Plasmodium Chabaudi Infection Research Articles

Propriedades supressoras da bile de ovelha contra o parasita Plasmodium chabaudi em camundongos

ABSTRACT Plasmodium species are responsible for the transmission of malaria, which is still one of the most dangerous diseases to humans in the world. This study aimed to evaluate the suppressive effect of SB on parasitemia in mice infected with Plasmodium chabaudi infection. A total of 30 disease-free mice were randomly assigned to six groups. The first control non-infected group received only distilled water daily for 7 days by oral route. After being infected with 106 of P. chabaudi in the other five groups, the mice were gavaged with 0.2mL/mice of a solution containing either 25%, 50%, or 100% of SB, respectively. The fifth group orally received 10mg/ kg chloroquine phosphate (CQ). The sixth set of mice served as the infected group. Following the administration of treatments during a suppression test that lasted for five days, a daily examination of blood smears stained with Giemsa was performed. Sheep bile was able to decrease parasitemia nearly to the used reference drug, chloroquine. In addition, bile significantly decreased the diarrhea rate of infection in mice, the survival rate of mice, the parasitemia percentage, and the suppression ratio. The parasite's caused histological change was enhanced by the SB. After treatment, there was also a rise in the amounts of the liver enzymes alkaline phosphatase, aspartate aminotransferase, and alanine aminotransferase. Findings indicate that bile has antimalarial activity and can control parasitemia percentage and parasite suppression. We need further investigations to determine the mechanisms of action of the bile in vivo.

TNFR1 signaling converging on FGF14 controls neuronal hyperactivity and sickness behavior in experimental cerebral malaria

BackgroundExcess tumor necrosis factor (TNF) is implicated in the pathogenesis of hyperinflammatory experimental cerebral malaria (eCM), including gliosis, increased levels of fibrin(ogen) in the brain, behavioral changes, and mortality. However, the role of TNF in eCM within the brain parenchyma, particularly directly on neurons, remains underdefined. Here, we investigate electrophysiological consequences of eCM on neuronal excitability and cell signaling mechanisms that contribute to observed phenotypes.MethodsThe split-luciferase complementation assay (LCA) was used to investigate cell signaling mechanisms downstream of tumor necrosis factor receptor 1 (TNFR1) that could contribute to changes in neuronal excitability in eCM. Whole-cell patch-clamp electrophysiology was performed in brain slices from eCM mice to elucidate consequences of infection on CA1 pyramidal neuron excitability and cell signaling mechanisms that contribute to observed phenotypes. Involvement of identified signaling molecules in mediating behavioral changes and sickness behavior observed in eCM were investigated in vivo using genetic silencing.ResultsExploring signaling mechanisms that underlie TNF-induced effects on neuronal excitability, we found that the complex assembly of fibroblast growth factor 14 (FGF14) and the voltage-gated Na+ (Nav) channel 1.6 (Nav1.6) is increased upon tumor necrosis factor receptor 1 (TNFR1) stimulation via Janus Kinase 2 (JAK2). On account of the dependency of hyperinflammatory experimental cerebral malaria (eCM) on TNF, we performed patch-clamp studies in slices from eCM mice and showed that Plasmodium chabaudi infection augments Nav1.6 channel conductance of CA1 pyramidal neurons through the TNFR1–JAK2–FGF14–Nav1.6 signaling network, which leads to hyperexcitability. Hyperexcitability of CA1 pyramidal neurons caused by infection was mitigated via an anti-TNF antibody and genetic silencing of FGF14 in CA1. Furthermore, knockdown of FGF14 in CA1 reduced sickness behavior caused by infection.ConclusionsFGF14 may represent a therapeutic target for mitigating consequences of TNF-mediated neuroinflammation.

