Plasmodium falciparum employs sophisticated strategies to subvert host immunity, whereas the specific parasite-derived factors governing this critical process remain elusive. Here, by utilizing P. falciparum 3D7 and P. berghei ANKA infection models, we investigated the role of parasite-derived PI3K in immune evasion, and found that Plasmodium PI3K prevents the externalization of phosphatidylserine (PS), a canonical prophagocytic ‘eat-me’ signal. Inhibiting PI3K activity in infected red blood cells (iRBCs) significantly increased M2 macrophage polarization and iRBC recognition. Mechanistically, we identified that PfPI3K preserves mitochondrial membrane potential and prevents calcium efflux by promoting the 2-hydroxyisobutyrylation of the 14–3-3 protein to maintain a calcium-homeostatic environment. Therefore, PfPI3K could phosphorylate P. falciparum phospholipid scramblase 1 (PfPLSCR1) to maintain PS internalization in iRBCs while preventing their exposure to immune cells. Collectively, these results revealed a mechanism through which Plasmodium parasites leverage PI3K to actively suppress PS-associated ‘eat-me’ signalling in iRBCs, thereby circumventing host macrophage-mediated surveillance and facilitating persistent infection.

The pathogenesis of Plasmodium falciparum malaria involves coordinated molecular events, including host cell invasion, intraerythrocytic replication cycles, and antigenic variation, which are critically dependent on the stage-specific regulation of parasite proteins. Despite their biological significance, the molecular governance of these pathogenic mechanisms remains inadequately characterized. Our investigation reveals that the expression dynamics of an ApiAP2 family transcription factor, PfAP2-V (PF3D7_1239200), exhibit strong temporal coordination with the transcriptional activation of virulence-associated genes during the blood-stage development of P. falciparum parasites. These genes encompass those coding for merozoite surface antigens and the inner membrane complex families and the var gene clusters encoding P. falciparum erythrocyte membrane protein 1 (PfEMP1) cytoadherence proteins. Conditional knockdown of pfap2-v expression significantly decreased parasite intraerythrocytic proliferation, resulted in structural abnormalities in infected erythrocyte surface topology, and markedly reduced the cytoadhesion capacity of infected erythrocytes to human endothelial receptors, such as CD36, ICAM-1, and PECAM-1/CD31. Mechanistic analyses revealed that PfAP2-V directly associates with specific chromosomal regions, where it is involved in chromatin interactions and facilitates transcriptional activation. These findings establish PfAP2-V as a master transcriptional regulator that governs both parasite proliferation and the expression of the virulence factors critical for P. falciparum malaria pathogenesis.

Toxoplasma gondii is an infectious disease that infects nearly one third of the world’s population and endangers the health of immunocompromised people, pregnant women, and livestock. There are no existing drugs able to treat the infection and prevent tissue cysts from developing. Therefore, the creation of a safe vaccine should be considered as a matter of great importance. While many of the vaccines have not proven successful in the past, recently created live-attenuated vaccines (LAVs) using CRISPR–Cas9 gene editing technology were able to outperform the previous ones. The current review aims to highlight the recent progress in genetically engineered LAVs against T. gondii. In particular, the knockout strains affecting metabolic genes (ompdc, uprt, and adsl), virulence genes (rop18), and host–parasite interactions (gra5, gra72, had2a, and cdpk3) will be mentioned. LAVs described above demonstrate high attenuating effects and ability to protect mice by inducing immunity on the basis of specific IgG (IgG2a), IFN-γ, IL-12, and CD4+, CD8+ T cells. Furthermore, vaccination provides protection from a lethal infection caused by types I, II, and Chinese 1 strains of T. gondii as well as preventing development of tissue cysts in chronic infection. RHΔompdcΔuprt is an example of an LAV that can be used to reduce oocyst shedding in cats and promote the One Health concept. In general terms, genetically engineered LAVs can effectively deal with toxoplasmosis infection with better attenuation immunogenicity balance than other vaccines. Nonetheless, several problems need consideration.

