Biology subjects

Tolia, N. H.

Publications and source records attributed to Tolia, N. H..

8 recordsLinked to original sources

bioRxiv2026

Comprehensive characterization of Plasmodium vivax antigens using a high-density peptide array

Plasmodium vivax is the second most prevalent Plasmodium species, with 2.5 billion people at risk of infection worldwide and around 10 million cases of clinical vivax malaria every year. Despite the clinical importance of this pathogen, very little is known about the P. vivax proteins recognized by the host immune system, which hinders our ability to select vaccine candidates or develop efficient serological markers. To comprehensively characterize immunogenic P. vivax proteins, we designed a high-density peptide array containing 4.2 million peptides covering the entire protein sequence of all P. vivax genes and analyzed antibody responses of infected and malaria-naive individuals. We identified a total of 283 proteins that are commonly immunogenic in symptomatic individuals. These proteins included most proteins known to be involved in erythrocyte invasion, a putative new invasion protein, several nucleoporins, and many uncharacterized proteins that should be further investigated for their roles during blood-stage infections. These analyses also revealed a unique pattern of antibody response against PIR proteins in asymptomatic individuals, that could be associated with protection against clinical vivax malaria. Overall, these data provide an agnostic and comprehensive perspective on immunogenic P. vivax proteins and constitute an important resource for the malaria community to develop new tools for better detecting and eliminating this important human pathogen.

microbiology↗

bioRxiv2025

Plasmodium falciparum exploits NUAK1 to establish infection in human erythrocytes

The malaria parasite Plasmodium falciparum continues to demonstrate growing drug resistance, raising the need for innovative treatments. Host-directed therapeutics are emerging as a promising approach for many infectious diseases, but knowledge of critical host factors for malaria is limited. P. falciparum is an obligate intracellular parasite of human erythrocytes, suggesting it has evolved to exploit specific host pathways to establish infection. Here, we report that the AMPK-related kinase NUAK1 is a critical host factor for P. falciparum in erythrocytes and has potential as a therapeutic target. We show that NUAK1 is present in human erythrocytes and undergoes increased phosphorylation in P. falciparum-infected cells. Two highly selective NUAK1 inhibitors, HTH-01-015 and WZ4003, inhibited P. falciparum growth throughout its asexual life cycle, including during erythrocyte invasion. Chemoproteomic profiling confirmed the inhibitors selectivity for human NUAK1. We further show that treatment with the inhibitors reduces phosphorylation of the well-characterized NUAK1 substrate MYPT1 in erythroid cells. Moreover, we find that genetic overexpression of NUAK1 in erythroid cells partially rescues both the signaling and invasion phenotypes elicited by the small molecule inhibitors. These results establish a critical role for the NUAK1 signaling pathway in P. falciparum-infected erythrocytes and highlight its potential as a vulnerable target for host-directed malaria control.

microbiology↗

bioRxiv2025

CD44 cross-linking promotes Plasmodium falciparum invasion

The ability of the malaria parasite Plasmodium falciparum to invade and replicate asexually within human red blood cells (RBCs) is central to its pathogenicity, accounting for hundreds of thousands of deaths each year. RBC invasion is a multi-step process involving several host-parasite interactions, yet the host factors acting during invasion remain underexplored, largely due to the intractability of mature enucleated RBCs. The transmembrane protein CD44 was identified as a host factor for P. falciparum invasion through a forward genetic screen using genetically modified RBCs derived from primary human hematopoietic stem cells. Here, we identify an anti-CD44 monoclonal antibody, BRIC 222, that significantly promotes P. falciparum invasion, and demonstrate that its effect is mediated through CD44 cross-linking. CD44 cross-linking induced changes in the phosphorylation of RBC cytoskeletal proteins, consistent with a proposed role for CD44 as a co-receptor during invasion. CD44 cross-linking also altered the RBC membrane, increasing the accessibility of several surface proteins, including the essential invasion receptor Basigin. The parasite ligand Erythrocyte Binding Antigen-175 (EBA-175), which interacts with CD44, enhanced P. falciparum invasion and induced RBC membrane changes similarly to BRIC 222. Moreover, both BRIC 222 and EBA-175 increased binding of the PfRH5/PCRCR invasion complex to Basigin, an interaction known to be essential for invasion. We propose that CD44 cross-linking, potentially by EBA-175, serves to coordinate and enhance downstream ligand-receptor interactions and to promote signaling to the host cell cytoskeleton, making RBCs more permissive to P. falciparum invasion.

