I. Abrahamsohn | University of Sao Paulo (original) (raw)
Papers by I. Abrahamsohn
Journal of Autoimmunity, 2004
Trypanosoma cruzi is an intracellular parasite that induces a strong Th1-type response and immuno... more Trypanosoma cruzi is an intracellular parasite that induces a strong Th1-type response and immunosuppression during the acute phase of infection. To study how the infection with T. cruzi would modulate the development of an autoimmune disease, we immunized C57BL/6 mice and IL-10 or iNOS knock-out mice of the same background with the encephalitogenic MOG 35-55 peptide and infected them with T. cruzi. Our results demonstrate that infection with T. cruzi completely prevents EAE development and furthermore induces complete and lasting remission in mice that were infected with this parasite after they had developed clinical EAE. Nitric oxide and IL-10 participate in triggering the mechanisms associated with EAE suppression by the infection. Decreased lymphoproliferation and increased frequencies of Annexin-positive cells and of T cells bearing CD95, CD95L or CTLA-4 were observed in the spleen from immunized/infected mice, as well as lower IL-2 and increased TGF-beta production in comparison with only immunized mice. Our results indicate that several effector and regulatory mechanisms of the immune response that arise during the acute phase of T. cruzi infection lastingly affect the expansion and/or effector functions of encephalitogenic cells, preventing the onset or inducing complete remission of EAE.
Trypanosoma cruzi (Y strain)-infected interleukin-4 ؊/؊ (IL-4 ؊/؊) mice of strains 129/J, BALB/c,... more Trypanosoma cruzi (Y strain)-infected interleukin-4 ؊/؊ (IL-4 ؊/؊) mice of strains 129/J, BALB/c, and C57BL/6 showed no significant difference in parasitemia levels or end point mortality rates compared to wild-type (WT) mice. Higher production of gamma interferon (IFN-␥) by parasite antigen (Ag)-stimulated splenocytes was observed only for C57BL/6 IL-4 ؊/؊ mice. Treatment of 129/J WT mice with recombinant IL-4 (rIL-4), rIL-10, anti-IL-4, and/or anti-IL-10 monoclonal antibodies (MAbs) did not modify parasitism. However, WT mice treated with rIL-4 and rIL-10 had markedly increased parasitism and suppressed IFN-␥ synthesis by spleen cells stimulated with parasite Ag, concanavalin A, or anti-CD3. Addition of anti-IL-4 MAbs to splenocyte cultures from infected WT 129/J, BALB/c, or C57BL/6 mice failed to modify IFN-␥ synthesis levels; in contrast, IL-10 neutralization increased IFN-␥ production and addition of rIL-4 and/or rIL-10 diminished IFN-␥ synthesis. We conclude that endogenous IL-4 is not a major determinant of susceptibility to Y strain T. cruzi infection but that IL-4 can, in association with IL-10, modulate IFN-␥ production and resistance.
Memórias do Instituto Oswaldo Cruz
The specific antibody responses were compared among susceptible (A/Sn), moderately susceptible (B... more The specific antibody responses were compared among susceptible (A/Sn), moderately susceptible (Balb/c) and resistant (C57 BL/10J) mice infected with Trypanosoma cruzi (Y strain). Sera obtained during the second week of infection recognized a surface trypomastigote antigen of apparent Mr 80 kDa while displaying complex reactivity to surface epimastigote antigens. Complex trypomastigote antigens recognition was detected around the middle of the third week of infection. No major differences were observed along the infection, among the three strains of mice, neither in the patterns of surface antigen recognition by sera, nor in the titres of antibodies against blood trypomastigotes (lytic antibodies), tissue culture trypomastigotes or epimastigotes. On immunoblot analysis, however, IgG of the resistant strain displayed the most complex array of specificities against both trypo and epimastigote antigens, followed by the susceptible strain. IgM antibodies exhibited a more restricted anti...
Infection and Immunity, 1981
C57BL/10J mice treated with Mycobacterium bovis BCG and cyclophosphamide were immunized with disr... more C57BL/10J mice treated with Mycobacterium bovis BCG and cyclophosphamide were immunized with disrupted epimastigotes or with living blood trypomastigotes from Trypanosoma cruzi and assayed for delayed hypersensitivity by footpad testing with epimastigote antigens. Enhanced and lasting reactions were observed in mice pretreated with BCG or cyclophosphamide or both and immunized with epimastigotes. Whereas BCG pretreatment clearly reduced the mortality rates of mice immunized with living blood forms, no enhancement of the delayed hypersensitivity responses was observed in animals treated with BCG or cyclophosphamide or both before infection. The production of high levels of delayed hypersensitivity in the absence of infection and its adoptive transfer with cells could help to evaluate the participation of cell-mediated immunity in the protection against T. cruzi.
Parasitology, 1980
LLC-MK2 cell monolayers infected with Trypanosoma cruzi were shown by immunofluorescence to prese... more LLC-MK2 cell monolayers infected with Trypanosoma cruzi were shown by immunofluorescence to present parasite antigens on the surface of both parasitized and non-parasitized cells after completion of the first intracellular cycle and rupture of infected cells. The cell-culture supernatant fluid at this stage, as well as the supernatant fluid of parasites left overnight in culture medium were concentrated and contained antigen capable of binding to uninfected cell monolayers. The origin of this antigen, as well as its eventual role in the pathogenesis of Chagas' disease, are discussed.
