Biomedical subjects

J A Louis

Publications and source records attributed to J A Louis.

At least 37 records · Page 2Linked to original sources

PubMed1996

Genetically resistant mice lacking interleukin-12 are susceptible to infection with Leishmania major and mount a polarized Th2 cell response.

Mice with homologous disruption of the gene coding for either the p35 subunit or the p40 subunit of interleukin-12 (IL-12) and derived from a strain genetically resistant to infection with Leishmania major have been used to study further the role of this cytokine in resistance to infection and the differentiation of functional CD4+ T cell subsets in vivo. Wild-type 129/Sv/Ev mice are resistant to infection with L. major showing only small lesions which resolve spontaneously within a few weeks and develop a type 1 CD4+ T cell response. In contrast, mice lacking bioactive IL-12 (IL-12p35-/- and IL-12p40-/-) developed large, progressing lesions. Whereas resistant mice were able to mount a delayed-type hypersensitivity (DTH) response to Leishmania antigen, susceptible BALB/c mice as well as IL-12-deficient 129/Sv/Ev mice did not show any DTH reaction. To characterize the functional phenotype of CD4+ T cells triggered in infected wild-type mice and IL-12-deficient mice, the expression of mRNA for interferon-gamma (IFN-gamma) and interleukin-4 (IL-4) in purified CD4+ lymph node cells was analyzed. Wild-type 129/Sv/Ev mice showed high levels of mRNA for IFN-gamma and low levels of mRNA for IL-4 which is indicative of a Th1 response. In contrast, IL-12- deficient mice and susceptible BALB/c mice developed a strong Th2 response with high levels of IL-4 mRNA and low levels of IFN-gamma mRNA in CD4+ T cells. Similarly, lymph node cells from infected wild-type 129 mice produced predominantly IFN-gamma in response to stimulation with Leishmania antigen in vitro whereas lymph node cells from IL-12-deficient mice and susceptible BALB/c mice produced preferentially IL-4. Taken together, these results confirm in vivo the importance of IL-12 in induction of Th1 responses and protective immunity against L. major.

Animals↗

PubMed1995

Mice from a genetically resistant background lacking the interferon gamma receptor are susceptible to infection with Leishmania major but mount a polarized T helper cell 1-type CD4+ T cell response.

Mice with homologous disruption of the gene coding for the ligand-binding chain of the interferon (IFN) gamma receptor and derived from a strain genetically resistant to infection with Leishmania major have been used to study further the role of this cytokine in the differentiation of functional CD4+ T cell subsets in vivo and resistance to infection. Wild-type 129/Sv/Ev mice are resistant to infection with this parasite, developing only small lesions, which resolve spontaneously within 6 wk. In contrast, mice lacking the IFN-gamma receptor develop large, progressing lesions. After infection, lymph nodes (LN) and spleens from both wild-type and knockout mice showed an expansion of CD4+ cells producing IFN-gamma as revealed by measuring IFN-gamma in supernatants of specifically stimulated CD4+ T cells, by enumerating IFN-gamma-producing T cells, and by Northern blot analysis of IFN-gamma transcripts. No biologically active interleukin (IL) 4 was detected in supernatants of in vitro-stimulated LN or spleen cells from infected wild-type or deficient mice. Reverse transcription polymerase chain reaction analysis with primers specific for IL-4 showed similar IL-4 message levels in LN from both types of mice. The IL-4 message levels observed were comparable to those found in similarly infected C57BL/6 mice and significantly lower than the levels found in BALB/c mice. Anti-IFN-gamma treatment of both types of mice failed to alter the pattern of cytokines produced after infection. These data show that even in the absence of IFN-gamma receptors, T helper cell (Th) 1-type responses still develop in genetically resistant mice with no evidence for the expansion of Th2 cells.

Animals↗

PubMed1995

In susceptible mice, Leishmania major induce very rapid interleukin-4 production by CD4+ T cells which are NK1.1-.

