Abstract
Recently we proposed exploring the potential of treatment stimulated testing as diagnostic method for tuberculosis (TB). An infection controlled placebo controlled mouse study was performed to investigate whether serum cytokine levels changed measurably during the early phase of TB chemotherapy. Serum was collected prior to and during the first 3 weeks of isoniazid (INH) and rifampicin (RIF) chemotherapy, and levels of 23 selected cytokines/chemokines were measured using a liquid bead array. The serum levels of IFNγ, IP-10, MIG, MCP-1, IL-17 and IL-6 were elevated in the TB infected mice compared to non-infected mice at least at 1 time point measured. In infected mice, IFNγ, IP-10, MIG and MCP-1 levels decreased within 7 days of treatment with RIF+INH compared to placebo. Treatment of non-infected mice in the absence of tuberculosis infection had no effect on these cytokines. IL-17 and IL-6 had decreased to baseline in all infected mice prior to the initiation of treatment. This study demonstrates that systemic levels of some cytokines, more specifically IFNγ, IP-10, MIG and MCP-1, rapidly and specifically change upon starting TB chemotherapy only in the presence of infection in a mouse model. Thus, IFNγ, IP-10, MIG and MCP-1 are promising ‘Treat-to-Test’ targets for the diagnosis of TB and deserve further investigation in a study on human TB suspects.
Highlights
Tuberculosis (TB) diagnosis remains challenging, especially in low income countries where molecular tools and culture are often not available or difficult to widely apply
Of the 23 analytes measured in this study, all but 6 (IFNc, IP-10, MIG, MCP-1, IL-17 and IL-6) showed no discernible association with 4–9 weeks infection or with chemotherapy
Four (IFNc, IP-10, MIG and MCP-1) of these 6 cytokines responded to therapy, all of which have been previously associated with TB disease [6,7,13]
Summary
Tuberculosis (TB) diagnosis remains challenging, especially in low income countries where molecular tools and culture are often not available or difficult to widely apply. At the other side of the immunological spectrum, the humoral immune response to TB is very variable and no accurate diagnosis can be made based on the presence or levels of antibodies against any target [3] In view of these intrinsic difficulties, and the lack of progress towards a true simple near patient diagnostic, we recently proposed to research the feasibility of a Treat-to-Test strategy, a pragmatic alternative to single point testing [4]. This strategy would consist of prescribing a few doses of TB drugs to a suspect, and measuring the bacteriological or immunological response to this intervention. In patients not showing a response this approach should be backed up by more extensive testing, for (drug resistant) tuberculosis or another differential diagnosis
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