Apicomplexan protozoans employ an intricate invasion mechanism involving dynamic interactions with host cells, characterized by sequential secretion of adhesins and lectins. Our laboratory previously identified TgSABP1, a novel Toxoplasma gondii adhesin, demonstrating specific binding affinity for sialic acid (SA) receptors on host cell surfaces. However, the structural determinants governing SA recognition by this adhesin remain undefined. Three-dimensional structural predictions of TgSABP1 and homologous proteins were generated using AlphaFold2. Bio-layer interferometry (BLI) quantified the binding affinities between the recombinant proteins and ligands. Competitive BLI assays evaluated small molecules that potentially inhibit the TgSABP1–sialyllactose interactions. Molecular docking simulations employing AutoDock Vina software elucidated ligand-binding site interactions. In vitro invasion inhibition assays were performed to assess the therapeutic potential of lead compounds targeting TgSABP1 against T. gondii tachyzoites. AlphaFold2 structural predictions revealed that TgSABP1 and its homologues contain a conserved globular domain (pLDDT > 90) with significant structural homology (with root-mean-square deviation [RMSD] < 4 Å) to a Plasmodium falciparum invasion-related protein PfIMP2 (PDB: 5LG9). BLI quantification demonstrated the micromolar binding affinities of the recombinant proteins for 3′-sialyllactose-polyacrylamide (PAA) and 6′-sialyllactose (6′SL)-PAA. Intriguingly, although recombinant TgSABP1 showed stronger lactose binding (KD = 0.02 ± 0.01 M) compared to SA (KD = 2.07 ± 0.45 M), only the latter exhibited an inhibition on the TgSABP1-6′SL-PAA interaction. Virtual screening of Food and Drug Administration (FDA)-approved compounds identified eltrombopag as a high-affinity molecule (ΔGbind = −8.3 kcal/mol) targeting the SA-binding pocket in TgSABP1. Functional validation demonstrated that eltrombopag effectively blocked the TgSABP1/6′SL-PAA interaction and significantly decreased host cell invasion of T. gondii tachyzoites. Our study reveals a conserved globular domain of apicomplexan parasites as a novel SA-binding domain. Structural and functional characterization demonstrates its critical role in mediating TgSABP1-host cell interactions. Targeting this SA-binding pocket with eltrombopag effectively decreased T. gondii tachyzoite invasion, suggesting its therapeutic potential as an anti-invasion target. These findings not only elucidate a conserved mechanism underlying host receptor recognition in apicomplexans, but also establish a structural framework for the rational design of broad-spectrum inhibitors targeting invasion-related lectin domains.

Environmental factors restrict malaria parasite development, but the influence of host metabolic variations on the infectivity of the blood stage parasite is not fully understood. Here we show that mice on a ketogenic diet are completely protected from infection with the malaria parasite Plasmodium berghei. We further show that administration of the ketone body β-hydroxybutyrate (βOHB), but not of acetoacetate, increases survival of infected mice and inhibits proliferation of both P. berghei and Plasmodium falciparum in vitro. Administration of either a ketogenic diet or βOHB induces metabolic reprogramming in parasites, including reduced levels of nicotinamide adenine dinucleotide, which is associated with the downregulation of genes controlling parasite development, erythrocyte invasion and pathogenicity. Our data indicate that a ketogenic diet and the ketone body βOHB confer resistance to malaria in mice by causing developmental arrest of Plasmodium parasites, highlighting the potential of dietary and metabolic strategies to fight malarial infection. A ketogenic diet and the ketone body β-hydroxybutyrate are shown to confer resistance to malaria in mice by inducing metabolic reprogramming in Plasmodium parasites, suggesting a dietary strategy for malaria prevention.

