Publications by Year: 2018

Current tuberculosis (TB) treatments include chemotherapy and preventative vaccination with Mycobacterium bovis Bacillus Calmette-Guérin (BCG). In humans, however, BCG vaccination fails to fully protect against pulmonary TB. Few studies have considered the impact of the human lung mucosa (alveolar lining fluid (ALF)), which modifies the Mycobacterium tuberculosis (M.tb) cell wall, revealing alternate antigenic epitopes on the bacterium surface that alter its pathogenicity. We hypothesized that ALF-induced modification of BCG would induce better protection against aerosol infection with M.tb. Here we vaccinated mice with ALF-exposed BCG, mimicking the mycobacterial cell surface properties that would be present in the lung during M.tb infection. ALF-exposed BCG-vaccinated mice were more effective at reducing M.tb bacterial burden in the lung and spleen, and had reduced lung inflammation at late stages of M.tb infection. Improved BCG efficacy was associated with increased numbers of memory CD8+ T cells, and CD8+ T cells with the potential to produce interferon-γ in the lung in response to M.tb challenge. Depletion studies confirmed an essential role for CD8+ T cells in controlling M.tb bacterial burden. We conclude that ALF modifications to the M.tb cell wall in vivo are relevant in the context of vaccine design.

BACKGROUND: Rural settings where molecular tuberculosis diagnostics are not currently available need easy-to-use tests that do not require additional processing or equipment. While acid-fast bacilli (AFB) smear is the most common and often only tuberculosis diagnosis test performed in rural settings, it is labour intensive, has less-than-ideal sensitivity, and cannot assess tuberculosis drug susceptibility patterns.

OBJECTIVE: The objective of this study was to determine the feasibility of a multidrug-resistant (MDR) or extensively drug-resistant (XDR)-tuberculosis coloured agar-based culture test (tuberculosis CX-test), which can detect Mycobacterium tuberculosis growth and evaluate for drug susceptibility to isoniazid, rifampicin and a fluoroquinolone (i.e. ciprofloxacin) in approximately 14 days.

METHOD: In this study, 101 participants were enrolled who presented to a rural health clinic in central Malawi. They were suspected of having active pulmonary tuberculosis. Participants provided demographic and clinical data and submitted sputum samples for tuberculosis testing using the AFB smear and tuberculosis CX-test.

RESULTS: The results showed a high level of concordance between the AFB smear (12 positive) and tuberculosis CX-test (13 positive); only one sample presented discordant results, with the molecular GeneXpert MTB/RIF® test confirming the tuberculosis CX-test results. The average time to a positive tuberculosis CX-test was 10 days. Of the positive samples, the tuberculosis CX-test detected no cases of drug resistance, which was later confirmed by the GeneXpert MTB/RIF®.

CONCLUSION: These findings demonstrate that the tuberculosis CX-test could be a reliable low-cost diagnostic method for active pulmonary tuberculosis in high tuberculosis burden rural areas.

Mannose-capped lipoarabinomannan (ManLAM), present in all members of the Mycobacterium tuberculosis complex and in other pathogenic Mycobacterium spp, is a high molecular mass amphipathic lipoglycan with a defined critical role in mycobacterial survival during infection. In particular, ManLAM is well-characterized for its importance in providing M. tuberculosis a safe portal of entry to phagocytes, regulating the intracellular trafficking network, as well as immune responses of infected host cells. These ManLAM immunological characteristics are thought to be linked to the subtle but unique and well-defined structural characteristics of this molecule, including but not limited to the degree of acylation, the length of the D-mannan and D-arabinan cores, the length of the mannose caps, as well as the presence of other acidic constituents such as succinates, lactates and/or malates, and also the presence of 5-methylthioxylosyl. The impact of all these structural features on ManLAM spatial conformation and biological functions during M. tuberculosis infection is still uncertain. In this review, we dissect the relationship between ManLAM structure and biological function addressing how this relationship determines M. tuberculosis interactions with host cells, and how it aids this exceptional pathogen during the course of infection.

Autophagy and inflammasome complex assembly are physiological processes that control homeostasis, inflammation, and immunity. Autophagy is a ubiquitous pathway that degrades cytosolic macromolecules or organelles, as well as intracellular pathogens. Inflammasomes are multi-protein complexes that assemble in the cytosol of cells upon detection of pathogen- or danger-associated molecular patterns. A critical outcome of inflammasome assembly is the activation of the cysteine protease caspase-1, which activates the pro-inflammatory cytokine precursors pro-IL-1β and pro-IL-18. Studies on chronic inflammatory diseases, heart diseases, Alzheimer's disease, and multiple sclerosis revealed that autophagy and inflammasomes intersect and regulate each other. In the context of infectious diseases, however, less is known about the interplay between autophagy and inflammasome assembly, although it is becoming evident that pathogens have evolved multiple strategies to inhibit and/or subvert these pathways and to take advantage of their intricate crosstalk. An improved appreciation of these pathways and their subversion by diverse pathogens is expected to help in the design of anti-infective therapeutic interventions.

