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Small-Saunders et al. uncovered a new facet of artemisinin resistance in Plasmodium in which parasites use a previously underexplored arm of stress response mechanisms. Through altered epitranscriptomic modifications on tRNA, changed translation patterns adapt resistant cells to facilitate entry into a quiescent-like state which provides the parasite an escape from many drugs. [ABSTRACT FROM AUTHOR]

Gametocytes, the precursor cells of malaria-parasite gametes, circulate in the blood and are responsible for transmission for host to mosquito vector. Of all the malaria life cycles stages analyzed the male gametocyte has the most distinct proteome, containing many proteins involved in flagellar-based motility and rapid genome replication.

Results show that the surface protein PFS48/45 of male gametes of Plasmodium falciparum mediates fertilization process as evidenced by mutant male gamete's inability to penetrate fertile female gametes.

To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.cell.2007.11.026 Byline: Chris J. Janse (1), Andrew P. Waters (1) Abstract: Malaria parasites must invade the erythrocytes of its host, to be able to grow and multiply. Having depleted the host cell of its nutrients, the parasites break out to invade new erythrocytes. In this issue of Cell, discover a new organelle, the exoneme, that contains a protease SUB1, which helps the parasite to escape from old erythrocytes and invade new ones. Author Affiliation: (1) Department of Parasitology, Leiden University Medical Centre, Albinusdreef 2, 2333ZA Leiden, The Netherlands

The life cycle of the malaria parasite (plasmodium) is very complex as they engage in highly specific and varied interactions with cell types of both the mammalian host and the mosquito vector. A detailed molecular insight into an intimate interaction between a malaria parasite protein and its host cell receptor that enable the parasite to invade erythrocytes is reported.

Background: The bioreactance technique is a relatively new, totally noninvasive technique that is used to measure cardiac output (CO) and is easy to use. The Non-Invasive Cardiac Output Monitor (NICOM) is 1 such system. Although approved by the Food and Drug Administration for measurement of stroke volume, there is a paucity of literature validating this technology in decompensated heart failure and cardiogenic shock.Methods and Results: Fifty patients admitted to our cardiac intensive care unit for cardiogenic shock and Swan-Ganz catheter-guided therapy were prospectively enrolled in the study after informed consent. Simultaneous measurements of CO were obtained using NICOM, indirect Fick and bolus thermodilution. The intraclass correlation coefficient (ICC) was used to assess the precision of NICOM for CO using the 3 repeated measurements of CO over the pooled data. The agreement of the NICOM device in the defined clinical population, compared to indirect Fick and thermodilution, was evaluated by comparing the Pearson correlation coefficient, the Bland-Altman plot and the Lin concordance correlation coefficient. The ICC for cardiac output measured by NICOM showed excellent repeatability (ICC = 0.93, 95% CI = 0.92-0.94, n = 262) in the pooled data. The Pearson correlation coefficient for cardiac output measured by NICOM was poor when compared to indirect Fick (n = 263, r = 0.132, P = 0.033) and TD (n = 258, r = 0.275, P < 0.001).Conclusions: NICOM technology is not a reliable method of measuring CO in patients with decompensated heart failure and cardiogenic shock. [ABSTRACT FROM AUTHOR]

In 2004 the first annual BioMalPar meeting was held at EMBL Heidelberg, bringing together researchers from around the world with the goal of building connections between malaria research groups in Europe. Twenty years on it is time to reflect on what was achieved and to look ahead to the future. [ABSTRACT FROM AUTHOR]

Anopheles mosquitoes are major vectors of human malaria in Africa that transmits malaria parasites. The hemocyte-specific complement-like protein TEP1 from mosquito Anopheles gambiae that binds to and mediates killing of midgut stages of the rodent malaria parasite Plasmodium berghei is reported.