Susceptibility of BALB/c mice to infection with Leishmania major is associated with a T helper type 2 (Th2) response. Since interleukin-4 (IL-4) is critically required early for Th2 cell development, the kinetics of IL-4 mRNA expression was compared in susceptible and resistant mice during the first days of infection. In contrast to resistant mice, susceptible mice exhibited a peak of IL-4 mRNA in their spleens 90 min after i.v. injection of parasites and in lymph nodes 16 h after s.c. injection. IL-12 and interferon-gamma (IFN-gamma) down-regulated this early peak of IL-4 mRNA; the effect of IL-12 was IFN-gamma dependent. Treatment of resistant C57BL/6 mice with anti-IFN-gamma allowed the expression of this early IL-4 response to L. major. The increased IL-4 mRNA expression occurred in V beta 8, 7, 2- CD4+ cells in BALB/c mice and NK1.1- CD4+ cells in anti-IFN-gamma treated C57BL/6 mice. These results show that the NK1.1+ CD4+ cells, responsible for the rapid burst of IL-4 production after i.v. injection of anti-CD3, do not contribute to the early IL-4 response to L. major.

Animals↗

PubMed1995

Immunobiology of experimental cutaneous leishmaniasis.

The study of the murine model of infection with Leishmania major is providing important insights into the understanding of the complex interactions between the host and intracellular pathogens. Using this model system, basic research is actively leading to the identification of host factors promoting or circumventing the development of immunity to L. major. Here, Geneviève Milon, Giuseppe Del Giudice and Jacques A. Louis review recent results related to the characterization of immunological host factors determining resistance and susceptibility to this parasite, and try to identify areas where further research is required for a better understanding of the complex events triggered by intracellular parasites within their hosts. Extrapolation to the human leishmaniases of the rapid advances made in this murine model of infection, should pave the way to the rational design of future immunoprophylactic and immunotherapeutic measures.

Journal Article↗

PubMed1994

Selective expansion of activated V delta 4+ cells during experimental infection of mice with Leishmania major.

Previous work from this laboratory has revealed that infection of mice with Leishmania major leads to an expansion of gamma delta+ T cells in the spleen. Further examination of the gamma delta+ T cells expanding in infected mice has shown that the majority of these cells in the spleen, lymph nodes, blood and liver expressed the V delta 4 gene segment. Cell cycle analysis, using propidium iodide incorporation, demonstrated that while only 1% of alpha beta+ T cells in the spleen were in either S + G2/M phase, up to 10% of the gamma delta+ T cells were in cycling phase 8 weeks after infection. Comparison of the state of activation of the two populations in different organs after infection, confirmed that gamma delta+ T cells are actively dividing in lymph nodes, liver and blood, but not in the thymus or among intraepithelial lymphocytes. Examination of the expression of different activation markers on the surface of gamma delta+ T cells in the spleen of both normal and chronically infected BALB/c mice by FACS analysis, revealed increased expression of LFA-1, CD25, CD44, 4F2, CD28 and the heat-stable antigen, whereas Thy-1 and CD5 decreased. Collectively, these results suggest an oligoclonal expansion and activation of gamma delta+ T cells in response to L. major infection.

Animals↗

PubMed1994

Leishmania major-specific CD8+ T cells are inducers and targets of nitric oxide produced by parasitized macrophages.

Lines of Leishmania major-specific CD8+ T cells were derived from the lymph nodes and spleens of CBA mice, immune following resolution of a primary infection, 7 days after secondary challenge with viable L. major. Specific stimulation of these CD8+ T cells by bone marrow-derived macrophages infected with L. major led to the release of interferon-gamma by CD8+ T cells and nitric oxide by macrophages. Interestingly, the nitric oxide released by bone marrow-derived macrophages down-regulated the production of interferon-gamma by specifically activated CD8+ T cells. The proliferation and long-term maintenance of these parasite-specific CD8+ T cells was impaired by the nitric oxide produced by stimulating infected macrophages as a result of cytokines released by activated stimulating infected macrophages as a result of cytokines released by activated CD8+ T cells. Taken together, the results indicate that L. major-specific CD8+ T cells are sensitive to the toxic effect of the nitric oxide that they induce.