Previous observations demonstrated that the delivery of recombinant Salmonella enterica serovar D... more Previous observations demonstrated that the delivery of recombinant Salmonella enterica serovar Dublin strains to mice via mucosal routes did not efficiently activate systemic and secreted antibody responses to either type d flagellin or genetically fused heterologous B-cell epitopes, thus reducing the usefulness of the protein as a carrier of epitopes for vaccine purposes. In this work, we investigated murine systemic and mucosal flagellin immunogenicity after oral immunization with attenuated Salmonella strains. The reduced anti-type d flagellin antibody responses in mice immunized via mucosal routes with three doses of flagellated S. enterica serovar Dublin strains were not caused by oral tolerance and could not be restored by coadministration of a mucosal adjuvant. The induction of antibody responses to Salmonella flagellins was shown to differ according to the genetic background, but not the haplotype, of the mouse lineage. Moreover, BALB/c mice orally immunized with S. enterica serovar Typhimurium strains developed anti-type i flagellin sera and secreted antibody responses, which indicated that the serovar of the Salmonella vaccine strain also affected flagellin immunogenicity. Analyses of cytokine responses of BALB/c mice immunized with three oral doses of flagellated S. enterica serovar Dublin vaccine strains showed that, in spite of the lack of antibody responses, elevated type d flagellin-specific CD4-cell-activation-dependent gamma interferon (IFN-␥) and interleukin-10 responses were elicited after the administration of the vaccine strains via either parenteral or mucosal routes. Similar cytokine production patterns were detected to a T-cell heterologous epitope, derived from the CFA/I fimbriae of enterotoxigenic Escherichia coli (ETEC), in mice orally immunized with a Salmonella vaccine strain expressing hybrid flagella. These results indicate that the immunogenicities of Salmonella flagellins can differ significantly, depending on the murine host and on the bacterial vector used, and demonstrate that the induction of CD4-cell-activation-dependent IFN-␥ production represents a major immune response triggered by flagellin and in-frame fused heterologous T-cell epitopes after the oral administration of recombinant S. enterica serovar Dublin vaccine strains.
Parasitology, 1977
This paper describes in vitro antibody dependent cytotoxicity against Trypanosoma cruzi epimastig... more This paper describes in vitro antibody dependent cytotoxicity against Trypanosoma cruzi epimastigotes by normal mouse splenic lymphocytes. Cytotoxicity was expressed as the percentage reduction in the number of motile parasites upon incubation with lymphocytes at 37 degrees C in a defined medium. Failure of the non-motile parasites to regain motility and their ensuing degeneration of 28 degrees C in liver infusion tryptose (LIT) medium confirmed loss of motility as a criterion of cytotoxicity. Incubation of T. cruzi cruzi at 37 degrees C for 18 h in a defined medium per se did not interfere with motility but was followed by a lag phase of the growth curve in LIT medium at 28 degrees C. The lag phase was prolonged for T. cruzi which had previously been incubated at 37 degrees C in the absence of cells.
Acta tropica, 1985
Trypanosoma cruzi amastigotes were isolated from liver and spleen of previously infected mice and... more Trypanosoma cruzi amastigotes were isolated from liver and spleen of previously infected mice and purified in discontinuous gradients of Metrizamide and Percoll. The amastigotes were well preserved as judged by electron microscopy. The amastigotes were readily interiorized by macrophages and multiplied actively within these cells in vitro. However, their capacity of differentiation was hampered as estimated by the absence of trypomastigotes until day 6 of cultivation. The purified amastigotes were infective for mice but the onset of parasitemia was somewhat delayed and less intense when compared to mice infected with trypomastigotes.
Acta tropica, 1984
The rapid disappearance of infective forms of Trypanosoma cruzi from the site of inoculation as w... more The rapid disappearance of infective forms of Trypanosoma cruzi from the site of inoculation as well as the initial phase of infection produced by the parasite are not yet fully understood. To investigate this problem we used the hamster as an animal model considering the existence of the cheek pouch--a peculiar region devoid of lymphatic vessels. T. cruzi trypomastigotes were inoculated into the cheek pouch or into the footpad of animals previously infected or not with the same parasite. The results were followed from 3 up to 21 days postinoculation, by histological examination. In the cheek pouch of normal animals a large number of parasites could be seen up to 15 days post-inoculation and the inflammatory infiltrate had a focal distribution. Conversely, in the footpad the infiltrate was diffuse and no parasites could be detected. These observations indicate that the lymphatic system is the main route of T. cruzi dissemination from the site or inoculation. When hamsters were first...
