National Hansen's Disease Program

Research Interests: James L. Krahenbuhl

Throughout my 30 year career in leprosy research, there have been two underlying focal points of my work. First, to understand the fascinating relationship between the leprosy bacillus and its preferred host cell, the mononuclear phagocyte or macrophage and the role this relationship plays in the pathogenesis of this disease. Second, to characterize the concept of “viability” in M. leprae, an organism that cannot yet be cultivated in the laboratory.

The second area of my interests stems largely from the incredible obstacle that is presented to leprosy researchers unable to have access to large numbers of pure, live M. leprae, which remains uncultivated in the laboratory more than 130 years after its discovery as the first bacterial agent of human disease. We have developed a metabolic and microscopic assay that allows us to differentiate live from dead bacilli in 1 – 7 days rather than 12 months or more using the classic mouse foot pad infection assay and we have defined the strict temperature requirements of M. leprae (several degrees below body temperature, i.e. the temperature found in the skin and cooler parts of the body). By employing expensive, fastidious highly immunocompromised “nude” mice and by carefully scheduling the dose and timing of infection we can harvest billions of pure, highly viable leprosy bacilli on a weekly basis from the mouse's infected foot pads. As a federally funded laboratory we feel it is our obligation to supply this unique, valuable research resource to the qualified leprosy researchers of the world and do so on a weekly basis

The viability of the leprosy bacilli used in an experiment seems to be of paramount importance in studying the host / parasite relationship at the cellular level. Live bacilli seem able to down-regulate various anti-microbial host cell pathways that protect M. leprae from the destruction that normally ensues with other organisms. We think it is this unique skill on the part of M. leprae that allows it to persist in the tissues for years, multiplying very slowly and creating relatively little inflammation or immunological excitement, and defining the slow chronic nature of the disease leprosy.

Representative publications

Truman, R. W. and J.L. Krahenbuhl .; Viable M. leprae as a research reagent. Inter.J. Lepr. 69: 1-12, 2001.

Adams , L.B. and J.L. Krahenbuhl . Human Leprosy. In Granulomatous Infections and Inflammations., D. L. Boros, ed., ASM Press, Washington D.C. , 207-244, 2003.

Fukutomi, Y., Matsuoka, M., Minagaw, M., Toratani, A., McCormick, G. and J. Krahenbuhl , IL-10 treatment of macrophages bolsters intracellular survival of Mycobacterium leprae, Int. J. Leprosy, 72: 16-26, 2004.

Lahiri, R., Randhawa, B. and J. Krahenbuhl , Application of a viability-staining method for Mycobacterium leprae derived from the athymic (nu/nu) mouse footpad. J Med Microbio. 54:1-8, 2005.

Lahiri, R., Randhawa, B. and J. Krahenbuhl , Effects of Purification and Fluorescent Staining on Viability of Mycobacterium leprae. Int. J. Leprosy, 73:194-202, 2005.

Murray , R., Siddiqui, R, Mendillo, M., Krahenbuhl , J. and G. Kaplan. Mycobacterium leprae inhibits dendritic cell activation and maturation. J. Immunol. 178:338-344, 2007.