IP-10 differentiates between active and latent tuberculosis irrespective of HIV status and declines during therapy.

OBJECTIVES: Biomarkers for diagnosis and therapy efficacy in tuberculosis (TB) are requested. We have studied biomarkers that may differentiate between active and latent TB infection (LTBI), the influence of HIV infection and changes during anti-TB chemotherapy. METHODS: Thirty-eight plasma cytokines, assessed by multiplex and enzyme immunoassays, were analyzed in patients with active TB before and during 24 weeks of anti-TB chemotherapy (n = 65), from individuals with LTBI (n = 34) and from QuantiFERON-TB (QFT) negative controls (n = 65). The study participants were grouped according to HIV status. RESULTS: Plasma levels of the CXC chemokine IP-10 and soluble TNF receptor type 2 (sTNFr2) significantly differentiated active TB from the LTBI group, irrespective of HIV status. In the HIV-infected group the sensitivity and specificity was 100% for IP-10 with a cut-off of 2547 pg/mL. Plasma IP-10 declined gradually during anti-TB chemotherapy (12-24 weeks, p = 0.002) to a level comparable to LTBI and QFT negative control groups. sTNFr2 fluctuated throughout therapy, but was decreased after 12-24 weeks (p = 0.006). CONCLUSIONS: IP-10 distinguished with high accuracy active TB from LTBI irrespective of HIV infection and declined during anti-TB chemotherapy. Plasma IP-10 may serve as a diagnostic biomarker to differentiate between the stages of TB infection and for monitoring therapy efficacy.

T regulatory cells and immune activation in Mycobacterium tuberculosis infection and the effect of preventive therapy.

Mycobacterium tuberculosis (TB) often causes persistent infection and many immune cell subsets and regulatory mechanisms may operate throughout the various stages of infection. We have studied dendritic cell (DC) subsets, regulatory T cells (Treg) and the expression of activation and apoptosis markers on CD4+ and CD8+ T cells in blood from patients with active TB (n=20), subjects with positive QuantiFERON-TB GOLD (QFT) test (LTBI, latent TB infection) (n=20) before and after 3 months of preventive anti-tuberculous therapy and from QFT-negative controls (n=28). The frequency of CD4+ CD25+ CD127⁻ Treg was highest in the group with active TB (P=0.001), but also increased in the LTBI group (P=0.006) compared to controls. The highest level of activated T cells, defined as CD38+ HLA-DR+ cells, was found in the active TB group, for the CD4+ T cell subset positively correlated to the level of CD25+ CD127⁻ Treg (P<0.001, r=0.4268). After 3 months of preventive therapy, there was an increase in the fraction of foxp3+ Treg, but no differences in markers of activation or apoptosis. In conclusion, there seems to be an increased level of immune activation and Treg in both latent and active TB infection that is only modestly influenced by preventive therapy.

Subpassaging cells on microcarriers: the importance for scaling up to production.

Optimization of microcarrier processes is dependent upon efficient, serial subcultivation routines. Established methods have been modified for a high degree of cell detachment from microcarriers, and transfer of a maximum number of viable cells from one culture to the next during the scale up process. Cultures of MRC-5 and Vero cells were studied, and cell inocula were obtained from different growth phases (i.e. exponential versus stationary) to investigate growth in subsequent cultures. Microcarrier cultures containing confluent cells were washed with EDTA-PBS and then exposed to trypsin (185 U/ml) in PBS (pH 8.0, 37 degrees C). 95-100% of the cells detached from the microcarriers with a viability greater than 95% following a 10 minute exposure to the trypsin. The presence of residual trypsin in the inoculum was investigated with respect to subsequent growth, and no significant effect was found. The methods developed at the laboratory scale (0.25 to 1.5 l cultures) were successfully applied to pilot scale (1 to 100 l cultures), and resulted in split ratios of up to 1:10 for MRC-5 cells and 1:100 for Vero cells. These results show that the modified subpassaging method and an optimal cell inoculum are vital in establishing efficient, industrial scale microcarrier processes.