Comparative chemical genomics in Babesia species identifies the alkaline phosphatase PhoD as a determinant of antiparasitic resistance.

Babesiosis is an emerging zoonosis and widely distributed veterinary infection caused by 100+ species of Babesia parasites. The diversity of Babesia parasites and the lack of specific drugs necessitate the discovery of broadly effective antibabesials. Here, we describe a comparative chemogenomics (CCG) pipeline for the identification of conserved targets. CCG relies on parallel in vitro evolution of resistance in independent populations of Babesia spp. (B. bovis and B. divergens). We identified a potent antibabesial, MMV019266, from the Malaria Box, and selected for resistance in two species of Babesia. After sequencing of multiple independently derived lines in the two species, we identified mutations in a membrane-bound metallodependent phosphatase (phoD). In both species, the mutations were found in the phoD-like phosphatase domain. Using reverse genetics, we validated that mutations in bdphoD confer resistance to MMV019266 in B. divergens. We have also demonstrated that BdPhoD localizes to the endomembrane system and partially with the apicoplast. Finally, conditional knockdown and constitutive overexpression of BdPhoD alter the sensitivity to MMV019266 in the parasite. Overexpression of BdPhoD results in increased sensitivity to the compound, while knockdown increases resistance, suggesting BdPhoD is a pro-susceptibility factor. Together, we have generated a robust pipeline for identification of resistance loci and identified BdPhoD as a resistance mechanism in Babesia species.

Comparative chemical genomics in Babesia species identifies the alkaline phosphatase phoD as a novel determinant of resistance.

Babesiosis is an emerging zoonosis and widely distributed veterinary infection caused by 100+ species of Babesia parasites. The diversity of Babesia parasites, coupled with the lack of potent inhibitors necessitates the discovery of novel conserved druggable targets for the generation of broadly effective antibabesials. Here, we describe a comparative chemogenomics (CCG) pipeline for the identification of novel and conserved targets. CCG relies on parallel in vitro evolution of resistance in independent populations of evolutionarily-related Babesia spp. ( B. bovis and B. divergens ). We identified a potent antibabesial inhibitor from the Malaria Box, MMV019266. We were able to select for resistance to this compound in two species of Babesia, achieving 10-fold or greater resistance after ten weeks of intermittent selection. After sequencing of multiple independently derived lines in the two species, we identified mutations in a single conserved gene in both species: a membrane-bound metallodependent phosphatase (putatively named PhoD). In both species, the mutations were found in the phoD-like phosphatase domain, proximal to the predicted ligand binding site. Using reverse genetics, we validated that mutations in PhoD confer resistance to MMV019266. We have also demonstrated that PhoD localizes to the endomembrane system and partially with the apicoplast. Finally, conditional knockdown and constitutive overexpression of PhoD alter the sensitivity to MMV019266 in the parasite: overexpression of PhoD results in increased sensitivity to the compound, while knockdown increases resistance, suggesting PhoD is a resistance mechanism. Together, we have generated a robust pipeline for identification of resistance loci, and identified PhoD as a novel determinant of resistance in Babesia species. Highlights: Use of two species for in vitro evolution identifies a high confidence locus associated with resistance Resistance mutation in phoD was validated using reverse genetics in B. divergens Perturbation of phoD using function genetics results in changes in the level of resistance to MMV019266Epitope tagging reveals localization to the ER/apicoplast, a conserved localization with a similar protein in diatoms Together, phoD is a novel resistance determinant in multiple Babesia spp .

Babesia divergens egress from host cells is orchestrated by essential and druggable kinases and proteases.

Apicomplexan egress from host cells is fundamental to the spread of infection and is poorly characterized in Babesia spp., parasites of veterinary importance and emerging zoonoses. Through the use of video microscopy, transcriptomics and chemical genetics, we have implicated signaling, proteases and gliding motility as key drivers of egress by Babesia divergens. We developed reverse genetics to perform a knockdown screen of putative mediators of egress, identifying kinases and proteases involved in distinct steps of egress (ASP3, PKG and CDPK4) and invasion (ASP2, ASP3 and PKG). Inhibition of egress leads to continued intracellular replication, indicating exit from the replication cycle is uncoupled from egress. Chemical genetics validated PKG, ASP2 and ASP3 as druggable targets in Babesia spp. All taken together, egress in B. divergens more closely resembles T. gondii than the more evolutionarily-related Plasmodium spp. We have established a molecular framework for biological and translational studies of B. divergens egress.

