Endogenous reactivation and true treatment failure as causes of recurrent tuberculosis in a high incidence setting with a low HIV infection

Mesenchymal stem cells-derived extracellular vesicles for therapeutics of renal tuberculosis

Extrapulmonary tuberculosis with a renal involvement can be a manifestation of a disseminated infection that requires therapeutic intervention, particularly with a decrease in efficacy of conventional regimens. In the present study, we investigated the therapeutic potency of mesenchymal stem cell-derived extracellular vesicles (MSC-EVs) in the complex anti-tuberculosis treatment (ATT). A rabbit model of renal tuberculosis (rTB) was constructed by injecting of the standard strain Mycobacterium tuberculosis H37Rv into the cortical layer of the kidney parenchyma. Isolated rabbit MSC-EVs were intravenously administered once as an addition to standard ATT (isoniazid, pyrazinamide, and ethambutol). The therapeutic efficacy was assessed by analyzing changes of blood biochemical biomarkers and levels of anti- and pro-inflammatory cytokines as well as by renal computed tomography with subsequent histological and morphometric examination. The therapeutic effect of therapy with MSC-EVs was shown by ELISA method that confirmed a statistically significant increase of the anti-inflammatory and decrease of pro-inflammatory cytokines as compared to conventional treatment. In addition, there is a positive trend in increase of ALP level, animal weigh, and normalization of ADA activity that can indicate an improvement of kidney state. A significant reduction of the area of specific and interstitial inflammation indicated positive affect of MSC-EVs that suggests a shorter duration of ATT. The number of MSC-EVs proteins (as identified by mass-spectometry analysis) with anti-microbial, anti-inflammatory and immunoregulatory functions reduced the level of the inflammatory response and the severity of kidney damage (further proved by morphometric analysis). In conclusion, MSC-EVs can be a promising tool for the complex treatment of various infectious diseases, in particularly rTB.

Endogenous relapse and exogenous reinfection in recurrent pulmonary tuberculosis: A retrospective study revealed by whole genome sequencing

Background

Tuberculosis may reoccur due to reinfection or relapse after initially successful treatment. Distinguishing the cause of TB recurrence is crucial to guide TB control and treatment. This study aimed to investigate the source of TB recurrence and risk factors related to relapse in Hunan province, a high TB burden region in southern China.

Methods

A population-based retrospective study was conducted on all culture-positive TB cases in Hunan province, China from 2013 to 2020. Phenotypic drug susceptibility testing and whole-genome sequencing were used to detect drug resistance and distinguish between relapse and reinfection. Pearson chi-square test and Fisher exact test were applied to compare differences in categorical variables between relapse and reinfection. The Kaplan-Meier curve was generated in R studio (4.0.4) to describe and compare the time to recurrence between different groups. p < 0.05 was considered statistically significant.

Results

Of 36 recurrent events, 27 (75.0%, 27/36) paired isolates were caused by relapse, and reinfection accounted for 25.0% (9/36) of recurrent cases. No significant difference in characteristics was observed between relapse and reinfection (all p > 0.05). In addition, TB relapse occurs earlier in patients of Tu ethnicity compared to patients of Han ethnicity (p < 0.0001), whereas no significant differences in the time interval to relapse were noted in other groups. Moreover, 83.3% (30/36) of TB recurrence occurred within 3 years. Overall, these recurrent TB isolates were predominantly pan-susceptible strains (71.0%, 49/69), followed by DR-TB (17.4%, 12/69) and MDR-TB (11.6%, 8/69), with mutations mainly in codon 450 of the rpoB gene and codon 315 of the katG gene. 11.1% (3/27) of relapse cases had acquired new resistance during treatment, with fluoroquinolone resistance occurring most frequently (7.4%, 2/27), both with mutations in codon 94 of gyrA.

