Recent progress in understanding host-fungal interactions

Lipid peroxidation in the liver of mice during development of granulomatous inflammation after combined infection with C. albicans and M. tuberculosis

Activity of LPO in the liver of CBA mice during the development of granulomatous inflammation after combined infection with C. albicans and M. tuberculosis was evaluated by the levels of conjugated dienes, ketodienes, conjugated trienes, and products of interactions between intermediate LPO products and 2-TBA. The content of primary and secondary LPO products peaked on days 3 and 10 after infection by C. albicans, respectively. After M. tuberculosis infection, the maximum accumulation of TBA-active LPO products in the liver was noted on day 3, while the level of primary lipid peroxides virtually did not increase. The dynamics of primary and secondary LPO products in the liver during granulomatous inflammation development was similar to that during infection of mice with C. albicans alone. Hence, the development of granulomatous inflammation induced by C. albicans or M. tuberculosis or both these agents, was associated with increased LPO activity in the liver. The dynamics of primary and secondary LPO products depended on the infectious agent or combination of agents.

Requisite elements in vaccine immunity to Blastomyces dermatitidis: plasticity uncovers vaccine potential in immune-deficient hosts

Understanding fundamental mechanisms of vaccine immunity will allow proper use and optimization of vaccines. Vaccination with a genetically engineered, live, attenuated strain of Blastomyces dermatitidis carrying a targeted deletion at the BAD1 locus confers sterilizing immunity against experimental lethal pulmonary infection. We found in this study that alphabeta T cells are requisite for durable vaccine immunity, whereas other T and B cells are dispensable. In immune-competent animals, CD4(+) T-cell derived cytokines TNF-alpha and IFN-gamma mediate vaccine immunity. Surprisingly, these factors are dispensable in immune-deficient animals, which rely on alternate mechanisms for robust vaccine immunity, yet still require O(2)(-) production rather than generation of NO. Our results clarify the cellular and molecular bases behind the first genetically engineered fungal vaccine. They also illustrate a sharp difference in vaccine mechanisms between immune-competent and immune-deficient hosts, which underscores the plasticity of residual immune elements in compromised hosts, and points to the feasibility of developing vaccines against invasive fungal infection in this fast growing patient population.

Microbiology. Turning up the heat on Histoplasma capsulatum

Many fungal pathogens are opportunistic, that is, they infect individuals who have a compromised immune system. Histoplasma capsulatum is a common pathogenic fungus that lives happily inside the phagosomes of macrophages. As Klein explains in his Perspective, an important H. capsulatum virulence factor, CBP1, has been found, which mops up free calcium ions within the phagosome, enabling the yeast to live under calcium-poor conditions (Sebhgati et al.). Chelating calcium ions may also have the added benefit that when the phagosome fuses with the lysosome, destructive lysosomal enzymes that require calcium ions for activity remain inactive.