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Regular, systematic, and independent assessment of computational tools used to predict the pathogenicity of missense variants is necessary to evaluate their clinical and research utility and suggest directions for future improvement. Here, as part of the sixth edition of the Critical Assessment of Genome Interpretation (CAGI) challenge, we assess missense variant effect predictors (or variant impact predictors) on an evaluation dataset of rare missense variants from disease-relevant databases. Our assessment evaluates predictors submitted to the CAGI6 Annotate-All-Missense challenge, predictors commonly used by the clinical genetics community, and recently developed deep learning methods for variant effect prediction. To explore a variety of settings that are relevant for different clinical and research applications, we assess performance within different subsets of the evaluation data and within high-specificity and high-sensitivity regimes. We find strong performance of many predictors across multiple settings. Meta-predictors tend to outperform their constituent individual predictors; however, several individual predictors have performance similar to that of commonly used meta-predictors. The relative performance of predictors differs in high-specificity and high-sensitivity regimes, suggesting that different methods may be best suited to different use cases. We also characterize two potential sources of bias. Predictors that incorporate allele frequency as a predictive feature tend to have reduced performance when distinguishing pathogenic variants from very rare benign variants, and predictors supervised on pathogenicity labels from curated variant databases often learn label imbalances within genes. Overall, we find notable advances over the oldest and most cited missense variant effect predictors and continued improvements among the most recently developed tools, and the CAGI Annotate-All-Missense challenge (also termed the Missense Marathon) will continue to assess state-of-the-art methods as the field progresses. Together, our results help illuminate the current clinical and research utility of missense variant effect predictors and identify potential areas for future development.
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Genomic deep learning models can predict genome-wide epigenetic features and gene expression levels directly from DNA sequence. While current models perform well at predicting gene expression levels across genes in different cell types from the reference genome, their ability to explain expression variation between individuals due to cis-regulatory genetic variants remains largely unexplored. Here, we evaluate four state-of-the-art models on paired personal genome and transcriptome data and find limited performance when explaining variation in expression across individuals. In addition, models often fail to predict the correct direction of effect of cis-regulatory genetic variation on expression.
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Apprentissage profond , Transcriptome , Humains , Transcriptome/génétique , Variation génétique/génétique , Génome , GénomiqueRÉSUMÉ
BACKGROUND: Genetic variation in the human genome is a major determinant of individual disease risk, but the vast majority of missense variants have unknown etiological effects. Here, we present a robust learning framework for leveraging saturation mutagenesis experiments to construct accurate computational predictors of proteome-wide missense variant pathogenicity. RESULTS: We train cross-protein transfer (CPT) models using deep mutational scanning (DMS) data from only five proteins and achieve state-of-the-art performance on clinical variant interpretation for unseen proteins across the human proteome. We also improve predictive accuracy on DMS data from held-out proteins. High sensitivity is crucial for clinical applications and our model CPT-1 particularly excels in this regime. For instance, at 95% sensitivity of detecting human disease variants annotated in ClinVar, CPT-1 improves specificity to 68%, from 27% for ESM-1v and 55% for EVE. Furthermore, for genes not used to train REVEL, a supervised method widely used by clinicians, we show that CPT-1 compares favorably with REVEL. Our framework combines predictive features derived from general protein sequence models, vertebrate sequence alignments, and AlphaFold structures, and it is adaptable to the future inclusion of other sources of information. We find that vertebrate alignments, albeit rather shallow with only 100 genomes, provide a strong signal for variant pathogenicity prediction that is complementary to recent deep learning-based models trained on massive amounts of protein sequence data. We release predictions for all possible missense variants in 90% of human genes. CONCLUSIONS: Our results demonstrate the utility of mutational scanning data for learning properties of variants that transfer to unseen proteins.