microbiology↗

bioRxiv2023

Plasmodium falciparum exploits CD44 as a co-receptor for erythrocyte invasion

The malaria parasite Plasmodium falciparum invades and replicates asexually within human erythrocytes. CD44 expressed on erythrocytes was previously identified as an important host factor for P. falciparum infection through a forward genetic screen, but little is known about its regulation or function in these cells, nor how it may be utilized by the parasite. We found that CD44 can be efficiently deleted from primary human hematopoietic stem cells using CRISPR/Cas9 genome editing, and that the efficiency of ex-vivo erythropoiesis to enucleated cultured red blood cells (cRBCs) is not impacted by lack of CD44. However, the rate of P. falciparum invasion was substantially reduced in CD44-null cRBCs relative to isogenic wild-type (WT) control cells, validating CD44 as an important host factor for this parasite. We identified two P. falciparum invasion ligands as binding partners for CD44, Erythrocyte Binding Antigen-175 (EBA-175) and EBA-140, and demonstrated that their ability to bind to human erythrocytes relies primarily on their canonical receptors-glycophorin A and glycophorin C, respectively. We further show that EBA-175 induces phosphorylation of erythrocyte cytoskeletal proteins in a CD44-dependent manner. Our findings support a model where P. falciparum exploits CD44 as a co-receptor during invasion of human erythrocytes, stimulating CD44-dependent phosphorylation of host cytoskeletal proteins that alter host cell deformability and facilitate parasite entry.

microbiology↗

bioRxiv2022

Conformational flexibility, lipid binding, and regulatory domains in CelTOS

CelTOS is an essential Plasmodium traversal protein and conserved in apicomplexan parasites. We showed that CelTOS forms pores in cell membranes to enable traversal of parasites through cells (Jimah et al., 2016). Here, we establish roles for the distinct regions of CelTOS, examine the mechanism of pore formation and evaluate the immunogenicity of engineered CelTOS variants. CelTOS dimer dissociation is required for pore formation as disulfide bridging between monomers inhibits pore formation and this inhibition is rescued by disulfide-bridge reduction. A helix destabilizing Pro127 allows CelTOS to undergo significant conformational changes to assemble into pores. The flexible C-terminus of CelTOS is a negative regulator that limits pore formation. Lipid binding is a pre-requisite for pore assembly as mutation of a phospholipid binding site in CelTOS resulted in loss of lipid binding and abrogated pore formation. The disulfide-locked and N-terminal deletion mutants showed improved immunogenicity relative to wild-type CelTOS in mice. These findings have implications for pore-forming proteins that are essential for diverse functions, identify critical regions in CelTOS, and will guide the design of effective CelTOS-targeting vaccines to combat infection and transmission of malaria and apicomplexan parasites.

microbiology↗

bioRxiv2022

Inhibition of a critical malaria host-pathogen interaction by a computationally designed inhibitor targeting Plasmodium vivax DBP

