IL-1R1-Dependent Signals Improve Control of Cytosolic Virulent Mycobacteria In Vivo.

Mycobacterium tuberculosis infections claim more than a million lives each year, and better treatments or vaccines are required. A crucial pathogenicity factor is translocation from phagolysosomes to the cytosol upon phagocytosis by macrophages. Translocation from the phagolysosome to the cytosol is an ESX-1-dependent process, as previously shown in vitro Here, we show that in vivo, mycobacteria also translocate to the cytosol but mainly when host immunity is compromised. We observed only low numbers of cytosolic bacilli in mice, armadillos, zebrafish, and patient material infected with M. tuberculosis, M. marinum, or M. leprae In contrast, when innate or adaptive immunity was compromised, as in severe combined immunodeficiency (SCID) or interleukin-1 receptor 1 (IL-1R1)-deficient mice, significant numbers of cytosolic M. tuberculosis bacilli were detected in the lungs of infected mice. Taken together, in vivo, translocation to the cytosol of M. tuberculosis is controlled by adaptive immune responses as well as IL-1R1-mediated signals.IMPORTANCE For decades, Mycobacterium tuberculosis has been one of the deadliest pathogens known. Despite infecting approximately one-third of the human population, no effective treatment or vaccine is available. A crucial pathogenicity factor is subcellular localization, as M. tuberculosis can translocate from phagolysosome to the cytosol in macrophages. The situation in vivo is more complicated. In this study, we establish that high-level cytosolic escape of mycobacteria can indeed occur in vivo but mainly when host resistance is compromised. The IL-1 pathway is crucial for the control of the number of cytosolic mycobacteria. The establishment that immune signals result in the clearance of cells containing cytosolic mycobacteria connects two important fields, cell biology and immunology, which is vital for the understanding of the pathology of M. tuberculosis.

Tumor-reducing effect of the clinically used drug clofazimine in a SCID mouse model of pancreatic ductal adenocarcinoma.

Pancreatic ductal adenocarcinoma (PDAC) represents the most common form of pancreatic cancer with rising incidence in developing countries. Unfortunately, the overall 5-year survival rate is still less than 5%. The most frequent oncogenic mutations in PDAC are loss-of function mutations in p53 and gain-of-function mutations in KRAS. Here we show that clofazimine (Lamprene), a drug already used in the clinic for autoimmune diseases and leprosy, is able to efficiently kill in vitro five different PDAC cell lines harboring p53 mutations. We provide evidence that clofazimine induces apoptosis in PDAC cells with an EC50 in the µM range via its specific inhibitory action on the potassium channel Kv1.3. Intraperitoneal injection of clofazimine resulted in its accumulation in the pancreas of mice 8 hours after administration. Using an orthotopic PDAC xenotransplantation model in SCID beige mouse, we show that clofazimine significantly and strongly reduced the primary tumor weight. Thus, our work identifies clofazimine as a promising therapeutic agent against PDAC and further highlights ion channels as possible oncological targets.

Severe combined immunodeficiency mouse-psoriatic human skin xenograft model: a modern tool connecting bench to bedside.

Psoriasis is a multifactorial chronic inflammatory disease. Research into the pathogenesis of this disease is hindered by the lack of a proper animal model. Over the past two decades, many scientists were involved in the development of animal models that nearly mirror the immunopathogenesis of psoriasis. One such model, which has opened doors to the study of molecular complexities of psoriasis as well as its treatment, is the severe combined immunodeficiency (SCID) mouse-human skin chimera model. This model not only mirrors the clinical and histopathological features of psoriasis but also help in the study of cell proliferation, angiogenesis, function of T cells, neurogenic inflammation and cytokines involved in inflammatory reactions. In this article, we have reviewed the prospects and the limitations of the SCID mouse model of psoriasis.

Susceptibility of severe combined immunodeficient mice to Mycobacterium leprae.

The susceptibility of severe combined immunodeficient (SCID) mice to human leprosy bacilli was investigated. Nude mice were used as controls. SCID mice were found to be highly susceptible to Mycobacterium leprae and the progress of infection was comparatively 2-3 months earlier than observed in the nude mice. After reaching a maximum of approximately 1 x 10(9) acid fast bacilli/foot pad at about 8 months postinfection the number of bacilli gradually decreased. The progress of infection in nude mice was different from that found in SCID mice. The multiplication of M. leprae in the foot pads of nude mice continued and reached approximately 2.0 x 10(10) bacilli/foot pad and then nearly remained the same. The results indicate that SCID mice can be used as a suitable model for screening antileprosy drugs while nude mice should be involved in the production of M. leprae for use in other fields of leprosy research.

