectious Reservoirs.

J Infect Dis 2017 12;216(10):1264-1272

Laboratory of Emerging Pathogens, Division of Emerging and Transfusion Transmitted Diseases.

Background: Complete malaria eradication and optimal use of transmission-reducing interventions require knowledge of submicroscopic infectious reservoirs among asymptomatic individuals. Even submicroscopic levels of Plasmodium falciparum gametocytes can infect mosquitoes and promote onward transmission. Most efforts to identify gametocyte carriers use polymerase chain reaction amplification of the gametocyte-specific transcript Pfs25.

Methods: To expand the repertoire of biomarkers available for superior gametocyte detection, we compared the gene expression profiles of gametocytes and asynchronous blood-stage P. falciparum parasites by microarray technology. This allowed the identification of 56 molecules abundantly expressed in the gametocyte stage of the parasite. The analytical sensitivity for gametocyte detection was evaluated for 25 genes with the highest expression levels.

Results: One candidate, Pfg17, exhibited superior analytical sensitivity against a panel of gametocyte-spiked whole blood, detecting 10 gametocytes/mL; in comparison, Pfs25 detected only 25.3 gametocytes/mL. Pfg17 also exhibited superior clinical sensitivity, identifying 19.1% more samples from blood-film microscopy-negative Ghanaian children and 40% more samples from asymptomatic adults as gametocyte positive.

Conclusions: Cumulatively, our results suggest Pfg17 is an excellent biomarker for detecting asymptomatic infectious reservoirs otherwise missed by the most sensitive molecular method available. Our study has also improved the repertoire of transmission-stage antigens available for evaluation as candidate vaccines.
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http://dx.doi.org/10.1093/infdis/jix442DOI Listing
December 2017

Molecular Markers of Radiation Induced Attenuation in Intrahepatic Plasmodium falciparum Parasites.

PLoS One 2016 2;11(12):e0166814. Epub 2016 Dec 2.

Division of Emerging and Transfusion Transmitted Diseases, Center for Biologics Evaluation and Research, Food and Drug Administration, Silver Spring, Maryland, United States.

Experimental immunization with radiation attenuated sporozoites (RAS) and genetically attenuated sporozoites has proved to be a promising approach for malaria vaccine development. However, parasite biomarkers of growth attenuation and enhanced immune protection in response to radiation remain poorly understood. Here, we report on the effect of an attenuating dose of γ-irradiation (15 krad) on the Plasmodium falciparum sporozoite (PfSPZ) ultrastructure by electron microscopy, growth rate of liver stage P. falciparum in liver cell cultures, and genome-wide transcriptional profile of liver stage parasites by microarray. We find that γ-irradiation treated PfSPZ retained a normal cellular structure except that they were vacuous with a partially disrupted plasma membrane and inner membrane complex. A similar infection rate was observed by γ-irradiation-treated and untreated PfSPZ in human HCO-4 liver cells (0.47% versus 0.49%, respectively) on day 3 post-infection. In the microarray studies, cumulatively, 180 liver stage parasite genes were significantly transcriptionally altered on day 3 and/or 6 post-infection. Among the transcriptionally altered biomarkers, we identified a signature of seven candidate parasite genes that associated with functionally diverse pathways that may regulate radiation induced cell cycle arrest of the parasite within the hepatocyte. A repertoire of 14 genes associated with protein translation is transcriptionally overexpressed within the parasite by radiation. Additionally, 37 genes encode proteins expressed on the cell surface or exported into the host cell, 4 encode membrane associated transporters, and 10 encode proteins related to misfolding and stress-related protein processing. These results have significantly increased the repertoire of novel targets for 1) biomarkers of safety to define proper attenuation, 2) generating genetically attenuated parasite vaccine candidates, and 3) subunit candidate vaccines against liver stage malaria.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0166814PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5135057PMC
June 2017

T-bet modulates the antibody response and immune protection during murine malaria.

Eur J Immunol 2014 Sep 20;44(9):2680-91. Epub 2014 Aug 20.

Division of Bacterial, Parasitic, and Allergenic Products, Center for Biologics Evaluation and Research, U.S. Food and Drug Administration, Rockville, MD, USA.