Experimental parasitology, 1996
Control of the acute phase of Trypanosoma cruzi infections is critically dependent on cytokine-me... more Control of the acute phase of Trypanosoma cruzi infections is critically dependent on cytokine-mediated macrophage activation to intracellular killing. We investigated the roles of IL-10, TNF, IFN-gamma, and IL-12 in the control of parasitism by innate and specific immunity. Mice with disrupted IL-10 genes (IL-10 KO) infected with Y strain T. cruzi have lower parasite numbers in the blood and tissues and higher IFN-gamma and nitric oxide (NO) production by spleen cells than wild type (WT) mice. Treatment of IL-10 KO and WT mice with recombinant IL-10 resulted in increased parasitemia. Mice with disrupted recombinase-activating genes (RAG/KO) that lack B and T cells provided a model for determining the importance of innate immunity to resistance. RAG/KO and WT mice had similar parasitemia levels until Day 13 of infection, suggestive of effective control of parasitism by the innate immune system during the early phase of infection; from them on parasitemia was higher in RAG/KO. Double...
The mechanisms that control TNF-alpha production by macrophages during Trypanosoma cruzi infectio... more The mechanisms that control TNF-alpha production by macrophages during Trypanosoma cruzi infection are still unknown. Destruction of intracellular forms by cytokine activated macrophages is considered to be a major mechanism of parasite elimination. Although in vitro TNF-alpha contributes to enhanced parasite destruction by macrophages, previous work in vivo has shown that as the parasite burden increases, serum TNF-alpha levels decline. In this report we show that TNF-alpha production by peritoneal adherent cells is elevated at the initial phase of T. cruzi infection. As infection progresses TNF-alpha production decreases. The observed reduction is partly due to inhibition, largely exerted by endogenous PG and secondarily by NO. Inhibition of their synthesis partially restored the ability to produce high levels of TNF-alpha to macrophages upon stimulation by LPS. Neither endogenous IL-10 nor TGF-beta seem to be involved in the negative regulation of TNF-alpha production.
By using the disappearance of the surface Ig from human peripheral lymphocytes as a parameter of ... more By using the disappearance of the surface Ig from human peripheral lymphocytes as a parameter of modulation, at 37°C it was shown that anti-Fab antibody is a more effective and faster modulator of the surface Ig than anti-Fc, anti-IgM, or anti-IgG antibodies. The C-binding site was demonstrated to be fully independent and distinct from the surface Ig and a stable marker of Ig-bearing cells. The C receptor can be blocked by the addition of fresh C5-sufficient, C5-deficient mouse serum, or fresh autologous human serum, at 37°C before binding to EAC by a mechanism still to be defined. Both IgM and IgG cells possess the C receptor. The relationship of Ig to C receptors and their role in cell activation by the specific antigen is discussed.
Immunol Lett, 1998
The mechanisms that control TNF-α production by macrophages during Trypanosoma cruzi infection ar... more The mechanisms that control TNF-α production by macrophages during Trypanosoma cruzi infection are still unknown. Destruction of intracellular forms by cytokine activated macrophages is considered to be a major mechanism of parasite elimination. Although in vitro TNF-α contributes to enhanced parasite destruction by macrophages, previous work in vivo has shown that as the parasite burden increases, serum TNF-α levels decline. In this report we show that TNF-α production by peritoneal adherent cells is elevated at the initial phase of T. cruzi infection. As infection progresses TNF-α production decreases. The observed reduction is partly due to inhibition, largely exerted by endogenous PG and secondarily by NO. Inhibition of their synthesis partially restored the ability to produce high levels of TNF-α to macrophages upon stimulation by LPS. Neither endogenous IL-10 nor TGF-β seem to be involved in the negative regulation of TNF-α production.
Journal of immunology (Baltimore, Md. : 1950), 1999
IL-4-dependent and -independent IgG1 Abs differ in their ability to induce mast cell degranulatio... more IL-4-dependent and -independent IgG1 Abs differ in their ability to induce mast cell degranulation as measured by passive cutaneous anaphylaxis (PCA). Mice immunized with OVA or PIII (fraction of Ascaris suum) produced high titers of IgG1 as shown by ELISA and PCA. In contrast, another A. suum fraction, PI, elicited IgG1 Abs with no PCA activity. IgG1 with anaphylactic activity required IL-4, as IgG1 responses to OVA and PIII in IL-4-/- mice gave no PCA. PI-specific IgG1 was IL-4-independent, because no difference was found between the responses of IL-4-/- and IL-4+/+ mice. Significant PCA reactions were elicited, however, with PI-specific IgG1 from IL-12-/- or anti-IFN-gamma Ab-treated mice, although less Ab was measured by ELISA. These results indicate that one type of IgG1 has anaphylactic activity and its synthesis is IL-4-dependent, being inhibited by IL-12 or IFN-gamma; the other lacks this activity and its synthesis is stimulated by IL-12 or IFN-gamma.
Journal of immunology (Baltimore, Md. : 1950), Jan 15, 1995
An intense suppression of splenic T cell proliferation to mitogens and to Ags from the parasite i... more An intense suppression of splenic T cell proliferation to mitogens and to Ags from the parasite is characteristic of the acute phase of Trypanosoma cruzi infection in mice. The impairment of proliferation is coincident with high levels of IFN-gamma and nitrite and decreased production of IL-2 in the supernatants of spleen cell cultures from infected mice. Previous work demonstrated that suppression of proliferation is largely mediated by the population of adherent cells in the infected spleen. In this study we confirmed the active suppression exerted by these cells on Con A, anti-CD3, and parasite Ag-stimulated proliferation of CD4+ splenic T cells. Inasmuch as the high production of IFN-gamma and of nitrite were compatible with intense macrophage activation and nitric oxide (NO) production, we determined the effects of cytokines that regulate macrophage activation and of NO on the proliferation of spleen cells from infected mice. We show that spleen cell proliferation to Ag and to ...