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Apprentissage machine , Protéome , Humains , Protéome/génétique , Séquence d'acides aminés , Mutation , Mutation faux-sens , Biologie informatique/méthodesRÉSUMÉ
BACKGROUND: Serological methods to conduct epidemiological survey are often directed only against the spike protein. To overcome this limitation, we have designed PRAK-03202, a virus-like particle (VLP), by inserting three antigens (Spike, envelope and membrane) of SARS-CoV-2 into a highly characterized S. cerevisiae-based D-Crypt™ platform. METHODS: Dot blot analysis was performed to confirm the presence of S, E, and M proteins in PRAK-03202. The number of particles in PRAK-03202 was measured using nanoparticle tracking analysis (NTA). The sensitivity of VLP-ELISA was evaluated in 100 COVID positive. PRAK-03202 was produced at a 5 L scale using fed-batch fermentation. RESULTS: Dot blot confirmed the presence of S, E, and M proteins in PRAK-03202. The number of particles in PRAK-03202 was 1.21 × 109 mL-1. In samples collected >14 days after symptom onset, the sensitivity, specificity, and accuracy of VLP-ELISA were 96%. We did not observe any significant differences in sensitivity, specificity, and accuracy when post-COVID-19 samples were used as negative controls compared to pre-COVID-samples. At a scale of 5 L, the total yield of PRAK-03202 was 100-120 mg/L. CONCLUSION: In conclusion, we have successfully developed an in-house VLP-ELISA to detect IgG antibodies against three antigens of SARS-CoV-2 as a simple and affordable alternative test.
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Viral infectious diseases threaten human health and global stability. Several vaccine platforms, such as DNA, mRNA, recombinant viral vectors, and virus-like particle-based vaccines have been developed to counter these viral infectious diseases. Virus-like particles (VLP) are considered real, present, licensed and successful vaccines against prevalent and emergent diseases due to their non-infectious nature, structural similarity with viruses, and high immunogenicity. However, only a few VLP-based vaccines have been commercialized, and the others are either in the clinical or preclinical phases. Notably, despite success in the preclinical phase, many vaccines are still struggling with small-scale fundamental research owing to technical difficulties. Successful production of VLP-based vaccines on a commercial scale requires a suitable platform and culture mode for large-scale production, optimization of transduction-related parameters, upstream and downstream processing, and monitoring of product quality at each step. In this review article, we focus on the advantages and disadvantages of various VLP-producing platforms, recent advances and technical challenges in VLP production, and the current status of VLP-based vaccine candidates at commercial, preclinical, and clinical levels.
Sujet(s)
Développement de vaccin , Vaccins à pseudo-particules virales , HumainsRÉSUMÉ
Genomic sequence-to-activity models are increasingly utilized to understand gene regulatory syntax and probe the functional consequences of regulatory variation. Current models make accurate predictions of relative activity levels across the human reference genome, but their performance is more limited for predicting the effects of genetic variants, such as explaining gene expression variation across individuals. To better understand the causes of these shortcomings, we examine the uncertainty in predictions of genomic sequence-to-activity models using an ensemble of Basenji2 model replicates. We characterize prediction consistency on four types of sequences: reference genome sequences, reference genome sequences perturbed with TF motifs, eQTLs, and personal genome sequences. We observe that models tend to make high-confidence predictions on reference sequences, even when incorrect, and low-confidence predictions on sequences with variants. For eQTLs and personal genome sequences, we find that model replicates make inconsistent predictions in >50% of cases. Our findings suggest strategies to improve performance of these models.
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Iron (Fe) sequestration is one of the most important strategies of the host to control the growth and survival of invading pathogens. Ferritin (Ft) plays a pivotal role in the sequestration mechanism of mammalian hosts by storing Fe. Recent evidence suggests that poly(rC)-binding proteins (PCBPs) act as chaperones for loading Fe into Ft. Incidentally, modulation of host PCBPs in respect to storing Fe in Ft during any infection remains unexplored. Among PCBPs, PCBP1 and PCBP2 are present in every cell type and involved in interacting with Ft for Fe loading. Leishmania donovani (LD) resides within macrophages during the mammalian stage of infection, causing life-threatening visceral leishmaniasis. Here, we reveal the ability of LD to cleave PCBP1 and PCBP2 in host monocytes/macrophages. LD cleaves PCBP1-FLAG into two fragments and PCBP2-FLAG into multiple fragments, thus affecting their interactions with Ft and resulting in decreased Fe loading into Ft. LD-derived culture supernatant or exosome-enriched fractions are also able to cleave PCBPs, suggesting involvement of a secreted protease of the parasite. Using an immune-depletion experiment and transgenic mutants, we confirmed the involvement of zinc-metalloprotease GP63 in cleaving PCBPs. We further revealed that by cleaving host PCBPs, Leishmania could inhibit Fe loading into Ft to accumulate available Fe for higher intracellular growth. This is the first report of a novel strategy adopted by a mammalian pathogen to interfere with Fe sequestration into Ft by cleaving chaperones for its survival advantage within the host.
