Trained innate immunity and resistance to Mycobacterium tuberculosis infection

Contains fulltext : 215553.pdf (publisher's version ) (Closed access)BACKGROUND: Some individuals, even when heavily exposed to an infectious tuberculosis patient, develop neither active nor latent tuberculosis infection (LTBI). This 'early clearance' of Mycobacterium tuberculosis is associated with a history of bacillus Calmette-Guerin (BCG) vaccination. As BCG vaccination can boost innate immune responses through a process termed 'trained immunity', we hypothesize that BCG-induced trained innate immunity contributes to early clearance of M. tuberculosis. OBJECTIVES: We describe the epidemiological evidence and biological concepts of early clearance and trained immunity, and the possible relation between these two processes through BCG vaccination. SOURCES: Relevant data from published reports up to November 2018 were examined in the conduct of this review. CONTENT: Several observational studies and one recent randomized trial support the concept that boosting innate immunity contributes to protection against M. tuberculosis infection, with BCG vaccination providing approximately 50% protection. The molecular mechanisms mediating early clearance remain largely unknown, but we propose that trained immunity, characterized by epigenetic and metabolic reprogramming of innate immune cells such as monocytes or macrophages, is at least partially responsible for eliminating the mycobacteria and inducing early clearance. IMPLICATIONS: Future studies should examine if BCG revaccination increases early clearance of M. tuberculosis through induction of trained immunity. Epigenetic or metabolic modulation may further boost BCG-induced trained innate immunity to promote tuberculosis prevention. New tuberculosis vaccine candidates should also be examined for their capacity to improve protection against M. tuberculosis infection and induce trained immunity

The emergence of community-onset Clostridium difficile infection in a tertiary hospital in Singapore: A cause for concern

10.1016/j.ijantimicag.2013.09.011International Journal of Antimicrobial Agents43147-51IAAG

IL-32 and its splice variants are associated with protection against Mycobacterium tuberculosis infection and skewing of Th1/Th17 cytokines

Contains fulltext : 218685.pdf (Publisher’s version ) (Open Access)Studies in IL-32 transgenic mice and in vitro suggest that IL-32 may have protective effects against Mycobacterium tuberculosis, but so far there are barely any studies in humans. We studied the role of IL-32 and its splice variants in tuberculosis (TB) in vivo and in vitro. Blood transcriptional analysis showed lower total IL-32 mRNA levels in pulmonary TB patients compared to patients with latent TB infection and healthy controls. Also, among Indonesian household contacts who were heavily exposed to an infectious TB patient, IL-32 mRNA levels were higher among those who remained uninfected compared to those who became infected with M. tuberculosis. In peripheral blood mononuclear cells from healthy donors, we found that IL-32gamma, the most potent isoform, was down-regulated upon M. tuberculosis stimulation. This decrease in IL-32gamma was mirrored by an increase of another splice variant, IL-32beta. Also, a higher IL-32gamma/IL-32beta ratio correlated with IFN-gamma production, whereas a lower ratio correlated with production of IL-1Ra, IL-6, and IL-17. These data suggest that IL-32 contributes to protection against M. tuberculosis infection, and that this effect may depend on the relative abundance of different IL-32 isoforms

Lower Bacillus Calmette-Guerin Protection against Mycobacterium tuberculosis Infection after Exposure to Beijing Strains

Contains fulltext : 220108.pdf (Publisher’s version ) (Closed access

Early Clearance of Mycobacterium tuberculosis: The INFECT Case Contact Cohort Study in Indonesia

Item does not contain fulltextBACKGROUND: Early clearance of Mycobacterium tuberculosis is the eradication of infection before an adaptive immune response develops. We aimed to identify host factors associated with early clearance. METHODS: Indonesian household contacts patients with smear-positive tuberculosis (TB) had an interferon-gamma release assay (IGRA) at baseline and 14 weeks later. Early clearance was defined as a persistently negative IGRA. Contact characteristics, exposure, and disease phenotype were assessed for association with a positive IGRA at each time point. RESULTS: Of 1347 contacts of 462 TB cases, 780 (57.9%) were IGRA positive and 490 (36.3%) were IGRA negative. After 14 weeks, 116 of 445 (26.1%) initially negative contacts were IGRA converters; 317 (71.2%) remained persistently negative. BCG vaccination reduced the risk of a positive baseline IGRA (relative risk [RR], 0.89 [95% confidence interval {CI} .83-.97]; P = .01), and strongly reduced the risk of IGRA conversion (RR, 0.56 [95% CI, .40-.77]; P < .001). BCG protection decreased with increasing exposure (P = .05) and increasing age (P = .004). Risk of IGRA conversion was positively associated with hemoglobin concentration (P = .04). CONCLUSIONS: A quarter of household TB case contacts were early clearers. Protection against M. tuberculosis infection was strongly associated with BCG vaccination. Lower protection from BCG with increasing M. tuberculosis exposure and age can inform vaccine development

Early Clearance of Mycobacterium tuberculosis Is Associated With Increased Innate Immune Responses

Item does not contain fulltextBACKGROUND: A proportion of tuberculosis (TB) case contacts do not become infected, even when heavily exposed. We studied the innate immune responses of TB case contacts to understand their role in protection against infection with Mycobacterium tuberculosis, termed "early clearance." METHODS: Indonesian household contacts of TB cases were tested for interferon-gamma release assay (IGRA) conversion between baseline and 14 weeks post recruitment. Blood cell populations and ex vivo innate whole blood cytokine responses were measured at baseline and, in a subgroup, flow cytometry was performed at weeks 2 and 14. Immunological characteristics were measured for early clearers, defined as a persistently negative IGRA at 3 months, and converters, whose IGRA converted from negative to positive. RESULTS: Among 1347 case contacts, 317 were early clearers and 116 were converters. Flow cytometry showed a resolving innate cellular response from 2 to 14 weeks in persistently IGRA-negative contacts but not converters. There were no differences in cytokine responses to mycobacterial stimuli, but compared to converters, persistently IGRA-negative contacts produced more proinflammatory cytokines following heterologous stimulation with Escherichia coli and Streptococcus pneumoniae. CONCLUSIONS: Early clearance of M. tuberculosis is associated with enhanced heterologous innate immune responses similar to those activated during induction of trained immunity