Conclusion

Endogenous relapse is the main mechanism leading to TB recurrences in Hunan province. Given that TB recurrences can occur more than 4 years after treatment completion, it is necessary to extend the post-treatment follow-up period to achieve better management of TB patients. Moreover, the relatively high frequency of fluoroquinolone resistance in the second episode of relapse suggests that fluoroquinolones should be used with caution when treating TB cases with relapse, preferably guided by DST results.

Mesenchymal Stem Cells and MSCs-Derived Extracellular Vesicles in Infectious Diseases: From Basic Research to Clinical Practice

Mesenchymal stem cells (MSCs) are attractive in various fields of regenerative medicine due to their therapeutic potential and complex unique properties. Basic stem cell research and the global COVID-19 pandemic have given impetus to the development of cell therapy for infectious diseases. The aim of this review was to systematize scientific data on the applications of mesenchymal stem cells (MSCs) and MSC-derived extracellular vesicles (MSC-EVs) in the combined treatment of infectious diseases. Application of MSCs and MSC-EVs in the treatment of infectious diseases has immunomodulatory, anti-inflammatory, and antibacterial effects, and also promotes the restoration of the epithelium and stimulates tissue regeneration. The use of MSC-EVs is a promising cell-free treatment strategy that allows solving the problems associated with the safety of cell therapy and increasing its effectiveness. In this review, experimental data and clinical trials based on MSCs and MSC-EVs for the treatment of infectious diseases are presented. MSCs and MSC-EVs can be a promising tool for the treatment of various infectious diseases, particularly in combination with antiviral drugs. Employment of MSC-derived EVs represents a more promising strategy for cell-free treatment, demonstrating a high therapeutic potential in preclinical studies.

Mesenchymal Stem Cells and Tuberculosis: Clinical Challenges and Opportunities

Tuberculosis (TB) is one of the communicable diseases caused by Mycobacterium tuberculosis (Mtb) infection, affecting nearly one-third of the world's population. However, because the pathogenesis of TB is still not fully understood and the development of anti-TB drug is slow, TB remains a global public health problem. In recent years, with the gradual discovery and confirmation of the immunomodulatory properties of mesenchymal stem cells (MSCs), more and more studies, including our team's research, have shown that MSCs seem to be closely related to the growth status of Mtb and the occurrence and development of TB, which is expected to bring new hope for the clinical treatment of TB. This article reviews the relationship between MSCs and the occurrence and development of TB and the potential application of MSCs in the treatment of TB.

Relapse, re-infection and mixed infections in tuberculosis disease

Tuberculosis (TB) disease can be characterized by genotypic and phenotypic complexity in Mycobacterium tuberculosis bacilli within a single patient. This microbiological heterogeneity has become an area of intense study due its perceived importance in drug tolerance, drug resistance and as a surrogate measure of transmission rates. This review presents a descriptive analysis of research describing the prevalence of mixed-strain TB infections in geographically distinct locations. Despite significant variation in disease burden and a rampant human immunodeficiency virus (HIV)-TB co-epidemic, there was no difference in the prevalence range of mixed infections reported in African countries when compared to the rest of the world. The occurrence of recurrent TB was associated with a higher prevalence of mixed-strain infections, but this difference was not reported as statistically significant. These interpretations were limited by differences in the design and overall size of the studies assessed. Factors such as sputum quality, culture media, number of repeated culture steps, molecular typing methods and HIV-infection status can affect the detection of mixed-strain infection. It is recommended that future clinical studies should focus on settings with varying TB burdens, with a common sample processing protocol to gain further insight into these phenomena and develop novel transmission blocking strategies.