Scandinavian Journal of Immunology, 1998
Simultaneous immunization of mice with an Ascaris suum extract (Asc) and ovalbumin (OA) markedly ... more Simultaneous immunization of mice with an Ascaris suum extract (Asc) and ovalbumin (OA) markedly affects the immune response to OA. The role of interleukin (IL)-4 and IL-10 induced by Asc immunization on the modulation of antigen-specific and mitogen-induced responses was investigated following single or combined cytokine-specific monoclonal antibody (MoAb) treatment of mice before immunization with OA + Asc. Immediate hypersensitivity reactions to aggregated OA and OA-specific immunoglobulin (Ig)G2a antibody production were completely restored only when both IL-4 and IL-10 were neutralized. These findings were associated with enhanced interferon (IFN)-gamma secretion by OA-stimulated lymph node (LN) cells. In addition, the Asc-specific cytokine response in anti-IL-4 plus anti-IL-10 MoAb treated mice was shifted towards a Th1 phenotype, with an increase in IFN-gamma and IL-2 levels and a decrease in IL-4, but not in IL-10, levels. Consequently, Asc-specific IgG2a antibody production increased, whereas IgE titres diminished in these animals. These results indicate that IL-4 and IL-10 act together in the Asc-induced mechanism of antigen-specific pansuppression. In contrast, modulation of Concanavalin A (Con A)-induced cytokine responses in Asc-immunized mice appears to be essentially mediated by an IL-4-dependent mechanism, since the neutralization of just IL-4 (and not of IL-10), either in vivo or in vitro, changed the cytokine profile from a Th2 towards a Th1 type. However, OA and Asc-specific cell responses were not modified by either anti-IL-4 or by anti-IL-4 + anti-IL-10 MoAbs in vitro treatments, suggesting that the induction of a Th2 response to Asc components concomitant to OA immunization has a strong suppressive effect on the priming stage of OA-specific Th1 type response.
Scandinavian Journal of Immunology, 1998
H-2 syngeneic H and L (Biozzi) mice provide a model to study Leishmania infections in which polar... more H-2 syngeneic H and L (Biozzi) mice provide a model to study Leishmania infections in which polar resistant and susceptible phenotypes are independent from H-2 differences. High-Ab-responder (H) and low-Ab-responder (L) mice syngeneic at the H-2 locus (H-2q) were, respectively, susceptible and highly resistant to Leishmania amazonensis infection. L-mice resistance was associated with high IFN-gamma and transient IL-4 production by lymph node (LN) cells, in contrast with sustained IL-4 and decreasing IFN-gamma production by susceptible H mice. IL-12 production could be detected only in LN from resistant mice. The cytokine production pattern was consistent with preferential progression to a Th1-type response in resistant L-mice, and to a Th2-type response in susceptible H-mice. We also investigated whether this shift towards Th1- or Th2-type cytokine responses was dependent upon H or L antigen presenting cells' (APC) intrinsic ability to preferentially stimulate either T-cell subset. To this end, LN-derived T-cell lines were grown from 12-day infected mice, when both strains produced IFN-gamma and IL-4. L-derived T-cell lines developed a Th2 cytokine pattern whereas H-derived T-cell lines produced IFN-gamma, IL-4 and IL-10 whatever the APC origin (H or L) used for their derivation. This work constitutes the first characterization of cellular immune responses to the intracellular parasite, L. amazonensis in H-2 syngeneic mice, an infection model in which polar resistant and susceptible phenotypes are determined by non-MHC genes.
Parasitology, 1980
SummaryLLC-MK2 cell monolayers infected with Trypanosoma cruzi were shown by immunofluorescence t... more SummaryLLC-MK2 cell monolayers infected with Trypanosoma cruzi were shown by immunofluorescence to present parasite antigens on the surface of both parasitized and non-parasitized cells after completion of the first intracellular cycle and rupture of infected cells. The cell-culture supernatant fluid at this stage, as well as the supernatant fluid of parasites left overnight in culture medium were concentrated and contained antigen capable of binding to uninfected cell monolayers. The origin of this antigen, as well as its eventual role in the pathogenesis of Chagas' disease, are discussed.
Parasitology, 1977
SummaryThis paper describes in vitro antibody dependent cytotoxicity against Trypanosoma cruzi ep... more SummaryThis paper describes in vitro antibody dependent cytotoxicity against Trypanosoma cruzi epimastigotes by normal mouse splenic lymphocytes. Cytotoxicity was expressed as the percentage reduction in the number of motile parasites upon incubation with lymphocytes at 37 °C in a denned medium. Failure of the non-motile parasites to regain motility and their ensuring degeneration at 28 °C in liver infusion tryptose (LIT) medium confirmed loss of motility as a criterion of cytotoxicity. Incubation of T. cruzi at 37 °C for 18 h in a defined medium per se did not interfere with motility but was followed by a lag phase of the growth curve in LIT medium at 28 °C. The lag phase was prolonged for T. cruzi which had previously been incubated at 37 °C in the absence of cells.
