Background: Mycobacterium africanum (MAF) and Mycobacterium tuberculosis sensu
strico (MTBss) are two members of a closely related bacterial species of Mycobacterium
tuberculosis complex (MTBC) that causes tuberculosis (TB) in humans. However MAF is
known to cause up to 50% of human pulmonary TB in West Africa only. MAF has been subdivided into MAF West African 1 (MAF1) (Lineage 5) and MAF West African 2 (MAF2)
(Lineage 6), as two distinct phylogenetical lineages within MTBC. Subsequently the absence
of Mycobacterium tuberculosis deletion gene (TbD1) strains in MTBss has been referred to
as modern lineage whilst ancient lineage (MAF1 and MAF2) have the presence of TbD1.
Ghana represents one of the few countries within Central West Africa known to have this
unique genetic diversity of MAF1, MAF2 and MTBss that causes TB cases in significant
proportions. While previously it was thought MAF is genetically very closely related to
MTBss such that there are no important phenotypic differences between the two species,
current advance in molecular biology indicate that substantial genetic difference exit between
the two that can translate into significant phenotypic differences including immunogenicity
Aim: The aim of the study was to analyze the phenotypic features of host-pathogen
interaction in Mycobacterium africanum and compared to Mycobacterium tuberculosis sensu
Methodology: The study was embedded in 2 different projects. Retrospective archived
cryopreserved peripheral blood mononuclear cells (PBMCs) of MAF-infected and MTBssinfected patients were stimulated with growth medium (negative control), Staphylococcus
enterotoxin B (SEB, positive control) and recombinant early secreted antigenic protein 6
kiloDalton/culture filtrate protein 10 kiloDalton fusion protein (rESAT-6/CFP-10), surface stained for T-subsets (CD4 and CD8) and intracellular cytokine, interferon gamma (IFN-),
and acquired with FACS Calibur flow cytometer. The second study used characterized large
sequence polymorphism (LSP) clinical isolates identified as MAF1, MAF2 and MTBss to
determine intracellular growth assay in human monocyte–derived macrophages (MDM),
mean doubling time and pro-inflammatory tumour necrosis factor–alpha (TNF-α), interleukin
6 (IL-6) and 12p70 cytokines by enzyme-linked immunosorbent assay (ELISA).
Results: The percentage frequencies of CD4+IFN-+ and CD8+ IFN-+ T cells of MAFinfected patients did not differ from the percentage frequencies CD4+ IFN-+ and CD8+
IFN-+ T cells of MTB-infected patients in response to rESAT-6/CFP-10 fusion protein
(p>0.05). Uptake of MAF1, MAF2 and MTBss representing modern and ancient strains
respectively at 4hours was not significant (p>0.05). Mean intracellular growth index from
24hours to 72hours was significantly rapid for MTBss (modern) lineage compared to MAF1
and MAF2 (ancient) lineages (p<0.05). In contrast the mean doubling time of MTBss
(modern) lineage was significantly lower compared to MAF1 and MAF2 (ancient) lineages
(p<0.05). Levels of pro-inflammatory cytokines released into the supernatants by MTBss,
MAF1 and MAF2 at 4hours was not statistically significant (p>0.05). However at 24hours to
72hours levels released by MAF1 and MAF2 (ancient) lineages was significantly higher than
MTBss (modern) lineage (p<0.05).
Conclusion: The study has shown that MAF-infected patients had similar T subset response
to rESAT-6/CFP-10 fusion protein relative to MTBss-infected patients. Furthermore MAF
had reduced uptake, low intracellular growth rate and a higher doubling time in MDM.
Likewise MAF (ancient) lineages have hyper-inflammatory response thereby inducing a
‘slow growth’ phenotype highlighting the point that MAF indeed has lower virulence and
longer latency leading to slower progression to active disease in the host.
CDR, C (2021). PHENOTYPIC CHARACTERIZATION OF HOST-PATHOGEN INTERACTION IN Mycobacterium africanum. Afribary.com: Retrieved April 11, 2021, from https://afribary.com/works/phenotypic-characterization-of-host-pathogen-interaction-in-mycobacterium-africanum
Coalition, CDR. "PHENOTYPIC CHARACTERIZATION OF HOST-PATHOGEN INTERACTION IN Mycobacterium africanum" Afribary.com. Afribary.com, 02 Apr. 2021, https://afribary.com/works/phenotypic-characterization-of-host-pathogen-interaction-in-mycobacterium-africanum . Accessed 11 Apr. 2021.
Coalition, CDR. "PHENOTYPIC CHARACTERIZATION OF HOST-PATHOGEN INTERACTION IN Mycobacterium africanum". Afribary.com, Afribary.com, 02 Apr. 2021. Web. 11 Apr. 2021. < https://afribary.com/works/phenotypic-characterization-of-host-pathogen-interaction-in-mycobacterium-africanum >.
Coalition, CDR. "PHENOTYPIC CHARACTERIZATION OF HOST-PATHOGEN INTERACTION IN Mycobacterium africanum" Afribary.com (2021). Accessed April 11, 2021. https://afribary.com/works/phenotypic-characterization-of-host-pathogen-interaction-in-mycobacterium-africanum