Plasmodium Falciparum Gametocytes Research Articles

Simple supplementation of serum-free medium produces gametocytes of Plasmodium falciparum that transmit to mosquitoes

BackgroundHuman serum is a major component of Plasmodium falciparum culture medium, and can be replaced with AlbuMAX™ II, a lipid-rich bovine serum albumin, for asexual cultures. However, gametocytes produced without serum are poorly infective to mosquitoes. Serum suffers from high cost, limited availability, and variability in quality.MethodsSeveral commercially-available media supplements were tested for their ability to support parasite growth and production of P. falciparum (3D7) gametocytes in standard RPMI1640 medium containing 0.5% AlbuMAX. The impact on asexual growth and gametocyte production with each supplement was assessed and compared to standard RPMI1640 medium containing 10% human serum, as well as to medium containing 0.5% AlbuMAX alone. The infectivity of gametocytes produced with one supplement to Anopheles gambiae sensu stricto was assessed by standard membrane feeding assay and measuring both prevalence of infection and oocyst intensity.ResultsSupplementation of medium containing 0.5% AlbuMAX with five supplements did not affect asexual growth of P. falciparum, and four of the five supplements supported early gametocyte production. The supplement producing the highest number of gametocytes, ITS-X, was further investigated and was found to support the production of mature gametocytes. Infection prevalence and oocyst intensity did not differ significantly between mosquitoes given a membrane feed containing gametocytes grown in medium with 0.5% AlbuMAX + ITS-X and those grown in medium with 10% human serum. Infection prevalence and oocyst intensity was significantly higher in case of ITS–X supplementation when compared to AlbuMAX alone. Infectious gametocytes were also produced from two field clones using ITS–X supplementation.ConclusionsSerum-free medium supplemented with ITS-X was able to support the growth of gametocytes of P. falciparum that were as infectious to An. gambiae as those grown in medium with 10% serum. This is the first fully serum-free culture system able to produce highly infectious gametocytes, thereby removing the requirement for access to serum for transmission assays.

TREATMENT FOR MALARIA PATIENTS IN PAKISTAN AND THE PREDOMINANCE OF GLUCOSE-6-PHOSPHATE DEHYDROGENASE (G6PD) DEFICIENCY

Even though it predisposes carriers to hemolysis, glucose-6-phosphate dehydrogenase (G6PD) deficiency is linked with malaria endemicity. This fact supports the malaria prevention theory. The objective of this paper to determine whether and how much there is a protective relationship between malaria and G6PD deficiency. Twelve databases were searched for studies describing any G6PD connection in malaria patients. 38 of the 50 included papers qualified for the review. Results indicated that there was no harmful association between G6PD deficiency and uncomplicated falciparum malaria in Even though it puts carriers at risk for hemolysis, glucose-6-phosphate dehydrogenase (G6PD) deficiency is widespread in areas of Pakistan where malaria is also prevalent. This data supports the malaria protection hypothesis. Pakistan's annual malaria burden is estimated to be 1.5 million cases. The government needs to execute a successful malaria control and eradication program, given the prevailing circumstances. Destroying Plasmodium falciparum gametocytes and eradicating Plasmodium vivax hypnozoite reservoirs are possible with primaquine. However, when using this medication, those who lack the enzyme glucose-6-phosphate (G6PD) experience hemolysis. The distribution of malaria and G6PD deficiency in Pakistan must be mapped to create an effective medication to suppress the disease. No significant reports of G6PD deficiency (G6PDd) in malaria patients have come from Pakistan. This review article seeks to establish the existence and magnitude of a protective connection between malaria and G6PD deficiency

Detection of the infective Plasmodium falciparum gametocytes by RT-qPCR assay from a malaria-endemic region of Northeastern India

