Young Mi Kim

Discovery of Q203, a potent clinical candidate for the treatment of tuberculosis

New therapeutic strategies are needed to combat the tuberculosis pandemic and the spread of multidrug-resistant (MDR) and extensively drug-resistant (XDR) forms of the disease, which remain a serious public health challenge worldwide. The most urgent clinical need is to discover potent agents capable of reducing the duration of MDR and XDR tuberculosis therapy with a success rate comparable to that of current therapies for drug-susceptible tuberculosis. The last decade has seen the discovery of new agent classes for the management of tuberculosis, several of which are currently in clinical trials. However, given the high attrition rate of drug candidates during clinical development and the emergence of drug resistance, the discovery of additional clinical candidates is clearly needed. Here, we report on a promising class of imidazopyridine amide (IPA) compounds that block Mycobacterium tuberculosis growth by targeting the respiratory cytochrome bc1 complex. The optimized IPA compound Q203 inhibited the growth of MDR and XDR M. tuberculosis clinical isolates in culture broth medium in the low nanomolar range and was efficacious in a mouse model of tuberculosis at a dose less than 1 mg per kg body weight, which highlights the potency of this compound. In addition, Q203 displays pharmacokinetic and safety profiles compatible with once-daily dosing. Together, our data indicate that Q203 is a promising new clinical candidate for the treatment of tuberculosis.

Polymorphisms Associated with Resistance and Cross-Resistance to Aminoglycosides and Capreomycin in Mycobacterium tuberculosis Isolates from South Korean Patients with Drug-Resistant Tuberculosis

ABSTRACT The aminoglycosides streptomycin, amikacin, and kanamycin and the cyclic polypeptide capreomycin are all widely used in second-line therapy for patients who develop multidrug-resistant tuberculosis. We have characterized a set of 106 clinical isolates of Mycobacterium tuberculosis using phenotypic drug susceptibility testing (DST) to determine the extent of resistance to each agent and cross-resistance between agents. These results were compared with polymorphisms in the DNA sequences of ribosome-associated genes previously implicated in resistance and with the clinical outcomes of subjects from whom these isolates were obtained. Thirty-six (34%) of these isolates displayed resistance to one or more of these agents, and the majority of these (20 of 36) showed cross-resistance to one or more agents. Most (33 of 36) of the resistant isolates showed polymorphisms in the 16S ribosome components RpsL and rrs. Three resistant strains (3 of 36) were identified that had no known polymorphisms in ribosomal constituents. For kanamycin and streptomycin, molecular DST significantly outperformed phenotypic DST using the absolute concentration method for predicting 4-month sputum conversion (likelihood ratios of 4.0 and 2.0, respectively) and was equivalent to phenotypic DST using the National Committee for Clinical Laboratory Standards (NCCLS)-approved agar proportion method for estimating MIC (likelihood ratio, 4.0). These results offer insight into mechanisms of resistance and cross-resistance among these agents and suggest that the development of rapid molecular tests to distinguish polymorphisms would significantly enhance clinical utility of this important class of second-line antituberculosis drugs.

Efficacy of inducible protein 10 as a biomarker for the diagnosis of tuberculosis

OBJECTIVE This study evaluated inducible protein 10 (IP-10) as a diagnostic biomarker for specific tuberculosis (TB) infection and evaluated the ability of IP-10 to distinguish between active TB and latent TB infection (LTBI). METHODS Forty-six patients with active pulmonary TB, 22 participants with LTBI, and 32 non-TB controls were enrolled separately. We measured IP-10 in serum and in supernatants from whole blood stimulated with TB-specific antigens. RESULTS TB antigen-dependent IP-10 secretion was significantly increased in the active TB patients and LTBI subjects compared with controls, but did not differ significantly between the active TB patients and LTBI subjects. Serum IP-10 levels were higher in active TB than in LTBI (174.9 vs. 102.7pg/ml, p=0.002). The respective rates of positive responders of TB antigen-dependent IP-10 were 97.8%, 90.9%, and 12.5% in active TB, LTBI, and non-TB controls, respectively. For serum IP-10, 87.5%, 45.5%, and 9.5% of responders were positive in the respective groups. CONCLUSIONS The IP-10 response to TB antigen may constitute a specific biomarker for TB infection, but does not by itself distinguish between active TB and LTBI. Serum IP-10 may enhance the diagnostic performance when used in combination with another marker.

