Development of a diagnostic gene expression assay for tuberculosis and its use under field conditions in African buffaloes (Syncerus caffer).
The development of diagnostic tests for tuberculosis (TB) in exotic species is constrained by host biology and the limited availability of suitable assay reagents. As such, we evaluated a gene expression assay (GEA) which is easily modified for novel species and allows for initial sample processing under field conditions. African buffaloes (Syncerus caffer) were categorized using the single comparative intradermal tuberculin test, and blood from test-positive and test-negative animals was incubated for 20 h in "Nil" tubes (containing saline) and "TB Antigen" tubes (containing Mycobacterium tuberculosis complex (MTC)-specific antigens) of a commercial human TB test, the QuantiFERON(®)-TB Gold (In-Tube) (QFT) assay. Blood samples were then stabilized in RNAlater(®) and transported to the laboratory for RNA extraction. A Custom TaqMan GEA was used to calculate the relative abundance of interferon-gamma (IFN-γ) mRNA in the TB Antigen tube compared to that in the Nil tube as a marker of immune activation in response to MTC antigen recognition. The GEA results from the two buffalo groups were compared and a cutoff value of 2.85 was calculated to differentiate between animals from these groups with a sensitivity of 80% (95% C.I.: 56-94%) and a specificity of 95% (95% C.I.: 75-100%). Further optimization of this assay could provide a highly useful tool for the diagnosis of MTC infection in exotic species.
DST/NRF Centre of Excellence for Biomedical TB Research/MRC Centre for Molecular and Cellular Biology/Division of Molecular Biology and Human Genetics, Stellenbosch University, P.O. Box 19063, Tygerberg, 7505, South Africa. sparsons@sun.ac.za
Sven D C
SD
Parsons
Angela M
AM
Menezes
David
D
Cooper
Gerhard
G
Walzl
Robin M
RM
Warren
Paul D
PD
van Helden
D000818:Animals; D002020:Buffaloes / Q000276:immunology / Q000382:microbiology*; D020869:Gene Expression Profiling / Q000379:methods / Q000662:veterinary*; D007111:Immunity, Cellular; D007371:Interferon-gamma / Q000097:blood; D009169:Mycobacterium tuberculosis / Q000378:metabolism; D013019:South Africa; D014374:Tuberculin Test / Q000662:veterinary; D014376:Tuberculosis / Q000175:diagnosis / Q000662:veterinary*
D007371:Interferon-gamma