Biology subjects

Torelli, F.

Publications and source records attributed to Torelli, F..

3 recordsLinked to original sources

bioRxiv2023

Mapping host-microbe transcriptional interactions by dual perturb-seq

Intracellular pathogens and other endosymbionts reprogram host cell transcription to suppress immune responses and recalibrate biosynthetic pathways. This reprogramming is critical in determining the outcome of infection or colonisation. Here, we combine pooled CRISPR knockout screening with dual host-microbe single-cell RNA-sequencing to identify the molecular mediators of these transcriptional interactions, a method we term dual perturb-seq. Applying dual perturb-seq to the intracellular pathogen Toxoplasma gondii, we are able to identify previously uncharacterised effector proteins and directly infer their function from the transcriptomic data. We show that TgGRA59 contributes to the export of other effector proteins from the parasite into the host cell and identify a novel effector, TgSOS1, that is necessary for sustained host STAT6 signalling and thereby contributes to parasite immune evasion and persistence. Together, this work demonstrates a novel tool that can be broadly adapted to interrogate host-microbe transcriptional interactions and reveal mechanisms of infection and immune evasion.

molecular biology↗

bioRxiv2022

A heterotrimeric complex of Toxoplasma proteins promotes parasite survival in interferon gamma stimulated human cells

Toxoplasma gondii secretes protein effectors to subvert the human immune system sufficiently to establish a chronic infection. Relative to murine infections, little is known about which parasite effectors disarm human immune responses. Here we used targeted CRISPR screening to identify secreted protein effectors required for parasite survival in IFN{gamma}-activated human cells. Independent screens were carried out using two Toxoplasma strains which differ in virulence in mice, leading to the identification of effectors required for survival in IFN{gamma}-activated human cells. We identify the secreted protein GRA57 and two other proteins, GRA70 and GRA71, that together form a complex which enhances the ability of parasites to persist in IFN{gamma}-activated human foreskin fibroblasts (HFFs). Components of the protein machinery required for export of Toxoplasma proteins into the host cell were also found to be important for parasite resistance to IFN{gamma} in human cells, but these export components function independently of the identified protein complex. Host-mediated ubiquitination of the parasite vacuole has previously been associated with increased parasite clearance from human cells, but we find that vacuoles from GRA57, GRA70 and GRA71 knockout strains are surprisingly less ubiquitinated by the host cell. We hypothesise that deletion of this trimeric complex renders parasites hypersensitive to remaining ubiquitination, resulting in increased parasite clearance.

microbiology↗

bioRxiv2022

Toxoplasma gondii ROP1 subverts murine and human innate immune restriction

Toxoplasma gondii is an intracellular parasite that can infect many different host species and is a cause of significant human morbidity worldwide. T. gondii secretes a diverse array of effector proteins into the host cell which are critical for infection; however, the vast majority of these secreted proteins are uncharacterised. Here, we carried out a pooled CRISPR knockout screen in the T. gondii Prugniaud strain in vivo to identify secreted proteins that contribute to parasite immune evasion in the host. We identify 22 putative virulence factors and demonstrate that ROP1, the first-identified rhoptry protein of T. gondii, has a previously unrecognised role in parasite resistance to interferon gamma-mediated innate immune restriction. This function is conserved in the highly virulent RH strain of T. gondii and contributes to parasite growth in both murine and human macrophages. While ROP1 affects the morphology of rhoptries, from where the protein is secreted, it does not affect rhoptry secretion. ROP1 interacts with the host cell protein C1QBP, which appears to facilitate parasite immune evasion. In summary, we identify 22 secreted proteins which contribute to parasite growth in vivo and show that ROP1 is an important and previously overlooked effector in counteracting both murine and human innate immunity.

microbiology↗