Amino Acid Oxidoreductases↗

PubMed1994

Leishmania major infection in mice primes for specific major histocompatibility complex class I-restricted CD8+ cytotoxic T cell responses.

This report shows that lymphoid tissues of mice which have resolved a primary infection with Leisihmania major contain parasite-specific major histocompatibility complex (MHC) class I-restricted cytolytic CD8+ T cell precusors that can be expanded after specific restimulation in vitro with syngeneic antigen-presenting cells pulsed with a cyanogen bromide digest of L. major. In H-2b mice, two distinct populations of CD8+ T cells were identified which both lysed target cells pulsed with L. major-derived peptides but were restricted by a different H-2b class I gene product. Interestingly, these two populations appear to recognize different parasite-derived peptides. It is noteworthy that one Kb-restricted CD8+ T cell line was able to specifically lyse syngeneic macrophages infected with viable L. major, indicating that some L. major-derived peptides may reach the MHC class I pathway of presentation from the phagolysosomal compartment where the parasites are confined in infected macrophages. The importance of these parasite-specific MHC class I restricted cytolytic CD8+ T cells for the elimination of L. major by the infected host remains to be determined.

Animals↗

PubMed1994

Tumor necrosis factor alpha (TNF-alpha) and TNF-beta and their receptors in experimental cutaneous leishmaniasis.

Experimental infection of BALB/c mice with Leishmania major leads to lesions which progress without healing and visceralization, reproducing the most severe forms of human leishmaniasis, while resistant mice like CBA spontaneously resolve lesions and develop protective immunity. Given the conflicting data pertaining to the role of tumor necrosis factor alpha (TNF) in Leishmania infection, we analyzed the expression of TNF, tumor necrosis factor beta (lymphotoxin), and TNF receptor type I (TNF-RI) and type II (TNF-RII) genes in vivo and correlated TNF gene expression in vivo with the production of biologically active TNF by lymphoid cells in vitro. No significant difference in the expression of TNF mRNA was found between susceptible and resistant strains of mice during the course of infection. The depletion of CD4+ T cells in vitro did not change the level of TNF mRNA in BALB/c lymph node cells but led to the total disappearance of TNF mRNA in CBA mice. Unprimed spleen cells did not produce detectable amounts of TNF, whereas 1 week after infection, TNF bioactivity was detected and increased in both strains of mice until 5 weeks of infection. While neutralization of TNF activity in vivo did not alter the course of infection in BALB/c mice, in CBA mice it led to an increase in lesion size and a delay in the healing process but did not interfere significantly with the outcome of infection. Finally, no significant difference in the levels of lymphotoxin, TNF-RI, or TNF RII mRNA expression was found between both strains. The information resulting from these investigations supports the notion that, in vivo, TNF is not the decisive factor responsible for the resistant versus susceptible phenotype in leishmania infection.

Animals↗

PubMed1994

Expansion of gamma interferon-producing CD8+ T cells following secondary infection of mice immune to Leishmania major.

Reinfection of immune mice with Leishmania major elicits a secondary gamma interferon (IFN-gamma) response to which specific CD8+ T cells are essential. We have shown previously that specific CD8+ T cells from reinfected immune mice release substantially higher levels of IFN-gamma, a cytokine essential for the efficient activation of parasitized macrophages to kill intracellular L. major. By using an ELISPOT assay, which allows the detection of IFN-gamma production by individual cells, it is shown here that this elevated IFN-gamma response is the result of an increase of up to 50-fold in the frequency of parasite-specific CD8+ T lymphocytes in the spleens and draining lymph nodes of both immune reinfected CBA and BALB/c mice. This observation is additional evidence of the role that CD8+ T cells play in immunity to reinfection with L. major.

Animals↗

PubMed1993

Leishmania major interferes with antigen presentation by infected macrophages.

