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The IFN-γ-inducible GTPase, Irga6, protects mice against Toxoplasma gondii but not against Plasmodium berghei and some other intracellular pathogens.

Liesenfeld O, Parvanova I, Zerrahn J, Han SJ, Heinrich F, Muñoz M, Kaiser F, Aebischer T, Buch T, Waisman A, Reichmann G, Utermöhlen O, von Stebut E, von Loewenich FD, Bogdan C, Specht S, Saeftel M, Hoerauf A, Mota MM, Könen-Waisman S, Kaufmann SH, Howard JC - PLoS ONE (2011)

Bottom Line: The in vivo role of another member of this family, Irga6 (IIGP, IIGP1) has been studied in less detail.Susceptibility to infection with T. gondii was associated with increased mortality and reduced time to death, increased numbers of inflammatory foci in the brains and elevated parasite loads in brains of infected Irga6-deficient mice.In vitro, Irga6-deficient macrophages and fibroblasts stimulated with IFN-γ were defective in controlling parasite replication.

View Article: PubMed Central - PubMed

Affiliation: Institute of Microbiology and Hygiene, Charité Universitätsmedizin Berlin, Berlin, Germany.

ABSTRACT
Clearance of infection with intracellular pathogens in mice involves interferon-regulated GTPases of the IRG protein family. Experiments with mice genetically deficient in members of this family such as Irgm1(LRG-47), Irgm3(IGTP), and Irgd(IRG-47) has revealed a critical role in microbial clearance, especially for Toxoplasma gondii. The in vivo role of another member of this family, Irga6 (IIGP, IIGP1) has been studied in less detail. We investigated the susceptibility of two independently generated mouse strains deficient in Irga6 to in vivo infection with T. gondii, Mycobacterium tuberculosis, Leishmania mexicana, L. major, Listeria monocytogenes, Anaplasma phagocytophilum and Plasmodium berghei. Compared with wild-type mice, mice deficient in Irga6 showed increased susceptibility to oral and intraperitoneal infection with T. gondii but not to infection with the other organisms. Surprisingly, infection of Irga6-deficient mice with the related apicomplexan parasite, P. berghei, did not result in increased replication in the liver stage and no Irga6 (or any other IRG protein) was detected at the parasitophorous vacuole membrane in IFN-γ-induced wild-type cells infected with P. berghei in vitro. Susceptibility to infection with T. gondii was associated with increased mortality and reduced time to death, increased numbers of inflammatory foci in the brains and elevated parasite loads in brains of infected Irga6-deficient mice. In vitro, Irga6-deficient macrophages and fibroblasts stimulated with IFN-γ were defective in controlling parasite replication. Taken together, our results implicate Irga6 in the control of infection with T. gondii and further highlight the importance of the IRG system for resistance to this pathogen.

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The IRG system does not interact with P. berghei.(A) No effect of Irga6 deficiency on P. berghei replication in the liver. K-Irga6−/− and wild-type C57BL/6 mice were infected intravenously with 20,000 fresh mosquito-derived P. berghei ANKA sporozoites. 40 hours after infection DNA was prepared from livers for qPCR with primers specific for the P. berghei 18S gene as described in Materials and Methods. 14 mice from each strain were assayed. (B) Irga6 does not accumulate on the P. berghei parasitophorous vacuole membrane. Hep1-6 cells were induced with 200 units of IFN-γ. After 24 h, cells were infected with fresh mosquito-derived sporozoites of P. berghei ANKA, fixed 6 h later and stained with a rabbit antiserum (165) against Irga6 (green). 2 infected cells are illustrated (panels A-D and E–H). The sporozoites (white arrows) were identified with a mouse antibody (2E6) directed against a P. berghei hsp70 (red). DAPI was used to identify nuclei of both the Hep1-6 and P. berghei.
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pone-0020568-g006: The IRG system does not interact with P. berghei.(A) No effect of Irga6 deficiency on P. berghei replication in the liver. K-Irga6−/− and wild-type C57BL/6 mice were infected intravenously with 20,000 fresh mosquito-derived P. berghei ANKA sporozoites. 40 hours after infection DNA was prepared from livers for qPCR with primers specific for the P. berghei 18S gene as described in Materials and Methods. 14 mice from each strain were assayed. (B) Irga6 does not accumulate on the P. berghei parasitophorous vacuole membrane. Hep1-6 cells were induced with 200 units of IFN-γ. After 24 h, cells were infected with fresh mosquito-derived sporozoites of P. berghei ANKA, fixed 6 h later and stained with a rabbit antiserum (165) against Irga6 (green). 2 infected cells are illustrated (panels A-D and E–H). The sporozoites (white arrows) were identified with a mouse antibody (2E6) directed against a P. berghei hsp70 (red). DAPI was used to identify nuclei of both the Hep1-6 and P. berghei.

Mentions: Irga6 is expressed constitutively in hepatocytes and is also strongly induced in liver by IFN-γ [39], [40]. This distribution hinted that Irga6 might act preferentially in the liver, and therefore be of special relevance in resistance to the related parasite P. berghei, which infects hepatocytes before infecting red blood cells and causing malaria [41] We therefore assessed a possible effect of Irga6 on P. berghei resistance by measuring parasite load during the early replication phase in the liver using quantitative PCR for PbA 18S ribosomal RNA following infection of wild type C57BL/6 and K-Irga6−/− mice with large doses of sporozoites from the ANKA strain. No significant difference was detected over a total of 14 animals per genotype in three experiments (Figure 6A).


