It is expected that the obligatory human pathogen Mycobacterium tuberculosis must adapt metabolically to the various nutrients available during its cycle of infection, persistence, and reactivation. Cholesterol, which is an important part of the mammalian cytoplasmic membrane, is a potential energy source. Here, we show that M. tuberculosis grown in medium containing a carbon source other than cholesterol is able to accumulate cholesterol in the free-lipid zone of its cell wall. This cholesterol accumulation decreases the permeability of the cell wall for the primary antituberculosis drug, rifampin, and partially masks the mycobacterial surface antigens. Furthermore, M. tuberculosis was able to grow on mineral medium supplemented with cholesterol as the sole carbon source. Targeted disruption of the Rv3537 ( kstD ) gene inhibited growth due to inactivation of the cholesterol degradation pathway, as evidenced by accumulation of the intermediate, 9-hydroxy-4-androstene-3,17-dione. Our findings that M. tuberculosis is able to accumulate cholesterol in the presence of alternative nutrients and use it when cholesterol is the sole carbon source in vitro may facilitate future studies into the pathophysiology of this important deadly pathogen.

Interleukin‐8 (IL‐8) has been implicated in the pathogenesis of several human respiratory diseases, including tuberculosis (TB). Importantly and in direct relevance to the objectives of this report quite a few findings suggest that the presence of IL‐8 may be beneficial for the host. IL‐8 may aid with mounting an adequate response during infection with Mycobacterium tuberculosis (M. tb); however, the underlying mechanism remains largely unknown. The major goal of our study was to investigate the contribution of IL‐8 to the inflammatory processes that are typically elicited in patients with TB. We have shown for the first time that IL‐8 can directly bind to tubercle bacilli. We have also demonstrated that association of IL‐8 with M. tb molecules leads to the augmentation of the ability of leukocytes (neutrophils and macrophages) to phagocyte and kill these bacilli. In addition, we have shown that significant amount of IL‐8 present in the blood of TB patients associates with erythrocytes. Finally, we have noted that IL‐8 is the major chemokine responsible for recruiting T lymphocytes (CD3⁺, CD4⁺, and CD8⁺ T cells). In summary, our data suggest that the association of IL‐8 with M. tb molecules may modify and possibly enhance the innate immune response in patients with TB.

Recent reports have indicated that cholesterol plays a crucial role during the uptake of mycobacteria by macrophages. However, the significance of ch

Toxoplasma gondii, a protozoan parasite, is capable of infecting a broad range of intermediate warm-blooded hosts including humans. The parasite undergoes sexual reproduction resulting in genetic variability only in the intestine of the definitive host (a member of the cat family). The parasite seems to be capable of altering the natural behavior of the host to favor its transmission in the environment. The aim of this study was to evaluate the number of parasite cysts formed in the hippocampus and amygdala of experimentally infected mice as these regions are involved in defense behaviors control and emotion processing, and to assess the influence of the infection on mice behavior. The obtained results revealed the presence of parasite cysts both in the hippocampus and the amygdala of infected mice; however, no clear region-dependent distribution was observed. Furthermore, infected mice showed significantly diminished exploratory activity described by climbing and rearing, smaller preference for the central, more exposed part of the OF arena and engaged in less grooming behavior compared to uninfected controls.