CD4(+) T-cell subtypes govern the synthesis of different Ab isotypes and other immune functions. The influence of CD4(+) T-cell differentiation programs on isotype switching and other aspects of host immunological networks during malaria infection are currently poorly understood. Here, we used Tbx21(-/-) mice deficient for T-bet, a regulator of Th1 CD4(+) T-cell differentiation, to examine the effect of Th1 CD4(+) T cells on the immune protection to nonlethal murine malaria Plasmodium yoelii 17XNL. We found that Tbx21(-/-) mice exhibited significantly lower parasite burden that correlated with elevated levels of IgG1, indicating that T-bet-dependent Ab isotype switching may be responsible for lower parasite burden. Absence of T-bet was also associated with a transient but significant loss of T cells during the infection, suggesting that T-bet may suppress malaria-induced apoptosis or induce proliferation of T cells. However, Tbx21(-/-) mice produced greater numbers of Foxp3(+) CD25(+) regulatory CD4(+) T cells, which may contribute to the early contraction of T cells. Lastly, Tbx21(-/-) mice exhibited unimpaired production of IFN-γ by a diverse repertoire of immune cell subsets and a selective expansion of IFN-γ-producing T cells. These observations may have implications in malaria vaccine design.
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http://dx.doi.org/10.1002/eji.201344437DOI Listing
September 2014

The transcription factor T-bet regulates parasitemia and promotes pathogenesis during Plasmodium berghei ANKA murine malaria.

J Immunol 2013 Nov 27;191(9):4699-708. Epub 2013 Sep 27.

Division of Bacterial, Parasitic, and Allergenic Products, U.S. Food and Drug Administration, Rockville, MD 20852.

The pathogenesis of experimental cerebral malaria (ECM) is an immunologic process, mediated in part by Th1 CD4(+) T cells. However, the role of the Th1 CD4(+) T cell differentiation program on the ability to control parasitemia and susceptibility to ECM disease during blood stage malaria has never been assessed directly. Using the Plasmodium berghei ANKA murine model of ECM and mice deficient for the transcription factor T-bet (the master regulator of Th1 cells) on the susceptible C57BL/6 background, we demonstrate that although T-bet plays a role in the regulation of parasite burden, it also promotes the pathogenesis of ECM. T-bet-deficient (Tbx21(-/-)) mice had higher parasitemia than wild type controls did during the ECM phase of disease (17.7 ± 3.1% versus 10.9 ± 1.5%). In addition, although 100% (10/10) of wild type mice developed ECM by day 9 after infection, only 30% (3/10) of Tbx21(-/-) mice succumbed to disease during the cerebral phase of infection. Resistance to ECM in Tbx21(-/-) mice was associated with diminished numbers of IFN-γ-producing CD4(+) T cells in the spleen and a lower accumulation of CD4(+) and CD8(+) T cells in the brain. An augmented Th2 immune response characterized by enhanced production of activated GATA-3(+) CD4(+) T cells and elevated levels of the eotaxin, MCP-1, and G-CSF cytokines was observed in the absence of T-bet. Our results suggest that in virulent malarias, immune modulation or therapy resulting in an early shift toward a Th2 response may help to ameliorate the most severe consequences of malaria immunopathogenesis and the prospect of host survival.
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http://dx.doi.org/10.4049/jimmunol.1300396DOI Listing
November 2013

Radiation-induced cellular and molecular alterations in asexual intraerythrocytic Plasmodium falciparum.

J Infect Dis 2013 Jan 24;207(1):164-74. Epub 2012 Oct 24.

Division of Bacterial, Center for Biologics Evaluation and Research, Food and Drug Administration, Rockville, USA.

Background: γ-irradiation is commonly used to create attenuation in Plasmodium parasites. However, there are no systematic studies on the survival, reversion of virulence, and molecular basis for γ-radiation-induced cell death in malaria parasites.

Methods: The effect of γ-irradiation on the growth of asexual Plasmodium falciparum was studied in erythrocyte cultures. Cellular and ultrastructural changes within the parasite were studied by fluorescence and electron microscopy, and genome-wide transcriptional profiling was performed to identify parasite biomarkers of attenuation and cell death.