Dynamic intravital imaging reveals reactive vessel-associated microglia play a protective role in cerebral malaria coagulopathy

Vascular congestion and coagulopathy have been shown to play a role in human and experimental cerebral malaria (eCM), but little is known about the role of microglia, or microglia-vascular interactions and hypercoagulation during disease progression in this fatal infection. Recent studies show microglia bind to fibrinogen, a glycoprotein involved in thrombosis. An eCM model of Plasmodium chabaudi infection in mice deficient in the regulatory cytokine IL-10 manifests neuropathology, including hypercoagulation with extensive fibrin(ogen) deposition and neuroinflammation. Intravital microscopy and immunofluorescence are applied to elucidate the role of microglia in eCM. Results show microgliosis and coagulopathy occur early in disease at 3 dpi (day post-infection), and both are exacerbated as disease progresses to 7dpi. Vessel associated microglia increase significantly at 7 dpi, and the expression of the microglial chemoattractant CCL5 (RANTES) is increased versus uninfected and localized with fibrin(ogen) in vessels. PLX3397 microglia depletion resulted in rapid behavioral decline, severe hypothermia, and greater increase in vascular coagulopathy. This study suggests that microglia play a prominent role in controlling infection-initiated coagulopathy and supports a model in which microglia play a protective role in cerebral malaria by migrating to and patrolling the cerebral vasculature, potentially regulating degree of coagulation during systemic inflammation.

Effects of Low-Level Persistent Infection on Maintenance of Immunity by CD4 T Cell Subsets and Th1 Cytokines.

CD4 T cells are required, along with antibodies, for complete protection from blood-stage infection with Plasmodium spp., which cause malaria. Without continuous exposure, as on emigration of people from endemic areas, protection from malaria decays. As in other persistent infections, low-level Plasmodium chabaudi infection protects the host from reinfection at 2 months postinfection, a phenomenon termed premunition. Premunition is correlated with T cell responses, rather than antibody levels. We previously showed that while both effector T cells (Teff) and memory T cells (Tmem) are present after infection, Teff protect better than Tmem. Here, we studied T cell kinetics post-infection by labeling dividing Ifng+ T cells with 5-bromo-2'-deoxyuridine (BrdU) in infected Ifng reporter mice. Large drops in specific T cell numbers and Ifng+ cells upon clearance of parasites suggest a mechanism for decay of protection. Although protection decays, CD4 Tmem persist, including a highly differentiated CD27- effector memory (Tem) subset that maintains some Ifng expression. In addition, pretreatment of chronically infected animals with neutralizing antibody to interferon gamma (IFN-γ) or with clodronate liposomes before reinfection decreases premunition, supporting a role for Th1-type immunity to reinfection. A pulse-chase experiment comparing chronically infected to treated animals showed that recently divided Ifng+ T cells, particularly IFN-γ+ TNF+ IL-2- T cells, are promoted by persistent infection. These data suggest that low-level persistent infection reduces CD4+ Tmem and multifunctional Teff survival, but promotes IFN-γ+ TNF+ IL-2- T cells and Ifng+ terminally differentiated effector T cells, and prolongs immunity.

Chloroquine treatment influences immunologicalmemory through the PD-1/PD-L1 pathway during the initiation of Plasmodium chabaudi infection.

Growing evidence describes the host immune response mechanism involved in malaria. Despite the spread of drug resistance, chloroquine (CQ) remains the main antimalarial drug in most countries in Latin America and Asia. Studies have indicated an immunomodulatory activity of CQ, however, the potential implications for CQ on immunological memory recognizing the malaria parasite are still being elucidated. Our study suggests that CQ treatment significantly delayed the initiation of parasitemia during infection of mice with the rodent malaria parasite, Plasmodium chabaudi (P.c.). Additionally, there was a decrease in T follicular helper cells (Tfh), CD4+ effector memory T cells, memory B cells (MBC), IgG2a memoryB cells, along with IgG2a plasma cells; while antibody production was not affected atthe observation time points. After PD-1 blockade and CQ treatment, no reductions in the numbers of CD4+ effector memory T cells, MBC, and IgG2a memoryB cells were observed compared with the P.c. group. Therefore, CQ might regulate immunological memory via the PD-1/PD-L1 signaling pathway. Compared with antibody secretion, the inhibition of CQ on immune memory cells was a more sensitive indicator.