Developmentally regulated mitochondrial biogenesis and cell death competence in maize pollen.

BACKGROUND: Cytoplasmic male sterility (CMS) is a maternally inherited failure to produce functional pollen that most commonly results from expression of novel, chimeric mitochondrial genes. In Zea mays, cytoplasmic male sterility type S (CMS-S) is characterized by the collapse of immature, bi-cellular pollen. Molecular and cellular features of developing CMS-S and normal (N) cytoplasm pollen were compared to determine the role of mitochondria in these differing developmental fates. RESULTS: Terminal deoxynucleotidyl transferase dUTP nick end labeling revealed both chromatin and nuclear fragmentation in the collapsed CMS-S pollen, demonstrating a programmed cell death (PCD) event sharing morphological features with mitochondria-signaled apoptosis in animals. Maize plants expressing mitochondria-targeted green fluorescent protein (GFP) demonstrated dynamic changes in mitochondrial morphology and association with actin filaments through the course of N-cytoplasm pollen development, whereas mitochondrial targeting of GFP was lost and actin filaments were disorganized in developing CMS-S pollen. Immunoblotting revealed significant developmental regulation of mitochondrial biogenesis in both CMS-S and N mito-types. Nuclear and mitochondrial genome encoded components of the cytochrome respiratory pathway and ATP synthase were of low abundance at the microspore stage, but microspores accumulated abundant nuclear-encoded alternative oxidase (AOX). Cytochrome pathway and ATP synthase components accumulated whereas AOX levels declined during the maturation of N bi-cellular pollen. Increased abundance of cytochrome pathway components and declining AOX also characterized collapsed CMS-S pollen. The accumulation and robust RNA editing of mitochondrial transcripts implicated translational or post-translational control for the developmentally regulated accumulation of mitochondria-encoded proteins in both mito-types. CONCLUSIONS: CMS-S pollen collapse is a PCD event coincident with developmentally programmed mitochondrial events including the accumulation of mitochondrial respiratory proteins and declining protection against mitochondrial generation of reactive oxygen species.

[Epidemiology of invasive pneumococcal disease in Tarragona, Spain, 2012-2015: incidence, lethality and serotype-coverage for distinct antipneumococcal vaccine formulations]. / Epidemiología de la enfermedad neumocócica invasiva en la región de Tarragona, 2012-2015: Incidencia, letalidad y cobertura de serotipos para las distintas formulaciones vacunales antineumocócicas.

OBJECTIVE: Nowadays, after licensure of the second generation new pneumococcal conjugate vaccines (PCV10/PCV13). The epidemiology of the pneumococcal disease must be re-evaluated. The present study described incidence, lethality and serotype distribution of invasive pneumococcal disease (IPD) in the general population of Tarragona's region (Spain) after licensure of these vaccines. METHODS: Retrospective study that included all cases of IPD (pneumococcus isolated in sterile sites) diagnosed among all-age individuals in the Spanish region of Tarragona (Tarragonés, Alt Camp and Baix Penedés counties) from 01/01/2012 to 31/12/2015. Incidence and lethality rates were estimated by age strata and globally. Similarly, it was determined the prevalence of IPD cases caused by serotypes included in the distinct formulations of multivalent conjugate vaccines (pcv7), PCV10 and PCV13) or 23-valent polysaccharide vaccine (PPV23). RESULTS: A total of 171 IPD cases were observed, which means a global incidence (per 100,000 persons-year) of 10.82 (7.86 in ≤14 years, 5.94 in 15-64 years and 36.46 in ≥65 years; p<0.001). Overall lethality rate was 6.8% (none in children, 9,3% in people 15-64 years and 6.9% in people ≥65 years). A serotype was identified in 132 (77.2%) of the 171 studied samples. Serotype-vaccine coverages (cases due to vaccine-type serotypes) were 14.4%, 26.5%, 42.4% and 78.8% for the PCV7, PCV10, PCV13 and PPV23, respectively (p<0.001). CONCLUSIONS: Incidence and lethality of IPD were intermediate-low in the region of Tarragona throughout 2012-2015. During this period, Serotype- vaccine coverage was almost double for the 23-valent than for the 13-valent vaccine.

