Contributions of animal and macrophage models to the understanding of host parasite interaction of Mycobacterium avium complex (MAC) disease

Effects of Elm Bark (Ulmus davidianavar.japonica) Extracts on the Modulation of Immunocompetence in Mice

The immunomodulative effects of elm bark extract were studied in vitro by the proliferation of splenocytes and the production capacity of three kinds of cytokines [interleukin (IL)-1beta, IL-6, and tumor necrosis factor (TNF)-alpha] by mouse peritoneal macrophages cultured with various fractions (methanol, hexane, chloroform, ethyl acetate, butanol, and water) of elm bark extract. Splenocyte proliferation and cell viability of peritoneal macrophages were increased with concentrations of polar fractions, such as butanol and water, in the range of 1-500 microg/mL. Significantly higher levels of the production of all three cytokines were detected with supplementation of methanol extract compared with other fractions. In order to elucidate its effect in vivo, elm bark water extract was orally administrated every other day for 2 weeks. Proliferation of splenocytes and the production capacity of cytokines (IL-1beta, IL-6, and TNF-alpha) by mouse peritoneal macrophages were used as indices for immune activity. Splenocyte proliferation induced by elm bark with lipopolysaccharide or concanavalin A stimulation was enhanced at 500 mg/kg of body weight concentrations compared to that of the control group. In the case of cytokines, the highest production of IL-6 and TNF was detected at 500 mg/kg of body weight concentrations. In conclusion, this study suggests through in vitro and in vivo experiments that Ulmus davidiana var. japonica (elm bark) extracts may enhance the immunocompetent properties such as splenocyte proliferation and cytokine production capacity by activated macrophages and have a protective effect in mice.

The modulating effects of proinflammatory cytokines interferon-gamma (IFN-gamma) and tumour necrosis factor-alpha (TNF-alpha), and immunoregulating cytokines IL-10 and transforming growth factor-beta (TGF-beta), on anti-microbial activity of murine peritoneal macrophages against Mycobacterium avium-intracellulare complex

We assessed the roles of proinflammatory cytokines IFN-gamma and TNF-alpha, and immunoregulatory cytokines IL-10 and TGF-beta in the modulation of the anti-microbial activity of murine peritoneal macrophages against Mycobacterium avium-intracellulare complex (MAIC). First, both IFN-gamma and TNF-alpha significantly reduced the bacterial growth in macrophages, indicating that these cytokines participate in up-regulation of macrophage anti-MAIC function. Second, although MAIC-infected macrophages produced substantial amounts of IL-10 and TGF-beta, neutralization of endogenous IL-10 and TGF-beta with anti-IL-10 and anti-TGF-beta antibodies, respectively, did not affect the intracellular growth of MAIC in macrophages from mice with BcgS (MAIC-susceptible) or BcgI (MAIC-resistant) genotype, regardless of the virulence of test MAIC strains. The same result was also obtained for macrophages stimulated with IFN-gamma or TNF-alpha. Third, in MAIC-infected mice, the growth of organisms at the sites of infection (lungs and spleens) was not affected by administration of anti-IL-10 or anti-TGF-beta antibodies. These findings indicate that, in the case of mice, endogenous IL-10 and TGF-beta are essentially ineffective in down-regulating macrophage anti-MAIC functions not only in vitro but also in vivo.

Evaluation of in vivo therapeutic efficacy of a new benzoxazinorifamycin, KRM-1648, in SCID mouse model for disseminated Mycobacterium avium complex infection

In this study, profiles of infection due to Mycobacterium avium complex (MAC) in CB-17 SCID mice deficient in T and B cell functions were examined, when mice were given or not given a new benzoxazinorifamycin, KRM-1648 (KRM), during the course of infection. When mice were infected intravenously with MAC, the bacterial loads in their visceral organs were larger than those of their co-isogenic CB-17 counterparts. The incidence and the degree of gross lung lesions were less in SCID mice compared to CB-17 mice. Athymic BALB/c nude mice showed similar profiles of the infection. Beige mice showed more severe gross lesions and larger bacterial loads in the lungs than did SCID and athymic BALB/c nude mice. When MAC was infected subcutaneously into the hind footpads of mice, disseminated growth of organisms in the footpads, blood, and visceral organs was seen in SCID mice, but not in CB-17 or BALB/c mice. KRM exhibited the same level of therapeutic effect on SCID mice infected with MAC via the intravenous route in terms of inhibiting bacterial growth in the lungs and kidneys, as in cases of CB-17 and BALB/c mice with normal T-cell functions. In beige mice, the degree of growth inhibition of MAC due to KRM treatment was significantly greater than that achieved in SCID mice.

Luciferase in vivo expression technology: use of recombinant mycobacterial reporter strains to evaluate antimycobacterial activity in mice

The development of new drugs and vaccines directed against Mycobacterium tuberculosis is severely impeded by the slow growth of this organism and the need to work under stringent biosafety conditions. These difficulties pose considerable obstacles when animal studies with M. tuberculosis are performed. We investigated whether a novel approach termed luciferase in vivo expression, using an enhanced luciferase-expressing mycobacterial strain, could be used to evaluate antimycobacterial activity in mice. Vectors that expressed firefly luciferase (lux gene) at high levels in the bacillus Calmette-Gu-erin (BCG) strain of Mycobacterium bovis were constructed for use in vivo. One recombinant BCG reporter strain (rBCG-lux) was selected for high-level expression of the lux gene product and for its ability to replicate in mice. Methodology to monitor in vivo growth of the rBCG-lux reporter strain in mice by direct assay of luciferase luminescence in organ homogenates was developed. The utility of this approach for assessing the in vivo efficacies of antimycobacterial compounds was evaluated. The activities of standard antimycobacterial drugs were directly apparent in mice infected with the rBCG-lux reporter strain by statistically significant reductions in spleen luminescence. In addition, antimycobacterial immunity was also evident in BCG-immunized mice, in which suppression of rBCG-lux growth in comparison with that in naive mice was clearly observed. The use of luciferase in vivo expression for the in vivo evaluation of antimycobacterial activity compared favorably with standard CFU determinations in terms of time, labor, expense, and statistical significance but permitted the evaluation of antimycobacterial drugs and immunity in mice in 7 days or less. Thus, the use of this technology can greatly accelerate the process of evaluation of antibiotics and immunogens in animal models for the slowly growing pathogenic mycobacteria.