Study of DTH and resistance in Mycobacterium lepraemurium infection using a T-cell line isolated from mice infected with Mycobacterium bovis (BCG)

In vitro study of the anti-leishmanial activity of biodegradable nanoparticles

Leishmania are obligate intracellular parasites, responsible for leishmaniasis. Leishmaniasis are transmitted via insect vector to vertebrate hosts including humans. The infection was reproduced in vitro with promastigotes which can infect murine resident peritoneal cells. Amphotericin B was incorporated into poly(D, L-lactide-co-glycolide) nanoparticles, biodegradable drug carriers, to allow specific targeting inside the cell. The interaction of the drug with infected cells was determined by exposing macrophage cultures to drug carriers. The toxic effects of polymeric drug carriers were defined prior to exposing cells to drug-loaded nanoparticles. For contact times up to 4h, cells tolerated polymer concentrations of 0.01%. The viability of parasites after treatment was determined. Infected macrophages were incubated at 26 degrees C (which allows the transformation of amastigote to promastigote) along with loaded and unloaded nanoparticles, as well as the free drug alone, and a count of the parasites in the medium was recorded. Anti-leishmanial activity was observed with drug-free nanoparticles. This activity may arise through the release of hydrogen peroxide following the activation of macrophages. The incorporation of amphotericin B did not enhance this effect. Interestingly, trehalose, a cryoprotector of the freeze-dried nanoparticles, altered parasite growth and activated macrophages.

Vaccination of mice with the protective F3G3 antigen of Toxoplasma gondii activates CD4+ but not CD8+ T cells and induces Toxoplasma specific IgG antibody

A major cytoplasmic Toxoplasma gondii (T. gondii) antigen recognized by monoclonal antibody F3G3 (F3G3-Ag), as well as two surface antigens recognized by monoclonal antibodies 2G11 and 1E11 respectively (2G11-Ag; 1E11-Ag), were isolated from crude Toxoplasma sonicates using affinity chromatography. Purified F3G3-Ag induced long term protection against Toxoplasma infection in mice and induced Toxoplasma specific IgG antibody. CD4+ but not CD8+ T cells from immune animals proliferated and produced IL-2 upon restimulation with either Toxoplasma sonicate or F3G3-Ag in vitro. Furthermore, CD4+ T cells from mice immunized with F3G3-Ag responded to purified 2G11- and 1E11-Ag. In contrast, CD4+ T cells from mice immunized with 2G11-Ag responded to Toxoplasma sonicate and 2G11-Ag, but not to F3G3- or 1E11-Ag. The results may indicate that the protective F3G3-Ag shares immunogenic epitopes present also on 2G11- and 1E11-Ag, since the F3G3-Ag used for the vaccination did not contain detectable amounts of 2G11- or 1E11-Ag, and none of the antigens displayed any mitogenicity. Taken together the results show that the cytoplasmic F3G3-Ag of T. gondii induces CD4+ T helper cells, Toxoplasma specific IgG antibodies and long term protection against Toxoplasma infection, but does not induce detectable sensitization of the CD8+ T cell compartment.

Vaccination with Mycobacterium bovis BCG affects the distribution of Fc receptor-bearing T lymphocytes in experimental pulmonary tuberculosis

Inbred strain 2 guinea pigs were vaccinated with Mycobacterium bovis BCG or were left unvaccinated and challenged 6 weeks later by the respiratory route with virulent Mycobacterium tuberculosis. By using a double rosette assay with isotype-specific antibody-coated ox and uncoated rabbit erythrocytes, the proportions of T lymphocytes bearing Fc receptors for immunoglobulin G (IgG) (T gamma cells) or IgM (T mu cells) were quantified in tissues taken from animals that were killed within 4 weeks postchallenge. Tuberculin reactivity in vivo and in vitro and antimycobacterial resistance were also measured. BCG vaccination protected the guinea pigs and resulted in significantly enhanced proportions of T mu cells in the blood during the first 3 weeks and in the spleen during weeks 2 and 3 postchallenge. Levels of T gamma cells declined in all tissues during the first 3 weeks of infection and were unaffected by prior vaccination with BCG. Increased proportions of T mu cells in the blood were accompanied by dramatic tuberculin skin reactions and purified protein derivative-induced lymphoproliferation in BCG-vaccinated guinea pigs during the first 2 weeks following virulent pulmonary challenge. Peak levels of T mu cells in the spleens of vaccinated animals at 2 weeks coincided with the first appearance of virulent mycobacteria in that organ. BCG vaccination appears to influence immunoregulatory events in pulmonary tuberculosis through effects on the distribution of IgM Fc receptor-bearing (T mu cell) T lymphocytes.