OBJETIVO: En la actualidad, tras la comercialización de las nuevas vacunas neumocócicas conjugadas de segunda generación (VNC10/VNC13), la epidemiología de la enfermedad neumocócica debe ser reevaluada. El presente estudio tuvo como objetivo describir la incidencia, letalidad y distribución serotípica de la enfermedad neumocócica invasiva (ENI) en la población general del área de Tarragona durante el cuatrienio posterior a la introducción de estas vacunas. METODOS: Estudio observacional retrospectivo que incluyó todos los casos de ENI (Streptococcus pneumoniae aislado en sangre, líquido cefalorraquídeo, líquido pleural/articular/peritoneal o muestras de tejidos profundos obtenidas de forma estéril mediante punción-aspiración o biopsia) diagnosticados en el área de Tarragona (comarcas del Tarragonés, Alt Camp y Baix Penedés) entre 01/01/2012 y 31/12/2015. Se estimaron tasas de incidencia y letalidad (globalmente y por estratos etarios) y se determinó la prevalencia de casos causados por serotipos incluidos en las distintas formulaciones de vacunas antineumocócicas conjugadas heptavalente (VNC7), decavalente (VNC10), tridecavalente (VNC13) y polisacárida tricosavalente (VNP23). RESULTADOS: Se observaron 171 casos de ENI, lo que representó una incidencia (por 100.000 personas-año) de 10,82 (7,86 en ≤14 años, 5,94 en 15-64 años y 36,46 en ≥65 años; p<0,001). La letalidad fue del 6,8% (ninguna en niños, 9,3% en 15-64 años y 6,9% en personas ≥65 años; p<0,001). El serotipo responsable fue identificado en 132 (77,2%) de las 171 muestras estudiadas. La cobertura serotípica (casos causados por serotipos vacunales) fue del 14,4%, 26,5%, 42,4% y 78,8% para la VNC7, VNC10, VNC13 y VNP23, respectivamente (p<0,001). CONCLUSIONES: Durante el periodo 2012-2015 la incidencia y letalidad por ENI fue intermedia-baja en el área de Tarragona, destacando que la cobertura serotípica fue casi doble para la vacuna 23-valente que para la 13-valente.

Epidemiología de la enfermedad neumocócica invasiva en la región de Tarragona, 2012-2015: incidencia, letalidad y cobertura de serotipos para las distintas formulaciones vacunales antineumocócicas / Epidemiology of invasive pneumococcal disease in Tarragona, Spain, 2012-2015: incidence, lethality and serotype-coverage for distinct antipneumococcal vaccine formulations