Toxoplasma gondii infects nucleated cells of warm-blooded animals and cause zoonotic toxoplasmosis. Lysine lactylation, as a novel post-translational modification, is essential for epigenetic regulation and cellular processes, and proteomic analyses have shown that lactylated proteins are involved in a wide range of biological processes including energy metabolism, gene regulation, and protein biosynthesis. Additionally, protein lactylation is prevalent in T. gondii, while its regulatory mechanisms have not been fully understood. In this study, we investigated the role of T. gondii phosphofructokinase-2 (TgPFKII) and the adenosine-5'-monophosphate-activated protein kinase (AMPK) signaling pathway in the invasion, replication, and lactylation regulation of T. gondii. We localized TgPFKII in the cytoplasm of T. gondii tachyzoites and demonstrated its necessity for parasite growth and protein lactylation through auxin-induced degradation. Our results showed that inhibition of the AMPK pathway led to decreased TgPFKII expression and reduced protein lactylation levels. Furthermore, AMPK-specific inhibitors significantly impaired parasite invasion and proliferation. These findings highlight TgPFKII as a crucial regulator of lactylation and underscore the importance of the AMPK pathway in T. gondii's pathogenic mechanisms, offering potential targets for therapeutic intervention.IMPORTANCEUnderstanding the intricate mechanisms by which Toxoplasma gondii invades and proliferates within host cells is essential for developing novel therapeutic strategies against toxoplasmosis. This study focuses on the pivotal roles of T. gondii phosphofructokinase-2 (TgPFKII) and the adenosine-5'-monophosphate-activated protein kinase (AMPK) signaling pathway in regulating protein lactylation in association with parasite invasion and growth. By elucidating the cellular localization and functional importance of TgPFKII, as well as its regulation through AMPK-specific inhibitors, we provide comprehensive insights into the metabolic and signaling networks that underpin T. gondii pathogenicity. Our findings reveal that TgPFKII is a critical regulator of lactylation and that the AMPK pathway significantly influences T. gondii's ability to invade and replicate within host cells. These insights pave the way for targeted interventions aimed at disrupting key metabolic and signaling pathways in T. gondii, potentially leading to more effective treatments for toxoplasmosis.

Hypothesis: Trypanosomiasis is one of the main threats to human and animal health in African countries. Trypanosoma brucei can evade the host immune recognition by rapidly altering its variant surface glycoprotein (VSG). The ATP synthase F1 1 subunit of the parasite exhibits extremely low similarity to that of its mammalian hosts, hypothetically making it an ideal target for the development of novel therapeutics. Experiments: Graphene quantum dots (GQDs) were synthesized, and their adhesion to T. brucei surface and internalization was observed microscopically. The activity of ATP synthase and mitochondrial membrane potential of T. brucei were measured after exposure to GQDs. Proteomics, biolayer interferometry, and molecular dynamic simulations were utilized to evaluate the interaction between GQDs with the target proteins. Findings: GQDs specifically adhered to the VSG of T. brucei and were conveyed inside the parasite via the VSG internalization pathway. The GQDs promoted intracellular ROS production, interacted with, and inhibited the activity of the p18 subunit of ATP synthase, disrupted parasite mitochondrial membrane potential. Additionally, the GQDs caused a decrease in aminoacyl - tRNA biosynthesis, and upregulated RNA and protein degradation pathways. The findings of this study offer a novel avenue for the target-oriented discovery of anti-trypanosome drugs.

BACKGROUND:The property of dihydroartemisinin (DHA) in promoting host immunohomeostasis, apart from its potent antimalarial activity, has been well-recognized. However, the mechanism of DHA in activating macrophages to enhance host resistance to malaria remains unexplored. PURPOSE:This study investigated the molecular mechanism by which DHA promotes the polarization of macrophages toward the M1 phenotype during the treatment of malaria. METHODS:The mouse macrophage cell line RAW 264.7 or the macrophages isolated from mice were stimulated with Plasmodium berghei ANKA infected red blood cells (iRBC) in the presence of DHA. The macrophage phenotypes in both in vivo and in vitro were determined using cytometric bead array and flow cytometry. To dissect the molecular mechanisms underlying macrophage responses to DHA, we initially profiled the expression of 90 genes associated with innate immunity, including the entire NLR family, in macrophages stimulated with DHA. This targeted screen strikingly revealed that only Nlrp12 was significantly upregulated among all tested NLR genes. The function of Nlrp12 was further dissected by Nlrp12 knockdown in macrophages with recombinant lentiviruses encoding Nlrp12-specific shRNA, within the context of DHA treatment. To comprehensively define the molecular consequences of Nlrp12 deficiency, we performed an integrated analysis by combining single-cell RNA sequencing with label-free quantitative proteomic profiling. This allowed us to systematically characterize the complex transcriptomic and proteomic dynamics in DHA-treated macrophages upon Nlrp12 deletion. RESULTS:DHA induced macrophage polarization to M1 phenotype and enhanced phagocytosis by up-regulating the expression of NLRP12. Nlrp12-knockdown in macrophages reduced the expression of M1 type-associated genes, resulting in a significantly increased expression of the translocator protein (TSPO), which suppressed the secretion of inflammation-associated cytokines and blunting macrophage M1 polarization. The results of single cell RNA sequencing further revealed that DHA promoted the conversion of classical M1 macrophages into lipocalin-2 (Lcn2) high M1 macrophages. CONCLUSION:The activation of NLRP12 induced by DHA is crucial for M1 macrophage polarization, which plays a significant role in the clearance of Plasmodium parasites.