IntroductionThe diagnosis of infectious reservoirs in malaria (gametocytes) is necessary, especially in low-density infections and asymptomatic malaria patients. The gametocyte stage is a surrogate marker for infection of P. falciparum malaria in healthy individuals. The early detection of infectious gametocytes and treatment will strengthen our efforts in curbing transmission. The nested PCR and real-time quantitative PCR (RT-qPCR) methods have been demonstrated for the diagnosis of infectious gametocyte reservoirs. In this study, RDT, blood smear microscopy, and nested-PCR were used for the detection of P. falciparum and P. vivax, and compared with RT-qPCR detection of Pfg27 gametocyte biomarker gene.MethodsIn the present cross-sectional study, 356 human blood samples were collected from endemic areas of Kokrajhar Assam (asymptomatic and symptomatic malaria patients) for malaria diagnosis.ResultsA total of 8.42%(30/356) incidence of malaria was observed. Malaria patients were observed to be both symptomatic, 80%(24/30; 13Pf+11Pv), and asymptomatic, 20%(6 (4Pf +2Pv)). More than 64%(11/17) of Pf and 92.3%(12/13) of Pv infections were observed in children and the adolescent population (age <20 years) by RDT, microscopy, nested PCR, and RT-qPCR methods. The prevalence of Pf infection was 4.77%(17/356) by RT-qPCR method. Of 16 the Pf positive samples 81.25%(13/16) were symptomatic and 18.75%(3/16) were asymptomatic. One asymptomatic individual was found positive for Pf infection by the RT-qPCR method.ConclusionThe findings from this research study revealed that the routine microscopy and RDT methods are insufficient for detecting all asymptomatic malaria and gametocyte infectious reservoirs. The early detection of infectious P. falciparum gametocytes and the treatment of patients will be helpful in preventing the transmission of malaria.

Delayed gametocyte clearance in Plasmodium vivax malaria is associated with polymorphisms in the cytochrome P450 reductase (CPR).

Primaquine (PQ) is the main drug used to eliminate dormant liver stages and prevent relapses in Plasmodium vivax malaria. It also has an effect on the gametocytes of Plasmodium falciparum; however, it is unclear to what extent PQ affects P. vivax gametocytes. PQ metabolism involves multiple enzymes, including the highly polymorphic CYP2D6 and the cytochrome P450 reductase (CPR). Since genetic variability can impact drug metabolism, we conducted an evaluation of the effect of CYP2D6 and CPR variants on PQ gametocytocidal activity in 100 subjects with P. vivax malaria. To determine gametocyte density, we measured the levels of pvs25 transcripts in samples taken before treatment (D0) and 72 hours after treatment (D3). Generalized estimating equations (GEEs) were used to examine the effects of enzyme variants on gametocyte densities, adjusting for potential confounding factors. Linear regression models were adjusted to explore the predictors of PQ blood levels measured on D3. Individuals with the CPR mutation showed a smaller decrease in gametocyte transcript levels on D3 compared to those without the mutation (P = 0.02, by GEE). Consistent with this, higher PQ blood levels on D3 were associated with a lower reduction in pvs25 transcripts. Based on our findings, the CPR variant plays a role in the persistence of gametocyte density in P. vivax malaria. Conceptually, our work points to pharmacogenetics as a non-negligible factor to define potential host reservoirs with the propensity to contribute to transmission in the first days of CQ-PQ treatment, particularly in settings and seasons of high Anopheles human-biting rates.

A Short Communication: An Imported Case of <i>Plasmodium falciparum</i> Malaria Infection from Ivory Coast leave to Iran

Malaria is the most common cause of fever in travellers returning from malaria-endemic areas. Imported malaria can hinder the progress of elimination programs. In the present study, we describe an imported malaria case in a 45-year-old Iranian man from Ivory Coast who had returned to Iran after taking annual leave. He was hospitalized in Kamkar-Arabnia Hospital, Qom, central Iran, in January 2023. Symptoms were fever, chills, sweating, cough, myalgia, sweating, anorexia, diarrhoea, and headache. Rapid detection test and blood smears were positive for Plasmodium falciparum gametocyte. The patient was treated with an antimalarial drug and discharged from the hospital with normal vital signs. Health education is recommended for people before leaving and screening after returning from travel. In addition, using RDT tests for screening people who return to the country is suggested to health staff and organizations.

Disruption of a Plasmodium falciparum patatin-like phospholipase delays male gametocyte exflagellation.

An essential process in transmission of the malaria parasite to the Anopheles vector is the conversion of mature gametocytes into gametes within the mosquito gut, where they egress from the red blood cell (RBC). During egress, male gametocytes undergo exflagellation, leading to the formation of eight haploid motile microgametes, while female gametes retain their spherical shape. Gametocyte egress depends on sequential disruption of the parasitophorous vacuole membrane and the host cell membrane. In other life cycle stages of the malaria parasite, phospholipases have been implicated in membrane disruption processes during egress, however their importance for gametocyte egress is relatively unknown. Here, we performed comprehensive functional analyses of six putative phospholipases for their role during development and egress of Plasmodium falciparum gametocytes. We localize two of them, the prodrug activation and resistance esterase (PF3D7_0709700) and the lysophospholipase 1 (PF3D7_1476700), to the parasite plasma membrane. Subsequently, we show that disruption of most of the studied phospholipase genes does neither affect gametocyte development nor egress. The exception is the putative patatin-like phospholipase 3 (PF3D7_0924000), whose gene deletion leads to a delay in male gametocyte exflagellation, indicating an important, albeit not essential, role of this enzyme in male gametogenesis.