Hepatoprotective activity of Eucalyptus camaldulensis extract in murine malaria mediated by suppression of oxidative and inflammatory processes

Herbal extracts are promising agents against various parasitic diseases, such as malaria. This study aimed to evaluate the ameliorative action of Eucalyptus camaldulensis extract (ECE) against hepatic damage caused by Plasmodium chabaudi infection. Mice were allocated into five groups as follows: two groups served as the control non-infected groups that received distilled water and ECE, respectively; subsequent three groups were infected with 106 P. chabaudi parasitized erythrocytes; the last two groups were infected with the parasite and then treated with ECE and chloroquine. On day 8 post-infection, the parasite count increased inside erythrocytes (59.4% parasitemia in the infected group). Parasitemia was successfully reduced to 9.4% upon ECE treatment. Phytochemical screening using GC mass spectrometry revealed that ECE contained 23 phytochemical components. Total phenolics and flavonoids in ECE were 104 ± 2 and 7.1± 3 µg/mL, respectively, with 57.2% antioxidant activity. ECE ameliorated changes in liver histopathology and enzymatic activity of alanine aminotransferase, aspartate aminotransferase, and alkaline phosphatase. In addition, ECE prevented oxidative damage induced by the parasite in the liver, as evidenced by the change in the liver concentrations of glutathione, nitric oxide, malondialdehyde, and catalase. Moreover, ECE was able to regulate the expression of liver cytokines, interleukins-1β and 6, as well as IFN-γ mRNA. ECE possesses antiplasmodial, antioxidant, and anti-inflammatory activity against liver injury induced by the parasite P. chabaudi.

ICOS Expression Is Required for Maintenance but Not the Formation of Germinal Centers in the Spleen in Response to Plasmodium yoelii Infection.

Inducible T cell costimulator (ICOS) plays a key role in the differentiation and maintenance of follicular helper T (Tfh) cells and, thus, germinal center (GC) formation. Previously, our laboratory showed in a Plasmodium chabaudi infection model that Icos-/- mice were significantly impaired in their ability to form GCs despite persistent infection and, thus, a continued antigen (Ag) load. Here, we show that the resolution of primary infection with Plasmodium yoelii was delayed in Icos-/- mice. This phenotype was associated with a reduction in the accumulation of Tfh-like and GC Tfh cells and an early deficiency in Ag-specific antibody (Ab) production. However, Icos-/- mice could form GCs, although they were less frequent in number than in wild-type (WT) mice. Nonetheless, the Ag-specific Abs from Icos-/- mice lacked signs of affinity maturation, suggesting functional defects associated with these GCs. Eventually, these GC structures dissipated more rapidly in Icos-/- mice than in WT mice. Moreover, the ability of Icos-/- mice to form these GC structures is not reliant on the high Ag loads associated with P. yoelii infections, as GC formation was preserved in Icos-/- mice treated with atovaquone. Finally, mice were unable to form secondary GCs in the absence of ICOS after rechallenge. Overall, these data demonstrate the necessity of ICOS in the maintenance of Tfh cells, the formation and maintenance of sufficient numbers of functioning GCs, and the ability to generate new GC structures after reinfection with P. yoelii.

Metabolomic Analysis of Diverse Mice Reveals Hepatic Arginase-1 as Source of Plasma Arginase in Plasmodium chabaudi Infection.

ABSTRACTInfections disrupt host metabolism, but the factors that dictate the nature and magnitude of metabolic change are incompletely characterized. To determine how host metabolism changes in relation to disease severity in murine malaria, we performed plasma metabolomics on eight Plasmodium chabaudi-infected mouse strains with diverse disease phenotypes. We identified plasma metabolic biomarkers for both the nature and severity of different malarial pathologies. A subset of metabolic changes, including plasma arginine depletion, match the plasma metabolomes of human malaria patients, suggesting new connections between pathology and metabolism in human malaria. In our malarial mice, liver damage, which releases hepatic arginase-1 (Arg1) into circulation, correlated with plasma arginine depletion. We confirmed that hepatic Arg1 was the primary source of increased plasma arginase activity in our model, which motivates further investigation of liver damage in human malaria patients. More broadly, our approach shows how leveraging phenotypic diversity can identify and validate relationships between metabolism and the pathophysiology of infectious disease.

Biosynthesized nanosilver as anti-oxidant, anti-apoptotic and anti-inflammatory agent against Plasmodium chabaudi infection in the mouse liver.