Results: γ-radiation induced the death of P. falciparum in a dose-dependent manner. These parasites had defective mitosis, sparse cytoplasm, fewer ribosomes, disorganized and clumped organelles, and large vacuoles-observations consistent with "distressed" or dying parasites. A total of 185 parasite genes were transcriptionally altered in response to γ-irradiation (45.9% upregulated, 54.1% downregulated). Loss of parasite survival was correlated with the downregulation of genes encoding translation factors and with upregulation of genes associated with messenger RNA-sequestering stress granules. Genes pertaining to cell-surface interactions, host-cell remodeling, and secreted proteins were also altered.

Conclusions: These studies provide a framework to assess the safety of γ-irradiation attenuation and promising targets for genetic deletion to produce whole parasite-based attenuated vaccines.
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http://dx.doi.org/10.1093/infdis/jis645DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3523796PMC
January 2013

Clinical and molecular aspects of malaria fever.

Trends Parasitol 2011 Oct 26;27(10):442-9. Epub 2011 Jul 26.

Division of Bacterial, Parasitic, and Allergenic Products, Center for Biologics Evaluation and Research, Food and Drug Administration, Rockville, MD, USA.

Although clinically benign, malaria fever is thought to have significant relevance in terms of parasite growth and survival and its virulence which in turn may alter the clinical course of illness. In this article, the historical literature is reviewed, providing some evolutionary perspective on the genesis and biological relevance of malaria fever, and the available molecular data on the febrile-temperature-inducible parasite factors that may contribute towards the regulation of parasite density and alteration of virulence in the host is also discussed. The potential molecular mechanisms that could be responsible for the induction and regulation of cyclical malaria fevers caused by different species of Plasmodium are also discussed.
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http://dx.doi.org/10.1016/j.pt.2011.06.004DOI Listing
October 2011

Molecular correlates of experimental cerebral malaria detectable in whole blood.

Infect Immun 2011 Mar 13;79(3):1244-53. Epub 2010 Dec 13.

Division of Bacterial, Parasitic, and Allergenic Products Center for Biologics Evaluation and Research, Food and Drug Administration, Rockville, Maryland, USA.

Cerebral malaria (CM) is a primary cause of deaths caused by Plasmodium falciparum in young children in sub-Saharan Africa. Laboratory tests based on early detection of host biomarkers in patient blood would help in the prognosis and differential diagnosis of CM. Using the Plasmodium berghei ANKA murine model of experimental cerebral malaria (ECM), we have identified over 300 putative diagnostic biomarkers of ECM in the circulation by comparing the whole-blood transcriptional profiles of resistant mice (BALB/c) to those of two susceptible strains (C57BL/6 and CBA/CaJ). Our results suggest that the transcriptional profile of whole blood captures the molecular and immunological events associated with the pathogenesis of disease. We find that during ECM, erythropoiesis is dysfunctional, thrombocytopenia is evident, and glycosylation of cell surface components may be modified. Furthermore, analysis of immunity-related genes suggests that slightly distinct mechanisms of immunopathogenesis may operate in susceptible C57BL/6 and CBA/CaJ mice. Furthermore, our data set has allowed us to create a molecular signature of ECM composed of a subset of circulatory markers. Complement component C1q, β-chain, nonspecific cytotoxic cell receptor protein 1, prostate stem cell antigen, DnaJC, member 15, glutathione S-transferase omega-1, and thymidine kinase 1 were overexpressed in blood during the symptomatic phase of ECM, as measured by quantitative real-time PCR analysis. These studies provide the first host transcriptome database that is uniquely altered during the pathogenesis of ECM in blood. A subset of these mediators of ECM warrant validation in P. falciparum-infected young African children as diagnostic markers of CM.
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http://dx.doi.org/10.1128/IAI.00964-10DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3067492PMC
March 2011

Pathogenic roles of CD14, galectin-3, and OX40 during experimental cerebral malaria in mice.

PLoS One 2009 Aug 27;4(8):e6793. Epub 2009 Aug 27.

Division of Bacterial, Parasitic and Allergenic Products, Center for Biologics and Evaluation Research, Food and Drug Administration, Bethesda, MD, USA.