Female anopheline mosquito reproduction is intimately linked to the Plasmodium sporogonic cycle, whereby malaria parasites ostensibly compete for the same resources required for mosquito egg development. However, in a recent study, Werling and colleagues (Cell 2019;177:315–325) uncovered a parasitic strategy supporting coexistence, exploiting mosquito nutrients without affecting mosquito fitness and reproductivity. [ABSTRACT FROM AUTHOR]

Abstract: The most critical bottleneck in the generation of recombinant Plasmodium berghei parasites is the mandatory in vivo cloning step following successful genetic manipulation. This study describes a new technique for rapid selection of recombinant P. berghei parasites. The method is based on flow cytometry to isolate isogenic parasite lines and represents a major advance for the field, in that it will speed the generation of recombinant parasites as well as cut down on animal use significantly. High expression of GFP during blood infection, a prerequisite for robust separation of transgenic lines by flow cytometry, was achieved. Isogenic recombinant parasite populations were isolated even in the presence of a 100-fold excess of wild-type (WT) parasites. Aquaglyceroporin (AQP) loss-of-function mutants and parasites expressing a tagged AQP were generated to validate this approach. aqp − parasites grow normally within the WT phenotypic range during blood infection of NMRI mice. Similarly, colonization of the insect vector and establishment of an infection after mosquito transmission were unaffected, indicating that AQP is dispensable for life cycle progression in vivo under physiological conditions, refuting its use as a suitable drug target. Tagged AQP localized to perinuclear structures and not the parasite plasma membrane. We suggest that flow-cytometric isolation of isogenic parasites overcomes the major roadblock towards a genome-scale repository of mutant and transgenic malaria parasite lines. [Copyright &y& Elsevier]

Abstract: The SIR2 family of NAD+-dependent protein deacetylases, collectively called sirtuins, has been of central interest due to their proposed roles in life-span regulation and ageing. Sirtuins are one group of environment sensors of a cell interpreting external information and orchestrating internal responses at the sub-cellular level, through participation in gene regulation mechanisms. Remarkably conserved across all kingdoms of life SIR2 proteins in several protozoan parasites appear to have both conserved and intriguing unique functions. This review summarises our current knowledge of the members of the sirtuin families in Apicomplexa, including Plasmodium, and other protozoan parasites such as Trypanosoma and Leishmania. The wide diversity of processes regulated by SIR2 proteins makes them targets worthy of exploitation in anti-parasitic therapies. [Copyright &y& Elsevier]

The Molecular Approaches to Malaria 2004 meeting provided an opportunity to see the impressive progress in all research fields and in the four years since the previous Molecular Approaches to Malaria meeting, when much of the Plasmodium falciparum genome sequence was already available. Study of the part of the Plasmodium life cycle associated with transmission through the vector, which begins with the commitment of blood-stage forms to sexual development, has been especially fruitful. This success is a result of several reasons including: (i) the availability of the genome sequence; (ii) the availability of good animal models that allow parasite culture and facile in vivo studies of many of the life cycle stages involved in transmission; (iii) the availability of genetic manipulation technologies for the animal models of malaria, as well as P. falciparum; and (iv) the ability to study lethal gene knockouts at this stage of the life cycle. [Copyright &y& Elsevier]

Abstract: Plasmodium falciparum malaria is the most important parasitic disease worldwide, responsible for an estimated 1 million deaths annually. Two P. falciparum genes code for putative phosphoglycerate mutases (PGMases), a widespread protein group characterized by the involvement of histidine residues in their catalytic mechanism. PGMases are responsible for the interconversion between 2 and 3-phosphoglycerate, an intermediate step in the glycolysis pathway. We have determined the crystal structures of one of the P. falciparum''s PGMases (PfPGM2) and a functionally distinct phosphoglycerate mutase from Cryptosporidium parvum, a related apicomplexan parasite. We performed sequence and structural comparisons between the two structures, another P. falciparum enzyme (PfPGM1) and several other PGM family members from other organisms. The comparisons revealed a distinct conformation of the catalytically active residues not seen in previously determined phosphoglycerate mutase structures. Furthermore, characterization of their enzymatic activities revealed contrasting behaviors between the PfPGM2 and the classical cofactor-dependent PGMase from C. parvum, clearly establishing PfPGM2 as a phosphatase with a residual level of mutase activity. Further support for this function attribution was provided by our structural comparison with previously characterized PGM family members. Genetic characterization of PGM2 in the rodent parasite Plasmodium berghei indicated that the protein might be essential to blood stage asexual growth, and a GFP tagged allele is expressed in both blood and zygote ookinete development and located in the cytoplasm. The P. falciparum PGM2 is either an enzyme implicated in the phosphate metabolism of the parasite or a regulator of its life cycle. [Copyright &y& Elsevier]