In recent years, the use of plant-mediated nanoparticle synthesis to combat infectious diseases has become increasingly significant. Malaria is one of the world's most infectious diseases caused by Plasmodium species. The antioxidant, anti-apoptotic, and anti-inflammatory properties of nanosilver biosynthesized from Indigofera oblongifolia leaf extracts (NS) against Plasmodium chabaudi infection of the mouse liver were investigated in this research. Male mice were infected with P. chabaudi infected erythrocytes then treated with NS for 7 days. The parasitemia was suppressed by approximately 24, 28, 47 and 75% on days 4, 5, 6 and 7 postinfection, respectively after treatment of mice with NS. Also, NS was able to regulate the leucocytes count and the IL1β and TNF-α-mRNA expression in mice. Ns could increase the antioxidant activity in liver of mice and was able to regulate the apoptotic genes, Bcl2 and Casp3. We showed that NS has antioxidant, anti-apoptotic, and anti-inflammatory properties when it was used to treat the livers of mice infected with P. chabaudi.

The plasma membrane calcium ATPase 4 does not influence parasite levels but partially promotes experimental cerebral malaria during murine blood stage malaria

BackgroundRecent genome wide analysis studies have identified a strong association between single nucleotide variations within the human ATP2B4 gene and susceptibility to severe malaria. The ATP2B4 gene encodes the plasma membrane calcium ATPase 4 (PMCA4), which is responsible for controlling the physiological level of intracellular calcium in many cell types, including red blood cells (RBCs). It is, therefore, postulated that genetic differences in the activity or expression level of PMCA4 alters intracellular Ca2+ levels and affects RBC hydration, modulating the invasion and growth of the Plasmodium parasite within its target host cell.MethodsIn this study the course of three different Plasmodium spp. infections were examined in mice with systemic knockout of Pmca4 expression.ResultsAblation of PMCA4 reduced the size of RBCs and their haemoglobin content but did not affect RBC maturation and reticulocyte count. Surprisingly, knockout of PMCA4 did not significantly alter peripheral parasite burdens or the dynamics of blood stage Plasmodium chabaudi infection or reticulocyte-restricted Plasmodium yoelii infection. Interestingly, although ablation of PMCA4 did not affect peripheral parasite levels during Plasmodium berghei infection, it did promote slight protection against experimental cerebral malaria, associated with a minor reduction in antigen-experienced T cell accumulation in the brain.ConclusionsThe finding suggests that PMCA4 may play a minor role in the development of severe malarial complications, but that this appears independent of direct effects on parasite invasion, growth or survival within RBCs.

Plasmodium chabaudi Infection Alters Intestinal Morphology and Mucosal Innate Immunity in Moderately Malnourished Mice.

Plasmodium falciparum is a protozoan parasite which causes malarial disease in humans. Infections commonly occur in sub-Saharan Africa, a region with high rates of inadequate nutrient consumption resulting in malnutrition. The complex relationship between malaria and malnutrition and their effects on gut immunity and physiology are poorly understood. Here, we investigated the effect of malaria infection in the guts of moderately malnourished mice. We utilized a well-established low protein diet that is deficient in zinc and iron to induce moderate malnutrition and investigated mucosal tissue phenotype, permeability, and innate immune response in the gut. We observed that the infected moderately malnourished mice had lower parasite burden at the peak of infection, but damaged mucosal epithelial cells and high levels of FITC-Dextran concentration in the blood serum, indicating increased intestinal permeability. The small intestine in the moderately malnourished mice were also shorter after infection with malaria. This was accompanied with lower numbers of CD11b+ macrophages, CD11b+CD11c+ myeloid cells, and CD11c+ dendritic cells in large intestine. Despite the lower number of innate immune cells, macrophages in the moderately malnourished mice were highly activated as determined by MHCII expression and increased IFNγ production in the small intestine. Thus, our data suggest that malaria infection may exacerbate some of the abnormalities in the gut induced by moderate malnutrition.

