4-Deoxybostrycin is a natural anthraquinone compound isolated from the Mangrove endophytic fungus Nigrospora sp. collected from the South China Sea. Nigrosporin is the deoxy-derivative of 4-deoxybostrycin. They were tested against mycobacteria, especially Mycobacterium tuberculosis. In the Kirby-Bauer disk diffusion susceptibility test, they both had inhibition zone sizes of over 25 mm. The results of the absolute concentration susceptibility test suggested that they had inhibitory effects against mycobacteria. Moreover, 4-deoxybostrycin exhibited good inhibition which was even better than that of first line anti-tuberculosis (TB) drugs against some clinical multidrug-resistant (MDR) M. tuberculosis strains. The gene expression profile of M. tuberculosis H37Rv after treatment with 4-deoxybostrycin was compared with untreated bacteria. One hundred and nineteen out of 3,875 genes were significantly different in M. tuberculosis exposed to 4-deoxybostrycin from control. There were 46 functionally known genes which are involved in metabolism, information storage and processing and cellular processes. The differential expressions of six genes were further confirmed by quantitative real-time polymerase chain reaction (qRT-PCR). The present study provides a useful experiment basis for exploitation of correlative new drugs against TB and for finding out new targets of anti-mycobacterial therapy.

This study investigates the epidemic trend of pyrazinamide (PZA)-resistant tuberculosis in Southern China over 11 years (2012-2022) and evaluates the mutation characteristics of PZA resistance-related genes (pncA, rpsA, and panD) in clinical Mycobacterium tuberculosis (M. tuberculosis) isolates. To fulfil these goals, we analyzed the phenotypic PZA resistance characteristics of 14,927 clinical isolates for which Bactec MGIT 960 PZA drug susceptibility testing (DST) results were available, revealing that 2,054 (13.76%) isolates were resistant to PZA. After evaluating the annual variation in the PZA resistance rate among tuberculosis cases in this region, it was observed that it decreased from 37.21% to 6.45% throughout the initial 7 years (2012-2018) and then increased from 8.01% to 12.12% over the subsequent 4 years (2019-2022). Sequences of pncA were obtained from 402 clinical M. tuberculosis complex isolates. For rpsA and panD, sequences were obtained from 360 clinical M. tuberculosis complex isolates. Mutations in pncA were found in 8 out of 223 PZA-sensitive isolates (3.59%) and 105 of 179 (58.66%) PZA-resistant isolates. Conversely, non-synonymous mutations in rpsA were identified in 5 of 137 (3.65%) PZA-resistant isolates, whereas the mutation ratio of rpsA among PZA-sensitive isolates was high at 14.03% (31/221). This difference in the rpsA mutation rate was statistically significant (P = 0.001, chi-square test). No panD mutations were observed in the 137 PZA-resistant isolates, whereas two PZA-sensitive isolates harboured point mutations in panD, including one nonsense mutation (C433 T) and another C-69 T mutation. These findings indicate that rpsA and panD may not significantly contribute to the development of PZA resistance in clinical M. tuberculosis isolates.

To establish a high-efficiency gamma interferon-specific enzyme-linked immunosorbent spot assay (IFN-γ ELISPOT assay) for detection of tuberculosis (TB), peptides (E6, E7, and C14) and peptide mixtures (E6 plus E7 and E6 plus E7 plus C14) were used to monitor peripheral blood (PBL) samples from patients with pulmonary TB (PTB), as well as control samples. The positive detection rates of the five IFN-γ ELISPOT assays were 78.38%, 74.86%, 55.83%, 90.43%, and 91.51%, respectively, and there were similar detection rates between the two combined peptide mixture IFN-γ ELISPOT assays and the tuberculin skin test (TST) (90.62% versus 95.59%). No significant difference was found between the detection rates of the two combined peptide mixture IFN-γ ELISPOT assays and the T-SPOT.TB assay for 86 patients with PTB (P> 0.05), but the median number of spot-forming cells/10⁶cells (SFP value) for positive results was higher by the former than by the latter assay (P< 0.05). In contrast, the 29.93% positive detection rate and median SFP value of 482 by the two combined peptide mixture IFN-γ ELISPOT assays were significantly higher than the corresponding values of 14.29% and 152 by T-SPOT.TB assay for the same 147 community donors (P< 0.05). For nine PTB patients tracked, the SFP value of 7 for the two peptide mixture IFN-γ ELISPOT assays began to decrease from the second month after regular treatment. A relatively low, almost normal, SFP level was reached and maintained after the third or fourth month. Two in-house IFN-γ ELISPOT assays and the T-SPOT.TB assay could reduce the false-positive and false-negative detection rates of TST and sputum acid-fast staining. Therefore, these two combined peptide mixture IFN-γ ELISPOT assays have a potential advantage, beyond their greater specificity and sensitivity, for use in screening and detection of active TB infection (TBI) and latent TB infection (LTBI) in China.