The RMgm database, www.pberghei.eu, is a web-based, manually curated, repository containing information on genetically modified rodent-malaria parasites. It provides easy and rapid access to information on the genotype and phenotype of mutant and reporter parasites. The database also contains information on unpublished mutants without a clear phenotype and negative trials to disrupt genes. Information can be searched using pre-defined key features, such as phenotype, life-cycle stage, gene model, gene-tags and mutations. The information relating to the mutants is reciprocally linked to PlasmoDB and GeneDB. Access to mutant-parasite information, and gene function/ontology inferred from mutant phenotypes provides a timely resource aimed at enhancing research into Plasmodium gene function and (systems) biology. [ABSTRACT FROM AUTHOR]

Abstract: Invasive forms of apicomplexan parasites contain secretory organelles (which may include micronemes, rhoptries or dense granules), the contents of which mediate invasion of host cells. Only few rhoptry proteins have been identified in Plasmodium and then only in merozoites and none in the sporozoite or ookinete. Epitope-tagged proteins (with either green fluorescent protein or C-MYC) were used to analyse the expression and cellular localisation of a known Plasmodium rhoptry protein (RAP2/3) and putative homologues of two Toxoplasma rhoptry proteins (rhoptry neck protein 2, RON2 and putative rhoptry protein 2, PRP2) at different stages across the life cycle. This analysis showed correct targeting to the merozoite rhoptries of GFP-tagged RAP2/3 and, for the first time, a distinct apical fluorescence pattern in sporozoites indicating a rhoptry location. In addition, tagged PBRON2 and PBPRP2 also show a merozoite rhoptry localisation similar to that of RAP2/3. RON2 is expressed in sporozoites and has the same timing of expression and location as RAP2/3. While PRP2 is also expressed in sporozoites, both its pattern of expression and location differ from RON2 and RAP2/3. None of the tagged proteins were detected in ookinetes, which is in agreement with the proposed lack of rhoptries in this third invasive form of Plasmodium. The analysis of tagged rhoptry proteins reveals new insights into the role of these proteins in host-cell invasion in different malarial ‘zoites’ and will facilitate more detailed studies into the role of rhoptries in establishing an infection of not only red blood cell but also the hepatocytes. [Copyright &y& Elsevier]

Abstract: Plasmodium encodes a family of six secreted multi-domain adhesive proteins, termed PCCps, which are released from gametocytes during emergence within the mosquito midgut. The expression and cellular localization of PCCp proteins predict a role either in gametocyte development or within the mosquito midgut during the transition from gametes into the ookinete stage. However, mutant parasites lacking expression of any single PCCp protein show a phenotype at the oocyst stage with a failure of oocyst maturation and sporozoite formation. In this study we investigated the stage-specific transcription of the PCCp genes of the rodent malaria parasite, Plasmodium berghei, and analyzed their promoter activities. Transcript expression analysis by quantitative real time RT-PCR showed that as in the human malaria parasite, Plasmodium falciparum, all PbCCp genes are predominantly transcribed in the gametocyte stage with a low level of transcription in the oocyst stage. Transgenic P. berghei parasites that contain the reporter protein GFP driven by the promoter regions of PbCCps showed pronounced GFP expression exclusively in gametocytes, in agreement with the RT-PCR data. To determine whether functional redundancies of different PCCp family members could explain the lack of a phenotype in gametocytes or gametes in single knockout mutant parasites, double gene null mutant P. berghei parasites were generated lacking either PCCp1 and PCCp3, or PCCp1 and PCCp4. The phenotype of these double knockout mutants was similar to that observed for single gene knockout mutants and manifest at the oocyst rather than the gametocyte or other stages within the mosquito midgut lumen. [Copyright &y& Elsevier]