Fundamentos: En la actualidad, tras la comercialización de las nuevas vacunas neumocócicas conjugadas de segunda generación (VNC10/VNC13), la epidemiología de la enfermedad neumocócica debe ser reevaluada. El presente estudio tuvo como objetivo describir la incidencia, letalidad y distribución serotípica de la enfermedad neumocócica invasiva (ENI) en la población general del área de Tarragona durante el cuatrienio posterior a la introducción de estas vacunas. Métodos: Estudio observacional retrospectivo que incluyó todos los casos de ENI (Streptococcus pneumoniae aislado en sangre, líquido cefalorraquídeo, líquido pleural/articular/peritoneal o muestras de tejidos profundos obtenidas de forma estéril mediante punción-aspiración o biopsia) diagnosticados en el área de Tarragona (comarcas del Tarragonés, Alt Camp y Baix Penedés) entre 01/01/2012 y 31/12/2015. Se estimaron tasas de incidencia y letalidad (globalmente y por estratos etarios) y se determinó la prevalencia de casos causados por serotipos incluidos en las distintas formulaciones de vacunas antineumocócicas conjugadas heptavalente (VNC7), decavalente (VNC10), tridecavalente (VNC13) y polisacárida tricosavalente (VNP23). Resultados: Se observaron 171 casos de ENI, lo que representó una incidencia (por 100.000 personas-año) de 10,82 (7,86 en ≤14 años, 5,94 en 15-64 años y 36,46 en ≥65 años; p<0,001). La letalidad fue del 6,8% (ninguna en niños, 9,3% en 15-64 años y 6,9% en personas ≥65 años; p<0,001). El serotipo responsable fue identificado en 132 (77,2%) de las 171 muestras estudiadas. La cobertura serotípica (casos causados por serotipos vacunales) fue del 14,4%, 26,5%, 42,4% y 78,8% para la VNC7, VNC10, VNC13 y VNP23, respectivamente (p<0,001). Conclusiones: Durante el periodo 2012-2015 la incidencia y letalidad por ENI fue intermedia-baja en el área de Tarragona, destacando que la cobertura serotípica fue casi doble para la vacuna 23-valente que para la 13-valente

Background: Nowadays, after licensure of the second generation new pneumococcal conjugate vaccines (PCV10/PCV13). The epidemiology of the pneumococcal disease must be re-evaluated. The present study described incidence, lethality and serotype distribution of invasive pneumococcal disease (IPD) in the general population of Tarragona's region (Spain) after licensure of these vaccines. Methods: Retrospective study that included all cases of IPD (pneumococcus isolated in sterile sites) diagnosed among all-age individuals in the Spanish region of Tarragona (Tarragonés, Alt Camp and Baix Penedés counties) from 01/01/2012 to 31/12/2015. Incidence and lethality rates were estimated by age strata and globally. Similarly, it was determined the prevalence of IPD cases caused by serotypes included in the distinct formulations of multivalent conjugate vaccines (pcv7), PCV10 and PCV13) or 23-valent polysaccharide vaccine (PPV23). Results: A total of 171 IPD cases were observed, which means a global incidence (per 100,000 persons-year) of 10.82 (7.86 in ≤14 years, 5.94 in 15-64 years and 36.46 in ≥65 years; p<0.001). Overall lethality rate was 6.8% (none in children, 9,3% in people 15-64 years and 6.9% in people ≥65 years). A serotype was identified in 132 (77.2%) of the 171 studied samples. Serotype-vaccine coverages (cases due to vaccine-type serotypes) were 14.4%, 26.5%, 42.4% and 78.8% for the PCV7, PCV10, PCV13 and PPV23, respectively (p<0.001). Conclusion: Incidence and lethality of IPD were intermediate-low in the region of Tarragona throughout 2012-2015. During this period, Serotype-vaccine coverage was almost double for the 23-valent than for the 13-valent vaccine

Extensive Shared Chemosensitivity between Malaria and Babesiosis Blood-Stage Parasites.

The apicomplexan parasites that cause malaria and babesiosis invade and proliferate within erythrocytes. To assess the potential for common antiparasitic treatments, we measured the sensitivities of multiple species of Plasmodium and Babesia parasites to the chemically diverse collection of antimalarial compounds in the Malaria Box library. We observed that these parasites share sensitivities to a large fraction of the same inhibitors and we identified compounds with strong babesiacidal activity.

The Plasmodium PHIST and RESA-Like Protein Families of Human and Rodent Malaria Parasites.