BCG infection in mice is promoted by naïve mesenchymal stromal cells (MSC) and suppressed by poly(A:U)-conditioned MSC

Mesenchymal stromal cells (MSC) transplantation is an actively studied therapeutic approach used in regenerative medicine and in the field of control of immunoinflammatory response. Conditioning of MSC in culture can form their predominantly pro- or anti-inflammatory phenotypes. We demonstrated that poly(A:U)-conditioning of bone marrow-derived mouse MSC induced predominantly pro-inflammatory phenotype. The effects of administration of naïve MSC (nMSC) or conditioned MSC (cMSC) on the course of mycobacterial infection were studied. BALB/c mice infected i.p. with 5 × 10⁶ M. bovis BCG were successively injected i.v. with 0.75 × 10⁶ of nMSC or cMSC in 11 and 12.5 weeks after infection and sacrificed at the week 14. Histological and bacteriological examination of BCG-infected animals revealed low bacterial loads in liver, lungs and spleen; the bacterial load in spleen was higher than in other organs. Treatment with nMSC induced 3-fold increase of the number of bacteria in spleen granulomas, while cMSC decreased significantly the number of bacteria in BCG-positive granulomas. Analysis of preparations of organ homogenates by luminescent microscopy, MGIT cultures and CFU count on Lowenstein-Jensen medium revealed that nMSC promoted mycobacterial growth whereas cMSC suppressed mycobacterial growth significantly. We concluded that MSC therapy can be effective in mycobacterial infection, but only in a case of appropriate conditioning of the cells.

Pathogenesis and Pathology of Intraocular Tuberculosis

Intraocular tuberculosis (TB) is an extremely paucibacillary form of extrapulmonary TB. It likely results from bacterial dissemination to the eye from lungs, localization in ocular tissues, followed later by reactivation and appearance of clinical signs. These have been partly demonstrated in the guinea pig model of ocular TB. Alternative hypotheses have been suggested but are not supported by adequate evidence. Mycobacterial recognition by macrophages and dendritic cells probably leads to activation of several immune pathways, primarily the Th1 and Th17 pathways, as in other TB infections. Histopathology of bacteriologically proven ocular TB tissues reveals granulomatous inflammation with central caseous necrosis containing occasional acid-fast organisms. Recent reports have also demonstrated intraretinal granuloma in the vicinity of retinal vessels and T-cell infiltration of epiretinal membranes, in cases of TB retinal vasculitis.

The temporal dynamics of relapse and reinfection tuberculosis after successful treatment: a retrospective cohort study

BACKGROUND

There is increasing evidence from tuberculosis high-burden settings that exogenous reinfection contributes considerably to recurrent disease. However, large longitudinal studies of endogenous reactivation (relapse) and reinfection tuberculosis are lacking. We hypothesize a relationship between relapse vs reinfection and the time between treatment completion and recurrent disease.

METHODS

Population-based retrospective cohort study on all smear-positive tuberculosis cases successfully treated between 1996 and 2008 in a suburban setting in Cape Town, South Africa. Inverse gaussian distributions were fitted to observed annual rates of relapse and reinfection, distinguished by DNA fingerprinting of Mycobacterium tuberculosis strains recultured from diagnostic samples.

RESULTS

Paired DNA fingerprint data were available for 130 (64%) of 203 recurrent smear-positive tuberculosis cases in the 13-year study period. Reinfection accounted for 66 (51%) of 130 recurrent cases overall, 9 (20%) of 44 recurrent cases within the first year, and 57 (66%) of 86 thereafter (P < .001). The relapse rate peaked at 3.93% (95% confidence interval [CI], 2.35%-5.96%) per annum 0.35 (95% CI, .15-.45) years after treatment completion. The reinfection tuberculosis rate peaked at 1.58% (95% CI, .94%-2.46%) per annum 1.20 (95% CI, .55-1.70) years after completion.

CONCLUSIONS

To our knowledge, this is the first study of sufficient size and duration using DNA fingerprinting to investigate tuberculosis relapse and reinfection over a lengthy period. Relapse occurred early after treatment completion, whereas reinfection dominated after 1 year and accounted for at least half of recurrent disease. This temporal relationship may explain the high variability in reinfection observed across smaller studies. We speculate that follow-up time in antituberculosis drug trials should take reinfection into account.

How host heterogeneity governs tuberculosis reinfection?