Augmented regulatory B cell (Breg) responses are commonly observed in malaria; however, the specific parasite components and Breg subtypes involved remain unclear. In this study, we investigated C57BL/6 mice infected with Plasmodium berghei ANKA, which induces cerebral malaria pathology, in comparison to P. yoelii YM, which does not. We found that distinct Breg types differentiated in response to these infections, driven by hemozoin-mediated Toll-like receptor 9 activation. Interleukin-35-positive (IL-35+) Breg expansion occurred in P. yoelii YM-infected mice but not in those infected with P. berghei ANKA. We demonstrated that stimulator of interferon genes (STING)-mediated interferon regulatory factor 3 (IRF3) phosphorylation suppressed IL-35+ Breg differentiation, potentially contributing to experimental cerebral malaria (ECM). In contrast, P. yoelii YM infection activated IRF3 in a STING-independent manner, promoting IL-35+ Breg expansion. These findings highlight IL-35+ Bregs as key modulators in malarial immunopathology.

The invasion of Plasmodium merozoites into host erythrocytes is initiated through specific ligand–receptor interactions. This interaction results in subsequent invasion events, facilitated by the formation of a moving junction via AMA-1 and associated molecular complexes. Previous studies have implicated erythrocyte surface glycosaminoglycans, particularly heparan sulfate proteoglycans, as critical receptor components in this invasion process. The binding affinity of the PbGAC protein to heparin and erythrocytes was assessed through western blotting, immunofluorescence, flow cytometry techniques, and heparinase II treatment. Mice were immunized with the recombinant PbGAC-His to generate specific polyclonal antibodies for subcellular localization, passive immunization, and immunoprecipitation. Global mass spectrometric analyses were conducted to identify its interacting proteins. We elucidated the molecular function of PbGAC (encoded by PbANKA_1137800), a previously uncharacterized Plasmodium berghei ANKA protein, in association with merozoite attachment and invasion via the heparan sulfate-dependent pathway. The PbGAC protein, predominantly located at the extreme apical region of the P. berghei merozoite, binds to heparin and the erythrocyte surface during merozoite invasion. Global mass spectrometric analysis reveals that PbGAC interacts with several secreted proteins that are critically involved in erythrocyte invasion. In addition, mice either immunized with the PbGAC protein or passively immunized with sera derived from vaccinated mice demonstrated enhanced immunity against lethal challenges. Our findings pinpointed that PbGAC is predominantly expressed at the extreme apical region of the P. berghei merozoite and engaged in binding to the heparin-like receptors on the erythrocyte surface during merozoite invasion.