The phist gene family has members identified across the Plasmodium genus, defined by the presence of a domain of roughly 150 amino acids having conserved aromatic residues and an all alpha-helical structure. The family is highly amplified in P. falciparum, with 65 predicted genes in the genome of the 3D7 isolate. In contrast, in the rodent malaria parasite P. berghei 3 genes are identified, one of which is an apparent pseudogene. Transcripts of the P. berghei phist genes are predominant in schizonts, whereas in P. falciparum transcript profiles span different asexual blood stages and gametocytes. We pursued targeted disruption of P. berghei phist genes in order to characterize a simplistic model for the expanded phist gene repertoire in P. falciparum. Unsuccessful attempts to disrupt P. berghei PBANKA_114540 suggest that this phist gene is essential, while knockout of phist PBANKA_122900 shows an apparent normal progression and non-essential function throughout the life cycle. Epitope-tagging of P. falciparum and P. berghei phist genes confirmed protein export to the erythrocyte cytoplasm and localization with a punctate pattern. Three P. berghei PEXEL/HT-positive exported proteins exhibit at least partial co-localization, in support of a common vesicular compartment in the cytoplasm of erythrocytes infected with rodent malaria parasites.

Medication fall risk in old hospitalized patients: a retrospective study.

BACKGROUND: While the causes of falls in old hospitalized patients are multifactorial, medication has been considered as one of the most significant factors. Given the large impact that this phenomenon has on the lives of the elderly and organizations, it is important to explore such phenomenon in greater depth. OBJECTIVE: The objective of this study was to explore the association between medication and falls and the recurrent falls (n≥2), and identify medication related risk for fall in hospitalized patients, in a large acute hospital. DESIGN: Retrospective and quantitative study from June 2008 to December 2010. SETTING: The study was conducted in a private hospital for acute patients in Lisbon, Portugal. PARTICIPANTS: The study included a sample of 214 episodes of fall event notifications which occurred in 193 patients. METHODS: The current study was conducted through the "face to face consensus" technique which emerged the treatment groups to investigate. Regarding the data analysis we used Student's t test, ANOVA and Odds Ratio. In the violation of the premises for the use of parametric statistics we used the Kruskal-Wallis test. To assess the fall risk, and the medication-related fall risk, we used the Morse Fall Risk Scale, and the Medication Fall Risk Score. RESULTS: Patients who received drugs from the therapy group of "Central Nervous System", are 10 times more likely to have fall risk (OR 9. 90, 95% CI 1.6-60.63). Association was found between falls (OR 6.09, 95% CI 1.30-28.54) and its recurrence (OR 3.32, 95% CI 1.61-6.85), among patients receiving haloperidol and receiving tramadol for recurrent falls (OR 3.10, 95% CI 1.59-6.07). In 34% of the patients the medication fall risk score was 6 or higher. CONCLUSIONS: This current study allowed identifying medication-related risk factors for falls, that nurses should consider when prescribing interventions to prevent falls and its recurrence, when patients are admitted to acute care hospitals.

Avaliação do pigmento de Lawsonia inermis (henna) como carreadorde antígenos inoculados por via transcutânea em camundongos / Evaluation of Lawsonia inermis (henna) pigment as a carrier of antigens inoculatedby transcutaneous immunization pigment in mice

Objetivos: Avaliar o papel do pigmento de Lawsonia inermis (henna) como carreador de antígenos em esquema de vacinação transcutânea em camundongos.Métodos: Camundongos foram imunizados por via transcutânea na pele do abdômen e na pele da orelha com antígeno bruto de Paracoccidioides brasiliensis e com albumina sérica bovina nas concentrações de 1, 10 e 50 mg/mL, por três vezes em intervalos de uma semana, na presença ou ausência de pigmentos de L. inermis. Uma semana após a última imunização, foram avaliadas a presença de anticorpos anti-antígenos no soro, das citocinas interleucina-4 e interferon-? e de óxido nítrico em sobrenadante de cultura.Resultados: Não foram detectados anticorpos específicos anti-antígenos de P.brasiliensis ou albumina sérica bovina no soro. No foram encontradas diferenças significativas na produção de óxido nítrico e nos níveis de interleucina-4 e interferon-? em sobrenadantes de cultura celular.Conclusões: As vacinações transcutâneas com antígeno bruto de P. brasiliensis e albumina sérica bovina em suspensão de pigmento de L. inermis não produziram resposta antigênica detectável em camundongos.