Journal of Autoimmunity, 2004
Trypanosoma cruzi is an intracellular parasite that induces a strong Th1-type response and immuno... more Trypanosoma cruzi is an intracellular parasite that induces a strong Th1-type response and immunosuppression during the acute phase of infection. To study how the infection with T. cruzi would modulate the development of an autoimmune disease, we immunized C57BL/6 mice and IL-10 or iNOS knock-out mice of the same background with the encephalitogenic MOG 35-55 peptide and infected them with T. cruzi. Our results demonstrate that infection with T. cruzi completely prevents EAE development and furthermore induces complete and lasting remission in mice that were infected with this parasite after they had developed clinical EAE. Nitric oxide and IL-10 participate in triggering the mechanisms associated with EAE suppression by the infection. Decreased lymphoproliferation and increased frequencies of Annexin-positive cells and of T cells bearing CD95, CD95L or CTLA-4 were observed in the spleen from immunized/infected mice, as well as lower IL-2 and increased TGF-beta production in comparison with only immunized mice. Our results indicate that several effector and regulatory mechanisms of the immune response that arise during the acute phase of T. cruzi infection lastingly affect the expansion and/or effector functions of encephalitogenic cells, preventing the onset or inducing complete remission of EAE.
Trypanosoma cruzi (Y strain)-infected interleukin-4 ؊/؊ (IL-4 ؊/؊) mice of strains 129/J, BALB/c,... more Trypanosoma cruzi (Y strain)-infected interleukin-4 ؊/؊ (IL-4 ؊/؊) mice of strains 129/J, BALB/c, and C57BL/6 showed no significant difference in parasitemia levels or end point mortality rates compared to wild-type (WT) mice. Higher production of gamma interferon (IFN-␥) by parasite antigen (Ag)-stimulated splenocytes was observed only for C57BL/6 IL-4 ؊/؊ mice. Treatment of 129/J WT mice with recombinant IL-4 (rIL-4), rIL-10, anti-IL-4, and/or anti-IL-10 monoclonal antibodies (MAbs) did not modify parasitism. However, WT mice treated with rIL-4 and rIL-10 had markedly increased parasitism and suppressed IFN-␥ synthesis by spleen cells stimulated with parasite Ag, concanavalin A, or anti-CD3. Addition of anti-IL-4 MAbs to splenocyte cultures from infected WT 129/J, BALB/c, or C57BL/6 mice failed to modify IFN-␥ synthesis levels; in contrast, IL-10 neutralization increased IFN-␥ production and addition of rIL-4 and/or rIL-10 diminished IFN-␥ synthesis. We conclude that endogenous IL-4 is not a major determinant of susceptibility to Y strain T. cruzi infection but that IL-4 can, in association with IL-10, modulate IFN-␥ production and resistance.
Memórias do Instituto Oswaldo Cruz
The specific antibody responses were compared among susceptible (A/Sn), moderately susceptible (B... more The specific antibody responses were compared among susceptible (A/Sn), moderately susceptible (Balb/c) and resistant (C57 BL/10J) mice infected with Trypanosoma cruzi (Y strain). Sera obtained during the second week of infection recognized a surface trypomastigote antigen of apparent Mr 80 kDa while displaying complex reactivity to surface epimastigote antigens. Complex trypomastigote antigens recognition was detected around the middle of the third week of infection. No major differences were observed along the infection, among the three strains of mice, neither in the patterns of surface antigen recognition by sera, nor in the titres of antibodies against blood trypomastigotes (lytic antibodies), tissue culture trypomastigotes or epimastigotes. On immunoblot analysis, however, IgG of the resistant strain displayed the most complex array of specificities against both trypo and epimastigote antigens, followed by the susceptible strain. IgM antibodies exhibited a more restricted anti...
Infection and Immunity, 1981
C57BL/10J mice treated with Mycobacterium bovis BCG and cyclophosphamide were immunized with disr... more C57BL/10J mice treated with Mycobacterium bovis BCG and cyclophosphamide were immunized with disrupted epimastigotes or with living blood trypomastigotes from Trypanosoma cruzi and assayed for delayed hypersensitivity by footpad testing with epimastigote antigens. Enhanced and lasting reactions were observed in mice pretreated with BCG or cyclophosphamide or both and immunized with epimastigotes. Whereas BCG pretreatment clearly reduced the mortality rates of mice immunized with living blood forms, no enhancement of the delayed hypersensitivity responses was observed in animals treated with BCG or cyclophosphamide or both before infection. The production of high levels of delayed hypersensitivity in the absence of infection and its adoptive transfer with cells could help to evaluate the participation of cell-mediated immunity in the protection against T. cruzi.
Parasitology, 1980
LLC-MK2 cell monolayers infected with Trypanosoma cruzi were shown by immunofluorescence to prese... more LLC-MK2 cell monolayers infected with Trypanosoma cruzi were shown by immunofluorescence to present parasite antigens on the surface of both parasitized and non-parasitized cells after completion of the first intracellular cycle and rupture of infected cells. The cell-culture supernatant fluid at this stage, as well as the supernatant fluid of parasites left overnight in culture medium were concentrated and contained antigen capable of binding to uninfected cell monolayers. The origin of this antigen, as well as its eventual role in the pathogenesis of Chagas' disease, are discussed.