Background The human sortilin protein is an important drug target and detection marker for cancer research. The sortilin from Toxoplasma gondii transports proteins associated with the apical organelles of the parasite. In this study, we aimed to determine the intracellular localization and structural domains of T. gondii sortilin, which may mediate protein transportation. Approaches to the functional inhibition of sortilin to establish novel treatments for T. gondii infections were explored. Methods A gene encoding the sortilin protein was identified in the T. gondii genome. Immunoprecipitation and mass spectrometry were performed to identify the protein species transported by T. gondii sortilin. The interaction of each structural domain of sortilin with the transported proteins was investigated using bio-layer interferometry. The binding regions of the transported proteins in sortilin were identified. The effect of the sortilin inhibitor AF38469 on the infectivity of T. gondii was investigated. The binding site of AF38469 on sortilin was determined. Results The subdomains Vps10, sortilin-C, and sortilin-M of the sortilin were identified as the binding regions for intracellular transportation of the target proteins. The sortilin inhibitor AF38469 bound to the Vps10 structural domain of T. gondii sortilin, which inhibited parasite invasion, replication, and intracellular growth in vitro and was therapeutic in mice infected with T. gondii . Conclusion The Vps10, sortilin-C, and sortilin-M subdomains of T. gondii sortilin were identified as functional regions for intracellular protein transport. The binding region for the sortilin inhibitor AF38469 was also identified as the Vps10 subdomain. This study establishes sortilin as a promising drug target against T. gondii and provides a valuable reference for the development of anti- T. gondii drug-target studies. Graphical Abstract

Neutrophils and macrophages confine pathogens by entrapping them in extracellular traps (ETs) through activating TLR9 function. However, plasmodial parasites secreted TatD-like DNases (TatD) to counteract ETs-mediated immune clearance. We found that TLR9 mutant mice increased susceptibility to rodent malaria, suggesting TLR9 is a key protein for host defense. We found that the proportion of neutrophils and macrophages in response to plasmodial parasite infection in the TLR9 mutant mice was significantly reduced compared to that of the WT mice. Importantly, PbTatD can directly bind to the surface TLR9 (sTLR9) on macrophages, which blocking the phosphorylation of mitogen-activated protein kinase and nuclear factor-κB, negatively regulated the signaling of ETs formation by both macrophages and neutrophils. Such, P. berghei TatD is a parasite virulence factor that can inhibit the proliferation of macrophages and neutrophils through directly binding to TLR9 receptors on the cell surface, thereby blocking the activation of the downstream MyD88-NF-kB pathways.

Trypanosoma brucei, a causative agent of human and animal trypanosomiasis, regularly switches its major surface antigen to avoid elimination by the immune system. Toll-like receptor 9 (TLR9) is a key modulator for resistance to host-infective trypanosomes; however, the underlying molecular mechanism remains indistinct. Thus, we first approached the issue using Tlr9-mutant mice that render them non-responsive to TLR9 agonists. After infection, T cells in the spleens of Tlr9-mutant mice were analyzed by flow cytometry and a reduction in CD8+, CD4+ T, and NKT cells was observed in Tlr9-mutant mice compared to WT mice. We further found that the responses of inflammatory cytokines in the sera were reduced in Tlr9-mutant mice after T. brucei infection. The underlying molecular mechanism was that T. b. brucei DNA activated TLR9, which consequently upregulated the expression of p38 and ERK/MAPK, resulting in host resistance to trypanosome infection. In conclusion, these findings provide novel insights into the TLR9-mediated host responses to trypanosome infection.

Toxoplasma gondii, the causative parasite of toxoplasmosis, is an apicomplexan parasite that infects warm-blooded mammals. The ability of the calcium-binding proteins (CBPs) to transport large amounts of Ca2+ appears to be critical for the biological activity of T. gondii. However, the functions of some members of the CBP family have not yet been deciphered. Here, we characterized a putative CBP of T. gondii, TgpCaBP (TGME49_229480), which is composed of four EF-hand motifs with Ca2+-binding capability. TgpCaBP was localized in the cytosol and ER of T. gondii, and parasites lacking the TgpCaBP gene exhibited diminished abilities in cell invasion, intracellular growth, egress, and motility. These phenomena were due to the abnormalities in intracellular Ca2+ efflux and ER Ca2+ storage, and the reduction in motility was associated with a decrease in the discharge of secretory proteins. Therefore, we propose that TgpCaBP is a Ca2+ transporter and signaling molecule involved in Ca2+ regulation and parasitization in the hosts.IMPORTANCECa2+ signaling is essential in the development of T. gondii. In this study, we identified a calcium-binding protein in T. gondii, named TgpCaBP, which actively regulates intracellular Ca2+ levels in the parasite. Deletion of the gene coding for TgpCaBP caused serious deficits in the parasite's ability to maintain a stable intracellular calcium environment, which also impaired the secretory protein discharged from the parasite, and its capacity of gliding motility, cell invasion, intracellular growth, and egress from host cells. In summary, we have identified a novel calcium-binding protein, TgpCaBP, in the zoonotic parasite T. gondii, which is a potential therapeutic target for toxoplasmosis.

