Comparison of Cytokines Expression from Human Monocyte-Derived Macrophages Infected with Different Species of Mycobacteria.

Cytokines have an important role in mounting effective host immune response against mycobacteria. Latent tuberculosis infection (LTBI) is an indication of containment of mycobacteria by the host immune response, whereas active TB is an indication of a failure of the immune response to contain Mycobacterium tuberculosis. The dynamics of this host-immune response during in vitro infection experiment is believed to be indicative of behavior in the LTBI and active-TB cases. This relationship is, however, not fully elucidated. We investigated the cytokines expression at mRNA and protein level across 2 different protocols, that is, an in vitro protocol comparing human monocyte-derived macrophages (hMDMs; n = 12) infected with different species of mycobacteria, and a clinical protocol comparing TB-Antigen-Nil specimens from LTBI (n = 12) and active-TB (n = 12) cases. We found that in vitro infection of hMDMs with Mycobacterium bovis Bacillus Calmette-Guérin (BCG) and M. tuberculosis R179 showed increased colony-forming units at all time points postinfection. M. bovis BCG-infected hMDMs demonstrated higher levels of 5 cytokines [interferon (IFN)-γ, interleukin (IL)-6, IL-1ß, IL-12p40, and IL-12p70] at different intervals compared to M. tuberculosis R179. Compared to LTBI, active-TB cases had higher mRNA expression of IFN-α, IL-6, and IL-8, and lower expression of IFN-γ, IL-1α, IL-1ß, IL-4, and tumor necrosis factor-α. Overall, we observed differential host responses at mRNA and protein levels during experimentally controlled in vitro infection, but no prominent differences were observed in the clinical protocol. Therefore, the result of the in vitro experiment model of cytokine response against mycobacteria should be interpreted cautiously when relating to LTBI and active-TB.

Cytokine gene expression assay as a diagnostic tool for detection of Mycobacterium bovis infection in warthogs (Phacochoerus africanus).

Mycobacterium bovis infection has been described in many wildlife species across Africa. However, diagnostic tests are lacking for many of these, including warthogs (Phacochoerus africanus). Most literature on suids has focused on using serological tools, with few studies investigating the use of cell-mediated immune response (CMI) assays. A recent study showed that warthogs develop measurable CMI responses, which suggests that cytokine gene expression assays (GEAs) may be valuable for detecting M. bovis-infection, as shown in numerous African wildlife species. Therefore, the aim of the study was to develop GEAs capable of distinguishing between M. bovis-infected and uninfected warthogs. Whole blood was stimulated using the QuantiFERON-TB Gold (In-Tube) system, using ESAT-6 and CFP-10 peptides, before determining the relative gene expression of five reference (B2M, H3F3A, LDHA, PPIA and YWHAZ) and five target (CXCL9, CXCL10, CXCL11, IFNG and TNFA) genes through qPCR. The reference gene H3F3A was the most stably expressed, while all target genes were significantly upregulated in M. bovis-infected warthogs with the greatest upregulation observed for CXCL10. Consequently, the CXCL10 GEA shows promise as an ante-mortem diagnostic tool for the detection of M. bovis-infected warthogs.