Recurrent episodes of tuberculosis (TB) can be due to relapse of latent infection or exogenous reinfection, and discrimination is crucial for control planning. Molecular genotyping of Mycobacterium tuberculosis isolates offers concrete opportunities to measure the relative contribution of reinfection in recurrent disease. Here, a mathematical model of TB transmission is fitted to data from 14 molecular epidemiology studies, enabling the estimation of relevant epidemiological parameters. Meta-analysis reveals that rates of reinfection after successful treatment are higher than rates of new TB, raising an important question about the underlying mechanism. We formulate two alternative mechanisms within our model framework: (i) infection increases susceptibility to reinfection or (ii) infection affects individuals differentially, thereby recruiting high-risk individuals to the group at risk for reinfection. The second mechanism is better supported by the fittings to the data, suggesting that reinfection rates are inflated through a population phenomenon that occurs in the presence of heterogeneity in individual risk of infection. As a result, rates of reinfection are higher when measured at the population level even though they might be lower at the individual level. Finally, differential host recruitment is modulated by transmission intensity, being less pronounced when incidence is high.

A description of patients with recurrence of Pulmonary Tuberculosis in a Tuberculosis Hospital, Ermelo

Background

Retreatment TB (tuberculosis) is a serious category of pulmonary TB with a treatment outcome that could include MDR-TB (multidrug resistant TB). In the Msukaligwa municipality of Mpumalanga Province, South Africa, the burden of TB is high with poor treatment outcome indicators, thus creating some preconditions for retreatment TB. Knowledge of the characteristics of the patients and related health system factors would help in designing interventions to improve the care for patients, the adherence to medication and the prevention of retreatment TB.

Aim of the study

The aim was to describe the occurrence, characteristics and management outcome of retreatment pulmonary tuberculosis in patients in a TB hospital in Ermelo.

Objectives

The specific objectives were to describe the socio-demographic, behavioural and clinical factors related to recurrence of TB in patients; to determine the contribution of defaulting treatment to recurrence of TB in the study population; to identify the prevalence of resistance to TB medication amongst patients with retreatment TB; and to identify treatment outcomes in patients who have been followed up for the duration of retreatment TB.

This study was set in the 58-bed TB hospital in Ermelo.

The study design was cross-sectional and descriptive, and the study population comprised of patients admitted with TB at the Ermelo TB hospital between 01 January 2005 and 31 December 2007. Data were collected from the patients’ medical records and the TB registers by using a predesigned form. Data were analysed with Microsoft Excel Spreadsheet at the Centre for Statistical Consultation at the University of Stellenbosch.

Results

All of the 388 patient records with retreatment TB, which formed 19.6% of TB patients admitted between 2005 and 2007, were reviewed. This comprised 66% male patients with a mean age of 41.4, and 34% female patients with a mean age of 35.3. They were mostly unemployed, and 93% had a primary education; 43% were unmarried and 34% were married. Retreatment TB was diagnosed with sputum smear microscopy in 71%, with a bacilli load of 3+ in 45% of the patients. Almost three-quarters (74%) of the patients have been afflicted by TB, 1–3 years before the episode under study. Retreatment TB categories were: ‘after treatment completed’, 69%; ‘default’, 19%; ‘after cure, 8%, and ‘treatment failure’, 4%. The majority, that is, 98% (169/172) of patients tested, had a HIV-positive status; the median CD4 cell count was 106 cells/µL at the time of retreatment, and very few (5%) were on ART (antiretroviral drug treatment). Drug resistance to primary TB drugs was as follows: Rifampicin (16%), Isoniazid (29%), Ethambutol (19%), and Streptomycin (23%). The treatment outcomes for those for whom data were available were: ‘successful’ (49.1%), ‘death’ (23.8%); and ‘treatment default’ (22.9%). MDR-TB caused complications in 3.3% of the patients.

