Mycobacterium tuberculosis Requires Cholesterol Oxidase to Disrupt TLR2 Signalling in Human Macrophages

Enhanced effectiveness in preventing Nocardia seriolae infection utilizing heterologous prime-boost approach in orange-spotted grouper Epinephelus coioides

Persistent nocardiosis has prompted exploration of the effectiveness of heterologous approaches to prevent severe infections. We have previously reported the efficacy of a nucleic acid vaccine in protecting groupers from highly virulent Nocardia seriolae infections. Ongoing research has involved the supplementation of recombinant cholesterol oxidase (rCho) proteins through immunization with a DNA vaccine to enhance the protective capacity of orange-spotted groupers. Recombinant rCho protein exhibited a maturity and biological structure comparable to that expressed in N. seriolae, as confirmed by Western blot immunodetection assays. The immune responses observed in vaccinated groupers were significantly higher than those observed in single-type homologous vaccinations, DNA or recombinant proteins alone (pcD:Cho and rCho/rCho), especially cell-mediated immune and mucosal immune responses. Moreover, the reduction in N. seriolae occurrence in internal organs, such as the head, kidney, and spleen, was consistent with the vaccine's efficacy, which increased from approximately 71.4 % to an undetermined higher percentage through heterologous vaccination strategies of 85.7 %. This study underscores the potential of Cho as a novel vaccine candidate and a heterologous approach for combating chronic infections such as nocardiosis.

Recognition of Mycobacterium tuberculosis by macrophage Toll-like receptor and its role in autophagy

BACKGROUND

The pathogen responsible for tuberculosis is called Mycobacterium tuberculosis. Its interaction with macrophages has a significant impact on the onset and progression of the disease.

METHODS

The respiratory pathway allows Mycobacterium tuberculosis to enter the body's lungs where it battles immune cells before being infected latently or actively. In the progress of tuberculosis, Mycobacterium tuberculosis activates the body's immune system and creates inflammatory factors, which cause tissue inflammation to infiltrate and the creation of granulomas, which seriously harms the body. Toll-like receptors of macrophage can mediate host recognition of Mycobacterium tuberculosis, initiate immune responses, and participate in macrophage autophagy. New host-directed therapeutic approaches targeting autophagy for drug-resistant Mycobacterium tuberculosis have emerged, providing new ideas for the effective treatment of tuberculosis.

CONCLUSIONS

In-depth understanding of the mechanisms by which macrophage autophagy interacts with intracellular Mycobacterium tuberculosis, as well as the study of potent and specific autophagy-regulating molecules, will lead to much-needed advances in drug discovery and vaccine design, which will improve the prevention and treatment of human tuberculosis.

[TRAF6 promotes Bacillus Calmette-Guérin-induced macrophage apoptosis through the intrinsic apoptosis pathway]

OBJECTIVE

To investigate the role of tumor necrosis factor receptor-associated factor 6 (TRAF6) in regulating Bacillus Calmette-Guérin (BCG)-induced macrophage apoptosis.

METHODS

The expression of TRAF6 in peripheral blood samples of 50 patients with active tuberculosis (TB) and 50 healthy individuals were detected using quantitative real-time PCR (qPCR). RAW264.7 macrophages were infected with BCG at different MOI and for different lengths of time, and the changes in expressions of Caspase 3 and TRAF6 were detected with Western blotting and qPCR. In a RAW264.7 cell model of BCG infection with TRAF6 knockdown established using RNA interference technique, the bacterial load was measured and cell apoptotic rate and mitochondrial membrane potential (MMP) were determined with flow cytometry. The expression levels of TRAF6, Caspase 3, PARP, BAX and Bcl-2 in the cells were detected using Western blotting, and the expressions of TRAF6 and Caspase 3 were also examined with immunofluorescence assay.

RESULTS

The expression of TRAF6 was significantly upregulated in the peripheral blood of patients with active TB as compared with healthy subjects (P < 0.001). In RAW264.7 cells, BCG infection significantly increased the expressions of Caspase 3 and TRAF6, which were the highest in cells infected for 18 h and at the MOI of 15. TRAF6 knockdown caused a significant increase of bacterial load in BCG-infected macrophages (P=0.05), lowered the cell apoptotic rate (P < 0.001) and reduced the expressions of Caspase 3 (P=0.002) and PARP (P < 0.001). BCG-infected RAW264.7 cells showed a significantly increased MMP (P < 0.001), which was lowered by TRAF6 knockdown (P < 0.001); the cells with both TRAF6 knockdown and BCG infection showed a lowered BAX expression (P=0.005) and an increased expression of Bcl-2 (P=0.04).

CONCLUSION

TRAF6 promotes BCG-induced macrophage apoptosis by regulating the intrinsic apoptosis pathway.

Determination of in vitro and in vivo immune response to recombinant cholesterol oxidase from Mycobacterium tuberculosis

Cholesterol oxidase (ChoD) is an enzyme that is involved but is dispensable in the process of cholesterol degradation by Mycobacterium tuberculosis (Mtb). Interestingly, ChoD is a virulence factor of Mtb, and it strongly modulates the function of human macrophages in vitro, allowing the intracellular survival of bacteria. Here, we determined the immunogenic activity of recombinant ChoD from Mtb in a mouse model. We found that peritoneal exudate cells obtained from mice injected i.p. with ChoD but not those from mice injected with PBS responded in vitro with highly spontaneous, as well as phorbol 12-myristate 13-acetate (PMA)-stimulated, production of reactive oxygen species (ROS). However, ChoD significantly reduced the ROS response to PMA in re-stimulated cells in vitro. The cytokine secretion pattern in mice immunized s.c. with ChoD emulsified with incomplete Freund's adjuvant (IFA) showed evidence of Th2-induced or proinflammatory immune responses. The main cytokines detected in sera were interleukin (IL) 6 and 5, tumour necrosis factor α (TNF-α) and monocyte chemoattractant protein 1, while IL-2 and IL-12 as well as interferon γ were undetectable. Similarly, ChoD protein alone activated THP-1-derived macrophages to release proinflammatory IL-6, IL-8 and TNF-α, in vitro. Moreover, a statistically significant predominance of the IgG1 isotype over that of IgG2a in the sera of mice immunized with ChoD/IFA was observed. In conclusion, we demonstrated here that ChoD of Mtb is an active protein, which is able to induce the immune response both in vivo and in vitro.