Prevalence of G6PD deficiency and submicroscopic malaria parasites carriage in malaria hotspot area in Northwest, Tanzania

BackgroundThe use of primaquine for mass drug administration (MDA) is being considered as a key strategy for malaria elimination. In addition to being the only drug active against the dormant and relapsing forms of Plasmodium vivax, primaquine is the sole potent drug against mature/infectious Plasmodium falciparum gametocytes. It may prevent onward transmission and help contain the spread of artemisinin resistance. However, higher dose of primaquine is associated with the risk of acute haemolytic anaemia in individuals with a deficiency in glucose-6-phosphate dehydrogenase. In many P. falciparum endemic areas there is paucity of information about the distribution of individuals at risk of primaquine-induced haemolysis at higher dose 45 mg of primaquine.MethodsA retrospective cross-sectional study was carried out using archived samples to establish the prevalence of G6PD deficiency in a malaria hotspot area in Misungwi district, located in Mwanza region, Tanzania. Blood samples collected from individuals recruited between August and November 2010 were genotyped for G6PD deficiency and submicroscopic parasites carriage using polymerase chain reaction.ResultsA total of 263 individuals aged between 0 and 87 were recruited. The overall prevalence of the X-linked G6PD A− mutation was 83.7% (220/263) wild type, 8% (21/263) heterozygous and 8.4% (22/263) homozygous or hemizygous. Although, assessment of the enzymatic activity to assign the phenotypes according to severity and clinical manifestation as per WHO was not carried out, the overall genotype and allele frequency for the G6PD deficiency was 16.4% and 13. 2%, respectively. There was no statistically significant difference in among the different G6PD genotypes (p > 0.05). Out of 248 samples analysed for submicroscopic parasites carriage, 58.1% (144/248) were P. falciparum positive by PCR. G6PD heterozygous deficiency were associated with carriage of submicroscopic P. falciparum (p = 0.029).ConclusionsThis study showed that 16.4% of the population in this part of North-western Tanzania carry the G6PD A− mutation, within the range of 15–32% seen in other parts of Africa. G6PD gene mutation is widespread and heterogeneous across the study area where primaquine would be valuable for malaria control and elimination. The maps and population estimates presented here reflect potential risk of higher dose of primaquine being associated with the risk of acute haemolytic anaemia (AHA) in individuals with a deficiency in glucose-6-phosphate dehydrogenase and call further research on mapping of G6PD deficiency in Tanzania. Therefore, screening and education programmes for G6PD deficiency is warranted in a programme of malaria elimination using a higher primaquine dose.

Cryogenic enrichment of Plasmodium falciparum gametocytes from spiked whole blood

Each individual cell type typically requires a unique set of conditions for optimal cryopreservation outcome, which relates to its specific response to cryoprotective agent (CPA) toxicity, osmotic behavior and sensitivity to ice crystallization. Cryopreservation of heterogenous cell populations is therefore exceedingly difficult as it requires separate and often conflicting conditions for each cell type. Conversely, these contrasting conditions could be utilized to favor cryogenic preference of a single cell population within a heterogenous sample, leading to its enrichment by elimination of remaining cells. To establish proof-of-concept for this overall approach, a protocol was developed for the cryogenic enrichment of Plasmodium falciparum gametocytes from whole blood. To accomplish this goal, we evaluated the effects of CPAs and cooling conditions during cryopreservation of whole blood samples spiked with P. falciparum gametocytes. We identified that cooling to −80 °C at a rate of −1 °C/min in the presence of 11 % glycerol selectively favors recovery of gametocytes. This protocol eliminates 95.3 ± 1.7 % of total blood cells and recovers 43.2 ± 6.5 % of parasites, leading to a 19-fold enrichment as assessed by microscopic examination of blood smears. This protocol is tunable, where gametocyte enrichment 900-fold may be feasible, however there is an apparent tradeoff in overall parasite recovery. Although translation of this protocol for point-of-care testing for malaria presents many challenges, the overall approach of cryogenic purification may prove useful for alternative diagnostic applications.