An in-depth knowledge of the host molecules and biological pathways that contribute towards the pathogenesis of cerebral malaria would help guide the development of novel prognostics and therapeutics. Genome-wide transcriptional profiling of the brain tissue during experimental cerebral malaria (ECM ) caused by Plasmodium berghei ANKA parasites in mice, a well established surrogate of human cerebral malaria, has been useful in predicting the functional classes of genes involved and pathways altered during the course of disease. To further understand the contribution of individual genes to the pathogenesis of ECM, we examined the biological relevance of three molecules -- CD14, galectin-3, and OX40 that were previously shown to be overexpressed during ECM. We find that CD14 plays a predominant role in the induction of ECM and regulation of parasite density; deletion of the CD14 gene not only prevented the onset of disease in a majority of susceptible mice (only 21% of CD14-deficient compared to 80% of wildtype mice developed ECM, p<0.0004) but also had an ameliorating effect on parasitemia (a 2 fold reduction during the cerebral phase). Furthermore, deletion of the galectin-3 gene in susceptible C57BL/6 mice resulted in partial protection from ECM (47% of galectin-3-deficient versus 93% of wildtype mice developed ECM, p<0.0073). Subsequent adherence assays suggest that galectin-3 induced pathogenesis of ECM is not mediated by the recognition and binding of galectin-3 to P. berghei ANKA parasites. A previous study of ECM has demonstrated that brain infiltrating T cells are strongly activated and are CD44(+)CD62L(-) differentiated memory T cells [1]. We find that OX40, a marker of both T cell activation and memory, is selectively upregulated in the brain during ECM and its distribution among CD4(+) and CD8(+) T cells accumulated in the brain vasculature is approximately equal.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0006793PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2728507PMC
August 2009

Host biomarkers and biological pathways that are associated with the expression of experimental cerebral malaria in mice.

Infect Immun 2008 Oct 21;76(10):4518-29. Epub 2008 Jul 21.

Laboratory of Malaria and Vector Research, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, Maryland, USA.

Cerebral malaria (CM) is a primary cause of malaria-associated deaths among young African children. Yet no diagnostic tools are available that could be used to predict which of the children infected with Plasmodium falciparum malaria will progress to CM. We used the Plasmodium berghei ANKA murine model of experimental cerebral malaria (ECM) and high-density oligonucleotide microarray analyses to identify host molecules that are strongly associated with the clinical symptoms of ECM. Comparative expression analyses were performed with C57BL/6 mice, which have an ECM-susceptible phenotype, and with mice that have ECM-resistant phenotypes: CD8 knockout and perforin knockout mice on the C57BL/6 background and BALB/c mice. These analyses allowed the identification of more than 200 host molecules (a majority of which had not been identified previously) with altered expression patterns in the brain that are strongly associated with the manifestation of ECM. Among these host molecules, brain samples from mice with ECM expressed significantly higher levels of p21, metallothionein, and hemoglobin alpha1 proteins by Western blot analysis than mice unaffected by ECM, suggesting the possible utility of these molecules as prognostic biomarkers of CM in humans. We suggest that the higher expression of hemoglobin alpha1 in the brain may be associated with ECM and could be a source of excess heme, a molecule that is considered to trigger the pathogenesis of CM. Our studies greatly enhance the repertoire of host molecules for use as diagnostics and novel therapeutics in CM.
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http://dx.doi.org/10.1128/IAI.00525-08DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2546852PMC
October 2008

Molecular factors and biochemical pathways induced by febrile temperature in intraerythrocytic Plasmodium falciparum parasites.

Infect Immun 2007 Apr 5;75(4):2012-25. Epub 2007 Feb 5.

Laboratory of Malaria and Vector Research, National Institute of Allergy and Infectious Diseases/NIH, Rockville, MD 20892, USA.