Abstract: Immunisation with live, radiation-attenuated sporozoites (RAS) or genetically attenuated sporozoites (GAS) of rodent plasmodial parasites protects against subsequent challenge infections. We recently showed that immunisation with Plasmodium berghei GAS that lack the microneme protein P36p protects mice for a period of up to 4 months. Here, we show that the period of full protection induced by p36p −-sporozoites lasts 12 and 18 months in C57Bl6 and BALB/c mice, respectively. Full protection is also achieved with three doses of only 1000 p36p − (but not RAS) sporozoites. Subcutaneous, intradermal or intramuscular routes of administration also lead to partial protection. In addition, immunisation with either P. berghei RAS- or, to a lesser extent, p36p −-sporozoites inhibits parasite intrahepatic development in mice challenged with Plasmodium yoelii sporozoites. Since naturally acquired malaria infections or subunit-based vaccines only induce short-term immune responses, the protection conferred by immunisation with p36p −-sporozoites described here further emphasises the potential of GAS as a vaccination strategy for malaria. [Copyright &y& Elsevier]

Abstract: P25 is a major surface protein of Plasmodium ookinetes. Antibodies against P25 prevent the formation of oocysts in the mosquito and thereby block transmission of the parasite through an endemic population. Plasmodium vivax transmission-blocking vaccines based on Pv25 have undergone human trials and inhibit transmission significantly. The current assay to determine transmission-blocking activity (TBA) of these sera, the ‘standard membrane feeding assay’, is complex and can be performed by few groups worldwide that require both mosquito breeding facilities and access to volunteers naturally infected with P.vivax—a costly, and uncontrolled source of parasites. Here we report the development of novel assays to determine TBA using two clones (Pv25DR and Pv25DR3) of transgenic rodent parasites (Plasmodium berghei) expressing Pv25. We show that oocyst development of the transgenic parasites is inhibited by monoclonal antibody against Pv25 with the same kinetics exhibited by wild type parasites when exposed to mouse monoclonal antibodies targeted to a paralogous protein P28. Human transmission-blocking sera from a clinical vaccine trial of Pv25 inhibited oocyst development of Pv25DR and Pv25DR3, whereas non-blocking sera did not. We further show transmission-blocking activity can be determined in a simple assays of ookinete development in vitro, assays that obviate the need for mosquito colonies. These results demonstrate that transgenic rodent malarias expressing proteins from human Plasmodium species can be cheap, safe, and simple tools for testing TBA from sera. To this end the cloned lines have been deposited with, and are freely available from, MR4. [Copyright &y& Elsevier]

Abstract: The genome of Plasmodium falciparum contains a small gene family that expresses proteins characterized by the presence of 6-cysteine domains. Most of these proteins are expressed on the surface of the parasite and some are known to play a role in cell–cell interactions. Two members of this family, Pfs48/45 and Pfs230, form a complex localized on the surface of gametes and are recognized as important targets for transmission-blocking vaccines. In this study we report the analysis of an additional member of this family, Pfs47 the closest paralog of Pfs48/45. We demonstrate that Pfs47 is expressed only in female gametocytes and is located on the surface of female gametes following emergence from red blood cells. In contrast to the critical function of P48/45 for male fertility, Pfs47 does not appear crucial for female fertility. Parasites lacking Pfs47 through targeted gene disruption, produce normal numbers of oocysts when included in the blood meal of the mosquito vector. In addition, three monoclonal antibodies against Pfs47 were unable to inhibit oocyst development when present in a blood meal containing wild type parasites. These results show redundancy in protein function for Pfs47 and reduce the support for candidacy of Pfs47 as a transmission-blocking vaccine target. [Copyright &y& Elsevier]

Abstract: The use of transfection in the study of the biology of malaria parasites has been limited due to poor transfection efficiencies (frequency of 10−6 to 10−9) and a paucity of selection markers. Here, a new method of transfection, using non-viral Nucleofector® technology, is described for the rodent parasite Plasmodium berghei. The transfection efficiency obtained (episomal and targeted integration into the genome) is in the range of 10−2 to 10−3. Such high transfection efficiency strongly reduces the time, number of laboratory animals and amount of materials required to generate transfected parasites. Moreover, it allows different experimental strategies for reverse genetics to be developed and we demonstrate direct selection of stably and non-reversibly transformed, fluorescent protein (FP)-expressing parasites using FACS. Since there is no need to use a drug-selectable marker, this method increases the (low) number of selectable markers available for transformation of P. berghei and can in principle be extended to utilise additional FP. Furthermore the FACS-selected, FP-expressing parasites may serve as easily visualized reference lines that may still be genetically manipulated with the existing drug-selectable markers. The combination of enhanced transfection efficiency and a versatile rodent model provides a basis for the further development of novel tools for high throughput genome manipulation. [Copyright &y& Elsevier]