Tissue macrophages and interferon-gamma signalling control blood-stage Plasmodium chabaudi infections derived from mosquito-transmitted parasites

Natural infection with Plasmodium parasites, the causative agents of malaria, occurs via mosquito vectors. However, most of our knowledge of the immune response to the blood stages of Plasmodium is from infections initiated by injection of serially blood-passaged infected red blood cells, resulting in an incomplete life cycle in the mammalian host. Vector transmission of the rodent malaria parasite, Plasmodium chabaudi chabaudi AS has been shown to give rise to a more attenuated blood-stage infection in C57Bl/6J mice, when compared to infections initiated with serially blood-passaged P. chabaudi-infected red blood cells. In mouse models, the host immune response induced by parasites derived from natural mosquito transmission is likely to more closely resemble the immune responses to Plasmodium infections in humans. It is therefore important to determine how the host response differs between the two types of infections.As the spleen is considered to be a major contributor to the protective host response to P. chabaudi, we carried out a comparative transcriptomic analysis of the splenic response to recently mosquito-transmitted and serially blood-passaged parasites in C57Bl/6J mice. The attenuated infection arising from recently mosquito-transmitted parasites is characterised by an earlier and stronger myeloid- and IFNγ-related response. Analyses of spleen lysates from the two infections similarly showed stronger or earlier inflammatory cytokine and chemokine production in the recently mosquito-transmitted blood-stage infections. Furthermore, tissue macrophages, including red pulp macrophages, and IFNγ-signalling in myeloid cells, are required for the early control of P. chabaudi recently mosquito-transmitted parasites, thus contributing to the attenuation of mosquito-transmitted infections.The molecules responsible for this early activation response to recently-transmitted blood-stage parasites in mice would be important to identify, as they may help to elucidate the nature of the initial interactions between blood-stage parasites and the host immune system in naturally transmitted malaria.

A Conserved TCRβ Signature Dominates a Highly Polyclonal T-Cell Expansion During the Acute Phase of a Murine Malaria Infection.

CD4+ αβ T-cells are key mediators of the immune response to a first Plasmodium infection, undergoing extensive activation and splenic expansion during the acute phase of an infection. However, the clonality and clonal composition of this expansion has not previously been described. Using a comparative infection model, we sequenced the splenic CD4+ T-cell receptor repertoires generated over the time-course of a Plasmodium chabaudi infection. We show through repeat replicate experiments, single-cell RNA-seq, and analyses of independent RNA-seq data, that following a first infection - within a highly polyclonal expansion - T-effector repertoires are consistently dominated by TRBV3 gene usage. Clustering by sequence similarity, we find the same dominant clonal signature is expanded across replicates in the acute phase of an infection, revealing a conserved pathogen-specific T-cell response that is consistently a hallmark of a first infection, but not expanded upon re-challenge. Determining the host or parasite factors driving this conserved response may uncover novel immune targets for malaria therapeutic purposes.

Toll-like receptor 4, Toll-like receptor 7 and Toll-like receptor 9 agonists enhance immune responses against blood-stage Plasmodium chabaudi infection in BALB/c mice

BackgroundToll-like receptor (TLR) signals play vital roles during the blood-stage of malaria infections. However, the roles of TLR agonists in the regulation of immune responses and the development of protective immunity to malaria remain poorly understood. MethodBALB/c mice were pre-treated with TLR4, TLR7 and TLR9 agonists, followed by infection with Plasmodium chabaudi. After infection, splenic dendritic cells (DCs), Th1 cells and programmed death-1 (PD-1) expressed on Th1 cells, as well as regulatory T cells (Tregs) were analyzed by flow cytometry. The levels of IFN-γ, TNF-α, TGF-β and IL-10 in splenocytes and IgG1 and IgG2a in serum were measured by ELISA. ResultAdministration of TLR4, TLR7 and TLR9 agonists prior to infection improved disease outcomes. All TLR agonists promoted DC activation, and the proportions of Th1 cells increased. In TLR4, TLR7 and TLR9 agonist treated groups the levels of pro-inflammatory cytokines IFN-γ and TNF-α were elevated, and IgG1 and IgG2a serum levels were also significantly increased. TLR4, TLR7 and TLR9 agonists diminished the activation of Tregs and down-regulated the anti-inflammatory cytokines TGF-β and IL-10. Finally, PD-1 expressed on Th1 cells were decreased in TLR4, TLR7 and TLR9 agonist treated groups compared with control groups. ConclusionTLR4, TLR7 and TLR9 agonists activated DC-mediated innate immune responses and adaptive immune response, which against the blood-stage of Plasmodium and might be applied to malaria protection and treatment.

