Vaccination with the Surface Proteins MUL_2232 and MUL_3720 of Mycobacterium ulcerans Induces Antibodies but Fails to Provide Protection against Buruli Ulcer
Miriam BolzAngèle BénardAnita M. DreyerSarah KerberAndrea VettigerWulf OehlmannMahavir SinghMalcolm S. DuthieGerd Pluschke
28
Citation
43
Reference
10
Related Paper
Citation Trend
Abstract:
Background Buruli ulcer, caused by infection with Mycobacterium ulcerans, is a chronic ulcerative neglected tropical disease of the skin and subcutaneous tissue that is most prevalent in West African countries. M. ulcerans produces a cytotoxic macrolide exotoxin called mycolactone, which causes extensive necrosis of infected subcutaneous tissue and the development of characteristic ulcerative lesions with undermined edges. While cellular immune responses are expected to play a key role against early intracellular stages of M. ulcerans in macrophages, antibody mediated protection might be of major relevance against advanced stages, where bacilli are predominantly found as extracellular clusters. Methodology/Principal Findings To assess whether vaccine induced antibodies against surface antigens of M. ulcerans can protect against Buruli ulcer we formulated two surface vaccine candidate antigens, MUL_2232 and MUL_3720, as recombinant proteins with the synthetic Toll-like receptor 4 agonist glucopyranosyl lipid adjuvant-stable emulsion. The candidate vaccines elicited strong antibody responses without a strong bias towards a TH1 type cellular response, as indicated by the IgG2a to IgG1 ratio. Despite the cross-reactivity of the induced antibodies with the native antigens, no significant protection was observed against progression of an experimental M. ulcerans infection in a mouse footpad challenge model. Conclusions Even though vaccine-induced antibodies have the potential to opsonise the extracellular bacilli they do not have a protective effect since infiltrating phagocytes might be killed by mycolactone before reaching the bacteria, as indicated by lack of viable infiltrates in the necrotic infection foci.Keywords:
Mycobacterium ulcerans
Buruli ulcer
Exotoxin
Pseudomonas exotoxin
Buruli ulcer is a neglected trophical disease. It is characterized by the development of painless open wounds. It causes large skin ulcers mainly in children aged 5 to 15 years. Buruli ulcer is a skin infection caused by a bacterium called Mycobacterium ulcerans. The disease is concentrated in West Africa and coastal Australia, with occasional cases in Japan, Papua, New Guinea and the Americas. In West Africa, the disease is predominantly reported from remote, rural communities, Côte d'Ivoire, Cameroon, Ghana, and Nigeria. In endemic areas, the disease occurs near stagnant bodies of water. This is in agreement with the long-standing hypothesis that M. ulcerans is somehow transmitted to humans from aquatic environments. The first sign of Buruli ulcer is a painless swollen bump on the arm or leg, often similar in appearance to an insect bite. Over the course of a few weeks, the original swollen area expands to form an irregularly shaped patch of raised skin. Buruli ulcer can be diagnosed using microscopy, culture, and polymerase chain reaction. For microscopy, fluid is typically taken from the ulcer's edge by fine-needle aspiration or by swabbing the edge of the ulcer. The fluid is then stained with the Ziehl–Neelsen stain which makes Mycobacterium visible. Buruli ulcer is treated with a combination of antibiotics such as streptomycin, azithromycin to kill the bacteria, wound care and surgery to support the healing of the ulcer. Buruli ulcer can be prevented by avoiding contact with aquatic environments in endemic areas. The risk of acquiring it can be reduced by wearing long sleeves and gardening gloves, and using suitable repellents to avoid the contamination of this disease. Buruli ulcer is a public health challenge especially in rural areas of developing countries that should be given more attention by the government and policy makers.