The global transcriptome of Plasmodium falciparum mid-stage gametocytes (stages II-IV) appears largely conserved and gametocyte-specific gene expression patterns vary in clinical isolates.

Our overall understanding of the developmental biology of malaria parasites has been greatly enhanced by recent advances in transcriptomic analysis. However, most of these investigations rely on laboratory strains (LS) that were adapted into in vitro culture many years ago, and the transcriptomes of clinical isolates (CI) circulating in human populations have not been assessed. In this study, RNA-seq was used to compare the global transcriptome of mid-stage gametocytes derived from three short-term cultured CI, with gametocytes derived from the NF54 reference laboratory strain. The core transcriptome appeared to be consistent between CI- and LS-derived gametocyte preparations, but some important differences were also observed. A majority of gametocyte-specific genes (43/53) appear to have relatively higher expression in CI-derived gametocytes than in LS-derived gametocytes, but a K-means clustering analysis showed that genes involved in flagellum- and microtubule-based processes (movement/motility) were more abundant in both groups, albeit with some differences between them. In addition, gametocytes from one CI described as CI group II gametocytes (CI:GGII) showed gene expression variation in the form of reduced gametocyte-specific gene expression compared to the other two CI-derived gametocytes (CI gametocyte group I, CI:GGI), although the mixed developmental stages used in our study is a potential confounder, only partially mitigated by the inclusion of multiple replicates for each CI. Overall, our study suggests that there may be subtle differences in the gene expression profiles of mid-stage gametocytes from CI relative to the NF54 reference strain of Plasmodium falciparum. Thus, it is necessary to deploy gametocyte-producing clinical parasite isolates to fully understand the diversity of gene expression strategies that may occur during the sequestered development of parasite sexual stages. IMPORTANCE Maturing gametocytes of Plasmodium falciparum are known to sequester away from peripheral circulation into the bone marrow until they are mature. Blocking gametocyte sequestration can prevent malaria transmission from humans to mosquitoes, but most studies aim to understand gametocyte development utilizing long-term adapted laboratory lines instead of clinical isolates. This is a particular issue for our understanding of the sexual stages, which are known to decrease rapidly during adaptation to long-term culture, meaning that many LS are unable to produce transmissible gametocytes. Using RNA-seq, we investigated the global transcriptome of mid-stage gametocytes derived from three clinical isolates and a reference strain (NF54). This identified important differences in gene expression profiles between immature gametocytes of CI and the NF54 reference strain of P. falciparum, suggesting increased investment in gametocytogenesis in clinical isolates. Our transcriptomic data highlight the use of clinical isolates in studying the morphological, cellular features and molecular biology of gametocytes.

Prevalence of Plasmodium Falciparum Gametocytes among Malaria Positive Cases at Korogwe District Hospital: The Use of Molecular Techniques in Comparison with Light Microscopy

BackgroundMonitoring gametocytes in the population can inform about the human infective reservoir, which greatly aids malaria transmission, and provide relevant data for transmission models. Using molecular techniques in preference to light microscopy to detect gametocytes may lead to most reliable results. Effective determination of gametocytes is inevitable to achieve the transmission-blocking interventions as a prime target to end malaria. We aimed to determine the prevalence of P. falciparum gametocytes in malaria-positive cases from Korogwe district hospital MethodologyArchived DNA samples collected from Korogwe district hospital collected in a cross-sectional study were used to determine the prevalence of P. falciparum gametocytes using specific primers for cPCR targeting a Pfg27 gene. Demographic data, including blood slides data were retrieved from the database for statistical analysis. ResultsWith light microscopy, prevalence of P. falciparum gametocytes was 9.8%; sensitivity and specificity were 35.6% and 99.2% respectively. The cPCR gave a prevalence of 25.9%, with a sensitivity of 94.1% and specificity of 81.5%. The cPCR was diagnostically found to be significantly superior over light microscopy technique (X2=45.780, P < 0.001). ConclusioncPCR is superior to light microscopy technique in detecting P. falciparum gametocytes when one considers a successive malaria transmission-blocking intervention.
 Rwanda J Med Health Sci 2023;6(2):175-183

Comparative proteomics of vesicles essential for the egress of Plasmodium falciparum gametocytes from red blood cells.