Intermittent episodes of febrile illness are the most benign and recognized symptom of infection with malaria parasites, although the effects on parasite survival and virulence remain unclear. In this study, we identified the molecular factors altered in response to febrile temperature by measuring differential expression levels of individual genes using high-density oligonucleotide microarray technology and by performing biological assays in asexual-stage Plasmodium falciparum parasite cultures incubated at 37 degrees C and 41 degrees C (an elevated temperature that is equivalent to malaria-induced febrile illness in the host). Elevated temperature had a profound influence on expression of individual genes; 336 of approximately 5,300 genes (6.3% of the genome) had altered expression profiles. Of these, 163 genes (49%) were upregulated by twofold or greater, and 173 genes (51%) were downregulated by twofold or greater. In-depth sensitive sequence profile analysis revealed that febrile temperature-induced responses caused significant alterations in the major parasite biologic networks and pathways and that these changes are well coordinated and intricately linked. One of the most notable transcriptional changes occurs in genes encoding proteins containing the predicted Pexel motifs that are exported into the host cytoplasm or inserted into the host cell membrane and are likely to be associated with erythrocyte remodeling and parasite sequestration functions. Using our sensitive computational analysis, we were also able to assign biochemical or biologic functional predictions for at least 100 distinct genes previously annotated as "hypothetical." We find that cultivation of P. falciparum parasites at 41 degrees C leads to parasite death in a time-dependent manner. The presence of the "crisis forms" and the terminal deoxynucleotidyltransferase-mediated dUTP-biotin nick end labeling-positive parasites following heat treatment strongly support the notion that an apoptosis-like cell death mechanism might be induced in response to febrile temperatures. These studies enhance the possibility of designing vaccines and drugs on the basis of disruption in molecules and pathways of parasite survival and virulence activated in response to febrile temperatures.
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http://dx.doi.org/10.1128/IAI.01236-06DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1865691PMC
April 2007

CpG oligodeoxynucleotide and Montanide ISA 51 adjuvant combination enhanced the protective efficacy of a subunit malaria vaccine.

Infect Immun 2004 Feb;72(2):949-57

Malaria Program, Naval Medical Research Center, Silver Spring, Maryland 20910, USA.

Unmethylated CpG dinucleotide motifs present in bacterial genomes or synthetic oligodeoxynucleotides (ODNs) serve as strong immunostimulatory agents in mice, monkeys and humans. We determined the adjuvant effect of murine CpG ODN 1826 on the immunogenicity and protective efficacy of the Saccharomyces cerevisiae-expressed 19-kDa C-terminal region of merozoite surface protein 1 (yMSP1(19)) of the murine malaria parasite Plasmodium yoelii. We found that in C57BL/6 mice, following sporozoite challenge, the degree of protective immunity against malaria induced by yMSP1(19) in a formulation of Montanide ISA 51 (ISA) plus CpG ODN 1826 was similar or superior to that conferred by yMSP1(19) emulsified in complete Freund's adjuvant (CFA/incomplete Freund's adjuvant). In total, among mice immunized with yMSP1(19), 22 of 32 (68.7%) with ISA plus CpG 1826, 0 of 4 (0%) with CFA/incomplete Freund's adjuvant, 0 of 4 (0%) with CpG 1826 mixed with ISA (no yMSP1(19)), and 0 of 11 (0%) with CpG 1826 alone were completely protected against development of erythrocytic stage infection after sporozoite challenge. The adjuvant effect of CpG ODN 1826 was manifested as both significantly improved complete protection from malaria (defined as the absence of detectable erythrocytic form parasites) (P = 0.007, chi square) and reduced parasite burden in infected mice. In vivo depletions of interleukin-12 and gamma interferon cytokines and CD4+ and CD8+ T cells in vaccinated mice had no significant effect on immunity. On the other hand, immunoglobulin G (IgG) isotype levels appeared to correlate with protection. Inclusion of CpG ODN 1826 in the yMSP1(19) plus ISA vaccine contributed towards the induction of higher levels of IgG2a and IgG2b (Th1 type) antibodies, suggesting that CpG ODN 1826 caused a shift towards a Th1 type of immune response that could be responsible for the higher degree of protective immunity. Our results indicate that this potent adjuvant formulation should be further evaluated for use in clinical trials of recombinant malarial vaccine candidates.
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http://www.ncbi.nlm.nih.gov/pmc/articles/PMC321633PMC
http://dx.doi.org/10.1128/iai.72.2.949-957.2004DOI Listing
February 2004