Infection of SCID mice with Mycobacterium leprae and control with antigen-activated "immune" human peripheral blood mononuclear cells.

The SCID (severe combined immunodeficient) mouse lacks both B and T cells and tolerates injected mononuclear cells from humans, the principal hosts of Mycobacterium leprae. A SCID mouse model of leprosy could be useful to investigate potential vaccine strategies using human cells in a context in which the growth of the organism is monitored. Initial experiments determined that SCID mice are more susceptible than normal mice to infection and dissemination of M. leprae. Cells from humans, either BCG vaccinated or from countries where leprosy is endemic, were stimulated in vitro with a number of mycobacterial antigens--whole M. leprae, M. leprae cell walls, purified protein derivative of M. tuberculosis, and Mycobacterium bovis BCG--and tested for proliferation and production of interleukin-6, tumor necrosis factor alpha, and gamma interferon. Cell walls were the most efficient and consistent in inducing all of these activities. In vitro-activated human cells retain function better after injection into SCID mice than nonactivated cells. To test the ability of cells to affect the growth of M. leprae in the footpads of SCID mice, cells from a known responder to mycobacterial antigens and from a nonresponder were activated by M. leprae cell wall antigens. The cells were harvested and coinjected with fresh M. leprae into the right hind footpads of SCID mice. After 3 months, there was no growth of M. leprae in the footpads of mice coinjected with cells from the mycobacterial antigen responder, while growth was uninhibited in mice receiving cells from the nonresponder. Future experiments will determine requirements for antigen specificity in inhibiting M. leprae multiplication.

Reconstitution of Mycobacterium leprae immunity in severe combined immunodeficient mice using a T-cell line.

To test whether Mycobacterium leprae-immune T cells can confer protection against infection with leprosy bacilli, severe combined immunodeficient (SCID) mice were reconstituted with a BALB/c-derived, M. leprae-responsive, T-cell line. Flow cytometric analysis of spleen and peripheral blood cells confirmed reconstitution with T cells. In vitro lymphokine production and the proliferation of spleen cells from the reconstituted animals established that the donor cells had maintained their functional activity for the duration of the study (275 days). The transfer of immune T cells 24 hr before foot pad infection with leprosy bacilli resulted in a profound reduction in M. leprae multiplication, as compared to the nonreconstituted SCID mice. The yield of acid-fast bacilli in the foot pads of SCID mice reconstituted with the M. leprae-immune T cells also was significantly lower than that found in naive BALB/c mice, and at levels previously found only in BALB/c mice that had been immunized effectively. These experiments demonstrate that M. leprae-immune T cells home effectively and control M. leprae infection in SCID mice.

[Infection and elimination of Mycobacterium leprae in SCID C.B.-17 mice (severe combined immunodeficiency)]. / Infection et élimination de Mycobacterium leprae par la souris SCID C.B.-17 (déficit immunitaire combiné sévère).

Previous studies documented that T-cell deficient nude mice failed to control M. leprae infection. In the present investigation we monitored the growth of M. leprae for up to 15 months in the SCID C.B.-17 mouse, a host deficient in both T and B lymphocytes. At 8 months post-infection 10(8) organisms/foot-pad were recovered from SCID mice vs 5 x 10(6) in normal BALB/c mice. Thereafter the number of bacilli decreased rapidly in mice infected with high-dose inoculum (10(7)); however, at all doses SCID mice eventually cleared M. leprae. During infection both T and B cells as well as serum Ig remained as low as in uninfected mice; however, in the spleen MAC-1+ cells which include macrophages and NK cells were substantially increased. These results suggest that MAC-1+ cells are involved in the anti-mycobacteria-1 defence mechanisms adopted by SCID mice to compensate their deficiency in T and B cells.

Susceptibility of severe combined immunodeficient (SCID) mice to Mycobacterium leprae: multiplication of the bacillus and dissemination of the infection at early stage.

Inoculation of M. leprae were made into the both hind feet at a dose of 4.8 x 10(6) bacilli per foot in order to determine the susceptibility to M. leprae of SCID mice which is severely deficient in both T- and B cell immunity. SCID mice was found to have an extremely high susceptibility to M. leprae, and the progress of infection observed in the SCID mice were shown a rapid systemic spread of infection at the all over the tissues as well as the growth of the leprosy bacilli at the site of inoculation. Therefore, SCID mice can be used as a suitable multibacillary model for the study of leprosy.