Biology subjects

Weiss, G. E.

Publications and source records attributed to Weiss, G. E..

3 recordsLinked to original sources

bioRxiv2026

MMV687794 blocks Plasmodium falciparum invasion of red blood cells by targeting a Surface-associated Lipid-Interacting Rhoptry Protein, PfSLIRP

Invasion of red blood cells (RBCs) by the human malaria parasite, Plasmodium falciparum, drives disease. During invasion, the parasite pushes its way into the RBC while wrapping the RBC membrane around itself to establish the parasitophorous vacuole, a stable niche within the RBC where the parasite grows. To better understand invasion, we investigated the mechanism of action of an invasion-inhibitory compound, MMV687794 (MMV794). Lattice light-sheet microscopy revealed that MMV794 blocks parasite entry by preventing parasitophorous vacuole formation. In vitro drug resistance selection of parasites with MMV794 found mutations to the /{beta} hydrolase, PF3D7_0403800, and engineering one of these mutations (C36W) into parasites by CRISPR/Cas9 recapitulated the resistance phenotype. Expansion microscopy demonstrated that this protein is expressed in schizonts, localising to the surface of rhoptries, which are specialised apical secretory organelles that function during invasion. Lipidomics and proteomics analyses of C36W parasites uncovered widespread changes to lipid composition/homeostasis and altered abundance of proteins involved in invasion, indicating a role for PF3D7_0403800 in invasion-associated lipid metabolism. Finally, we used solvent-induced proteome profiling and reactivity assays to confirm drug-target engagement. Together, our findings identify a novel Surface-associated Lipid-Interacting Rhoptry Protein (PfSLIRP) that coordinates lipid metabolism at the rhoptries to enable RBC invasion.

microbiology↗

bioRxiv2023

The Dual Action of Human Antibodies Specific to Plasmodium falciparum PfRH5 and PfCyRPA: Blocking Invasion and Inactivating Extracellular Merozoites

The Plasmodium falciparum reticulocyte-binding protein homolog 5 (PfRH5) is the current leading blood-stage malaria vaccine candidate. PfRH5 functions as part of the pentameric PCRCR complex containing PTRAMP, CSS, PfCyRPA and PfRIPR, all of which are essential for infection of human red blood cells (RBCs). To trigger RBC invasion, PfRH5 engages with RBC protein basigin in a step termed the RH5-basigin binding stage. Although we know increasingly more about how antibodies specific for PfRH5 can block invasion, much less is known about how antibodies recognizing other members of the PCRCR complex can inhibit invasion. To address this, we performed live cell imaging using monoclonal antibodies (mAbs) which bind PfRH5 and PfCyRPA. We measured the degree and timing of the invasion inhibition, the stage at which it occurred, as well as subsequent events. We show that parasite invasion is blocked by individual mAbs, and the degree of inhibition is enhanced when combining a mAb specific for PfRH5 with one binding PfCyRPA. In addition to directly establishing the invasion-blocking capacity of the mAbs, we identified a secondary action of certain mAbs on extracellular parasites that had not yet invaded where the mAbs appeared to inactivate the parasites by triggering a developmental pathway normally only seen after successful invasion. These findings suggest that epitopes within the PfCyRPA-PfRH5 sub-complex that elicit these dual responses may be more effective immunogens than neighboring epitopes by both blocking parasites from invading and rapidly inactivating extracellular parasites. These two protective mechanisms, prevention of invasion and inactivation of uninvaded parasites, resulting from antibody to a single epitope indicate a possible route to the development of more effective vaccines. Author SummaryMalaria is a sometimes-fatal disease caused by protozoan parasites of which Plasmodium falciparum is the most deadly species that causes hundreds of millions of infections and half a million deaths per year. A partially effective vaccine is available to block parasite forms transmitted by mosquitoes but not the subsequent blood stage which causes symptomatic disease. To fight blood stage parasites, proteins have been identified such as PfRH5, that aid parasite entry into human red blood cells (RBCs) and vaccines made from these proteins can trigger the production of antibodies that bind the parasite proteins thereby blocking RBC invasion. PfRH5 forms a complex with another parasite protein called PfCyRPA and together antibodies to PfCyRPA and PfRH5 are highly effective in reducing parasite growth. Here we investigated how antibodies to PfCyRPA and PfRH5 actually block invasion using video microscopy of live parasites. As anticipated, we found the antibodies not only stopped most parasites from invading but of those parasites that did invade, they took longer to do so, suggesting the antibodies were physically inhibiting the invasion process. One unanticipated effect of both PfRH5 antibodies and one of three PfCyRPA antibodies tested, was that they triggered the uninvaded parasites to change into cellular forms normally only seen inside RBCs. These intracellular forms are no longer competent to invade and so the PfRH5/CyRPA antibodies have the potential of both neutralize parasites by physically preventing RBC entry and by changing the parasites into invasion incompetent forms.

microbiology↗

bioRxiv2019

Screening the Medicines for Malaria Venture Pathogen Box for invasion and egress inhibitors of the blood stage of Plasmodium falciparum reveals several inhibitory compounds

To identify potential inhibitors of egress and invasion in the asexual blood stage of Plasmodium falciparum, we screened the Medicines for Malaria Venture (MMV) Pathogen Box. This compound library comprises of 400 drugs against neglected tropical diseases, including 125 with antimalarial activity. For this screen, we utilised transgenic parasites expressing a bioluminescent reporter, Nanoluciferase (Nluc), to measure inhibition of parasite egress and invasion in the presence of the Pathogen Box compounds. At a concentration of 2 {micro}M, we found 15 compounds that inhibited parasite egress by >40% and 24 invasion-specific compounds that inhibited invasion by >90%. We further characterised 11 of these inhibitors through cell-based assays and live cell microscopy and found two compounds that inhibited merozoite maturation in schizonts, one compound that inhibited merozoite egress, one compound that directly inhibited parasite invasion and one compound that slowed down invasion and arrested ring formation. The remaining compounds were general growth inhibitors that acted during the egress and invasion phase of the cell cycle. We found the sulfonylpiperazine, MMV020291, to be the most invasion-specific inhibitor, blocking successful merozoite internalisation within human RBCs and having no substantial effect on other stages of the cell cycle. This has greater implications for the possible development of an invasion-specific inhibitor as an antimalarial in a combination based therapy, in addition to being a useful tool for studying the biology of the invading parasite.\n\nImportancePlasmodium falciparum causes the most severe form of malaria and with emerging resistance to frontline treatments, there is the need to identify new drug targets in the parasite. One of the most critical processes during the asexual blood stage in the parasites lifecycle is the egress from old red blood cells (RBCs) and subsequent invasion of new RBCs. Many unique parasite ligands, receptors and enzymes are employed during egress and invasion that are essential for parasite proliferation and survival, therefore making these processes druggable targets. Identifying novel compounds that inhibit these essential processes would further their development into possible antimalarials that would be highly effective at killing asexual RBC stage parasites when used in combination with drugs that target the intraerythrocytic growth phase. These compounds potentially may also be used as novel tools to study the complex biology of parasites to gain further insight into the mechanisms behind egress and invasion.

cell biology↗