Abstract: Plasmodium falciparum contains two genes encoding different isotypes of α-tubulin, α-tubulin I and α-tubulin II. α-Tubulin II is highly expressed in male gametocytes and forms part of the microtubules of the axoneme of male gametes. Here we present the characterization of Plasmodium berghei α-tubulin I and α-tubulin II that encode proteins of 453 and 450 amino acids, respectively. α-Tubulin II lacks the well-conserved three amino acid C-terminal extension including a terminal tyrosine residue present in α-tubulin I. Investigation of transcription by Northern analysis and RT-PCR and analysis of promoter activity by GFP tagging showed that α-tubulin I is expressed in all blood and mosquito stages. As expected, α-tubulin II was highly expressed in the male gametocytes, but transcription was also observed in the asexual blood stages, female gametocytes, ookinetes and oocysts. Gene disruption experiments using standard transfection technologies did not produce viable parasites indicating that both α-tubulin isotypes are essential for the asexual blood stages. Targeted modification of α-tubulin II by the addition of the three C-terminal amino acids of α-tubulin I did not affect either blood stage development nor male gamete formation. Attempts to modify the C-terminal region by adding a TAP tag to the endogenous α-tubulin II gene were not successful. Introduction of a transgene, expressing TAP-tagged α-tubulin II, next to the endogenous α-tubulin II gene, had no effect on the asexual blood stages but strongly impaired formation of male gametes. These results show that α-tubulin II not only plays an important role in the male gamete but is also expressed in and essential for asexual blood stage development. [Copyright &y& Elsevier]

Abstract: Using an in vitro development system for Plasmodium berghei sporogonic stages and microarray technology we examined parasite gene expression during ookinete invasion of Aedes cells and the ensuing oocyst development. A number of genes were found to be differentially expressed. The most prominent class of up-regulated elements corresponded to products involved in protein synthesis and metabolism. Furthermore, several previously studied genes with a known in vivo developmental profile matched published data. A large number of genes with a hitherto unknown function during the life cycle stages studied also show a differential pattern of expression, indicating the involvement of their products in control and execution of active developmental processes. [Copyright &y& Elsevier]

Green fluorescent protein (GFP) is a well-established reporter protein for the examination of biological processes. This report describes a recombinant Plasmodium berghei, PbGFPCON, that constitutively expresses GFP in a growth responsive manner in its cytoplasm from a transgene that is integrated into the genome and controlled by the strong promoter from a P. berghei elongation factor-1α gene. All life cycle forms of PbGFPCON except for male gametes can be easily visualized by fluorescent microscopy. PbGFPCON showed similar growth characteristics to wild type P. berghei parasites throughout the whole life cycle and can therefore be used as a reference line for future investigations of parasite–host cell interactions. The principle of automated fluorescence-based counting and sorting of live parasites from host cell backgrounds and different parasite forms from complex mixtures such as asynchronous blood stages is established. PbGFPCON allows the visualization and investigation of live parasite stages that are difficult and labor-intensive to observe, such as the liver and mosquito stages. PbGFPCON can be employed to establish the phenotype of independent mutant parasites. With the recent development of a second, independent selectable marker in P. berghei, PbGFPCON is a useful tool to investigate the effect of further genetic modifications on host–parasite interactions. [Copyright &y& Elsevier]

A gene encoding a 352 amino acid protein with a putative signal sequence, transmembrane domain and thrombospondin structural homology repeat was identified in the genome of the human malaria parasite, Plasmodium falciparum and the rodent malaria parasite, Plasmodium berghei. The protein localises in the apical organelles of P. falciparum and P. berghei merozoites within intraerythrocytic schizonts and has, therefore, been termed the Plasmodium thrombospondin-related apical merozoite protein (PTRAMP). PTRAMP co-localises with the Apical Merozoite Antigen-1 (AMA-1) in developing micronemes and subsequently relocates onto the merozoite surface. Although the gene appears to be specific to the Plasmodium genus, orthologues are present in the genomes of all malaria parasite species examined suggesting a conserved function in host-cell invasion. PTRAMP, therefore, has all the features to merit further evaluation as a malaria vaccine candidate. [Copyright &y& Elsevier]