Transcriptional Memory-Like Imprints and Enhanced Functional Activity in γδ T Cells Following Resolution of Malaria Infection.

γδ T cells play an essential role in the immune response to many pathogens, including Plasmodium. However, long-lasting effects of infection on the γδ T cell population still remain inadequately understood. This study focused on assessing molecular and functional changes that persist in the γδ T cell population following resolution of malaria infection. We investigated transcriptional changes and memory-like functional capacity of malaria pre-exposed γδ T cells using a Plasmodium chabaudi infection model. We show that multiple genes associated with effector function (chemokines, cytokines and cytotoxicity) and antigen-presentation were upregulated in P. chabaudi-exposed γδ T cells compared to γδ T cells from naïve mice. This transcriptional profile was positively correlated with profiles observed in conventional memory CD8+ T cells and was accompanied by enhanced reactivation upon secondary encounter with Plasmodium-infected red blood cells in vitro. Collectively our data demonstrate that Plasmodium exposure result in “memory-like imprints” in the γδ T cell population and also promotes γδ T cells that can support antigen-presentation during subsequent infections.

Uncovering drivers of dose-dependence and individual variation in malaria infection outcomes.

To understand why some hosts get sicker than others from the same type of infection, it is essential to explain how key processes, such as host responses to infection and parasite growth, are influenced by various biotic and abiotic factors. In many disease systems, the initial infection dose impacts host morbidity and mortality. To explore drivers of dose-dependence and individual variation in infection outcomes, we devised a mathematical model of malaria infection that allowed host and parasite traits to be linear functions (reaction norms) of the initial dose. We fitted the model, using a hierarchical Bayesian approach, to experimental time-series data of acute Plasmodium chabaudi infection across doses spanning seven orders of magnitude. We found evidence for both dose-dependent facilitation and debilitation of host responses. Most importantly, increasing dose reduced the strength of activation of indiscriminate host clearance of red blood cells while increasing the half-life of that response, leading to the maximal response at an intermediate dose. We also explored the causes of diverse infection outcomes across replicate mice receiving the same dose. Besides random noise in the injected dose, we found variation in peak parasite load was due to unobserved individual variation in host responses to clear infected cells. Individual variation in anaemia was likely driven by random variation in parasite burst size, which is linked to the rate of host cells lost to malaria infection. General host vigour in the absence of infection was also correlated with host health during malaria infection. Our work demonstrates that the reaction norm approach provides a useful quantitative framework for examining the impact of a continuous external factor on within-host infection processes.

Transcriptome analysis of blood and spleen in virulent and avirulent mouse malaria infection

Malaria is a devastating infectious disease and the immune response is complex and dynamic during a course of a malarial infection. Rodent malaria models allow detailed time-series studies of the host response in multiple organs. Here, we describe two comprehensive datasets containing host transcriptomic data from both the blood and spleen throughout an acute blood stage infection of virulent or avirulent Plasmodium chabaudi infection in C57BL/6 mice. The mRNA expression profiles were generated using Illumina BeadChip microarray. These datasets provide a groundwork for comprehensive and comparative studies on host gene expression in early, acute and recovering phases of a blood stage infection in both the blood and spleen, to explore the interaction between the two, and importantly to investigate whether these responses differ in virulent and avirulent infections.

T Helper Plasticity Is Orchestrated by STAT3, Bcl6, and Blimp-1 Balancing Pathology and Protection in Malaria.

