Biology subjects

Jamwal, A.

Publications and source records attributed to Jamwal, A..

8 recordsLinked to original sources

bioRxiv2026

The helminth-derived effector protein HpBARI trimerises to selectively target membrane bound ST2 receptor

The ST2 receptor is activated by the alarmin cytokine IL-33, inducing and controlling immune responses. ST2-mediated signalling contributes to protection from parasitic infection, but is also involved in asthma, inflammatory bowel disease, fibrosis and allergic inflammation, making inhibitors of ST2 desirable. While signalling is mediated by membrane-associated ST2 on immune cells, extracellular fluids also contain a soluble form of ST2 which acts as a decoy, soaking up IL-33. An effective ST2-targeting therapeutic will selectively target membrane-associated ST2. The intestinal helminth H. polygyrus bakeri suppresses ST2-mediated signalling to reduce helminth clearance from the gut, with the effector HpBARI2 directly binding to and inhibiting ST2. Here, we present the structure of the ST2:HpBARI2 complex. HpBARI2 forms a stable, planar trimeric structure, with three vertices each binding a single ST2. HpBARI2 occludes the IL-33 binding site of ST2 and constraints the receptor in a conformation incompatible with recruitment of signalling co-receptor IL-1RAcP. The trimeric valency of HpBARI2 results in preferential binding to multiple membrane-associated ST2 molecules rather than the soluble decoy receptor. Therefore, HpBARI2 combines steric blockade, conformational restriction and multivalent binding to potently and selectively inhibit ST2 signalling in the context of soluble ST2. This insight will guide design of improved therapeutics which target ST2.

immunology↗

bioRxiv2026

Evolutionary adaptation of helminth immunomodulators to their hosts

Background: Parasitic nematodes have evolved secreted effector proteins which interact with host molecules to modulate the host immune response. These interactions can be highly specific and are under strong selective pressure. Here, we investigate the host-pathogen interaction between Heligmosomoides bakeri and its natural host Mus musculus, and between H. polygyrus and its natural host Apodemus sylvaticus. We focus on the Alarmin Release Inhibitor family (previously called HpARI) produced by heligmosomid parasites, which interact with IL-33 and heparan sulphate. Results: Using comparative genomics, we identified duplications and diversifications of the ARI family including multiple copies of ARI1 and conserved ARI3 homologues in both H. bakeri and H. polygyrus. We identify a new family member, HpolARI4, encoded by H. polygyrus, as well as a more distant homologue, HmixARI, encoded by Heligmosomum mixtum, a parasite of the bank vole (Myodes glareolus). Our functional assays identify that HpolARI4 preferentially blocks A. sylvaticus IL-33 but has little activity against M. musculus IL-33, whereas HbakARI2 is highly specific for M. musculus IL-33. We furthermore show differential interaction with host heparan sulphate, with HbakARI2 and HpolARI4 showing high affinity binding, whereas HbakARI3 shows no binding. We further test this family against non-host human IL-33 and show that functional suppression can be achieved by HbakARI3 in vitro and in vivo. Conclusion: By integrating genomic data, structural insights, and functional assays, we reveal how the expansion and diversification of the ARI family drive host-specific IL-33 modulation, providing a molecular model for nematode-host co-evolution.

immunology↗

bioRxiv2024

Heparan sulphate binding controls in vivo half-life of the HpARI protein family

The parasitic nematode Heligmosomoides polygyrus bakeri secretes the HpARI family, which bind to IL-33, either suppressing (HpARI1 and HpARI2) or enhancing (HpARI3) responses to the cytokine. We previously showed that HpARI2 also bound to DNA via its first Complement Control Protein (CCP1) domain. Here, we find that HpARI1 can also bind DNA, while HpARI3 cannot. Through the production of HpARI2/HpARI3 CCP1 domain-swapped chimeras, DNA-binding ability can be transferred, and correlates with in vivo half-life of administered proteins. We found that HpARI1 and HpARI2 (but not HpARI3) also binds to the extracellular matrix component heparan sulphate (HS), and structural modelling showed a basic charged patch in the CCP1 domain of HpARI1 and HpARI2 (but not HpARI3) which could facilitate these interactions. Finally, a mutant of HpARI2 was produced which lacked DNA and HS binding, and was also shown to have a short half-life in vivo. Therefore, we propose that during infection the suppressive HpARI1 and HpARI2 proteins have long-lasting effects at the site of deposition due to DNA and/or extracellular matrix interactions, while HpARI3 has a shorter half-life due to a lack of these interactions.

immunology↗

bioRxiv2023

IL-33-binding HpARI family homologues with divergent effects in suppressing or enhancing Type 2 immune responses

HpARI is an immunomodulatory protein secreted by the intestinal nematode Heligmosomoides polygyrus bakeri, which binds and blocks IL-33. Here, we find that the H. polygyrus bakeri genome contains 3 HpARI family members, and that these have different effects on IL-33-dependent responses in vitro and in vivo, with HpARI1+2 suppressing, and HpARI3 amplifying these responses. All HpARIs have sub-nanomolar affinity for mouse IL-33, however HpARI3 does not block IL-33-ST2 interactions. Instead, HpARI3 stabilises IL-33, increasing the half-life of the cytokine and amplifying responses to it in vivo. Together these data show that H. polygyrus bakeri secretes a family of HpARI proteins with both overlapping and distinct functions, comprising a complex immunomodulatory arsenal of host-targeted proteins.

immunology↗

bioRxiv2023

Structural basis for IL-33 recognition and its antagonism by the helminth effector protein HpARI