Buruli ulcer
Mycobacterium ulcerans
Skin ulcer
Tropical disease
Cite
Citations (0)
Buruli ulcer, caused by Mycobacterium ulcerans infections, is a necrotizing skin disease whose pathogenesis is associated with the exotoxin mycolactone. Despite the relevance of this emergent disease, little is known on the immune response against the pathogen. Following the recent demonstration of an intramacrophage growth phase for M. ulcerans, we investigated the biological relevance of IFN-gamma and the antimycobacterial mechanisms activated by this cytokine in M. ulcerans-infected macrophages. Three M. ulcerans strains were tested: 5114 (mutant mycolactone-negative, avirulent strain); 94-1327 (intermediate virulence); and 98-912 (high virulence). We show in this study that IFN-gamma is expressed in mouse-infected tissues and that IFN-gamma-deficient mice display increased susceptibility to infection with strains 5114 and, to a lesser extent, 94-1327, but not with the highly virulent strain. Accordingly, IFN-gamma-activated cultured macrophages controlled the proliferation of the avirulent and the intermediate virulent strains. Addition of mycolactone purified from strain 98-912 to cultures of IFN-gamma-activated macrophages infected with the mycolactone-negative strain led to a dose-dependent inhibition of the IFN-gamma-induced protective mechanisms, involving phagosome maturation/acidification and increased NO production, therefore resulting in increased bacterial burdens. Our findings suggest that the protection mediated by IFN-gamma in M. ulcerans-infected macrophages is impaired by the local buildup of mycolactone.
Mycobacterium ulcerans
Buruli ulcer
Exotoxin
Cite
Citations (55)
Buruli ulcer is an emerging chronic infectious skin disease caused by Mycobacterium ulcerans. Mycolactone, an exotoxin produced by the bacterium, is the only identified virulence factor so far, but the functions of this toxin and the mechanisms of disease progression remain unclear. By interfering Sec61 translocon, mycolactone inhibits the Sec61-dependent co-translational translocation of newly synthesized proteins, such as induced cytokines and immune cell receptors, into the endoplasmic reticulum. However, in regard to IL-1β, which is secreted by a Sec61-independent mechanism, mycolactone has been shown to induce IL-1β secretion via activation of inflammasomes. In this study, we clarified that cytokine induction, including that of IL-1β, in infected macrophages was suppressed by mycolactone produced by M. ulcerans subsp. shinshuense, despite the activation of caspase-1 through the inflammasome activation triggered in a manner independent of mycolactone. Intriguingly, mycolactone suppressed the expression of proIL-1β as well as TNF-α at the transcriptional level, suggesting that mycolactone of M. ulcerans subsp. shinshuense may exert additional inhibitory effect on proIL-1β expression. Remarkably, constitutively produced IL-18 was cleaved and mature IL-18 was actually released from macrophages infected with the causative mycobacterium. IL-18-deficient mice infected subcutaneously with M. ulcerans exhibited exacerbated skin inflammation during the course of disease progression. On the other hand, IL-1β controls bacterial multiplication in skin tissues. These results provide information regarding the mechanisms and functions of the induced cytokines in the pathology of Buruli ulcer.
Buruli ulcer
Mycobacterium ulcerans
Exotoxin
Cite
Citations (1)
Background Buruli ulcer is a neglected tropical disease caused by Mycobacterium ulcerans , an environmental mycobacterium. Although transmission of M . ulcerans remains poorly understood, the main identified risk factor for acquiring Buruli ulcer is living in proximity of potentially contaminated water sources. Knowledge about the clinical features of Buruli ulcer and its physiopathology is increasing, but little is known about recurrence due to reinfection. Methodology/Principal findings We describe two patients with Buruli ulcer recurrence due to reinfection with M . ulcerans , as demonstrated by comparisons of DNA from the strains isolated at the time of the first diagnosis and at recurrence. Based on the spatial distribution of M . ulcerans genotypes in this region and a detailed study of the behavior of these two patients with respect to sources of water as well as water bodies and streams, we formulated hypotheses concerning the sites at which they may have been contaminated. Conclusions/Significance Second episodes of Buruli ulcer may occur through reinfection, relapse or a paradoxical reaction. We formally demonstrated that the recurrence in these two patients was due to reinfection. Based on the sites at which the patients reported engaging in activities relating to water, we were able to identify possible sites of contamination. Our findings indicate that the non-random distribution of M . ulcerans genotypes in this region may provide useful information about activities at risk.