The IFN-γ-inducible GTPase, Irga6, protects mice against Toxoplasma gondii but not against Plasmodium berghei and some other intracellular pathogens.

Liesenfeld O, Parvanova I, Zerrahn J, Han SJ, Heinrich F, Muñoz M, Kaiser F, Aebischer T, Buch T, Waisman A, Reichmann G, Utermöhlen O, von Stebut E, von Loewenich FD, Bogdan C, Specht S, Saeftel M, Hoerauf A, Mota MM, Könen-Waisman S, Kaufmann SH, Howard JC - PLoS ONE (2011)

The IRG system does not interact with P. berghei.(A) No effect of Irga6 deficiency on P. berghei replication in the liver. K-Irga6−/− and wild-type C57BL/6 mice were infected intravenously with 20,000 fresh mosquito-derived P. berghei ANKA sporozoites. 40 hours after infection DNA was prepared from livers for qPCR with primers specific for the P. berghei 18S gene as described in Materials and Methods. 14 mice from each strain were assayed. (B) Irga6 does not accumulate on the P. berghei parasitophorous vacuole membrane. Hep1-6 cells were induced with 200 units of IFN-γ. After 24 h, cells were infected with fresh mosquito-derived sporozoites of P. berghei ANKA, fixed 6 h later and stained with a rabbit antiserum (165) against Irga6 (green). 2 infected cells are illustrated (panels A-D and E–H). The sporozoites (white arrows) were identified with a mouse antibody (2E6) directed against a P. berghei hsp70 (red). DAPI was used to identify nuclei of both the Hep1-6 and P. berghei.
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Related In: Results  -  Collection

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pone-0020568-g006: The IRG system does not interact with P. berghei.(A) No effect of Irga6 deficiency on P. berghei replication in the liver. K-Irga6−/− and wild-type C57BL/6 mice were infected intravenously with 20,000 fresh mosquito-derived P. berghei ANKA sporozoites. 40 hours after infection DNA was prepared from livers for qPCR with primers specific for the P. berghei 18S gene as described in Materials and Methods. 14 mice from each strain were assayed. (B) Irga6 does not accumulate on the P. berghei parasitophorous vacuole membrane. Hep1-6 cells were induced with 200 units of IFN-γ. After 24 h, cells were infected with fresh mosquito-derived sporozoites of P. berghei ANKA, fixed 6 h later and stained with a rabbit antiserum (165) against Irga6 (green). 2 infected cells are illustrated (panels A-D and E–H). The sporozoites (white arrows) were identified with a mouse antibody (2E6) directed against a P. berghei hsp70 (red). DAPI was used to identify nuclei of both the Hep1-6 and P. berghei.
Mentions: Irga6 is expressed constitutively in hepatocytes and is also strongly induced in liver by IFN-γ [39], [40]. This distribution hinted that Irga6 might act preferentially in the liver, and therefore be of special relevance in resistance to the related parasite P. berghei, which infects hepatocytes before infecting red blood cells and causing malaria [41] We therefore assessed a possible effect of Irga6 on P. berghei resistance by measuring parasite load during the early replication phase in the liver using quantitative PCR for PbA 18S ribosomal RNA following infection of wild type C57BL/6 and K-Irga6−/− mice with large doses of sporozoites from the ANKA strain. No significant difference was detected over a total of 14 animals per genotype in three experiments (Figure 6A).

Bottom Line: The in vivo role of another member of this family, Irga6 (IIGP, IIGP1) has been studied in less detail.Susceptibility to infection with T. gondii was associated with increased mortality and reduced time to death, increased numbers of inflammatory foci in the brains and elevated parasite loads in brains of infected Irga6-deficient mice.In vitro, Irga6-deficient macrophages and fibroblasts stimulated with IFN-γ were defective in controlling parasite replication.

View Article: PubMed Central - PubMed

Affiliation: Institute of Microbiology and Hygiene, Charité Universitätsmedizin Berlin, Berlin, Germany.

ABSTRACT
Clearance of infection with intracellular pathogens in mice involves interferon-regulated GTPases of the IRG protein family. Experiments with mice genetically deficient in members of this family such as Irgm1(LRG-47), Irgm3(IGTP), and Irgd(IRG-47) has revealed a critical role in microbial clearance, especially for Toxoplasma gondii. The in vivo role of another member of this family, Irga6 (IIGP, IIGP1) has been studied in less detail. We investigated the susceptibility of two independently generated mouse strains deficient in Irga6 to in vivo infection with T. gondii, Mycobacterium tuberculosis, Leishmania mexicana, L. major, Listeria monocytogenes, Anaplasma phagocytophilum and Plasmodium berghei. Compared with wild-type mice, mice deficient in Irga6 showed increased susceptibility to oral and intraperitoneal infection with T. gondii but not to infection with the other organisms. Surprisingly, infection of Irga6-deficient mice with the related apicomplexan parasite, P. berghei, did not result in increased replication in the liver stage and no Irga6 (or any other IRG protein) was detected at the parasitophorous vacuole membrane in IFN-γ-induced wild-type cells infected with P. berghei in vitro. Susceptibility to infection with T. gondii was associated with increased mortality and reduced time to death, increased numbers of inflammatory foci in the brains and elevated parasite loads in brains of infected Irga6-deficient mice. In vitro, Irga6-deficient macrophages and fibroblasts stimulated with IFN-γ were defective in controlling parasite replication. Taken together, our results implicate Irga6 in the control of infection with T. gondii and further highlight the importance of the IRG system for resistance to this pathogen.

Show MeSH
Related in: MedlinePlus