Artemisinin and its derivatives have been widely applied as the most effective drugs in the treatment of malaria since their introduction in the last century. However, challenges such as short half-life, limited bioavailability, and increasing drug resistance have prompted researchers to explore new strategies in the development of antimalarial drugs. In this study, a nano-targeting drug delivery system (HEP@ART@NEs) is developed consisted of heparin as the outer shell and artemisinin in the inner core, utilizing a high-pressure homogenization approach. The specific targeting effect of HEP@ART@NEs is achieved through surface multivalent interactions between heparin with both Plasmodium falciparum merozoites as well as the surface of infected red blood cells (iRBCs). The physical and chemical properties of HEP@ART@NEs, as well as its anti-malarial activity both in vitro and in vivo, are systematically investigated. HEP@ART@NEs demonstrate enhanced antimalarial effects, delay malaria recrudescence, and improve survivability in a rodent model with P. berghei ANKA infection compared to the treatment with conventional artemisinin treatment. Overall, this study indicates that HEP@ART@NEs hold promise as a platform for a rational design of targeted delivery of antimalarial drugs.

BackgroundArtemisinin (ART) is a frontline drug for the treatment of malaria; however, the emergence of ART-resistant Plasmodium strains necessitates increasing ART sensitivity. Given that taurine (TAU) has been shown to have immunomodulatory activity, we investigated the effects of TAU as an adjunct therapy to ART in mice infected with Plasmodium berghei.MethodsMice infected with P. berghei ANKA strain (P. berghei ANKA) were treated with TAU alone, ART alone or a combination of TAU and ART (TAU + ART), and their survival time and parasitaemia were recorded. The cytotoxic effects of TAU and ART were subsequently assessed. The expression levels of inflammasome-related genes and inflammatory factors in mice infected with P. berghei ANKA were analysed in relation to those in mice treated with TAU alone, ART alone or the TAU + ART combination. The therapeutic effects were further evaluated by histological analysis and measurement of the spleen index.ResultsCompared with the control mice, P. berghei ANKA-infected mice treated with ART in combination with TAU presented significantly lower parasitaemia and prolonged survival. The combined treatment resulted in significant reductions in the expression levels of inflammasome-related genes in the spleen, including absent in melanoma 2 (AIM2), caspase-1, NOD-, LRR- and pyrin domain-containing protein 3 (Nlrp3), Nlrp1b, Nlrp1b, NLR family CARD domain containing 4 (Nlrc4), Nlrp6, nucleotide binding oligomerization domain containing 1 (NOD1) and NOD2, and decreases in the levels of inflammatory cytokines in the serum, including interleukin (IL)-12p70, tumour necrosis factor-alpha, monocyte chemoattractant protein-1, IL-10 and IL-6. Histopathological analysis confirmed that TAU + ART combination treatment reduced spleen pathology caused by P. berghei ANKA infection.ConclusionsThe findings indicate that TAU potentiates ART efficacy by modulating the immune response in P. berghei-infected mice.

Neutrophils are essential in combating invading pathogens such as Plasmodium parasites, but the participation of their subpopulations and mechanisms in resistance to parasite infection are not fully understood. Our study identified a marked increase in Ly6G+ neutrophils in response to P. berghei ANKA infection. Depletion of these cells rendered mice more susceptible to infection. Elevated interleukin-17 (IL-17) levels, which increased the Ly6G+ neutrophil population, were also found to contribute to this protective effect. IL-17 depletion led to reduced neutrophil numbers and increased susceptibility. Furthermore, dihydroartemisinin (DHA) treatment enhanced neutrophil-mediated immune responses through up-regulation of CD18 and CXCR4 factors. These findings revealed key mechanisms of neutrophil and IL-17 interactions in malaria protection and highlighted DHA’s potential to promote neutrophil function in combating malaria.