The role of T cell--macrophage interactions in tuberculosis

Acquired resistance against tuberculosis paradigmatically depends on specific T lymphocytes and mononuclear phagocytes. The etiological agent, Mycobacterium tuberculosis is capable of replicating in mononuclear phagocytes which act both as habitat and as effectors of protection. Upon interaction with antigen-specific T lymphocytes infected mononuclear phagocytes acquire tuberculostatic activities. Here, data from experimental tuberculosis studies in mice are summarized which show that: interleukins produced by cloned T cells and recombinant interferon-gamma are capable of activating tuberculostatic capacities in macrophages; both CD4 and CD8 T cells, after adequate stimulation, produce interferon-gamma; CD8 T cells lyse macrophages in an antigen-specific way; not only CD8 but also CD4 T cells possess an antigen-specific cytolytic potential; lysis of infected macrophages results in mycobacterial growth inhibition. Evidence is also presented that tuberculostatic activities of activated macrophages depend on phagosome-lysosome fusion and are independent of reactive oxygen metabolites and that some strains of M. tuberculosis are resistant against interferon-gamma activities macrophages. These findings suggest that both helper and cytolytic T cells participate in the immune response to tuberculosis and that similar T cell mechanisms contribute to resistance as well as pathogenesis. Protection against tuberculosis, therefore, depends on subtle coordination of the immune response.

Protective immunity in murine histoplasmosis: functional comparison of adoptively transferred T-cell clones and splenic T cells

In this study, I examined whether a murine T-cell line and three clones that recognize Histoplasma capsulatum antigens in vitro could confer protection in vivo against a challenge of Histoplasma yeasts. C57BL/6 mice were each inoculated with 5 X 10(4) yeasts intravenously; 1 h later, 5 X 10(6) or 2 X 10(7) resting T cells were inoculated intravenously. At week 1 of infection, the T-cell line and all clones failed to reduce the number of H. capsulatum CFU in the spleens of mice compared with numbers in infected controls. Administration of recombinant interleukin 2 or cyclophosphamide to infected mice did not potentiate the functional activity in vivo of either the T-cell line or the clones. In contrast, inoculation with 2 X 10(7) CD4+ but not CD8+ cells isolated from the spleens of mice immunized with 10(6) viable yeast cells sharply diminished the number of CFU in the spleens of infected animals. Moreover, splenic CD4+ cells from immune mice transferred a delayed-type hypersensitivity response, whereas the T-cell line and clones did not. Injection Injection of an equal number of cloned T cells and CD8+ splenocytes from immune mice did not transfer resistance to infected mice. Additional studies were undertaken to determine if the ineffectiveness of cloned T cells was associated with a failure to migrate to and survive within spleens of infected mice. B6.PL Thy-1a/Cy mice, which are genetically identical to C57BL/6 mice except that T cells of the former bear Thy-1.1 rather than Thy-1.2, were inoculated with Histoplasma yeasts and then injected with immune CD4+ splenocytes or a T-cell clone. At days 1 and 7 of infection, virtually no Thy-1.2+ cells were detected in the spleens of infected mice given cloned T cells. However, the spleens of animals inoculated with immune CD4+ cells contained a small but significant (P less than 0.01) proportion of Thy-1.2+ cells at both day 1 and day 7 postinoculation of H. capsulatum. Thus, the failure of T-cell clones to transfer protection against H. capsulatum may be explained by defective trafficking or poor survival in vivo or both.

Mycobacteria-reactive Lyt-2+ T cell lines

The biological activities of mycobacteria-reactive Lyt-2+ T cells were characterized in vitro. T cells from mice immunized with killed Mycobacterium tuberculosis or viable M. bovis were restimulated in vitro and cloned under limiting dilution conditions. Several L3T4-Lyt-2+ T cell lines, some of them KJ16+, were established. These T cell lines were capable of lysing mycobacteria-primed macrophages in an antigen-specific way. The cytolytic activity of some T cell lines was found to be class I restricted, whereas others showed antigen-specific killing in the absence of apparent H-2 restriction. Several T cell lines produced interferon-gamma after appropriate stimulation. Furthermore, these T cell lines could induce tuberculostatic macrophage capacities by apparently two different mechanisms, namely by secretion of lymphokines (most probably interferon-gamma) and by direct cell contact. We conclude that CD8 T cells with antigen-specific cytolytic potential are generated during tuberculosis and that these T cells are involved in the immune response to tubercle bacilli.