Aims: To evaluate the role of pigment Lawsonia inermis (henna) as a carrier of antigens in transcutaneous vaccination in mice.Methods: Mice were immunized transcutaneously into the skin of the abdomen and the ear?s skin with crude antigen of Paracoccidioides brasiliensis and with bovine serum albumin at concentrations of 1, 10 and 50 mg/mL, three times at one week intervals in the presence or absence of pigments L. inermis. One week after last immunization, the animals were evaluated for the presence of serum antibodies, interleucin-4 and interferon-g cytokines, and nitric oxide in culture supernatants.Results: No specific antibodies were detected to P. brasiliensis or bovine serum albumin antigens. There were no significant differences in the production of nitric oxide, interleucin-4 and interferon-g in supernatants of cell culture.Conclusions: Transcutaneous immunization with crude antigen of P. brasiliensis or bovine serum albumin suspended in pigment of L. inermis produced no detectable antigenic response in mice.

Analysis of variant gene family expression by quantitative PCR.

Real-time polymerase chain reaction (PCR), or quantitative PCR (qPCR), is a rapid, sensitive, and specific method used for a broad variety of applications including quantitative gene expression analysis, DNA copy number measurement, characterization of gene and chromosomal deletions, and genotyping. Real-time reverse transcription (RT)-PCR has largely supplanted Northern blot and RNase protection assays, as two examples, as a means of quantifying transcript levels. The method utilizes small amounts of RNA and allows efficient screening of a large number of samples. Here, we describe the materials and methods required to perform real-time RT-PCR, including RNA purification, cDNA synthesis, and real-time PCR analysis of cDNA samples.

Characterization and developmental expression of genes encoding the early carotenoid biosynthetic enzymes in Citrus paradisi Macf.

In the present study, the full-length cDNA sequences of PSY, PDS, and ZDS, encoding the early carotenoid biosynthetic enzymes in the carotenoid pathway of grapefruit (Citrus paradisi), were isolated and characterized for the first time. CpPSY contained a 1311-bp open reading frame (ORF) encoding a polypeptide of 436 amino acids, CpPDS contained a 1659-bp ORF encoding a polypeptide of 552 amino acids, and CpZDS contained a 1713-bp ORF encoding a polypeptide of 570 amino acids. Phylogenetic analysis indicated that CpPSY shares homology with PSYs from Citrus, tomato, pepper, Arabidopsis, and the monocot PSY1 group, while CpPDS and CpZDS are most closely related to orthologs from Citrus and tomato. Expression analysis revealed fluctuations in CpPSY, CpPDS, and CpZDS transcript abundance and a non-coordinated regulation between the former and the two latter genes during fruit development in albedo and juice vesicles of white ('Duncan') and red ('Flame') grapefruits. A 3× higher upregulation of CpPSY expression in juice vesicles of red-fleshed 'Flame' as compared to white-fruited 'Duncan' was observed in the middle stages of fruit development, which correlates with the well documented accumulation pattern of lycopene in red grapefruit. Together with previous data, our results suggest that the primary mechanism controlling lycopene accumulation in red grapefruit involves the transcriptional upregulation of CpPSY, which controls the flux into the carotenoid pathway, and the downregulated expression of CpLCYB2, which controls the step of cyclization of lycopene in chromoplasts during fruit ripening. A correlation between CpPSY expression and fruit color evolution in red grapefruit is demonstrated.

Mortality by neoplasia and cellular telephone base stations in the Belo Horizonte municipality, Minas Gerais state, Brazil.