Previous observations demonstrated that the delivery of recombinant Salmonella enterica serovar D... more Previous observations demonstrated that the delivery of recombinant Salmonella enterica serovar Dublin strains to mice via mucosal routes did not efficiently activate systemic and secreted antibody responses to either type d flagellin or genetically fused heterologous B-cell epitopes, thus reducing the usefulness of the protein as a carrier of epitopes for vaccine purposes. In this work, we investigated murine systemic and mucosal flagellin immunogenicity after oral immunization with attenuated Salmonella strains. The reduced anti-type d flagellin antibody responses in mice immunized via mucosal routes with three doses of flagellated S. enterica serovar Dublin strains were not caused by oral tolerance and could not be restored by coadministration of a mucosal adjuvant. The induction of antibody responses to Salmonella flagellins was shown to differ according to the genetic background, but not the haplotype, of the mouse lineage. Moreover, BALB/c mice orally immunized with S. enterica serovar Typhimurium strains developed anti-type i flagellin sera and secreted antibody responses, which indicated that the serovar of the Salmonella vaccine strain also affected flagellin immunogenicity. Analyses of cytokine responses of BALB/c mice immunized with three oral doses of flagellated S. enterica serovar Dublin vaccine strains showed that, in spite of the lack of antibody responses, elevated type d flagellin-specific CD4-cell-activation-dependent gamma interferon (IFN-␥) and interleukin-10 responses were elicited after the administration of the vaccine strains via either parenteral or mucosal routes. Similar cytokine production patterns were detected to a T-cell heterologous epitope, derived from the CFA/I fimbriae of enterotoxigenic Escherichia coli (ETEC), in mice orally immunized with a Salmonella vaccine strain expressing hybrid flagella. These results indicate that the immunogenicities of Salmonella flagellins can differ significantly, depending on the murine host and on the bacterial vector used, and demonstrate that the induction of CD4-cell-activation-dependent IFN-␥ production represents a major immune response triggered by flagellin and in-frame fused heterologous T-cell epitopes after the oral administration of recombinant S. enterica serovar Dublin vaccine strains.
Parasitology, 1977
This paper describes in vitro antibody dependent cytotoxicity against Trypanosoma cruzi epimastig... more This paper describes in vitro antibody dependent cytotoxicity against Trypanosoma cruzi epimastigotes by normal mouse splenic lymphocytes. Cytotoxicity was expressed as the percentage reduction in the number of motile parasites upon incubation with lymphocytes at 37 degrees C in a defined medium. Failure of the non-motile parasites to regain motility and their ensuing degeneration of 28 degrees C in liver infusion tryptose (LIT) medium confirmed loss of motility as a criterion of cytotoxicity. Incubation of T. cruzi cruzi at 37 degrees C for 18 h in a defined medium per se did not interfere with motility but was followed by a lag phase of the growth curve in LIT medium at 28 degrees C. The lag phase was prolonged for T. cruzi which had previously been incubated at 37 degrees C in the absence of cells.
Acta tropica, 1985
Trypanosoma cruzi amastigotes were isolated from liver and spleen of previously infected mice and... more Trypanosoma cruzi amastigotes were isolated from liver and spleen of previously infected mice and purified in discontinuous gradients of Metrizamide and Percoll. The amastigotes were well preserved as judged by electron microscopy. The amastigotes were readily interiorized by macrophages and multiplied actively within these cells in vitro. However, their capacity of differentiation was hampered as estimated by the absence of trypomastigotes until day 6 of cultivation. The purified amastigotes were infective for mice but the onset of parasitemia was somewhat delayed and less intense when compared to mice infected with trypomastigotes.
Acta tropica, 1984
The rapid disappearance of infective forms of Trypanosoma cruzi from the site of inoculation as w... more The rapid disappearance of infective forms of Trypanosoma cruzi from the site of inoculation as well as the initial phase of infection produced by the parasite are not yet fully understood. To investigate this problem we used the hamster as an animal model considering the existence of the cheek pouch--a peculiar region devoid of lymphatic vessels. T. cruzi trypomastigotes were inoculated into the cheek pouch or into the footpad of animals previously infected or not with the same parasite. The results were followed from 3 up to 21 days postinoculation, by histological examination. In the cheek pouch of normal animals a large number of parasites could be seen up to 15 days post-inoculation and the inflammatory infiltrate had a focal distribution. Conversely, in the footpad the infiltrate was diffuse and no parasites could be detected. These observations indicate that the lymphatic system is the main route of T. cruzi dissemination from the site or inoculation. When hamsters were first...
Experimental parasitology, 1996
Control of the acute phase of Trypanosoma cruzi infections is critically dependent on cytokine-me... more Control of the acute phase of Trypanosoma cruzi infections is critically dependent on cytokine-mediated macrophage activation to intracellular killing. We investigated the roles of IL-10, TNF, IFN-gamma, and IL-12 in the control of parasitism by innate and specific immunity. Mice with disrupted IL-10 genes (IL-10 KO) infected with Y strain T. cruzi have lower parasite numbers in the blood and tissues and higher IFN-gamma and nitric oxide (NO) production by spleen cells than wild type (WT) mice. Treatment of IL-10 KO and WT mice with recombinant IL-10 resulted in increased parasitemia. Mice with disrupted recombinase-activating genes (RAG/KO) that lack B and T cells provided a model for determining the importance of innate immunity to resistance. RAG/KO and WT mice had similar parasitemia levels until Day 13 of infection, suggestive of effective control of parasitism by the innate immune system during the early phase of infection; from them on parasitemia was higher in RAG/KO. Double...
