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Updated: Jun 12, 2026
System for Efficacy and Cytotoxicity Screening of Inhibitors Targeting Intracellular Mycobacterium tuberculosis
Published on: April 5, 2017
Development of infection model for studying intracellular gene expression of Mycobacterium tuberculosis
O A T Alli1, D O Ogbolu, C L Spreadbury
1Department of Biomedical Sciences, College of Health Sciences, Ladoke Akintola University of Technology, Osogbo, Nigeria. alliot@hotmail.com
Abstract:
Mycobacterium tuberculosis complex owe their ability to cause infection because of their intracellular survival ability in professional phagocytic cells of human and the ability to enter into stage ofdormancy. The aim of this study was to develop an infection model that could be used to study M. tuberculosis and macrophage interactions at molecular level. Four infection models were examined namely opsonised M. bovis BCG / J774.2 macrophage cell line, non-opsonised M. bovis BCG / J774.2 macrophage cell line, opsonised M. tuberculosis / J774.2 macrophage cell line, and non-opsonised M. tuberculosis / J774.2 macrophage cell line infection models. A J774.2 macrophage cell line was synchronously infected with M. bovis (BCG strain) and M. tuberculosis (H37Rv), respectively at different multiplicity of infections (M.O.I). For opsonisation, the organisms were pre-incubated with human serum prior to infection. The infected cell lines were examined by light microscopy and electron microscopy with viable bacterial counts. Macrophage viability was assessed by trypan blue exclusion staining. The results showed higher significant level of infection of J774.2 macrophage cell line by opsonised M. bovis BCG (30 - 40%) compared to non-opsonised M. bovis BCG (< 0.1%) at an M.O.I of 50 (p < 0.05) with high macrophage viability. In contrast, there was no significant statistical difference (p > 0.05) in high infectivity (30 - 42%) with high macrophage viability achieved with using non-opsonised M. tuberculosis and opsonised M. tuberculosis, respectively, at an M.O.I of 10. In conclusion, opsonisation is not required for M. tuberculosis / J774.2 infection model in contrast to M. bovis BCG / J774.2 infection model where opsonisation is necessary to achieve high level of infection.
Insights
Developing an effective Mycobacterium tuberculosis infection model is crucial. Opsonisation is essential for Mycobacterium bovis BCG but not for Mycobacterium tuberculosis infection models in macrophages.
Area of Science:
- Immunology
- Microbiology
- Cell Biology
Background:
- Mycobacterium tuberculosis complex bacteria survive intracellularly within macrophages and can enter dormancy.
- Understanding host-pathogen interactions is key to developing effective tuberculosis treatments.
- Developing robust infection models is essential for studying Mycobacterium tuberculosis and macrophage dynamics.
Purpose of the Study:
- To establish and compare four Mycobacterium tuberculosis and Mycobacterium bovis BCG infection models using J774.2 macrophage cell lines.
- To investigate the role of opsonisation in macrophage infection by M. tuberculosis and M. bovis BCG.
- To evaluate bacterial infectivity and host cell viability in different infection models.
Main Methods:
- Four infection models were tested: opsonised and non-opsonised M. bovis BCG and M. tuberculosis with J774.2 macrophages.
- Synchronous infection was performed at various multiplicities of infection (MOI).
- Opsonisation involved pre-incubation with human serum; infection was assessed via microscopy, viable counts, and macrophage viability assays (trypan blue exclusion).
Main Results:
- Opsonised M. bovis BCG significantly increased infection rates (30-40%) compared to non-opsonised (<0.1%) at MOI 50 (p < 0.05), with high macrophage viability.
- No significant difference in infectivity (30-42%) was observed between opsonised and non-opsonised M. tuberculosis at MOI 10 (p > 0.05), maintaining high macrophage viability.
- Opsonisation was crucial for M. bovis BCG but not for M. tuberculosis in establishing macrophage infection models.
Conclusions:
- Opsonisation is a critical factor for efficient M. bovis BCG infection of macrophages.
- Opsonisation is not required for establishing M. tuberculosis infection models in J774.2 macrophages.
- These findings aid in selecting appropriate methods for studying tuberculosis pathogenesis and host-pathogen interactions.