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Ferritines , Fer , Leishmania donovani , Leishmaniose viscérale , Chaperons moléculaires , Animaux , Ferritines/métabolisme , Fer/métabolisme , Leishmania donovani/métabolisme , Macrophages/métabolisme , Chaperons moléculaires/métabolisme , Protéines de liaison à l'ADN/métabolisme , SourisRÉSUMÉ
Stopgain substitutions are the third-largest class of monogenic human disease mutations and often examined first in patient exomes. Existing computational stopgain pathogenicity predictors, however, exhibit poor performance at the high sensitivity required for clinical use. Here, we introduce a new classifier, termed X-CAP, which uses a novel training methodology and unique feature set to improve the AUROC by 18% and decrease the false-positive rate 4-fold on large variant databases. In patient exomes, X-CAP prioritizes causal stopgains better than existing methods do, further illustrating its clinical utility. X-CAP is available at https://github.com/bejerano-lab/X-CAP .
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Exome , Logiciel , Biologie informatique/méthodes , Humains , Mutation , Mutation faux-sens , VirulenceRÉSUMÉ
The rapid development of safe and effective vaccines against severe acute respiratory syndrome coronavirus 2 (SARS CoV-2) is a necessary response to coronavirus outbreak. Here, we developed PRAK-03202, the world's first triple antigen virus-like particle vaccine candidate, by cloning and transforming SARS-CoV-2 gene segments into a highly characterized S. cerevisiae-based D-Crypt™ platform, which induced SARS CoV-2 specific neutralizing antibodies in BALB/c mice. Immunization using three different doses of PRAK-03202 induced an antigen-specific (spike, envelope, and membrane proteins) humoral response and neutralizing potential. Peripheral blood mononuclear cells from convalescent patients showed lymphocyte proliferation and elevated interferon levels suggestive of epitope conservation and induction of T helper 1-biased cellular immune response when exposed to PRAK-03202. These data support further clinical development and testing of PRAK-03202 for use in humans.
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[This corrects the article DOI: 10.1016/j.heliyon.2021.e08124.].
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Leishmania internalize hemoglobin (Hb) via a specific receptor (HbR) for their survival. To identify the Hb-binding domain of HbR, we cloned and expressed several truncated proteins of HbR and determined their ability to bind Hb. Our findings reveal that 90% of Hb-binding activity is retained in HbR41-80 in comparison with HbR1-471 . We synthesized a 40 amino acid peptide (SSEKMKQLTMYMIHEMVEGLEGRPSTVRMLPSFVYTSDPA) corresponding to HbR41-80 and found that it specifically binds Hb. Subsequently, we found that the HbR41-80 peptide completely blocks Hb uptake in both promastigote and amastigote forms of Leishmania and, thereby, inhibits the growth of the parasite. These results demonstrate that HbR41-80 is the Hb-binding domain of HbR, which might be used as a potential therapeutic agent to inhibit the growth of Leishmania.
Sujet(s)
Antiprotozoaires/métabolisme , Hémoglobines/composition chimique , Leishmania donovani/métabolisme , Étapes du cycle de vie/génétique , Peptides/métabolisme , Protéines de protozoaire/composition chimique , Récepteurs de surface cellulaire/composition chimique , Séquence d'acides aminés , Antiprotozoaires/synthèse chimique , Antiprotozoaires/pharmacologie , Fixation compétitive , Clonage moléculaire , Escherichia coli/génétique , Escherichia coli/métabolisme , Expression des gènes , Vecteurs génétiques/composition chimique , Vecteurs génétiques/métabolisme , Hémoglobines/métabolisme , Leishmania donovani/effets des médicaments et des substances chimiques , Leishmania donovani/génétique , Leishmania donovani/croissance et développement , Étapes du cycle de vie/effets des médicaments et des substances chimiques , Modèles moléculaires , Peptides/synthèse chimique , Peptides/pharmacologie , Liaison aux protéines , Structure en hélice alpha , Structure en brin bêta , Motifs et domaines d'intéraction protéique , Protéines de protozoaire/génétique , Protéines de protozoaire/métabolisme , Récepteurs de surface cellulaire/génétique , Récepteurs de surface cellulaire/métabolisme , Protéines recombinantes/composition chimique , Protéines recombinantes/génétique , Protéines recombinantes/métabolisme , Similitude structurale de protéinesRÉSUMÉ