SummaryHybrid Th1/Tfh cells (IFN-γ+IL-21+CXCR5+) predominate in response to several persistent infections. In Plasmodium chabaudi infection, IFN-γ+ T cells control parasitemia, whereas antibody and IL-21+Bcl6+ T cells effect final clearance, suggesting an evolutionary driver for the hybrid population. We found that CD4-intrinsic Bcl6, Blimp-1, and STAT3 coordinately regulate expression of the Th1 master regulator T-bet, supporting plasticity of CD4 T cells. Bcl6 and Blimp-1 regulate CXCR5 levels, and T-bet, IL-27Rα, and STAT3 modulate cytokines in hybrid Th1/Tfh cells. Infected mice with STAT3 knockout (KO) T cells produced less antibody and more Th1-like IFN-γ+IL-21−CXCR5lo effector and memory cells and were protected from re-infection. Conversely, T-bet KO mice had reduced Th1-bias upon re-infection and prolonged secondary parasitemia. Therefore, each feature of the CD4 T cell population phenotype is uniquely regulated in this persistent infection, and the cytokine profile of memory T cells can be modified to enhance the effectiveness of the secondary response.

Vaccination accelerates hepatic erythroblastosis induced by blood-stage malaria

BackgroundVaccination induces survival of otherwise lethal blood-stage infections of the experimental malaria Plasmodium chabaudi. Blood-stage malaria induces extramedullary erythropoiesis in the liver. This study investigates how vaccination affects the course of malaria-induced expression of erythrocytic genes in the liver.MethodsFemale Balb/c mice were vaccinated at week 3 and week 1 before challenging with 106P. chabaudi-parasitized erythrocytes. The non-infectious vaccine consisted of erythrocyte ghosts isolated from P. chabaudi-infected erythrocytes. Gene expression microarrays and quantitative real-time PCR were used to compare mRNA expression of different erythrocytic genes in the liver of vaccination-protected and non-protected mice during infections on days 0, 1, 4, 8, and 11 p.i.ResultsGlobal transcriptomics analyses reveal vaccination-induced modifications of malaria-induced increases in hepatic gene expression on days 4 and 11 p.i. On these days, vaccination also alters hepatic expression of the erythropoiesis-involved genes Ermap, Kel, Rhd, Rhag, Slc4a1, Gypa, Add2, Ank1, Epb4.1, Epb4.2, Epb4.9, Spta1, Sptb, Tmod1, Ahsp, Acyp1, Gata1, Gfi1b, Tal1, Klf1, Epor, and Cldn13. In vaccination-protected mice, expression of these genes, except Epb4.1, is significantly higher on day 4 p.i. than in un-protected non-vaccinated mice, reaches maximal expression at peak parasitaemia on day 8 p.i., and is slowed down or even decreased towards the end of crisis phase on day 11 p.i.. After day 1 p.i., Epor expression takes about the same course as that of the other erythroid genes. Hepatic expression of Epo, however, is delayed in both vaccinated and non-vaccinated mice for the first 4 days p.i. and is maximal at significantly higher levels in vaccinated mice on day 8 p.i., before declining towards the end of crisis phase on day 11 p.i.ConclusionThe present data indicate that vaccination accelerates malaria-induced erythroblastosis in the liver for 1–2 days. This may contribute to earlier replenishment of peripheral red blood cells by liver-derived reticulocytes, which may favour final survival of otherwise lethal blood-stage malaria, since reticulocytes are not preferred as host cells by P. chabaudi.

Comparison of whole blood and spleen transcriptional signatures over the course of an experimental malaria infection

Although the spleen is broadly accepted as the major lymphoid organ involved in generating immune responses to the erythrocytic stages of the malaria parasite, Plasmodium, human splenic tissue is not readily available in most cases. As a result, most studies of malaria in humans rely on peripheral blood to assess cellular immune responses to malaria. The suitability of peripheral blood as a proxy for splenic immune responses is however unknown. Here, we have simultaneously analysed the transcriptomes of whole blood and spleen over 12 days of erythrocytic stage Plasmodium chabaudi infection in C57BL/6 mice. Using both unsupervised and directed approaches, we compared gene expression between blood and spleen over the course of infection. Taking advantage of publicly available datasets, we used machine learning approaches to infer cell proportions and cell-specific gene expression signatures from our whole tissue transcriptome data. Our findings demonstrate that spleen and blood are quite dissimilar, sharing only a small amount of transcriptional information between them, with transcriptional differences in both cellular composition and transcriptional activity. These results suggest that while blood transcriptome data may be useful in defining surrogate markers of protection and pathology, they should not be used to predict specific immune responses occurring in lymphoid organs.