Screening for latent tuberculosis infection in South Korean healthcare workers using a tuberculin skin test and whole blood interferon-γ assay

Abstract This study compared the results of a tuberculin skin test (TST) and a whole-blood interferon-γ release assay (IGRA) to screen latent tuberculosis (TB) infection (LTBI) according to risk of TB exposure in South Korea. A cross-sectional comparison of 82 healthcare workers (HCWs) was performed from June 2009 to January 2010. Participants were grouped according to their risk for TB exposure: group 1, frequent and direct contact with active TB patients (n = 35); group 2, no known history of direct contact with active TB patients (n = 47). For the TST (10-mm induration cut-off), the positive response rate was 42.9% in group 1 and 34.0% in group 2 (p = 0.42). For the IGRA, the positive response rate was 40% in group 1 and 10.6% in group 2 (p = 0.002). Results obtained from the TST and the IGRA were not in significant agreement. The working duration of HCWs in TB-related departments was the only significant risk factor for LTBI (odds ratio 1.03; p = 0.031). Further, the IGRA can more accurately discriminate LTBI compared to the TST, based on the risk of TB exposure. These results suggest that the IGRA is diagnostically useful for LTBI in South Korean HCWs.

Questionable role of interferon-γ assays for smear-negative pulmonary TB in immunocompromised patients

OBJECTIVE The purpose of this study was to examine the usefulness of the TST and the interferon-γ release assays (IGRA) for diagnosing smear-negative pulmonary TB in immunocompromised patients in an intermediate TB burden. METHODS We conducted a prospective study enrolling 119 immunocompromised participants with suspected smear-negative pulmonary TB in Seoul, South Korea. Clinical assessment, TST, QuantiFERON-TB Gold In Tube (QFT-GIT), and T-SPOT.TB were performed in immunosuppressed condition. RESULTS All participants were categorized according to the type of immunosuppression: 29 patients with diabetes mellitus, 53 with malignancy, 23 with taking immunosuppressive drugs, and 14 with end stage renal disease. IGRA sensitivity and specificity (95% CI) were: QFT-GIT [59.0% (44.9-72.0)] and [61.3% (54.4-67.6)] and T-SPOT.TB [72.0% (54.2-86.2)] and [42.3% (33.8-49.1)], respectively. For TST, sensitivity was 41.2% (28.3-50.8) and specificity was 91.8% (85.8-96.30). The sensitivities of the three diagnostic methods tended to be lower in the immunosuppressive drug group than in other groups (QFT-GIT 11.1%, T-SPOT.TB 40.0% and TST 25.0% in patients with taking immunosuppressive drugs). Among 111 patients who underwent a chest CT examination, there were no significant differences in the CT findings between the immunocompromised TB and non-TB patients. CONCLUSIONS The IGRAs and TST had no value as a single test either to rule-in or rule-out active TB in immunocompromised patients in an intermediate burden.

Adjunctive biomarkers for improving diagnosis of tuberculosis and monitoring therapeutic effects

OBJECTIVES To identify host biomarkers associated with latent tuberculosis infection (LTBI), active tuberculosis (TB), and nontuberculous mycobacteria (NTM) diseases to improve diagnosis and effective anti-TB treatment. METHODS Active TB and NTM patients at diagnosis, recent TB contacts, and normal healthy subjects were recruited. Tuberculin skin tests, QuantiFERON-TB Gold In-Tube tests, and multiplex bead arrays with 17 analytes were performed. TB patients were re-evaluated after 2 and 6 months of treatment. RESULTS Mycobacterium tuberculosis (M. tb) antigen-specific IFN-γ, IL-2, and CXCL10 responses were significantly higher in active TB and LTBI compared with controls (P < 0.01). Only serum VEGF levels varied between the active TB and LTBI groups (AUC = 0.7576, P < 0.001). Active TB and NTM diseases were differentiated by serum IL-2, IL-9, IL-13, IL-17, TNF-α and sCD40L levels (P < 0.05). Increased sCD40L and decreased M. tb antigen-specific IFN-γ levels correlated with sputum clearance of M. tb after 2 months of treatment (P < 0.001). CONCLUSIONS Serum IL-2, IL-9, IL-13, IL-17, TNF-α, sCD40L and VEGF-A levels may be adjunctive biomarkers for differential diagnosis of active TB, LTBI, and NTM disease. Assessment of serum sCD40L and M. tb antigen-specific IFN-γ, TNF-α, and IL-2 levels could help predict successful anti-TB treatment in conjunction with M. tb clearance.

Mycobacterial infections in coal workers’ pneumoconiosis patients in South Korea

Coal workers’ pneumoconiosis (CWP) is the most common occupational disease in South Korea and is an important factor in the development of infections with Mycobacterium tuberculosis (MTB) and non-tuberculous mycobacteria (NTM). In the current study, we identified mycobacterial species that cause pulmonary infections in CWP patients, using rpoB DNA-PCR-restriction analysis. Among the 129 CWP patients studied, 35 (27.1%) were diagnosed as having mycobacterial infections. Among these, the proportion of NTM infections (21/35, 60.0%) was higher than that for MTB infections (14/35, 40.0%). Of the 21 NTM strains, the most common was M. intracellulare (6/21, 28.6%), followed by M. avium (5/21, 23.8%). We also compared the characteristics of CWP patients between the MTB and NTM infection groups. A higher proportion of CWP patients with NTM infections compared with those with MTB infections had a history of having been involved in rock work (38.1% vs 21.4%), and had complicated CWP (85.7% vs 35.7%) and a past history of TB treatment (61.9% vs 50.0%). We also discovered 3 MTB mutants that are resistant to first-line anti-TB drugs, in CWP patients. These results demonstrate the features of pulmonary mycobacterial infections with a predominance of NTM in CWP patients in South Korea.