Malaria is a substantial global health burden with 229 million cases in 2019 and 450,000 deaths annually. Plasmodium vivax is the most widespread malaria-causing parasite putting 2.5 billion people at risk of infection. P. vivax has a dormant liver stage and therefore can exist for long periods undetected. Its blood-stage can cause severe reactions and hospitalization. Few treatment and detection options are available for this pathogen. To address this need, we developed nanomolar inhibitor that could serve as a therapeutic and a diagnostic. A unique characteristic of P. vivax is that it depends on the Duffy antigen/Receptor for chemokines (DARC) on the surface of host red blood cells for invasion. P. vivax employs the Duffy binding protein (DBP) to bind to DARC. We first de novo designed a three helical bundle scaffolding database which was screened via protease digestions for stability. Protease-resistant scaffolds highlighted thresholds for stability, which we utilized for selecting DARC mimetics that we subsequentially designed through grafting and redesign of these scaffolds. The optimized design small helical protein disrupts the DBP:DARC interaction. The inhibitor blocks the receptor binding site on DBP and thus forms a strong foundation for a therapeutic that will inhibit reticulocyte infection and prevent the pathogenesis of P. vivax malaria. TeaserDe novo designed proteins present a new alternative for the development of therapeutics. They can be small, highly stable and easily manufactured. Here we designed a potential new therapeutic to inhibit entry of Plasmodium vivax into red blood cells by interfering its interactions of surface displayed DBP molecules with the host receptor DARC.

bioengineering↗

bioRxiv2021

Design of the SARS-CoV-2 RBD vaccine antigen improves neutralizing antibody response

The receptor binding domain (RBD) of the SARS-CoV-2 spike protein is the primary target of neutralizing antibodies and is a component of almost all vaccine candidates. Here, RBD immunogens were created with stabilizing amino acid changes that improve the neutralizing antibody response, as well as characteristics for production, storage, and distribution. A computational design and in vitro screening platform identified three improved immunogens, each with approximately nine amino acid changes relative to the native RBD sequence and four key changes conserved between immunogens. The changes are adaptable to all vaccine platforms, are compatible with established changes in SARS-CoV-2 vaccines, and are compatible with mutations in emerging variants of concern. The immunogens elicit higher levels of neutralizing antibodies than native RBD, focus the immune response to structured neutralizing epitopes, and have increased production yields and thermostability. Incorporating these variant-independent amino acid changes in next-generation vaccines may enhance the neutralizing antibody response and lead to pan-SARS-CoV-2 protection.

molecular biology↗

bioRxiv2018

Duffy Antigen Expression in Erythroid Bone Marrow Precursor Cells of Genotypically Duffy Negative Individuals

The gene encoding the Duffy blood group protein (Fy, CD234; additional designations Duffy Antigen Receptor of Chemokines [DARC] and Atypical Chemokine Receptor 1 [ACKR1]) is characterized by a SNP in a GATA-1 transcription factor binding site associated with the erythrocyte silent (ES) phenotype. FYES homozygous people are viewed to be highly resistant to blood stage infection with Plasmodium vivax. Increasingly, however, studies are reporting P. vivax infections in Fy-negative individuals across malarious African countries where FYES approaches genetic fixation. This suggests that P. vivax has evolved a Fy-independent RBC invasion pathway, or that the GATA-1 SNP does not abolish Fy expression. Here, we tested the second hypothesis through binding studies to erythroid lineage cells using recombinant P. vivax Duffy binding protein, the parasites invasion ligand and Fy6-specific antibodies. We first observed variable Fy expression on circulating RBCs, irrespective of FY genotype; FYES RBCs were periodically Fy-positive. Furthermore, during the in vitro erythroid differentiation of CD34+ cells and on ex vivo bone marrow samples, we observed Fy expression on erythroid precursor cells from FYES people. Finally, the Fy6-specific nanobody, CA111 was used to capture Fy from the surface of FYES RBCs. Our findings reveal that the GATA-1 SNP does not fully abolish Fy expression and provide insight on potential susceptibility of Fy-negative people to vivax malaria.\n\nSignificanceDuffy blood group negativity results from a single nucleotide polymorphism (SNP) in the gene promoter, and reaches genetic fixation in many African ethnicities. Because the Duffy protein (Fy) is an important contact point during Plasmodium vivax human red blood cell invasion, Fy-negativity is considered to confer resistance to P. vivax malaria. With recent studies in African countries reporting P. vivax infection in Fy-negative people, we studied Fy expression across erythroid development. Here we report that the FY promoter SNP does not abolish Fy protein expression in erythroid progenitors developing in the bone marrow. These results further emphasizes the importance of reticulocytes as targets for P. vivax blood stage infection and propose a mechanism for P. vivax infections in Fy-negative people.

genetics↗