Impairment of the Ag-presenting capacity of macrophages harboring intracellular Leishmania might represent one of the several mechanisms by which these parasites can evade host-protective T cell responses. Thus, the present study was designed to investigate the ability of macrophages, parasitized with Leishmania major, to present Ag to relevant T cell hybridomas. Results show that bone marrow-derived macrophages from BALB/c mice, after infection with L. major, have a greatly reduced capacity to present OVA, beta-galactosidase, and L. major-derived Ag to specific T cell hybrids derived from mice immunized with those Ag. In contrast, after pulsing with relevant peptide, macrophages containing L. major have a normal Ag-presenting capacity. The inhibition of presentation of native Ag did not appear to result from decreased endocytosis or catabolism. Inasmuch as the inhibition of presentation could not be attributed to an impaired processing of the Ag or an unavailability of MHC class II molecules on the surface of infected cells, these results could indicate that the presence of L. major interferes with the intracellular loading of MHC class II molecules with antigenic peptides.

Animals↗

PubMed1993

A role for gamma delta + T cells during experimental infection of mice with Leishmania major.

To assess the importance of gamma delta + T lymphocyte responses in experimental murine cutaneous leishmaniasis, the expression of gamma delta + TCR on the surface of lymphocytes in spleen and draining lymph nodes of mice infected with Leishmania major was examined. In both susceptible BALB/c and resistant CBA/J mice, an increase in gamma delta + T cells was observed after s.c. infection. Whereas in chronically infected BALB/c mice, these cells can represent up to 35% of the CD3+ cells in the spleen, in CBA/J mice the percentage of gamma delta + T cells returns to a lower level after resolution of lesions. Further experiments, in which the disease outcome was modified in susceptible BALB/c and in resistant CBA/J mice by chemotherapy or immunointervention, have confirmed that a correlation existed between the multiplication of the parasites and the expansion of gamma delta + T cells in the spleen. Interestingly, in BALB/c mice infected for 4 mo, these gamma delta + T cells represent 80% of the activated blast population and a large proportion of them express the alpha-chain of the CD8 molecule. In an attempt to assess a potential role for the gamma delta + T cells in the control of infection with L. major, the effect of injection of mAb against gamma delta TCR on the course of infection was studied. In both BALB/c and CBA/J mice, blocking of the gamma delta TCR resulted in the development of larger lesions that contained increased numbers of parasites. This treatment significantly delayed the healing of cutaneous lesions in otherwise resistant CBA/J mice. Taken together these results indicate that gamma delta + T cells are expanded during experimental infection of mice with L. major and could be involved in host defense against this parasite.

Animals↗

PubMed1993

Gamma interferon response in secondary Leishmania major infection: role of CD8+ T cells.

CD8+ T cells have been shown to contribute to the rapid resolution of secondary lesions developing in immune mice challenged with Leishmania major. In the present study, we assessed directly the participation of specific CD8+ T cells in the memory response induced in immune mice by reinfection. Lymphocyte populations from reinfected immune mice exhibit marked secondary gamma interferon (IFN-gamma) responses. The participation of IFN-gamma-producing CD8+ T cells in the memory response elicited by secondary infectious challenge was demonstrated in both genetically resistant immune CBA mice and genetically susceptible immune BALB/c mice that were rendered resistant by administration of anti-CD4 monoclonal antibody in the early phase of the primary infection. The protective function of CD8+ T cells in experimental murine cutaneous leishmaniasis might thus be explained in part by their ability to secrete IFN-gamma. In this context, the neutralization of IFN-gamma at the time of reinfection reduced the Leishmania-specific delayed-type hypersensitivity response, showing that this cytokine is involved in the recall of immunological memory to L. major in vivo.

Animals↗

PubMed1993

[Importance of the different T lymphocytes subsets in immunity of mice against an intracellular protozoan parasite: Leishmania major].