Interferon gamma mRNA quantitative real-time polymerase chain reaction for the diagnosis of latent tuberculosis: a novel interferon gamma release assay.

The interferon gamma (IFN-γ) release assay (IGRA) is widely used as a diagnostic method for latent tuberculosis infection (LTBI). The QuantiFERON-TB Gold and QuantiFERON-TB Gold In-tube (QFT-IT) tests measure plasma IFN-γ levels using enzyme-linked immunosorbent assay (ELISA), and T-SPOT.TB counts IFN-γ-producing cells using enzyme-linked immunosorbent spot assay. IFN-γ mRNA was evaluated as an indicator of IGRA in comparison with QFT-IT IFN-γ ELISA in 46 subjects with active TB and in 73 at low risk for TB. Significant IFN-γ mRNA expression was detected from 30 min and peaked 4 h after stimulation with MTB antigens or mitogen. This was defined as the optimal time point for IFN-γ mRNA real-time polymerase chain reaction (PCR). The sensitivities of IFN-γ mRNA real-time PCR and IFN-γ ELISA were 84.8% (39/46) and 89.1% (41/46), respectively (no significant difference). Although the specificities of IFN-γ ELISA was 4.1% higher than that of IFN-γ mRNA real-time PCR (60.3% versus 56.2%), the difference was not statistically significant. The overall agreement between IFN-γ mRNA real-time PCR and IFN-γ ELISA was 79.8% (kappa = 0.475). Whilst there was no difference in the performance of IFN-γ mRNA real-time PCR and IFN-γ ELISA, IFN-γ mRNA real-time PCR was superior to IFN-γ ELISA in terms of the time required for detection of MTB infection.

Centrifugal Lithography: Self-Shaping of Polymer Microstructures Encapsulating Biopharmaceutics by Centrifuging Polymer Drops

Polymeric microstructures encapsulating biopharmaceutics must be fabricated in a controlled environment to preserve the biological activity. There is increasing demand for simple methods designed to preserve the biological activity by utilizing the natural properties of polymers. Here, the paper shows that centrifugal lithography (CL) can be used for the fabrication of such microstructures in a single centrifugation, by engineering the self-shaping properties of hyaluronic acid (HA). In this method, HA drops are self-shaped into hourglass-microstructures to produce two dissolving microneedles (DMN), which facilitate transdermal delivery via implantation on the skin. In addition, tuberculin purified protein derivatives are encapsulated into HA DMNs under refrigerated conditions (4 °C) during CL. Therefore, the tuberculin skin test (TST) with the DMNs indicates minimal damage, as opposed to the case of TST with traditional hypodermic needles. These findings on the fabrication of polymeric microstructures with biopharmaceutics may trigger the development of various biomedical devices and therapies.

Evaluation of Antigen-Specific Immunoglobulin G Responses in Pulmonary Tuberculosis Patients and Contacts

ABSTRACT This study aimed to evaluate the serodiagnostic potential of immunoglobulin G (IgG) responses to Mycobacterium tuberculosis antigens in pulmonary tuberculosis (TB) patients, recent TB contacts with latent TB infection (LTBI), and healthy subjects. Infections were assessed using tuberculin skin tests, QuantiFERON-TB Gold In-Tube tests, drug susceptibility testing, and molecular genotyping of clinical isolates. Serum IgG responses to selective M. tuberculosis antigens, including the 38-kDa and 16-kDa antigens, lipoarabinomannan (LAM), and recombinant early secreted antigen target 6 kDa (ESAT-6) and culture filtrate protein 10 kDa (CFP-10), were determined. We found that the serum IgG responses to all antigens might differentiate between active TB and LTBI, with LAM having the highest diagnostic value (area under the curve [AUC] of 0.7756, P < 0.001). Recurrent TB cases showed significantly higher IgG responses to 38 kDa, CFP-10 (P < 0.01), and LAM (P < 0.05) than new cases, and male patients had higher levels of antigen-specific IgG than females (P < 0.05). Conversely, drug resistance and patient body mass index did not affect IgG responses (P > 0.05). LAM-specific IgG responses differentiated between acid-fast bacillus (AFB) smear-positive and -negative patients (P < 0.01), whereas antigen-specific IgG responses did not vary with the M. tuberculosis genotype (P > 0.05). Significantly higher IgG responses to 38 kDa and 16 kDa were observed in AFB smear-negative patients than in controls. These results suggest that assessment of serum IgG responses to selective purified M. tuberculosis antigens may help improve the diagnosis of active TB, particularly for sputum smear-negative patients or recurrent cases, and these may also help to differentiate between active TB and LTBI.