The in vivo kinetics of antigen-presenting cells (APCs) in patients with advanced and convalescent tuberculosis (TB) is not well characterized. In order to target Mycobacterium tuberculosis (MTB) peptides- and HLA-DR-holding monocytes and macrophages, 2 MTB peptide-specific CD4⁺ T-cell receptor (TCR) tetramers eu and hu were successfully constructed. Peripheral blood (PBL) samples from inpatients with advanced pulmonary TB (PTB) were analyzed using flow cytometry, and the percentages of tetramer-bound CD14⁺ monocytes ranged from 0.26–1.44% and 0.21–0.95%, respectively; significantly higher than those measured in PBL samples obtained from non-TB patients, healthy donors, and umbilical cords. These tetramers were also able to specifically detect macrophages in situ via immunofluorescent staining. The results of the continuous time-point tracking of the tetramer-positive rates in PBL samples from active PTB outpatients undergoing treatment show that the median percentages were at first low before treatment, increased to their highest levels during the first month, and then began to decrease during the second month until finally reaching and maintaining a relatively low level after 3–6 months. These results suggest that there is a relatively low level of MTB-specific monocytes in advanced and untreated patients. Further experiments show that MTB induces apoptosis in CD14⁺ cells, and the percentage of apoptotic monocytes dramatically decreases after treatment. Therefore, the relatively low level of MTB-specific monocytes is probably related to the apoptosis or necrosis of APCs due to live bacteria and their growth. The bactericidal effects of anti-TB drugs, as well as other unknown factors, would induce a peak value during the first month of treatment, and a relatively low level would be subsequently reached and maintained until all of the involved factors reached equilibrium. These tetramers have diagnostic potential and can provide valuable insights into the mechanisms of antigen presentation and its relationship with TB infection and latent TB infection. Mycobacterium tuberculosis (MTB) is one of the most dangerous pathogens in the world. It is estimated that one-third of the world population contracts the bacteria during their lives. Approximately 5–10% of infected individuals will eventually develop an active form of the disease. Cellular immunity plays an important role in immunity against tuberculosis (TB); however, the host's defense mechanisms are not completely understood. Here, we developed a novel tool: MTB antigen-specific tetrameric CD4⁺ T-cell receptor (TCR) complexes that can detect MTB peptide-specific antigen presenting cells (APCs) in blood and local tissues. We found that a relatively low level of antigen-specific monocytes (i.e., APCs) was detected in peripheral blood (PBL) samples from untreated TB patients, and then increased to their peak levels during the first month after treatment, which probably had something to do with the decrease in APC apoptosis. Our research provides a new method for tracking dynamic changes in APCs that are associated with TB infection and latent TB infection, and an additional tool for the studies of TB immunity and its pathogenesis.

Human CD4⁺T cells play an important role in the immune response toMycobacterium tuberculosis(MTB). However, little is known about the spectratyping characteristics of the CD4⁺T-cell receptor (TCR) α- and β-chains CDR3 region in tuberculosis (TB) patients. We sorted MTB peptide E7-bound CD4⁺T cells by using E7/HLA-DR tetramers constructed with different HLA-DRB1 alleles and extracted the CDR3 amino-acid sequences of TCR α- and β-chains. The results showed that the CDR3 sequences of E7-bound CD4⁺T cells were completely or partially identical in a single patient. The sequences of MTB peptide C5-bound CD4⁺T cells shared another, and non-peptide bound CD4⁺T cells, as well as unbound CD4⁺T cells with tetramers were different from each other. Specifically, diverse CDR3 sequences of E7-bound CD4⁺T cells displayed similar protein tertiary structure in one TB patient. In summary, the TCR α- and β-chains of CDR3 lineage of CD4⁺T cells in TB patients apparently drifted, and the predominant CDR3 sequences of TCR α- and β-chains that recognized the MTB antigen exhibited peptide specificity, and certain HLA-DR restriction was also established. This study elucidates the possible causes and mechanisms of peptide-specific CD4⁺T-cell-related presentation against MTB.