Pollution caused by the electromagnetic fields (EMFs) of radio frequencies (RF) generated by the telecommunication system is one of the greatest environmental problems of the twentieth century. The purpose of this research was to verify the existence of a spatial correlation between base station (BS) clusters and cases of deaths by neoplasia in the Belo Horizonte municipality, Minas Gerais state, Brazil, from 1996 to 2006 and to measure the human exposure levels to EMF where there is a major concentration of cellular telephone transmitter antennas. A descriptive spatial analysis of the BSs and the cases of death by neoplasia identified in the municipality was performed through an ecological-epidemiological approach, using georeferencing. The database employed in the survey was composed of three data banks: 1. death by neoplasia documented by the Health Municipal Department; 2. BSs documented in ANATEL ("Agência Nacional de Telecomunicações": 'Telecommunications National Agency'); and 3. census and demographic city population data obtained from official archives provided by IBGE ("Instituto Brasileiro de Geografia e Estatística": 'Brazilian Institute of Geography and Statistics'). The results show that approximately 856 BSs were installed through December 2006. Most (39.60%) of the BSs were located in the "Centro-Sul" ('Central-Southern') region of the municipality. Between 1996 and 2006, 7191 deaths by neoplasia occurred and within an area of 500 m from the BS, the mortality rate was 34.76 per 10,000 inhabitants. Outside of this area, a decrease in the number of deaths by neoplasia occurred. The greatest accumulated incidence was 5.83 per 1000 in the Central-Southern region and the lowest incidence was 2.05 per 1000 in the Barreiro region. During the environmental monitoring, the largest accumulated electric field measured was 12.4 V/m and the smallest was 0.4 V/m. The largest density power was 40.78 µW/cm(2), and the smallest was 0.04 µW/cm(2).

Sexual stage adhesion proteins form multi-protein complexes in the malaria parasite Plasmodium falciparum.

The sexual phase of the malaria parasite Plasmodium falciparum is accompanied by the coordinated expression of stage-specific adhesive proteins. Among these are six secreted proteins with multiple adhesion domains, termed P. falciparum LCCL domain-containing protein (PfCCp) proteins, which are expressed in the parasitophorous vacuole of the differentiating gametocytes and which are later associated with macrogametes. Although the majority of the PfCCp proteins are implicated in parasite development in the mosquito vector, their functions remain unknown. In the present study we investigated the molecular interactions between the PfCCp proteins during gametocyte development and emergence. Using five different gene-disruptant parasite lines, we show that the lack of one PfCCp protein leads to the loss of other PfCCp family members. Co-immunoprecipitation assays on gametocyte lysates revealed formation of complexes involving all PfCCp proteins, and affinity chromatography co-elution binding assays with recombinant PfCCp domains further indicated direct binding between distinct adhesion domains. PfCCp-coated latex beads bind to newly formed macrogametes but not to gametocytes or older macrogametes 6 or 24 h post-activation. In view of these data, we propose that the PfCCp proteins form multi-protein complexes that are exposed during gametogenesis, thereby mediating cell contacts of macrogametes.

TREP, a novel protein necessary for gliding motility of the malaria sporozoite.

The invasive stages of parasites of the protozoan phylum Apicomplexa have the capacity to traverse host tissues and invade host cells using a unique type of locomotion called gliding motility. Gliding motility is powered by a sub-membranous actin-myosin motor, and the force generated by the motor is transduced to the parasite surface by transmembrane proteins of the apicomplexan-specific thrombospondin-related anonymous protein (TRAP) family. These proteins possess short cytoplasmic tails that interact with the actin-myosin motor via the glycolytic enzyme aldolase. Gliding motility of the Plasmodium sporozoite, the stage of the malaria parasite that is transmitted by the mosquito to the mammalian host, depends on the TRAP protein. We describe a second protein, herein termed TREP, which also plays a role in the gliding motility of the Plasmodium sporozoite. TREP is a transmembrane protein that possesses a short cytoplasmic tail typical of members of the TRAP family of proteins, as well as a large extracellular region that contains a single thrombospondin type 1 repeat domain. TREP transcripts are expressed predominantly in oocyst stage sporozoites. Plasmodium berghei sporozoites harbouring a disrupted TREP gene have a highly diminished capacity to invade mosquito salivary glands and display a severe defect in gliding motility. We conclude that the gliding motility of the Plasmodium sporozoite in the mosquito depends on at least two proteins, TRAP and TREP.

Analysis of mutant Plasmodium berghei parasites lacking expression of multiple PbCCp genes.

