Toxoplasma gondii: in vivo expression of BAG-5 and cyst formation is independent of TNF p55 receptor and inducible nitric oxide synthase functions

Microbes Infect. 2002 Mar;4(3):261-70. doi: 10.1016/s1286-4579(02)01537-x.


Wild type, TNFRp55(-/-), iNOS(-/-) and IFN-gamma(-/-) mice were infected with Toxoplasma gondii strain ME-49, and the central nervous system (CNS), lungs, liver, spleen, heart and kidneys were examined for the presence of parasites expressing tachyzoite-specific (SAG-1) and bradyzoite-specific (BAG-5) antigens. During the acute phase of infection, the peripheral organs, but not the CNS, of the IFN-gamma(-/-) mice are heavily parasitized by tachyzoites and there are no signs of parasites expressing BAG-5. In contrast, the tissues from TNFRp55(-/-) and inducible nitric oxide synthase (iNOS)(-/-) mice, mainly the CNS, presented high numbers of parasites expressing SAG-1 and/or BAG-5. Tachyzoite transformation into bradyzoite and cyst development was shown to be normal in the tissues from TNFRp55(-/-) and iNOS(-/-) mice, as indicated by the high numbers of BAG-5/PAS positive cysts. Consistently, reactivation of infection in IFN-gamma(-/-) mice was rapid and characterized by a dramatic increase in SAG-1, contrasting with slow course in the TNFRp55(-/-) or iNOS(-/-) mice associated with a relatively small increase in SAG-1- and/or BAG-5-positive parasites. In conclusion, our results suggest that the control of multiplication of tachyzoites is largely dependent on endogenous IFN-gamma with partial involvement of TNFRp55 and iNOS. In contrast, induction of BAG-5 expression and cyst formation during toxoplasmosis seems to be dependent on IFN-gamma, but independent of TNFRp55 and iNOS functions.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Antigens, CD / genetics
  • Antigens, CD / physiology*
  • Antigens, Protozoan / metabolism
  • Cysts / parasitology
  • Female
  • Host-Parasite Interactions
  • Mice
  • Mice, Inbred Strains
  • Mice, Knockout
  • Nitric Oxide Synthase / genetics
  • Nitric Oxide Synthase / physiology*
  • Nitric Oxide Synthase Type II
  • Protozoan Proteins / metabolism
  • Receptors, Tumor Necrosis Factor / genetics
  • Receptors, Tumor Necrosis Factor / physiology*
  • Receptors, Tumor Necrosis Factor, Type I
  • Toxoplasma / growth & development*
  • Toxoplasma / immunology
  • Toxoplasma / metabolism
  • Toxoplasmosis, Animal / enzymology
  • Toxoplasmosis, Animal / immunology*
  • Toxoplasmosis, Animal / parasitology*


  • Antigens, CD
  • Antigens, Protozoan
  • Protozoan Proteins
  • Receptors, Tumor Necrosis Factor
  • Receptors, Tumor Necrosis Factor, Type I
  • SAG1 antigen, Toxoplasma
  • Nitric Oxide Synthase
  • Nitric Oxide Synthase Type II
  • Nos2 protein, mouse