Conclusion

The majority of the retreatment TB patients were male patients with an average age of 41, and unemployed. More than two-thirds of the patients had completed TB treatment previously, and defaulting treatment accounted for less than one-quarter of retreatment categories. The process of care was better in terms of the diagnosis of TB with sputum smear. Improvement in the documentation of key factors such as smoking, alcohol, drug use amongst patients and co-morbidity, as well as counselling and testing for HIV and provision of ARTs, is required. Treatment outcomes with regard to successful outcomes should be monitored and improved.

Interferon γ responses to mycobacterial antigens protect against subsequent HIV-associated tuberculosis

BACKGROUND

The cellular immune responses that protect against tuberculosis have not been identified.

METHODS

We assessed baseline interferon γ (IFN‐γ) and lymphocyte proliferation assay (LPA) responses to antigen 85 (Ag85), early secretory antigenic target 6 (ESAT‐6), and Mycobacterium tuberculosis whole cell lysate (WCL) in human immunodeficiency virus (HIV)-infected and bacille Calmette‐Guérin (BCG)-immunized adults with CD4 cell counts of >or= 200 cells/μL who received placebo in the DarDar tuberculosis vaccine trial in Tanzania. Subjects were followed prospectively to diagnose definite or probable tuberculosis.

RESULTS

Tuberculosis was diagnosed in 92 of 979 subjects during a mean follow‐up of 3.2 years. The relative risk of tuberculosis among subjects with positive IFN‐γ responses to Ag85 was 0.51 (95% confidence interval [CI], 0.26-0.99; P = .049), to ESAT‐6 was 0.44 (95% CI, 0.23-0.85; P = .004), and to WCL was 0.67 (95% CI, 0.49-0.88; P = .002). The relative risk of tuberculosis was not significantly associated with baseline LPA responses. In a multivariate Cox regression model, subjects with IFN‐γ responses to ESAT‐6 and WCL had a lower hazard of developing tuberculosis, with a hazard ratio for ESAT‐6 of 0.35 (95% CI, 0.16–0.77; P = .009) and a hazard ratio for WCL of 0.30 (95% CI, 0.16-0.56; P < .001).

CONCLUSIONS

Baseline IFN‐γ responses to ESAT-6 and WCL were associated with protection from subsequent tuberculosis among HIV-infected subjects with childhood BCG immunization in a region of high tuberculosis prevalence. Trial registration. ClinicalTrials.gov identifier: NCT00052195.

Genetic diversity of Mycobacterium tuberculosis isolates from a tertiary care tuberculosis hospital in South Korea

Tuberculosis (TB) remains an immense public health problem in the Republic of Korea despite a more than fivefold decrease in the prevalence of the disease over the last 3 decades. The rise in drug-resistant TB has compounded the situation. We analyzed 208 clinical isolates of M. tuberculosis from the National Masan Tuberculosis Hospital by spoligotyping, IS6110 restriction fragment length polymorphism (RFLP), and 24-locus-based mycobacterial interspersed repetitive unit-variable number tandem repeat (MIRU-VNTR) typing to assess the diversity and transmission dynamics of the tubercle bacilli in the Republic of Korea. The majority of the isolates (97.1%) belonged to the Beijing genotype. Cluster analysis by MIRU-VNTR yielded a low clustering rate of 22.3%, with most of the clusters comprising isolates with diverse drug resistance patterns. The discriminatory capacity of the typing methods was high for RFLP and MIRU-VNTR (allelic diversity [h] = 0.99) but low for spoligotyping (h = 0.31). Although analysis of 19 MIRU-VNTR loci was needed to achieve maximum discrimination, an informative set of 8 loci (960, 1955, 2163b, 2165, 2996, 3192, 4052, and 4348) (h = 0.98) that was able to differentiate most of the closely related strains was identified. These findings suggest that 24-locus-based MIRU-VNTR typing is a likely suitable alternative to RFLP to differentiate clinical isolates in this setting, which is dominated by M. tuberculosis Beijing strains. Within the study limits, our results also suggest that the problem of drug-resistant TB in the Republic of Korea may be largely due to acquired resistance as opposed to transmission.