Previously, we showed that Rab5a and Rab5b differentially regulate fluid-phase and receptor-mediated endocytosis in Leishmania, respectively. To unequivocally demonstrate the role of Rab5b in hemoglobin endocytosis in Leishmania, we generated null-mutants of Rab5b parasites by sequentially replacing both copies of LdRab5b with the hygromycin and neomycin resistance gene cassettes. LdRab5b-/- null-mutant parasite was confirmed by qPCR analysis of genomic DNA using LdRab5b specific primers. LdRab5b-/- cells showed severe growth defect indicating essential function of LdRab5b in parasite. To characterize the role of Rab5b in Hb endocytosis in parasites, LdRab5b-/- cells were rescued by exogenous addition of hemin in growth medium. Our results showed that LdRab5b-/- cells are relatively smaller in size. Ultrastructural analysis revealed the presence of relatively enlarged flagellar pocket and bigger intracellular vesicles in these cells in comparison to control cells. Both promastigotes and amastigotes of Rab5b null-mutant parasites were unable to internalize Hb but fluid phase endocytosis of different markers was not affected. However, complementation of LdRab5b:WT in LdRab5b-/- cells (LdRab5b-/-:pRab5b:WT) rescued Hb internalization in these cells. Interestingly, LdRab5b-/- cells showed significantly less Hb-receptor on cell surface in comparison to control cells indicating a block in HbR trafficking. Finally, we showed that LdRab5b-/- parasites can infect the macrophages but are unable to survive after 96 h of infection in comparison to control cells. However, supplementation of hemin in the growth medium significantly rescued LdRab5b-/-Leishmania survival in macrophage indicating that LdRab5b function is essential for the acquisition of heme from internalized Hb for the survival of Leishmania.
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Hème/génétique , Leishmania donovani/génétique , Leishmaniose viscérale/génétique , Protéines G rab5/génétique , Séquence d'acides aminés/génétique , Animaux , Endocytose/génétique , Techniques de knock-out de gènes , Hémoglobines/génétique , Humains , Leishmania donovani/pathogénicité , Leishmaniose viscérale/parasitologie , Transport des protéines/génétiqueRÉSUMÉ
Leishmania donovani possess two isoforms of Rab5 (Rab5a and Rab5b), which are involved in fluid phase and receptor-mediated endocytosis, respectively. We have characterized the solution structure and dynamics of a stabilized truncated LdRab5a mutant. For the purpose of NMR structure determination, protein stability was enhanced by systematically introducing various deletions and mutations. Deletion of hypervariable C-terminal and the 20 residues LdRab5a specific insert slightly enhanced the stability, which was further improved by C107S mutation. The final construct, truncated LdRab5a with C107S mutation, was found to be stable for longer durations at higher concentration, with an increase in melting temperature by 10°C. Solution structure of truncated LdRab5a shows the characteristic GTPase fold having nucleotide and effector binding sites. Orientation of switch I and switch II regions match well with that of guanosine 5'-(ß, γ-imido)triphosphate (GppNHp)-bound human Rab5a, indicating that the truncated LdRab5a attains the canonical GTP bound state. However, the backbone dynamics of the P-loop, switch I, and switch II regions were slower than that observed for guanosine 5'-(ß, γ-imido)triphosphate (GMPPNP)-bound H-Ras. This dynamic profile may further complement the residue-specific complementarity in determining the specificity of interaction with the effectors. In parallel, biophysical investigations revealed the urea induced unfolding of truncated LdRab5a to be a four-state process that involved two intermediates, I1 and I2. The maximal 4,4'-dianilino-1,1'-binaphthyl-5,5'-disulfonic acid (Bis-ANS) binding was observed for I2 state, which was inferred to have molten globule like characteristics. Overall, the strategy presented would have significant impact for studying other Rab and small GTPase proteins by NMR spectroscopy.