Remodeling the erythrocyte membrane and skeleton by the malarial parasite Plasmodium falciparum is closely associated with intraerythrocytic development. However, the mechanisms underlying this association remain unclear. In this study, we present evidence that erythrocytic α-spectrin, but not β-spectrin, was dynamically ubiquitinated and progressively degraded during the intraerythrocytic development of P. falciparum, from the ring to the schizont stage. We further observed an upregulated expression of P. falciparum phosphatidylinositol 3-kinase (PfPI3K) in the infected red blood cells during the intraerythrocytic development of the parasite. The data indicated that PfPI3K phosphorylated and activated erythrocytic ubiquitin-protein ligase, leading to increased α-spectrin ubiquitination and degradation during P. falciparum development. We further revealed that inhibition of the activity of PfPI3K impaired P. falciparum development in vitro and Plasmodium berghei infectivity in mice. These findings collectively unveil an important mechanism of PfPI3K-ubiquitin-mediated degradation of α-spectrin during the intraerythrocytic development of Plasmodium species. Proteins in the PfPI3K regulatory pathway are novel targets for effective treatment of severe malaria. IMPORTANCE:Plasmodium falciparum is the causative agent of severe malaria that causes millions of deaths globally. The parasite invades human red blood cells and induces a cascade of alterations in erythrocytes for development and proliferation. Remodeling the host erythrocytic cytoskeleton is a necessary process during parasitization, but its regulatory mechanisms remain to be elucidated. In this study, we observed that erythrocytic α-spectrin is selectively degraded after P. falciparum invasion, while β-spectrin remained intact. We found that the α-spectrin chain was profoundly ubiquitinated by E3 ubiquitin ligase and degraded by the 26S proteasome. E3 ubiquitin ligase activity was regulated by P. falciparum phosphatidylinositol 3-kinase (PfPI3K) signaling. Additionally, blocking the PfPI3K-ubiquitin-proteasome pathway in P. falciparum-infected red blood cells reduced parasite proliferation and infectivity. This study deepens our understanding of the regulatory mechanisms of host and malarial parasite interactions and paves the way for the exploration of novel antimalarial drugs.

Host immune responses are tightly controlled by various immune factors during infection, and protozoan parasites also manipulate the immune system to evade surveillance, leading to an evolutionary arms race in host‒pathogen interactions; however, the underlying mechanisms are not fully understood. We observed that the level of superoxide dismutase 3 (SOD3) was significantly elevated in both Plasmodium falciparum malaria patients and mice infected with four parasite species. SOD3-deficient mice had a substantially longer survival time and lower parasitemia than control mice after infection, whereas SOD3-overexpressing mice were much more vulnerable to parasite infection. We revealed that SOD3, secreted from activated neutrophils, bound to T cells, suppressed the interleukin-2 expression and concomitant interferon-gamma responses crucial for parasite clearance. Overall, our findings expose active fronts in the arms race between the parasites and host immune system and provide insights into the roles of SOD3 in shaping host innate immune responses to parasite infection.

Dihydroartemisinin (DHA), a potent antimalarial drug, also exhibits distinct property in modulation on Treg and B cells, which has been recognized for decades, but the underlying mechanisms remain understood. Herein we revealed that DHA could promote Treg proliferation, meanwhile, suppress B cell expansion in germinal centers, and consequently decrease the number of circulating plasma cells and the content of serum immunoglobulins. Further, DHA-activated Treg significantly mitigated lipopolysaccharide-induced and malaria-associated inflammation. All these scenarios were attributed to the upregulation of c-Fos expression by DHA and enhancement of its interaction with target genes in both Treg and circulating plasma cells with bilateral cell fates. In Treg, the c-Fos-DHA complex upregulated cell proliferation-associated genes and promoted cell expansion; whereas in plasma cells, it upregulated the apoptosis-related genes resulting in decreased circulating plasma cells. Thus, the bilateral immunoregulatory mechanism of DHA was elucidated and its application in the treatment of autoimmune diseases is further justified.