The resolution of lesions in mice experimentally infected with L. major requires the expansion of CD4+ T cells specific for parasite antigens which release or express on their membranes lymphokines typical of those secreted by CD4+ Th1 cells. These lymphokines activate macrophages containing L. major to a parasiticidal state through the production of molecules toxic for the parasite. The anti-Leishmania effector function of parasite-specific CD4+ Th1 cells was found dependent upon their fine specificity. Specific CD8+ T cells are induced during infection and evidence exist that they contribute to the elimination of parasites, an effect probably resulting from the Interferon gamma that they release. Their role in controlling secondary lesions that develop upon challenge of immune mice is even more important. The severity of lesions induced by L. major in mice depends upon the expansion of parasite-specific CD4+ cells with functional characteristics of Th2 cells. This effect appears to be the result of their ability to secrete lymphokines capable of inhibiting the activation of macrophages in response to IFN-gamma and the secretion of this lymphokine by Th1 cells. Recently, a possible role for gamma delta+ T cells in containing parasites growth in vivo has been suggested.

Animals↗

PubMed1992

Central role for TCR/CD3 ligation in the differentiation of CD4+ T cells toward A Th1 or Th2 functional phenotype.

Activated CD4+ T cells can be classified into distinct subsets; the most divergent among them may be considered to be the IL-2 and IFN-gamma-producing Th1 clones and the IL-4 and IL-5-producing Th2 clones. Because Th1 and Th2 clones can usually be detected only after several months of culture, we used conditions that modulate the IL-2 and IL-4 production in short term culture. Here we show that freshly isolated and subsequently in vitro-activated CD4+ T cells that were cultured for 11 days with rIL-2 and restimulated showed a IFN-gamma+ IL-2+ IL-3+ IL-4- IL-5- pattern. Because these cells were not capable of providing B cell help for IgG1, IgG2a, or IgE in an APC- and TCR-dependent T-B cell assay, they expressed a phenotype typical for most Th1 clones. In contrast, activated T cells that were cultured for 11 days with IL-2 plus a mAb to CD3 and then restimulated produced a IFN-gamma- IL-2- IL-3+ IL-4+ IL-5+ pattern. These cells were capable of providing B cell help for IgG1, IgG2a, and IgE synthesis and thus presented a phenotype typical for Th2 clones. Similar results were observed when mitogenic mAb to Thy-1.2 or to framework determinants of the alpha beta TCR were used. The induction of Th1- and Th2-like cells did not depend on the relative expression of CD44 or CD45 by the T cells before activation in vitro. Because the incubation of activated T cells with anti-CD3/TCR mAb induced high unrestricted lymphokine production, the latter might be responsible for the Th2-like lymphokine pattern observed after restimulation. To address this point, TCR V beta 8+ and V beta 8- T cell blasts were co-cultured in the presence of mAb to V beta 8. After restimulation, V beta 8+ cells had a IL-4high IL-2low phenotype and V beta 8- cells had a IL-4low IL-2high phenotype. This demonstrates that TCR ligation but not lymphokines alone are capable of inducing Th2-like cells, and this points out a central role for the TCR in the generation of T cell subsets.

Animals↗

PubMed1992

Mycobacterial heat-shock proteins as carrier molecules. II: The use of the 70-kDa mycobacterial heat-shock protein as carrier for conjugated vaccines can circumvent the need for adjuvants and Bacillus Calmette Guérin priming.

In a recent work, we have shown that mycobacterial heat-shock proteins (hsp) of 65-kDa (GroEL-type) and 70-kDa (DnaK-type) acted as carrier molecules in mice, previously primed with Mycobacterium tuberculosis var. bovis (bacillus Calmette-Guérin, BCG), for the induction of high and long-lasting titers of IgG against the repetitive malaria synthetic peptide (NANP)40. Anti-peptide antibodies were induced when the malaria peptide, conjugated to the mycobacterial hsp, was given in the absence of any adjuvants (Lussow et al., Eur. J. Immunol. 1991. 87:2960). In this report, we show that mice immunized with peptides or oligosaccharides conjugated to the 70-kDa hsp produced high titers of IgG antibodies in the absence of any previous priming with BCG. The anti-peptide antibody response persisted for at least 1 year. This adjuvant-free carrier effect of the 70-kDa hsp was T cell dependent, since no anti-peptide nor anti-70-kDa IgG antibodies were induced in athymic nu/nu mice. Previous immunization of mice with the 65-kDa or 70-kDa hsp did not have any negative effect on the induction of anti-peptide IgG antibodies after immunization with hsp-peptide conjugates in the absence of adjuvants. Furthermore, preimmunization with the 65-kDa hsp could substitute for BCG in providing an effective priming for the induction of anti-(NANP) antibodies. Finally, both the 65-kDa and 70-kDa hsp acted as carrier molecules for the induction of IgG antibodies to group C meningococcal oligosaccharides, in the absence of adjuvants. These findings strongly suggest that the use of hsp as carriers in conjugated constructs for the induction of anti-peptide and anti-oligosaccharide antibodies could be of value in the design of new vaccines for eventual use in humans.