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Leishmania donovani , Protéines G rab5/composition chimique , Protéines G rab5/métabolisme , Modèles moléculaires , Résonance magnétique nucléaire biomoléculaire , Conformation des protéines , Stabilité protéique , Dépliement des protéines , Alignement de séquences , Délétion de séquence , Température , Protéines G rab5/génétiqueRÉSUMÉ
Several intracellular pathogens arrest the phagosome maturation in the host cells to avoid transport to lysosomes. In contrast, the Leishmania containing parasitophorous vacuole (PV) is shown to recruit lysosomal markers and thus Leishmania is postulated to be residing in the phagolysosomes in macrophages. Here, we report that Leishmania donovani specifically upregulates the expression of Rab5a by degrading c-Jun via their metalloprotease gp63 to downregulate the expression of miR-494 in THP-1 differentiated human macrophages. Our results also show that miR-494 negatively regulates the expression of Rab5a in cells. Subsequently, L. donovani recruits and retains Rab5a and EEA1 on PV to reside in early endosomes and inhibits transport to lysosomes in human macrophages. Similarly, we have also observed that Leishmania PV also recruits Rab5a by upregulating its expression in human PBMC differentiated macrophages. However, the parasite modulates the endosome by recruiting Lamp1 and inactive pro-CathepsinD on PV via the overexpression of Rab5a in infected cells. Furthermore, siRNA knockdown of Rab5a or overexpression of miR-494 in human macrophages significantly inhibits the survival of the parasites. These results provide the first mechanistic insights of parasite-mediated remodeling of endo-lysosomal trafficking to reside in a specialized early endocytic compartment.
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Endosomes/parasitologie , Leishmania donovani/physiologie , Agranulocytes/parasitologie , Macrophages/parasitologie , microARN/génétique , Protéines G rab5/métabolisme , Animaux , Régulation négative , Endosomes/microbiologie , Humains , Lysosomes/métabolisme , Phagosomes/microbiologie , Activation de la transcription/génétique , Régulation positive , Vacuoles/parasitologieRÉSUMÉ
The role of GDP dissociation inhibitor (GDI) protein in regulation of Rab cycle in Leishmania is not known. Here, we have cloned and characterized the functions of GDI homologue in vivo in Leishmania. Our results have shown that LdGDI:WT along with GDP removes the Rab5 from purified endosomes and inhibits the homotypic fusion between early endosomes. Whereas, LdGDI:R239A, a dominant negative mutant of GDI, under the same condition neither removes the Rab5 from endosome nor inhibits fusion. To determine the role of Ld-GDI in vivo, transgenic parasites overexpressing GFP-LdGDI:WT or GFP-LdGDI:R239A, are co-expressed with RFP-LdRab5:WT, RFP-LdRab7:WT or RFP-LdRab1:WT. Our results have shown that overexpression of GFP-LdGDI:WT extracts the RFP-LdRab5, RFP-LdRab7 or RFP-LdRab1 from their discrete endomembrane predominantly into cytosol. No change in the distribution of indicated Rabs is detected with overexpression of GFP-LdGDI:R239A. To determine the functional significance, we have used hemoglobin as an endocytic marker and gp63 as a marker for secretory pathway. We have found that overexpression of GFP-LdGDI:WT enhances the lysosomal targeting of internalized hemoglobin and the secretion of gp63 in the parasites possibly by triggering Rab cycle. This is the first demonstration of a single GDI ubiquitously regulating both endocytic and secretory pathways in Leishmania.
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Endocytose/physiologie , Endosomes/métabolisme , Inhibiteurs de la dissociation de nucléotides guanyliques/métabolisme , Leishmania donovani/métabolisme , Metalloendopeptidases/métabolisme , Protéines de protozoaire/métabolisme , Endosomes/génétique , Inhibiteurs de la dissociation de nucléotides guanyliques/génétique , Leishmania donovani/génétique , Metalloendopeptidases/génétique , Micro-organismes génétiquement modifiés/génétique , Micro-organismes génétiquement modifiés/métabolisme , Protéines de protozoaire/génétique , Protéines G rab5/génétique , Protéines G rab5/métabolismeRÉSUMÉ
Differential functions of Rab5 isoforms in endocytosis are not well characterized. Here, we cloned, expressed, and characterized Rab5a and Rab5b from Leishmania and found that both of them are localized in the early endosome. To understand the role of LdRab5 isoforms in different modes of endocytosis in Leishmania, we generated transgenic parasites overexpressing LdRab5a, LdRab5b, or their dominant-positive (LdRab5a:Q93L and LdRab5b:Q80L) or dominant-negative mutants (LdRab5a:N146I and LdRab5b:N133I). Using LdRab5a or its mutants overexpressing parasites, we found that LdRab5a specifically regulates the fluid-phase endocytosis of horseradish peroxidase and also specifically induced the transport of dextran-Texas Red to the lysosomes. In contrast, cells overexpressing LdRab5b or its mutants showed that LdRab5b explicitly controls receptor-mediated endocytosis of hemoglobin, and overexpression of LdRab5b:WT enhanced the transport of internalized Hb to the lysosomes in comparison with control cells. To unequivocally demonstrate the role of Rab5 isoforms in endocytosis in Leishmania, we tried to generate null-mutants of LdRab5a and LdRab5b parasites, but both were lethal indicating their essential functions in parasites. Therefore, we used heterozygous LdRab5a(+/-) and LdRab5b(+/-) cells. LdRab5a(+/-) Leishmania showed 50% inhibition of HRP uptake, but hemoglobin endocytosis was uninterrupted. In contrast, about 50% inhibition of Hb endocytosis was observed in LdRab5b(+/-) cells without any significant effect on HRP uptake. Finally, we tried to identify putative LdRab5a and LdRab5b effectors. We found that LdRab5b interacts with clathrin heavy chain and hemoglobin receptor. However, LdRab5a failed to interact with the clathrin heavy chain, and interaction with hemoglobin receptor was significantly less. Thus, our results showed that LdRab5a and LdRab5b differentially regulate fluid phase and receptor-mediated endocytosis in Leishmania.