The mechanisms that control TNF-alpha production by macrophages during Trypanosoma cruzi infectio... more The mechanisms that control TNF-alpha production by macrophages during Trypanosoma cruzi infection are still unknown. Destruction of intracellular forms by cytokine activated macrophages is considered to be a major mechanism of parasite elimination. Although in vitro TNF-alpha contributes to enhanced parasite destruction by macrophages, previous work in vivo has shown that as the parasite burden increases, serum TNF-alpha levels decline. In this report we show that TNF-alpha production by peritoneal adherent cells is elevated at the initial phase of T. cruzi infection. As infection progresses TNF-alpha production decreases. The observed reduction is partly due to inhibition, largely exerted by endogenous PG and secondarily by NO. Inhibition of their synthesis partially restored the ability to produce high levels of TNF-alpha to macrophages upon stimulation by LPS. Neither endogenous IL-10 nor TGF-beta seem to be involved in the negative regulation of TNF-alpha production.
By using the disappearance of the surface Ig from human peripheral lymphocytes as a parameter of ... more By using the disappearance of the surface Ig from human peripheral lymphocytes as a parameter of modulation, at 37°C it was shown that anti-Fab antibody is a more effective and faster modulator of the surface Ig than anti-Fc, anti-IgM, or anti-IgG antibodies. The C-binding site was demonstrated to be fully independent and distinct from the surface Ig and a stable marker of Ig-bearing cells. The C receptor can be blocked by the addition of fresh C5-sufficient, C5-deficient mouse serum, or fresh autologous human serum, at 37°C before binding to EAC by a mechanism still to be defined. Both IgM and IgG cells possess the C receptor. The relationship of Ig to C receptors and their role in cell activation by the specific antigen is discussed.
Immunol Lett, 1998
The mechanisms that control TNF-α production by macrophages during Trypanosoma cruzi infection ar... more The mechanisms that control TNF-α production by macrophages during Trypanosoma cruzi infection are still unknown. Destruction of intracellular forms by cytokine activated macrophages is considered to be a major mechanism of parasite elimination. Although in vitro TNF-α contributes to enhanced parasite destruction by macrophages, previous work in vivo has shown that as the parasite burden increases, serum TNF-α levels decline. In this report we show that TNF-α production by peritoneal adherent cells is elevated at the initial phase of T. cruzi infection. As infection progresses TNF-α production decreases. The observed reduction is partly due to inhibition, largely exerted by endogenous PG and secondarily by NO. Inhibition of their synthesis partially restored the ability to produce high levels of TNF-α to macrophages upon stimulation by LPS. Neither endogenous IL-10 nor TGF-β seem to be involved in the negative regulation of TNF-α production.
Journal of immunology (Baltimore, Md. : 1950), 1999
IL-4-dependent and -independent IgG1 Abs differ in their ability to induce mast cell degranulatio... more IL-4-dependent and -independent IgG1 Abs differ in their ability to induce mast cell degranulation as measured by passive cutaneous anaphylaxis (PCA). Mice immunized with OVA or PIII (fraction of Ascaris suum) produced high titers of IgG1 as shown by ELISA and PCA. In contrast, another A. suum fraction, PI, elicited IgG1 Abs with no PCA activity. IgG1 with anaphylactic activity required IL-4, as IgG1 responses to OVA and PIII in IL-4-/- mice gave no PCA. PI-specific IgG1 was IL-4-independent, because no difference was found between the responses of IL-4-/- and IL-4+/+ mice. Significant PCA reactions were elicited, however, with PI-specific IgG1 from IL-12-/- or anti-IFN-gamma Ab-treated mice, although less Ab was measured by ELISA. These results indicate that one type of IgG1 has anaphylactic activity and its synthesis is IL-4-dependent, being inhibited by IL-12 or IFN-gamma; the other lacks this activity and its synthesis is stimulated by IL-12 or IFN-gamma.
Journal of immunology (Baltimore, Md. : 1950), Jan 15, 1995
An intense suppression of splenic T cell proliferation to mitogens and to Ags from the parasite i... more An intense suppression of splenic T cell proliferation to mitogens and to Ags from the parasite is characteristic of the acute phase of Trypanosoma cruzi infection in mice. The impairment of proliferation is coincident with high levels of IFN-gamma and nitrite and decreased production of IL-2 in the supernatants of spleen cell cultures from infected mice. Previous work demonstrated that suppression of proliferation is largely mediated by the population of adherent cells in the infected spleen. In this study we confirmed the active suppression exerted by these cells on Con A, anti-CD3, and parasite Ag-stimulated proliferation of CD4+ splenic T cells. Inasmuch as the high production of IFN-gamma and of nitrite were compatible with intense macrophage activation and nitric oxide (NO) production, we determined the effects of cytokines that regulate macrophage activation and of NO on the proliferation of spleen cells from infected mice. We show that spleen cell proliferation to Ag and to ...