Interleukin 33 (IL-33) plays a significant role in inflammation, allergy, and host defence against parasitic helminths. The model gastrointestinal nematode Heligmosomoides polygyrus bakeri (Hp) secretes the Alarmin Release Inhibitor (HpARI), a potent effector protein which suppresses protective immune responses and asthma in its host by inhibiting IL-33 signalling. Here we reveal the structure of HpARI bound to mouse IL-33. HpARI contains three CCP-like domains, and we show that it contacts IL-33 primarily through the second and third of these. A large loop which emerges from CCP3 directly contacts IL-33 and structural comparison shows that this overlaps with the binding site on IL-33 for its receptor, ST2, preventing formation of a signalling complex. Truncations of HpARI which lack the large loop from CCP3 are not able to block IL-33-mediated signalling in a cell-based assay and in an in vivo model of asthma. This shows that direct competition between HpARI and ST2 is responsible for suppression of IL-33-dependent responses. This first structure of IL-33 bound to a pathogen-based inhibitor will guide future approaches to design therapeutics blocking IL-33-mediated allergic and inflammatory conditions.

microbiology↗

bioRxiv2023

Structure of the PfRCR complex which bridges the malaria parasite and erythrocyte during invasion

The symptoms of malaria occur during the blood stage of infection, when parasites invade and replicate within human erythrocytes. The five-component PfPCRCR complex, containing PfRH5, PfCyRPA, PfRIPR, PfCSS and PfPTRAMP, is essential for erythrocyte invasion by the deadliest human malaria parasite, Plasmodium falciparum. Invasion can be prevented by antibodies or nanobodies against each of these five conserved proteins, making them the leading blood stage malaria vaccine candidates. However, little is known about the molecular mechanism by which PfPCRCR functions during invasion. Here we present the structure of the PfRCR complex, containing PfRH5, PfCyRPA and PfRIPR, determined by cryogenic-electron microscopy. This reveals that PfRIPR consists of an ordered multi-domain core flexibly linked to an elongated tail. We test the hypothesis that PfRH5 opens to insert into the membrane, but instead show that a rigid, disulphide-locked PfRH5 can mediate efficient erythrocyte invasion. Finally, we show that the elongated tail of PfRIPR, which is the target of growth- neutralising antibodies, binds to the PfCSS-PfPTRAMP complex on the parasite membrane. Therefore, a modular PfRIPR is linked to the merozoite membrane through an elongated tail, while its structured core presents PfCyRPA and PfRH5 to interact with erythrocyte receptors. This provides novel insight into the mechanism of erythrocyte invasion and opens the way to new approaches in rational vaccine design.

microbiology↗

bioRxiv2022

Erythrocyte invasion-neutralising antibodies prevent Plasmodium falciparum RH5 from binding to basigin-containing membrane protein complexes

Basigin is an essential host receptor for invasion of Plasmodium falciparum into human erythrocytes, interacting with parasite surface protein PfRH5. PfRH5 is a leading blood-stage malaria vaccine candidate and a target of growth-inhibitory antibodies. However, basigin is not alone on the erythrocyte surface. Instead, we show that it is exclusively found in one of two macromolecular complexes, bound predominantly to either plasma membrane Ca2+-ATPase 1/4, PMCA1/4, or monocarboxylate transporter 1, MCT1. PfRH5 binds to either of these complexes with a higher affinity than to isolated basigin ectodomain, making it likely that these are the physiological targets of PfRH5. PMCA-mediated Ca2+ export is not affected by PfRH5, ruling this out as the mechanism underlying changes in calcium flux at the interface between an erythrocyte and the invading parasite. However, our studies rationalise the function of the most effective growth inhibitory antibodies targeting PfRH5. While these antibodies do not reduce the binding of PfRH5 to monomeric basigin, they do reduce its binding to basigin-PMCA and basigin-MCT complexes. This indicates that the most effective PfRH5-targeting antibodies inhibit growth by sterically blocking the essential interaction of PfRH5 with basigin in its physiological context.

microbiology↗

bioRxiv2017

Engagement rules that underpin DBL-DARC interactions for ingress of Plasmodium knowlesi and Plasmodium vivax into human erythrocytes

The molecular mechanisms by which P. knowlesi and P. vivax invade human red blood cells have long been studied. Malaria parasite erythrocytic stages comprise of repeated bursts of parasites via cyclical invasion of host RBCs using dedicated receptor-ligand interactions. A family of erythrocyte-binding proteins (EBPs) from P. knowlesi and P. vivax attach to human Duffy antigen receptor for chemokines (DARC) via their Duffy binding-like domains (Pv-DBL and Pk-DBL respectively) for invasion. Here, we provide a comprehensive overview that presents new insights on the atomic resolution interactions that underpin the binding of human DARC with Pk/Pv-DBLs. Based on extensive structural and biochemical data, we provide a novel, testable and overarching interaction model that rationalizes even contradictory pieces of evidence that have so far existed in the literature on Pk/Pv-DBL/DARC binding determinants. We address the conundrum of how parasite-encoded Pk/Pv-DBLs recognize human DARC via its two sulfated tyrosine residues. We collate evidence for two distinct DARC integration sites on Pk/Pv-DBLs that together likely engage the DARCs sulfated extracellular domain. These analyses are important for both malaria vaccine and inhibitor development efforts that are targeted at abrogating Pk/Pv-DBL/DARC coupling as one avenue to prevent invasion of P. vivax into human red blood cells.

microbiology↗