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Endocytose/physiologie , Leishmania donovani/métabolisme , Isoformes de protéines/physiologie , Protéines G rab5/physiologie , Séquence d'acides aminés , Animaux , Mutation , Similitude de séquences d'acides aminés , Protéines G rab5/composition chimique , Protéines G rab5/génétiqueRÉSUMÉ
The purpose of this study was to modulate macrophage polarity from the pro-inflammatory M1 to anti-inflammatory M2 phenotype using plasmid DNA (pDNA) expressing interleukin-4 (IL4) or interleukin-10 (IL10)-encapsulated in hyaluronic acid-poly(ethyleneimine) (HA-PEI) nanoparticles (NPs). The HA-PEI/pDNA NPs with spherical shape, average size of 186 nm were efficiently internalized by J774A.1 macrophages. Transfection of HA-PEI/pDNA-IL4 and HA-PEI/pDNA-IL10 NPs increased IL4 and IL10 gene expression in J774 macrophages which could re-program the macrophages from M1 to M2 phenotype as evidenced by a significant increase in the Arg/iNOS level, and upregulation of CD206 and CD163 compared to untreated macrophages. Following intraperitoneal (IP) injection to C57BL/6 mice, HA-PEI NPs effectively targeted peritoneal macrophages over-expressing CD44 receptor. In an in vivo model of stimulated peritoneal macrophages, IP administration of HA-PEI/pDNA-IL4 and HA-PEI/pDNA-IL10 to C57BL/6 mice significantly increased the Arg/iNOS ratio and CD163 expression in the cells. Furthermore, HA-PEI/pDNA-IL10 NPs significantly increased peritoneal and serum IL10 levels which effectively suppressed LPS-induced inflammation by reducing level of TNF-α and IL-1ß in peritoneal macrophages and in the peritoneal fluid. The results demonstrated that pDNA-IL10-encapsulate HA-PEI NPs skewed macrophage functional polarity from M1 toward an anti-inflammatory M2 phenotype which may be a promising platform for the treatment of inflammatory diseases.
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Antigènes CD44/métabolisme , Acide hyaluronique , Macrophages/immunologie , Macrophages/métabolisme , Nanoparticules , Phénotype , Plasmides/génétique , Animaux , Cytokines/métabolisme , Expression des gènes , Acide hyaluronique/composition chimique , Médiateurs de l'inflammation/métabolisme , Interleukine-10/génétique , Interleukine-4/génétique , Macrophages péritonéaux/immunologie , Macrophages péritonéaux/métabolisme , Souris , Souris de lignée C57BL , Nanoparticules/composition chimique , TransfectionRÉSUMÉ
Leishmaniasis is a severe infectious disease. Drugs used for leishmaniasis are very toxic, and no vaccine is available. We found that the hemoglobin receptor (HbR) of Leishmania was conserved across various strains of Leishmania, and anti-HbR antibody could be detected in kala-azar patients' sera. Our results showed that immunization with HbR-DNA induces complete protection against virulent Leishmania donovani infection in both BALB/c mice and hamsters. Moreover, HbR-DNA immunization stimulated the production of protective cytokines like interferon-γ (IFN-γ), interleukin-12 (IL-12), and tumor necrosis factor-α (TNF-α) with concomitant down-regulation of disease-promoting cytokines like IL-10 and IL-4. HbR-DNA vaccination also induced a protective response by generating multifunctional CD4(+) and CD8(+) T cells. All HbR-DNA-vaccinated hamsters showed sterile protection and survived during an experimental period of 8 months. These findings demonstrate the potential of HbR as a vaccine candidate against visceral leishmaniasis.