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.

The Plasmodium TRAP/MIC2 family member, TRAP-Like Protein (TLP), is involved in tissue traversal by sporozoites.

In the apicomplexan protozoans motility and cell invasion are mediated by the TRAP/MIC2 family of transmembrane proteins, members of which link extracellular adhesion to the intracellular actomyosin motor complex. Here we characterize a new member of the TRAP/MIC2 family, named TRAP-Like Protein (TLP), that is highly conserved within the Plasmodium genus. Similar to the Plasmodium sporozoite protein, TRAP, and the ookinete protein, CTRP, TLP possesses an extracellular domain architecture that is comprised of von Willebrand factor A (vWA) and thrombospondin type 1 (TSP1) domains, plus a short cytoplasmic domain. Comparison of the vWA domain of TLP genes from multiple Plasmodium falciparum isolates showed relative low sequence diversity, suggesting that the protein is not under selective pressures of the host immune system. Analysis of transcript levels by quantitative reverse transcription polymerase chain reaction (RT-PCR) showed that TLP is predominantly expressed in salivary gland sporozoites of P. falciparum and P. berghei. Targeted disruption of P. berghei TLP resulted in a decreased capacity for cell traversal by sporozoites, and reduced infectivity of sporozoites in vivo, whereas in vitro sporozoite motility and hepatocyte invasion were unaffected. These results indicate a role of TLP in cell traversal by sporozoites.

Effect of the antimicrobial peptide gomesin against different life stages of Plasmodium spp.

While seeking strategies for interfering with Plasmodium development in vertebrate/invertebrate hosts, we tested the activity of gomesin, an antimicrobial peptide isolated from the hemocytes of the spider Acanthoscurria gomesiana. Gomesin was tested against asexual, sexual and pre-sporogonic forms of Plasmodium falciparum and Plasmodium berghei parasites. The peptide inhibited the in vitro growth of intraerythrocytic forms of P. falciparum. When gomesin was added to in vitro culture of P. berghei mature gametocytes, it significantly inhibited the exflagellation of male gametes and the formation of ookinetes. In vivo, the peptide reduced the number of oocysts of both Plasmodium species in Anopheles stephensi mosquitoes, and did not appear to affect the mosquitoes. These properties make gomesin an excellent candidate as a transmission blocking agent for the genetic engineering of mosquitoes.

Using bacteria to express and display anti-Plasmodium molecules in the mosquito midgut.

Bacteria capable of colonizing mosquito midguts are attractive vehicles for delivering anti-malaria molecules. We genetically engineered Escherichia coli to display two anti-Plasmodium effector molecules, SM1 and phospholipase-A(2), on their outer membrane. Both molecules significantly inhibited Plasmodium berghei development when engineered bacteria were fed to mosquitoes 24h prior to an infective bloodmeal (SM1=41%, PLA2=23%). Furthermore, prevalence and numbers of engineered bacteria increased dramatically following a bloodmeal. However, E. coli survived poorly in mosquitoes. Therefore, Enterobacter agglomerans was isolated from mosquitoes and selected for midgut survival by multiple passages through mosquitoes. After four passages, E. agglomerans survivorship increased from 2 days to 2 weeks. Since E. agglomerans is non-pathogenic and widespread, it is an excellent candidate for paratransgenic control strategies.

Mosquito transgenesis: what is the fitness cost?

The generation of transgenic mosquitoes with a minimal fitness load is a prerequisite for the success of strategies for controlling mosquito-borne diseases using transgenic insects. It is important to assemble as much information as possible on this subject because realistic estimates of transgene fitness costs are essential for modeling and planning release strategies. Transgenic mosquitoes must have minimal fitness costs, because such costs would reduce the effectiveness of the genetic drive mechanisms that are used to introduce the transgenes into field mosquito populations. Several factors affect fitness of transgenic mosquitoes, including the potential negative effect of transgene products and insertional mutagenesis. Studies to assess fitness of transgenic mosquitoes in the field (as opposed to the laboratory) are still needed.