Transmission of malaria parasites to the mosquito is mediated by sexual precursor cells, the gametocytes. Upon entering the mosquito midgut, the gametocytes egress from the enveloping erythrocyte while passing through gametogenesis. Egress follows an inside-out mode during which the membrane of the parasitophorous vacuole (PV) ruptures prior to the erythrocyte membrane. Membrane rupture requires exocytosis of specialized egress vesicles of the parasites; that is, osmiophilic bodies (OBs) involved in rupturing the PV membrane, and vesicles that harbor the perforin-like protein PPLP2 (here termed P-EVs) required for erythrocyte lysis. While some OB proteins have been identified, like G377 and MDV1/Peg3, the majority of egress vesicle-resident proteins is yet unknown. Here, we used high-resolution imaging and BioID methods to study the two egress vesicle types in Plasmodium falciparum gametocytes. We show that OB exocytosis precedes discharge of the P-EVs and that exocytosis of the P-EVs, but not of the OBs, is calcium sensitive. Both vesicle types exhibit distinct proteomes with the majority of proteins located in the OBs. In addition to known egress-related proteins, we identified novel components of OBs and P-EVs, including vesicle-trafficking proteins. Our data provide insight into the immense molecular machinery required for the inside-out egress of P. falciparum gametocytes.

Assessment of the transmission blocking activity of antimalarial compounds by membrane feeding assays using natural Plasmodium falciparum gametocyte isolates from West-Africa.

Antimalarial drugs that can block the transmission of Plasmodium gametocytes to mosquito vectors would be highly beneficial for malaria elimination efforts. Identifying transmission-blocking drugs currently relies on evaluation of their activity against gametocyte-producing laboratory parasite strains and would benefit from a testing pipeline with genetically diverse field isolates. The aims of this study were to develop a pipeline to test drugs against P. falciparum gametocyte field isolates and to evaluate the transmission-blocking activity of a set of novel compounds. Two assays were designed so they could identify both the overall transmission-blocking activity of a number of marketed and experimental drugs by direct membrane feeding assays (DMFA), and then also discriminate between those that are active against the gametocytes (gametocyte killing or sterilizing) or those that block development in the mosquito (sporontocidal). These DMFA assays used venous blood samples from naturally infected Plasmodium falciparum gametocyte carriers and locally reared Anopheles gambiae s.s. mosquitoes. Overall transmission-blocking activity was assessed following a 24 hour incubation of compound with gametocyte infected blood (TB-DMFA). Sporontocidal activity was evaluated following addition of compound directly prior to feeding, without incubation (SPORO-DMFA); Gametocyte viability was retained during 24-hour incubation at 37°C when gametocyte infected red blood cells were reconstituted in RPMI/serum. Methylene-blue, MMV693183, DDD107498, atovaquone and P218 showed potent transmission-blocking activity in the TB-DMFA, and both atovaquone and the novel antifolate P218 were potent inhibitors of sporogonic development in the SPORO-DMA. This work establishes a pipeline for the integral use of field isolates to assess the transmission-blocking capacity of antimalarial drugs to block transmission that should be validated in future studies.

Retraction Note: Molecular detection and quantification of Plasmodium falciparum gametocytes carriage in used RDTs in malaria elimination settings in northern Senegal

Retraction Note: Molecular detection and quantification of Plasmodium falciparum gametocytes carriage in used RDTs in malaria elimination settings in northern Senegal

New 4-(N-cinnamoylbutyl)aminoacridines as potential multi-stage antiplasmodial leads

A novel family of 4-aminoacridine derivatives was obtained by linking this heteroaromatic core to different trans-cinnamic acids. The 4-(N-cinnamoylbutyl)aminoacridines obtained exhibited in vitro activity in the low- or sub-micromolar range against (i) hepatic stages of Plasmodium berghei, (ii) erythrocytic forms of Plasmodium falciparum, and (iii) early and mature gametocytes of Plasmodium falciparum. The most active compound, having a meta-fluorocinnamoyl group linked to the acridine core, was 20- and 120-fold more potent, respectively, against the hepatic and gametocyte stages of Plasmodium infection than the reference drug, primaquine. Moreover, no cytotoxicity towards mammalian and red blood cells at the concentrations tested was observed for any of the compounds under investigation. These novel conjugates represent promising leads for the development of new multi-target antiplasmodials.