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ADN/immunologie , Leishmania donovani/immunologie , Leishmaniose viscérale/immunologie , Leishmaniose viscérale/prévention et contrôle , Protéines de protozoaire/immunologie , Récepteurs de surface cellulaire/immunologie , Vaccination , Animaux , Lymphocytes T CD8+/immunologie , Prolifération cellulaire , Séquence conservée , Cricetinae/immunologie , Cricetinae/parasitologie , Humains , Immunité/immunologie , Immunoglobuline G/biosynthèse , Leishmania donovani/croissance et développement , Leishmania donovani/pathogénicité , Leishmaniose viscérale/parasitologie , Souris , Souris de lignée BALB C , Lymphocytes auxiliaires Th1/immunologieRÉSUMÉ
Leishmania is auxotroph for heme. Previously, we have shown that Leishmania acquire heme from the degradation of endocytosed hemoglobin via a specific receptor located in the flagellar pocket. Here, we report the cloning and expression of clathrin heavy chain from Leishmania (Ld-CHC) and provide evidences that Ld-CHC is localized in flagellar pocket and regulates Hb-endocytosis in Leishmania. Kinetic analysis of Hb trafficking in GFP-Ld-CHC overexpressed Leishmania reveals that Hb is internalized through Ld-CHC coated region and remains associated with Ld-CHC containing vesicles at early time points of internalization and subsequently starts dissociating from Hb-containing vesicles at later time points indicating that clathrin-coating and uncoating regulate Hb trafficking in Leishmania. Interestingly, overexpression of dominant negative mutant of clathrin heavy chain of Leishmania (GFP-Ld-CHC-Hub) blocks the Hb internalization and causes severe growth defect in parasite. Moreover, we have shown that chlorpromazine, a pharmacological agent, blocks Hb internalization in Leishmania by depolymerizing Ld-CHC and thereby inhibits the growth of the parasites. Taken together, our results have shown that Hb endocytosis in Leishmania is a clathrin dependent process and is essential for the survival of the parasites.
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Chaines lourdes de la clathrine , Endocytose , Leishmania , Séquence d'acides aminés , Chlorpromazine/pharmacologie , Chaines lourdes de la clathrine/génétique , Chaines lourdes de la clathrine/métabolisme , Clonage moléculaire , Endocytose/effets des médicaments et des substances chimiques , Endocytose/génétique , Expression des gènes/effets des médicaments et des substances chimiques , Hème/métabolisme , Hémoglobines/métabolisme , Cinétique , Leishmania/génétique , Leishmania/métabolisme , Leishmania/parasitologie , Données de séquences moléculairesRÉSUMÉ
Several intracellular pathogens have developed diverse strategies to avoid targeting to lysosomes. However, they universally recruit lysosome-associated membrane protein 1 (LAMP1); the mechanism of LAMP1 recruitment remains unclear. Here, we report that a Salmonella effector protein, SipC, specifically binds with host Syntaxin6 through its C terminus and thereby recruits Syntaxin6 and other accessory molecules like VAMP2, Rab6, and Rab8 on Salmonella-containing phagosomes (SCP) and acquires LAMP1 by fusing with LAMP1-containing Golgi-derived vesicles. In contrast, sipC knock-out:SCP (sipC(-):SCP) or sipC(M398K):SCP fails to obtain significant amounts of Syntaxin6 and is unable to acquire LAMP1. Moreover, phagosomes containing respective knock-out Salmonella like sipA(-), sipB(-), sipD(-), sopB(-), or sopE(-) recruit LAMP1, demonstrating the specificity of SipC in this process. In addition, depletion of Syntaxin6 by shRNA in macrophages significantly inhibits LAMP1 recruitment on SCP. Additionally, survival of sipC(-):Salmonella in mice is found to be significantly inhibited in comparison with WT:Salmonella. Our results reveal a novel mechanism showing how Salmonella acquires LAMP1 through a SipC-Syntaxin6-mediated interaction probably to stabilize their niche in macrophages and also suggest that similar modalities might be used by other intracellular pathogens to recruit LAMP1.