Mycobacterium ulcerans
Buruli ulcer
Tropical disease
Cite
Citations (0)
Buruli ulcer, classified as a neglected tropical disease by the World Health Organization, is caused by a mycobacterium which secretes a macrolidic exotoxin called mycolactone A/B. In this article, several synthetic strategies for the preparation of this toxin are discussed, highlighting the importance of total synthesis for the exploration of biological mechanism underpinning relevant human diseases.
Buruli ulcer
Mycobacterium ulcerans
Exotoxin
Cite
Citations (12)
Buruli ulcer
Mycobacterium ulcerans
Skin ulcer
Cite
Citations (0)
The pathogenicity of Mycobacterium ulcerans, the agent of Buruli ulcer, depends on the cytotoxic exotoxin mycolactone. Little is known about the immune response to this pathogen. Following the demonstration of an intracellular growth phase in the life cycle of M. ulcerans, we investigated the production of tumor necrosis factor (TNF) induced by intramacrophage bacilli of diverse toxigenesis/virulence, as well as the biological relevance of TNF during M. ulcerans experimental infections. Our data show that murine bone marrow-derived macrophages infected with mycolactone-negative strains of M. ulcerans (nonvirulent) produce high amounts of TNF, while macrophages infected with mycolactone-positive strains of intermediate or high virulence produce intermediate or low amounts of TNF, respectively. These results are in accordance with the finding that TNF receptor P55-deficient (TNF-P55 KO) mice are not more susceptible than wild-type mice to infection by the highly virulent strains but are more susceptible to nonvirulent and intermediately virulent strains, demonstrating that TNF is required to control the proliferation of these strains in animals experimentally infected by M. ulcerans. We also show that mycolactone produced by intramacrophage M. ulcerans bacilli inhibits, in a dose-dependent manner, but does not abrogate, the production of macrophage inflammatory protein 2, which is consistent with the persistent inflammatory responses observed in experimentally infected mice.
Mycobacterium ulcerans
Buruli ulcer
Exotoxin
Virulence factor
Anthrax toxin
Cite
Citations (94)
Mycobacterium ulcerans infection is an emerging disease that causes indolent, necrotizing skin lesions known as Buruli ulcer (BU) and occasional contiguous or metastatic bone lesions. Buruli ulcer is named after Buruli County in Uganda (east Africa), where an epidemic occurred in the 1960s. Today, BU is most common in central and west Africa. We describe clinical and molecular evidence for a case of BU in Kenya.
Buruli ulcer
Mycobacterium ulcerans
Skin ulcer
Cite
Citations (11)
Abstract Buruli Ulcer is a devastating skin disease caused by the pathogen Mycobacterium ulcerans . Emergence and distribution of Buruli ulcer cases is clearly linked to aquatic ecosystems, but the specific route of transmission of M. ulcerans to humans remains unclear. Relying on the most detailed field data in space and time on M. ulcerans and Buruli ulcer available today, we assess the relative contribution of two potential transmission routes –environmental and water bug transmission– to the dynamics of Buruli ulcer in two endemic regions of Cameroon. The temporal dynamics of Buruli ulcer incidence are explained by estimating rates of different routes of transmission in mathematical models. Independently, we also estimate statistical models of the different transmission pathways on the spatial distribution of Buruli ulcer. The results of these two independent approaches are corroborative and suggest that environmental transmission pathways explain the temporal and spatial patterns of Buruli ulcer in our endemic areas better than the water bug transmission.
Buruli ulcer
Mycobacterium ulcerans
Cite
Citations (31)
Mycobacterium ulcerans infection (Buruli ulcer) is the third most common mycobacterial infection of immunocompetent humans, and is an emerging disease in West Africa. We describe the first two reported patients with Buruli ulcer in Togo, establishing a geographical continuum of the disease in all countries bordering the Gulf of Guinea. The aetiological agent was identified by molecular biological analysis of biopsy material. We speculate that changing environmental factors related to human habitation may influence rates of incidence of Buruli ulcer.
Buruli ulcer
Mycobacterium ulcerans
Etiology
Tropical disease
Skin ulcer
Cite
Citations (74)