Interleukin-1 or tumor necrosis factor-alpha augmented the cytotoxic effect of mycobacteria on human fibroblasts: application to evaluation of pathogenesis of clinical isolates of Mycobacterium tuberculosis and M. avium complex

CD271(+) bone marrow mesenchymal stem cells may provide a niche for dormant Mycobacterium tuberculosis

Mycobacterium tuberculosis (Mtb) can persist in hostile intracellular microenvironments evading immune cells and drug treatment. However, the protective cellular niches where Mtb persists remain unclear. We report that Mtb may maintain long-term intracellular viability in a human bone marrow (BM)-derived CD271(+)/CD45(-) mesenchymal stem cell (BM-MSC) population in vitro. We also report that Mtb resides in an equivalent population of BM-MSCs in a mouse model of dormant tuberculosis infection. Viable Mtb was detected in CD271(+)/CD45(-) BM-MSCs isolated from individuals who had successfully completed months of anti-Mtb drug treatment. These results suggest that CD271(+) BM-MSCs may provide a long-term protective intracellular niche in the host in which dormant Mtb can reside.

Mai infection simulating metastatic breast cancer

We represent a case of an asymptomatic female who was found to have a mass in the right breast which confirmed an invasive ductal carcinoma by core biopsy. After 3 months of completion of chemo-radiotherapy, the patient remained totally asymptomatic. However, positron emission tomography scan showed four hypermetabolic lesions in the left lung thought to be consistent with metastatic disease. Standard uptake value ranged between 3.86 and 6; the results were consistent with metastatic breast cancer, so wedge resection was performed. Caseating granulomatous inflammation with necrosis was reported. Ultimately culture revealed Mycobacterium avium intracellulare infection. The lesions resolved completely after a course of antibiotics.

Dual mechanism for Mycobacterium tuberculosis cytotoxicity on lung epithelial cells

Mycobacterium tuberculosis strains CDC1551 and Erdman were used to assess cytotoxicity in infected A549 human alveolar epithelial cell monolayers. Strain CDC1551 was found to induce qualitatively greater disruption of A549 monolayers than was strain Erdman, although total intracellular and cell-associated bacterial growth rates over the course of the infections were not significantly different. Cell-free culture supernatants from human monocytic cells infected with either of the 2 M. tuberculosis strains produced a cytotoxic effect on A549 cells, correlating with the amount of tumor necrosis factor alpha (TNF-α) released by the infected monocytes. The addition of TNF-α-neutralizing antibodies to the supernatants from infected monocyte cultures did prevent the induction of a cytotoxic effect on A549 cells overlaid with this mixture but did not prevent the death of epithelial cells when added prior to infection with M. tuberculosis bacilli. Thus, these data agree with previous observations that lung epithelial cells infected with M. tuberculosis bacilli are rapidly killed in vitro. In addition, the data indicate that some of the observed epithelial cell killing may be collateral damage; the result of TNF-α released from M. tuberculosis-infected monocytes.

Simple fibroblast-based assay to test the pyrazinamide susceptibility of Mycobacterium tuberculosis

A simple fibroblast-based assay (SFA) was found to be efficient in evaluating the susceptibilities of clinical isolates of Mycobacterium tuberculosis to pyrazinamide (PZA). Forty-five clinical isolates were examined. The MICs of PZA for susceptible strains in an SFA were between 3.13 and 12.5 microg/ml, and the MICs of PZA for resistant strains were more than 100 microg/ml.

Changes in TNF-α mRNA Levels in the Peripheral Blood of Patients with Chronic Hepatitis C Virus (HCV) Infection during α-Interferon and Ribavirin Therapy

HCV virus infections have become a serious epidemiological problem throughout the world. Hepatitis C therapy includes the administration of IFN-alpha and ribavirin, but results in the complete eradication of HCV viremia in only 30% of patients. TNF-alpha is one of the factors involved in hepatitis C pathogenesis and the results of therapy. In this study, we present the results of applying real-time RT-PCR for assessing the TNF-alpha mRNA level in the peripheral blood of patients treated with IFN-alpha and ribavirin. We found the TNF-alpha mRNA level to be higher in HCV-infected patients compared with healthy controls when analyzed after 4 weeks (p = 0.001) and 3 months (p = 0.003) of IFN-alpha/RIBA therapy. The pretreatment level and the level after six months of therapy were not significantly different from the level of healthy controls. There were no significant differences in TNF-alpha mRNA levels between patients who responded to anti-HCV therapy, resulting in a decrease in HCV viremia below detection limit over 6 months and patients whose HCV RNA was not eliminated (p = 0.881). These results indicate that there is a transient increase of TNF-alpha gene expression during anti-HCV therapy. This fact may be connected with the host organism's response to IFN-alpha/RIBA therapy.

Simple fibroblast-based assay for screening of new antimicrobial drugs against Mycobacterium tuberculosis

In this study, we propose a simple and reproducible host-cell-based assay for the screening of antimycobacterial drugs that is suitable for drug discovery. The method evaluates both antimycobacterial activity of the drugs and their cytotoxicity to host cells. The basis of this simple fibroblast-based assay (SFA) is that cells of human lung fibroblast cell line MRC-5, which are highly sensitive to mycobacterial cytotoxicity, are killed by virulent Mycobacterium tuberculosis strain H(37)Rv bacilli in response to the viability of bacilli. Clinically used antimycobacterial drugs inhibited the mycobacterial cytotoxicity to MRC-5 cells in a dose-dependent manner. MICs of isoniazid, streptomycin, rifampin, and ethambutol determined by this SFA (0.428, 1.816, 0.013, and 3.465 microg/ml, respectively) were within 1 log of MICs determined by the broth dilution test (BDT) using Middlebrook 7H9 medium. The MIC of pyrazinamide, which exhibits bactericidal activity only at a high dose by BDT (1,231 microg/ml at pH 6.6 and 492 microg/ml at pH 5.8), was 3.847 microg/ml in the modified method of SFA. On the other hand, sodium azide, a toxic agent for both mammalian cells and bacteria, exhibited cytotoxicity to fibroblasts at a dose lower than that required to inhibit mycobacterial growth. Thus, this fibroblast-based method enabled us to evaluate both antibacterial activity of drugs and their cytotoxicity to human cells within a short period of time.