Scandinavian Journal of Immunology, 1998
Simultaneous immunization of mice with an Ascaris suum extract (Asc) and ovalbumin (OA) markedly ... more Simultaneous immunization of mice with an Ascaris suum extract (Asc) and ovalbumin (OA) markedly affects the immune response to OA. The role of interleukin (IL)-4 and IL-10 induced by Asc immunization on the modulation of antigen-specific and mitogen-induced responses was investigated following single or combined cytokine-specific monoclonal antibody (MoAb) treatment of mice before immunization with OA + Asc. Immediate hypersensitivity reactions to aggregated OA and OA-specific immunoglobulin (Ig)G2a antibody production were completely restored only when both IL-4 and IL-10 were neutralized. These findings were associated with enhanced interferon (IFN)-gamma secretion by OA-stimulated lymph node (LN) cells. In addition, the Asc-specific cytokine response in anti-IL-4 plus anti-IL-10 MoAb treated mice was shifted towards a Th1 phenotype, with an increase in IFN-gamma and IL-2 levels and a decrease in IL-4, but not in IL-10, levels. Consequently, Asc-specific IgG2a antibody production increased, whereas IgE titres diminished in these animals. These results indicate that IL-4 and IL-10 act together in the Asc-induced mechanism of antigen-specific pansuppression. In contrast, modulation of Concanavalin A (Con A)-induced cytokine responses in Asc-immunized mice appears to be essentially mediated by an IL-4-dependent mechanism, since the neutralization of just IL-4 (and not of IL-10), either in vivo or in vitro, changed the cytokine profile from a Th2 towards a Th1 type. However, OA and Asc-specific cell responses were not modified by either anti-IL-4 or by anti-IL-4 + anti-IL-10 MoAbs in vitro treatments, suggesting that the induction of a Th2 response to Asc components concomitant to OA immunization has a strong suppressive effect on the priming stage of OA-specific Th1 type response.
Scandinavian Journal of Immunology, 1998
H-2 syngeneic H and L (Biozzi) mice provide a model to study Leishmania infections in which polar... more H-2 syngeneic H and L (Biozzi) mice provide a model to study Leishmania infections in which polar resistant and susceptible phenotypes are independent from H-2 differences. High-Ab-responder (H) and low-Ab-responder (L) mice syngeneic at the H-2 locus (H-2q) were, respectively, susceptible and highly resistant to Leishmania amazonensis infection. L-mice resistance was associated with high IFN-gamma and transient IL-4 production by lymph node (LN) cells, in contrast with sustained IL-4 and decreasing IFN-gamma production by susceptible H mice. IL-12 production could be detected only in LN from resistant mice. The cytokine production pattern was consistent with preferential progression to a Th1-type response in resistant L-mice, and to a Th2-type response in susceptible H-mice. We also investigated whether this shift towards Th1- or Th2-type cytokine responses was dependent upon H or L antigen presenting cells' (APC) intrinsic ability to preferentially stimulate either T-cell subset. To this end, LN-derived T-cell lines were grown from 12-day infected mice, when both strains produced IFN-gamma and IL-4. L-derived T-cell lines developed a Th2 cytokine pattern whereas H-derived T-cell lines produced IFN-gamma, IL-4 and IL-10 whatever the APC origin (H or L) used for their derivation. This work constitutes the first characterization of cellular immune responses to the intracellular parasite, L. amazonensis in H-2 syngeneic mice, an infection model in which polar resistant and susceptible phenotypes are determined by non-MHC genes.
Parasitology, 1980
SummaryLLC-MK2 cell monolayers infected with Trypanosoma cruzi were shown by immunofluorescence t... more SummaryLLC-MK2 cell monolayers infected with Trypanosoma cruzi were shown by immunofluorescence to present parasite antigens on the surface of both parasitized and non-parasitized cells after completion of the first intracellular cycle and rupture of infected cells. The cell-culture supernatant fluid at this stage, as well as the supernatant fluid of parasites left overnight in culture medium were concentrated and contained antigen capable of binding to uninfected cell monolayers. The origin of this antigen, as well as its eventual role in the pathogenesis of Chagas' disease, are discussed.
Parasitology, 1977
SummaryThis paper describes in vitro antibody dependent cytotoxicity against Trypanosoma cruzi ep... more SummaryThis paper describes in vitro antibody dependent cytotoxicity against Trypanosoma cruzi epimastigotes by normal mouse splenic lymphocytes. Cytotoxicity was expressed as the percentage reduction in the number of motile parasites upon incubation with lymphocytes at 37 °C in a denned medium. Failure of the non-motile parasites to regain motility and their ensuring degeneration at 28 °C in liver infusion tryptose (LIT) medium confirmed loss of motility as a criterion of cytotoxicity. Incubation of T. cruzi at 37 °C for 18 h in a defined medium per se did not interfere with motility but was followed by a lag phase of the growth curve in LIT medium at 28 °C. The lag phase was prolonged for T. cruzi which had previously been incubated at 37 °C in the absence of cells.