Plasmodium falciparum gametocyte carriage in longitudinally monitored incident infections is associated with duration of infection and human host factors

Malaria transmission depends on the presence of Plasmodium gametocytes that are the only parasite life stage that can infect mosquitoes. Gametocyte production varies between infections and over the course of infections. Infection duration is highly important for gametocyte production but poorly quantified. Between 2017 and 2019 an all-age cohort of individuals from Tororo, eastern Uganda was followed by continuous passive and routine assessments. We longitudinally monitored 104 incident infections from 98 individuals who were sampled once every 28 days and on any day of symptoms. Among infections that lasted ≥ 3 months, gametocyte appearance was near-universal with 96% of infections having detectable gametocytes prior to clearance. However, most infections were of much shorter duration; 55.7% of asymptomatic infections were detected only once. When considering all asymptomatic infections, regardless of their duration, only 36.3% had detectable gametocytes on at least one time-point prior to parasite clearance. Infections in individuals with sickle-cell trait (HbAS) were more likely to have gametocytes detected (Hazard Rate (HR) = 2.68, 95% CI 1.12, 6.38; p = 0.0231) and had gametocytes detected at higher densities (Density Ratio (DR) = 9.19, 95% CI 2.79, 30.23; p = 0.0002) compared to infections in wildtype (HbAA) individuals. Our findings suggest that a large proportion of incident infections is too short in duration and of too low density to contribute to onward transmission.

Plasmodium falciparum gametocytes display global chromatin remodelling during sexual differentiation

BackgroundThe protozoan malaria parasite Plasmodium falciparum has a complex life cycle during which it needs to differentiate into multiple morphologically distinct life forms. A key process for transmission of the disease is the development of male and female gametocytes in the human blood, yet the mechanisms determining sexual dimorphism in these haploid, genetically identical sexual precursor cells remain largely unknown. To understand the epigenetic program underlying the differentiation of male and female gametocytes, we separated the two sexual forms by flow cytometry and performed RNAseq as well as comprehensive ChIPseq profiling of several histone variants and modifications.ResultsWe show that in female gametocytes the chromatin landscape is globally remodelled with respect to genome-wide patterns and combinatorial usage of histone variants and histone modifications. We identified sex specific differences in heterochromatin distribution, implicating exported proteins and ncRNAs in sex determination. Specifically in female gametocytes, the histone variants H2A.Z/H2B.Z were highly enriched in H3K9me3-associated heterochromatin. H3K27ac occupancy correlated with stage-specific gene expression, but in contrast to asexual parasites this was unlinked to H3K4me3 co-occupancy at promoters in female gametocytes.ConclusionsCollectively, we defined novel combinatorial chromatin states differentially organising the genome in gametocytes and asexual parasites and unravelled fundamental, sex-specific differences in the epigenetic code. Our chromatin maps represent an important resource for future understanding of the mechanisms driving sexual differentiation in P. falciparum.

SICKLE CELL THALASSEMIA IN AN ADULT FROM CENTRAL INDIA SHOWING MASSIVE SPLENIC INFARCTION AND GAMNA-GANDY BODIES IN SPLENIC PARENCHYMA WITH CONCOMITANT PLASMODIUM FALCIPARUM INFECTION

Background. Sickle cell thalassemia is a heterozygous state of HbS/β+ or HbS/β0 manifested clinically either as an asymptomatic carrier or have features akin to sickle cell anemia. Objective. The aim of the study is to review the literature and discuss the varied clinical manifestations and diagnosis of a case report of haemoglobinopathy in an adult from Central India. Methods. A case of haemoglobinopathy from central part of India is being investigated. Results. A case of haemoglobinopathy in an adult presenting to a tertiary hospital with chronic back ache was reported. The patient was found to have massive splenomegaly with evidence of splenic infarction. Gross examination of spleen revealed multiple soft yellowish pasty areas, which on microscopic examination showed significant necrosis with presence of great amount pale amorphous yellow substance, Gamna-Gandy bodies (GGBs) and massive foreign body cell reaction in splenic parenchyma. Post-splenectomy peripheral blood smear (PBS) showed thrombocytosis and plasmodium falciparum gametocytes. The Hb electrophoresis revealed both elevation of Hb S (49.7%), Hb F (46.7%); Hb A2 (3.0%) and (Hb A 0.7%) consistent with as Sickle Cell Thalassemia Hb S/β+ Thalassemia. Conclusion. Sickle cell thalassemia with long standing huge splenomegaly, splenic infarction with GGBs deposition and concomitant falciparum malaria in clinically stable patient is rare indeed.

