Dynamics of interferon-gamma release assay and cytokine profiles in blood and respiratory tract specimens from mice with tuberculosis and the effect of therapy.

There are limitations on diagnostic methods to differentiate between active and latent tuberculosis (TB), and the prediction of latent progression to TB disease is yet complex. Traditionally, tuberculosis-specific host immune response was visualized using the tuberculin skin test. Nowadays, IFN-γ release assays (IGRA) provide a more specific and sensitive tool, by which exposure to Mtb could be determined. However, the merit of IGRA aids in diagnosing active TB is yet unclear. We adapted IGRA for use in mice, and quantifying bead-based flow cytometry techniques were used to assess cytokine profiles during the course of untreated infection and to investigate the value of IGRA and cytokines as biomarkers for therapy response. High variability of IGRA results during progression of active TB infection related to various phases of infection was obtained. However, a significant decrease in IGRA results and in levels of IFN-γ, IL-17, IP-10 or MIG was observed and appeared to be associated with successful therapy. This outcome does not support the value of IGRA to accurately diagnose active TB or to monitor infection progression. However, IGRA proved to be a useful biomarker to monitor therapy success. In addition, different cytokines might serve as biomarkers.

Course of murine tuberculosis and response to first-line therapy depends on route of infection and inoculum size.

BACKGROUND: In the search for new anti-tuberculosis drugs, numerous potential drugs are being screened in vitro. In animal models, promising new anti-tuberculosis drugs are assessed in terms of toxic side effects and comparative therapeutic efficacy. Mice are frequently used and experimental infections are established in different ways. OBJECTIVE: To investigate to what extent the route of Mycobacterium tuberculosis inoculation is a determinant in the pathogenesis of tuberculosis (TB) and the therapeutic outcome. Results will contribute to insight into the translational value of TB models used for preclinical studies. DESIGN: TB in mice was established through intratracheal or intravenous mycobacterial inoculation. The efficacy of a 26-week treatment regimen was evaluated, including assessment of relapse of infection 13 weeks post-treatment. RESULTS: It was shown that the course of TB and the therapeutic response, in terms of histopathological characteristics and mycobacterial load, in lungs and extra- pulmonary organs is substantially different and dependent on the route of infection applied and the inoculum size used. CONCLUSION: When evaluating the comparative therapeutic potential of novel anti-tuberculosis drugs or drug treatment schedules investigated in different studies, it should be noted that the route of infection applied and the inoculum size used influence the course of murine TB and the therapeutic response to the standard first- line anti-tuberculosis drug regimen.

Immunological parameters to define infection progression and therapy response in a well-defined tuberculosis model in mice.

To evaluate novel approaches for tuberculosis (TB) diagnostics and treatment, well-validated animal TB models are needed. Especially the emergence and spread of drug resistant TB requires innovative therapy and accurate parameters for monitoring success or failure of therapy. We developed a TB model in BALB/c mice, in which Mycobacterium tuberculosis (Mtb) infection was induced through the natural respiratory route, mimicking human TB infection. The lung showed a mild inflammatory infiltrate consisting of granulomas in the first phase of infection, followed by progressive increase of pneumonic lesions resulting in extensive lung consolidation in the chronic phase. Dissemination to the extra-pulmonary sites was observed. The model was validated in terms of therapeutic outcome. The 26-week standard therapy administered in human pharmacokinetic-equivalent doses, resulted in complete elimination of Mtb in all infected organs, without relapse of infection in the post-treatment period. However, a 13-week therapy, simulating patient non-adherence resulted in relapse of infection. In our quest to find biomarkers for monitoring success or failure of therapy, the concentrations of various cytokines in serum and lung, determined by cytometric bead array (CBA), were evaluated in relation to the in situ cytokine expression in the lung, assessed by immunohistochemistry. The level of IFN-gamma concentration in serum increased with infection progression, and decreased during effective therapy, and as such appeared to be an appropriate immunological parameter for success or failure of therapy. Relapse of infection, after inappropriate therapy, manifested as an increase in the serum IFN-gamma concentration.