Amino Acid Sequence↗

PubMed1992

Immunobiology of experimental leishmaniasis.

Self-cure versus uncontrolled disease progression in experimental murine cutaneous leishmaniasis depends upon a delicate interplay among various activated cells of the host's immune system. Susceptibility or resistance to infection with Leishmania major is correlated with the ability of different inbred strains of mice to produce the characteristic spectra of lymphokines upon infection. Appropriate experimental interventions now allow the modulation of these responses, providing the possibility to render genetically susceptible mice resistant to infection and, vice versa, to cause genotypically "healer" strains to express a "non-healer" phenotype. These experimental manipulations have proven to be powerful tools in the dissection of the underlying immune mechanisms and cellular parameters responsible for susceptibility and resistance, and will perhaps allow the identification of molecules of parasite origin that induce deleterious immune responses to infection with Leishmania, and thus to exclude them from future vaccines. More importantly, rational immune intervention could permit the diversion of established host-damaging immune responses to host-protective immunization.

Animals↗

PubMed1992

Immunology of leishmaniasis.

Resolution of leishmanial infections requires the expansion of specific type 1 T helper cells that secrete or express on their membrane lymphokines capable of activating macrophages that contain these parasites to a microbicidal state. Specific CD8+ T cells, which are triggered during infection, also appear to play a role in protective immunity, possibly through their ability to secrete interferon-gamma. In the mouse model of infection with Leishmania major, the expansion of specific type 2 T helper cells exacerbates disease, an effect that appears to result from the properties of type 2 T helper derived lymphokines to deactivate macrophages and inhibit release of activating cytokines by type 1 T helper cells. In the mouse, destruction of intracellular Leishmania by activated macrophages depends upon the L-arginine-dependent production of nitrogen oxides. Molecules from the parasite that can induce, and are the target of, the protective T-cell response are being characterized.

Animals↗

PubMed1991

Exacerbation of experimental murine cutaneous leishmaniasis with CD4+ Leishmania major-specific T cell lines or clones which secrete interferon-gamma and mediate parasite-specific delayed-type hypersensitivity.

Leishmania major-specific T cell lines were derived from mice sensitized to the parasite. The cells were of the CD4+ T cell lineage and, upon adoptive transfer, were found to be capable of inducing parasite-specific delayed-type hypersensitivity. Adoptive transfer of these L. major-specific T cells to syngeneic recipients which were either normal, T cell deficient or B cell and antibody deficient led to exacerbation of infection upon subsequent challenge with L. major. This suggested that host T cells, B cells and antibody were not required for the L. major-specific T cells to exert their exacerbative effect on the course of cutaneous leishmaniasis. Additional studies revealed that the adoptive transfer of graded doses of these L. major-specific T cells always resulted in exacerbation of infection. Study of the localization pattern of the cells following transfer showed that they migrate preferentially to the site of the lesions. Furthermore, although the induction phase of this phenomenon was immunologically specific, its effector phase was not. Finally, T cell clones were derived from the L. major-specific T cell lines. The T cell clones were phenotypically and functionally identical to the T cell lines from which they were derived. Adoptive transfer of these parasite-specific T cell clones to normal syngeneic recipients induced an exacerbated course of infection with L. major. Interestingly, when these cloned T cells were specifically activated in vitro, the cells produced interleukin 2 and interferon-gamma, but no interleukin 4, indicating that they belong to the murine Th1 subset of CD4+ T cells.

Animals↗