Contribution of hematology analyzers (Sysmex XN-Series) in the rapid diagnosis of malaria: case reports

Malaria is a potentially severe disease, particularly in Africa. In Europe, the majority of malaria cases come from travelers returning from endemic areas. The non-specific symptomatology may not alert the clinician if this notion of travel is not addressed. However, diagnosis and rapid initiation of treatment prevent the evolution of severe forms of the disease, especially in the case of Plasmodium falciparum infection, which can be life-threatening within 24 hours. Thin and thick blood smears microscopy is the main tools for diagnosis, but some automated hematology analyzers have demonstrated their ability to participate in early diagnosis. We describe two cases illustrating the contribution of the Sysmex XN-9100 automated system for the diagnosis of malaria. The first clinical case described a young man infected with numerous Plasmodium falciparum gametocytes. WNR (white blood cell count) and WDF (white blood cell differenciation) scattergrams showed an additional population, corresponding to gametocytes. The second case focused on a man with neuromalaria and high Plasmodium falciparum parasitaemia. Parasitized red blood cells form an inconspicuous double population on the reticulocyte scattergram, located at the discrimination limit between mature red blood cells and reticulocytes. Scattergram abnormalities, which can be visualized in a few minutes, offer an anticipation of the diagnosis of malaria in comparison to thin and thick smears microscopy, that requiring considerable time and expertise.

Phosphodiesterase delta governs the mechanical properties of erythrocytes infected with Plasmodium falciparum gametocytes

To persist in the blood circulation and to be available for mosquitoes, Plasmodium falciparum gametocytes modify the deformability and the permeability of their erythrocyte host via cyclic AMP (cAMP) signaling pathway. Cyclic nucleotide levels are tightly controlled by phosphodiesterases (PDE), however in Plasmodium these proteins are poorly characterized. Here, we characterize the P. falciparum phosphodiesterase delta (PfPDEδ) and we investigate its role in the cAMP signaling-mediated regulation of gametocyte-infected erythrocyte mechanical properties. Our results revealed that PfPDEδ is a dual-function enzyme capable of hydrolyzing both cAMP and cGMP, with a higher affinity for cAMP. We also show that PfPDEδ is the most expressed PDE in mature gametocytes and we propose that it is located in parasitophorous vacuole at the interface between the host cell and the parasite. We conclude that PfPDEδ is the master regulator of both the increase in deformability and the inhibition of channel activity in mature gametocyte stages, and may therefore play a crucial role in the persistence of mature gametocytes in the bloodstream.

A Novel Ex Vivo Drug Assay for Assessing the Transmission-Blocking Activity of Compounds on Field-Isolated Plasmodium falciparum Gametocytes.

The discovery and development of transmission-blocking therapies challenge malaria elimination and necessitate standard and reproducible bioassays to measure the blocking properties of antimalarial drugs and candidate compounds. Most of the current bioassays evaluating the transmission-blocking activity of compounds rely on laboratory-adapted Plasmodium strains. Transmission-blocking data from clinical gametocyte isolates could help select novel transmission-blocking candidates for further development. Using freshly collected Plasmodium falciparum gametocytes from asymptomatic individuals, we first optimized ex vivo culture conditions to improve gametocyte viability and infectiousness by testing several culture parameters. We next pre-exposed ex vivo field-isolated gametocytes to chloroquine, dihydroartemisinin, primaquine, KDU691, GNF179, and oryzalin for 48 h prior to direct membrane feeding. We measured the activity of the drug on the ability of gametocytes to resume the sexual life cycle in Anopheles after drug exposure. Using 57 blood samples collected from Malian volunteers aged 6 to 15 years, we demonstrate that the infectivity of freshly collected field gametocytes can be preserved and improved ex vivo in a culture medium supplemented with 10% horse serum at 4% hematocrit for 48 h. Moreover, our optimized drug assay displays the weak transmission-blocking activity of chloroquine and dihydroartemisinin, while primaquine and oryzalin exhibited a transmission-blocking activity of ~50% at 1 μM. KDU691 and GNF179 both interrupted Plasmodium transmission at 1 μM and 5 nM, respectively. This new approach, if implemented, has the potential to accelerate the screening of compounds with transmission-blocking activity.