In the version of this Letter originally published, in Fig. 2d, in the third graph, the label for the y axis was incorrect as 'TNF-α (pg ml-1)'; it should have read 'IL-1β (pg ml-1)'. This has now been corrected.

OBJECTIVE: To describe and compare trends in prevalence, sexual behaviour and HIV transmission knowledge data related to sexually transmitted infections (STI) and HIV in patients attending three STI clinics over an 8-year period in Escuintla Department, Guatemala.

METHODS: STI clinic attendees were classified into transmission groups as follows: female sex workers (FSW), men who have sex with men (MSM) and 'high-risk heterosexuals' (HRH). Annual cross-sectional analysis and multivariable Poisson regression adjusted for sociodemographic variables were used for prevalence comparisons and adjusted prevalence trends for HIV/STI outcomes and used for adjusted trends in proportions in sexual behaviour and HIV transmission knowledge outcomes. Endocervical swabs were obtained to detect trichomonas, chlamydia and neisseria infections. Serologies for syphilis and HIV were performed using rapid tests. For reactive HIV samples, positivity was confirmed by an ELISA. All reactive syphilis samples were further confirmed for diagnosis of active syphilis disease.

RESULTS: From a total of 4027 clinic attendees, 3213 (79.78%) were FSW, 229 (5.69%) were MSM and 585 (14.53%) were HRH. The proportion of FSW, MSM and HRH who had a single visit was 56.42%, 57.23% and 91.10%, respectively. Overall, HIV prevalence was 2.10% in FSW, 8.17% in MSM and 4.12% in HRH. Prevalence trends in HIV and syphilis decreased in FSW. Prevalence trends in gonorrhoea did not decrease over time neither in FSW nor in HRH. Chlamydia and trichomonas infections in HRH showed an increase prevalence trend. In FSW, trends in condom use in last sexual intercourse with regular and occasional clients were above 93%.

CONCLUSIONS: FSW show a decreasing trend in HIV, syphilis and chlamydia prevalence. Gonorrhoea prevalence in FSW and HRH did not decrease over time. HRH is a hard to engage population with low follow-up rates and high potential to act as a bridge population.

Tuberculosis is a significant global health threat, with one-third of the world's population infected with its causative agent Mycobacterium tuberculosis (Mtb). The emergence of multidrug-resistant (MDR) Mtb that is resistant to the frontline anti-tubercular drugs rifampicin and isoniazid forces treatment with toxic second-line drugs. Currently,  4% of new and  21% of previously treated tuberculosis cases are either rifampicin-drug-resistant or MDR Mtb infections1. The specific molecular host-pathogen interactions mediating the rapid worldwide spread of MDR Mtb strains remain poorly understood. W-Beijing Mtb strains are highly prevalent throughout the world and associated with increased drug resistance2. In the early 1990s, closely related MDR W-Beijing Mtb strains (W strains) were identified in large institutional outbreaks in New York City and caused high mortality rates3. The production of interleukin-1β (IL-1β) by macrophages coincides with the shift towards aerobic glycolysis, a metabolic process that mediates protection against drug-susceptible Mtb4. Here, using a collection of MDR W-Mtb strains, we demonstrate that the overexpression of Mtb cell wall lipids, phthiocerol dimycocerosates, bypasses the interleukin 1 receptor, type I (IL-1R1) signalling pathway, instead driving the induction of interferon-β (IFN-β) to reprogram macrophage metabolism. Importantly, Mtb carrying a drug resistance-conferring single nucleotide polymorphism in rpoB (H445Y)5 can modulate host macrophage metabolic reprogramming. These findings transform our mechanistic understanding of how emerging MDR Mtb strains may acquire drug resistance single nucleotide polymorphisms, thereby altering Mtb surface lipid expression and modulating host macrophage metabolic reprogramming.

Macrophages and their monocyte precursors mediate innate immune responses and can promote a spectrum of phenotypes from pro-inflammatory to pro-resolving. Currently, there are few markers that allow for robust dissection of macrophage phenotype. We recently identified CD38 as a marker of inflammatory macrophages in murine in vitro and in vivo models. However, it is unknown whether CD38 plays a similar marker and/or functional role in human macrophages and inflammatory diseases. Here, we establish that CD38 transcript and protein are robustly induced in human macrophages exposed to LPS (±IFN-γ) inflammatory stimuli, but not with the alternative stimulus, IL-4. Pharmacologic and/or genetic CD38 loss-of-function significantly reduced the secretion of inflammatory cytokines IL-6 and IL-12p40 and glycolytic activity in human primary macrophages. Finally, monocyte analyses in systemic lupus erythematosus patients revealed that, while all monocytes express CD38, high CD38 expression in the non-classical monocyte subpopulation is associated with disease. These data are consistent with an inflammatory marker role for CD38 in human macrophages and monocytes.