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Essential Role of mGBP7 for Survival of Toxoplasma gondii Infection.

ABSTRACT: Members of the murine guanylate-binding protein family (mGBP) are induced by interferon gamma (IFN-?) and have been shown to be important factors in cell-autonomous immunity toward the intracellular pathogen Toxoplasma gondii Previously, we identified that mGBP2 mediates disruption of the parasitophorous vacuole membrane (PVM) and directly assaults the plasma membrane of the parasite. Here, we show that mGBP7-deficient mice are highly susceptible to T. gondii infection. This is demonstrated by the loss of parasite replication control, pronounced development of ascites, and death of the animals in the acute infection phase. Interestingly, live-cell microscopy revealed that mGBP7 recruitment to the PVM occurs after mGBP2 recruitment, followed by disruption of the PVM and T. gondii integrity and accumulation of mGBP7 inside the parasite. This study defines mGBP7 as a crucial effector protein in resistance to intracellular T. gondii IMPORTANCE Guanylate-binding proteins (GBPs) are induced by the inflammatory cytokine interferon gamma (IFN-?) and have been shown to be important factors in the defense of the intracellular pathogen Toxoplasma gondii In previous studies, we showed that members of the mouse GBP family, such as mGBP2 and mGBP7, accumulate at the parasitophorous vacuole of T. gondii, which is the replicatory niche of the parasite. In this study, we show that mice deficient in mGBP7 succumb early after infection with T. gondii, showing a complete failure of resistance to the pathogen. On a molecular level, mGBP7 is found directly at the parasite, likely mediating its destruction.

SUBMITTER: Steffens N

PROVIDER: S-EPMC6974569 | biostudies-literature | 2020 Jan

REPOSITORIES: biostudies-literature

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Essential Role of mGBP7 for Survival of Toxoplasma gondii Infection.

Steffens Nora N Beuter-Gunia Cornelia C Kravets Elisabeth E Reich Artur A Legewie Larissa L Pfeffer Klaus K Degrandi Daniel D

mBio 20200121 1

Members of the murine guanylate-binding protein family (mGBP) are induced by interferon gamma (IFN-γ) and have been shown to be important factors in cell-autonomous immunity toward the intracellular pathogen <i>Toxoplasma gondii</i> Previously, we identified that mGBP2 mediates disruption of the parasitophorous vacuole membrane (PVM) and directly assaults the plasma membrane of the parasite. Here, we show that mGBP7-deficient mice are highly susceptible to <i>T. gondii</i> infection. This is dem ...[more]

PMID: 31964735

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Project description:Ingestion of the obligate intracellular protozoan parasite Toxoplasma gondii causes an acute infection that leads to chronic infection of the host. To facilitate the acute phase of the infection, T. gondii manipulates the host response by secreting rhoptry organelle proteins (ROPs) into host cells during its invasion. A few key ROP proteins with signatures of kinases or pseudokinases (ROPKs) act as virulence factors that enhance parasite survival against host gamma interferon-stimulated innate immunity. However, the roles of these and other ROPK proteins in establishing chronic infection have not been tested. Here, we deleted 26 ROPK gene loci encoding 31 unique ROPK proteins of type II T. gondii and show that numerous ROPK proteins influence the development of chronic infection. Cyst burdens were increased in the Δrop16 knockout strain or moderately reduced in 11 ROPK knockout strains. In contrast, deletion of ROP5, ROP17, ROP18, ROP35, or ROP38/29/19 (ROP38, ROP29, and ROP19) severely reduced cyst burdens. Δrop5 and Δrop18 knockout strains were less resistant to host immunity-related GTPases (IRGs) and exhibited >100-fold-reduced virulence. ROP18 kinase activity and association with the parasitophorous vacuole membrane were necessary for resistance to host IRGs. The Δrop17 strain exhibited a >12-fold defect in virulence; however, virulence was not affected in the Δrop35 or Δrop38/29/19 strain. Resistance to host IRGs was not affected in the Δrop17, Δrop35, or Δrop38/29/19 strain. Collectively, these findings provide the first definitive evidence that the type II T. gondii ROPK proteome functions as virulence factors and facilitates additional mechanisms of host manipulation that are essential for chronic infection and transmission of T. gondii Reactivation of chronic Toxoplasma gondii infection in individuals with weakened immune systems causes severe toxoplasmosis. Existing treatments for toxoplasmosis are complicated by adverse reactions to chemotherapy. Understanding key parasite molecules required for chronic infection provides new insights into potential mechanisms that can interrupt parasite survival or persistence in the host. This study reveals that key secreted rhoptry molecules are used by the parasite to establish chronic infection of the host. Certain rhoptry proteins were found to be critical virulence factors that resist innate immunity, while other rhoptry proteins were found to influence chronic infection without affecting virulence. This study reveals that rhoptry proteins utilize multiple mechanisms of host manipulation to establish chronic infection of the host. Targeted disruption of parasite rhoptry proteins involved in these biological processes opens new avenues to interfere with chronic infection with the goal to either eliminate chronic infection or to prevent recrudescent infections.

Project description:BackgroundToxoplasmosis is a widespread zoonosis caused by the intracellular protozoan parasite Toxoplasma gondii. Limited epidemiological information is available about the prevalence of T. gondii in sheep in Romania, and a high incidence would have implications for both the economy and public health. To our knowledge, no studies are available about the T. gondii strains circulating in lambs. The objective of this study was to assess the prevalence of T. gondii in sheep (serology), lambs (serology, bioassay, PCR) and sheep abortions (PCR) in Romania. Moreover, the study aimed to perform the genetic characterization of T. gondii isolates from lambs.MethodsSerum samples collected from 2650 sheep (2067 adults and 583 lambs) were tested for anti-T. gondii antibodies (IgG) using a commercial ELISA kit. Likewise, 328 pairs of diaphragmatic muscle-serum samples were collected from lambs aged between 2 and 4 months. Lamb serum samples were analyzed using MAT for anti-T. gondii antibody detection. The diaphragm tissue samples from MAT-positive lambs (at a dilution ≥ 1:25) were bioassayed in mice. The T. gondii strains were genotyped using 15 microsatellites markers. Additionally, brain and heart samples from 76 sheep abortions were analyzed for T. gondii DNA by polymerase chain reaction (PCR) targeting the 529-bp repeat region (REP529).ResultsThe results showed that more than half of the tested sheep were T. gondii seropositive (53.5%). The seroprevalence was significantly higher in adults (61.1%) than in lambs (26.4%). The seroprevalence of T. gondii infection in slaughtered lambs, by MAT, was 37.5% (123/328). There were bioassayed in mice 56 diaphragmatic tissues from 123 seropositive lambs. Toxoplasma gondii strains were isolated from 18 (32.1%) lambs intended for human consumption. All T. gondii strains were confirmed by PCR. Six strains were genotyped using 15 microsatellite markers and belonged to genotype II. Toxoplasma gondii DNA was detected in 11.8% (9/76) of sheep abortions.ConclusionsThe present study showed the presence of T. gondii in sheep in all the regions considered in the study. The high prevalence of T. gondii infection in sheep and lambs, demonstrated by serology, molecular analysis and bioassay, highlighted that there is an important risk of human infection in consuming raw or undercooked sheep/lamb meat.

Dataset Information

Essential Role of mGBP7 for Survival of Toxoplasma gondii Infection.

Publications

Essential Role of mGBP7 for Survival of Toxoplasma gondii Infection.

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