Effect of interferon on the development of Trypanosoma cruzi in tissue culture "Vero" cells

To study the role of tryptophan degradation by indoleamine 2,3-dioxygenase (INDO) in the control of Trypanosoma cruzior Toxoplasma gondii replication, we used human fibroblasts and a fibrosarcoma cell line (2C4). The cells were cultured in the presence or absence of recombinant gamma interferon (rIFN-γ) and/or recombinant tumor necrosis factor alpha (rTNF-α) for 24 h and were then infected with either T. cruzi or T. gondii. Intracellular parasite replication was evaluated 24 or 48 h after infection. Treatment with rIFN-γ and/or rTNF-α had no inhibitory effect on T. cruzi replication. In contrast, 54, 73, or 30% inhibition of T. gondii replication was observed in the cells treated with rIFN-γ alone, rIFN-γ plus rTNF-α, or TNF-α alone, respectively. The replication of T. gondii tachyzoites in cytokine-activated cells was restored by the addition of extra tryptophan to the culture medium. Similarly,T. gondii tachyzoites transfected with bacterial tryptophan synthase were not sensitive to the microbiostatic effect of rIFN-γ. We also investigated the basis of the cytokine effect on parasite replication by using the three mutant cell lines B3, B9, and B10 derived from 2C4 and expressing defective STAT1α (signal transducer and activator of transcription), JAK2 (Janus family of cytoplasmic tyrosine kinases), or JAK1, respectively, three important elements of a signaling pathway triggered by rIFN-γ. We found that rTNF-α was able to induce low levels expression of INDO mRNA in the parental cell line, as well as the cell line lacking functional JAK2. In contrast to the parental cell line (2C4), rIFN-γ was not able to induce the expression of INDO mRNA or microbiostatic activity in any of the mutant cell lines. These findings indicate the essential requirement of the JAK/STAT pathway for the induction of high levels of INDO mRNA, tryptophan degradation, and the anti-Toxoplasma activity inside human nonprofessional phagocytic cells.

Section: Discussionsupporting

confidence: 92%

Replication ofToxoplasma gondii, but NotTrypanosoma cruzi, Is Regulated in Human Fibroblasts Activated with Gamma Interferon: Requirement of a Functional JAK/STAT Pathway

Cerávolo¹,

Chaves²,

Bonjardim³

et al. 1999

“…The finding that IFN--y enhances macrophage uptake and killing of the invasive blood form of T. cruzi is in keeping with the recent report by Plata et al (15) that IFN-y increases the killing of culture forms of the parasite by 3T3 (fibroblast-like) and J774 (macrophage-like) cells and supports the notion that this lymphokine may play a role in host defense. Other interferon types may be a part of this scenario since beta interferon acts on T. cruzi trypomastigotes but not on host cells (2, 7), reducing parasite association with host cells in vitro (2), and administration of exogenous alpha and beta interferon to mice has a protective effect against T. cruzi infection (6). A similar in vivo study with IFN-y could not be done at this time due to the presence of IL-2 in the IFN-y-CM and the lack of a sufficient amount of Rec.IFN-,y.…”

Section: Discussionmentioning

confidence: 99%

Enhancing effects of gamma interferon on phagocytic cell association with and killing of Trypanosoma cruzi

Wirth¹,

Kierszenbaum²,

Sonnenfeld³

et al. 1985

The effects of gamma interferon (IFN-y) on P388D1 cell or mouse resident peritoneal macrophage association (i.e., binding and internalization) with the protozoan Trypanosoma cruzi were studied, as well as the effects of this lymphokine on intracellular parasite killing. Incubation of either type of cell with a conditioned medium containing IFN-'y and traces of interleukin 2 markedly increased the capacities of the cells to associate with virulent blood forms of T. cruzi, as evidenced by significant increases in both the proportion of parasite-associated cells and the number of parasites associated with the cells. Three lines of evidence pointed to IFN-y, and not interleukin 2, as the lymphokine responsible for the noted effect. First, a conditioned medium containing interleukin 2 but not IFN-y failed to enhance P338D1 cell-parasite association. Second, treatment of the IFN-y preparation at pH 2 to selectively inactivate IFN-y reduced its enhancing effect. Third, recombinant IFN-y, devoid of other lymphokines, also enhanced parasite association with P388D1 cells. Incubation of P388D1 cells with IFN-y for 24, 48, or 72 h increased cell association with T. cruzi, whereas a 12-h incubation period was insufficient, suggesting that IFN-y triggered time-dependent cellular events leading to the enhancement. Treatment of mouse resident peritoneal macrophages with the IFN-y-containing conditioned medium also increased the capacity of these cells to kill internalized trypanosomes. P388D1 cells, which showed minimal or no cytotoxicity after mock treatment with medium, displayed cytotoxicity after incubation with the IFN-y-containing conditioned medium; similar results were obtained with recombinant IFN-y. Catalase prevented parasite killing by P388D1 cells, indicating that H202 mediated the cytotoxicity. These results, underscoring the regulatory effects of IFN-y on macrophage-parasite interactions, suggest a possible role for this lymphokine in the mechanisms of host defense active against T. cruzi infection.

“…Nor does the effect appear to be due to a direct interaction of interferon with the parasites, since tilerone also stimulated significant levels of interferon in the serum of the unprotected A/J mice (Table 1). In vitro studies have also indicated that interferon has no direct effect on the infectivity or the multiplication of T. cruzi (5); however, these studies in which human interferon and primate kidney cell cultures are used may not be representative of the in vivo situation.…”

Section: Discussionmentioning

confidence: 99%

Enhanced resistance to acute infection with Trypanosoma cruzi in mice treated with an interferon inducer

James¹,

Kipnis²,

Sher³

et al. 1982

For an exploration of the effects of interferon-inducible resistance mechanisms in acute American trypanosomiasis, the synthetic interferon inducer tilerone hydrochloride was administered to mice of the C57BL/6J strain, which is highly resistant to Trypanosoma cruzi, 18 to 24 h before infection with a potentially lethal dose of bloodstream trypomastigotes. Although all of the control mice died within 30 days of the acute infection, approximately 50% of the tilerone-treated animals were able to survive indefinitely (P less than 0.05). The tilerone-treated mice demonstrated significant levels of serum interferon and splenic natural killer cells at the time of infection. Macrophages isolated from the peritoneal cavities of tilerone-treated C57BL/6J mice appeared to kill significant numbers of trypanosomes during 2 to 3 days of in vitro culture, indicating that activated macrophages may contribute to the enhanced resistance to T. cruzi infection in these mice. Beige mice treated with tilerone did not survive T. cruzi infection as well as tilerone-treated heterozygotes did, suggesting a role for natural killer cells in interferon-induced resistance. These results suggest that interferon or effector mechanisms enhanced by interferon induction can play a significant role in influencing resistance to T. cruzi infection.