Development of Highly Organized Lymphoid Structures in Buruli Ulcer Lesions after Treatment with Rifampicin and Streptomycin

Abstract

BackgroundBuruli ulcer caused by Mycobacterium ulcerans is an infection of the subcutaneous tissue leading to chronic necrotising skin ulcers. The pathogenesis is associated with the cytocidal and immunosuppressive activities of a macrolide toxin. Histopathological hallmark of progressing disease is a poor inflammatory response despite of clusters of extracellular bacilli. While traditionally wide excision of the infected tissue was the standard treatment, provisional WHO guidelines now recommend an eight week pre-treatment with streptomycin and rifampicin.Methodology/Principal FindingsWe conducted a detailed immunohistochemical analysis of tissue samples from Buruli patients who received antibiotic treatment. Cellular immune response along with bacterial load and distribution were monitored. We demonstrate that this treatment leads to the development of highly organized cellular infiltration surrounding areas of coagulative necrosis. Diffuse infiltrates, granulomas and dense lymphocyte aggregation close to vessels were observed. Mycobacterial material was primarily located inside mononuclear phagocytes and microcolonies consisting of extracellular rod-shaped mycobacteria were no longer found. In observational studies some patients showed no clinical response to antibiotic treatment. Corresponding to that, one of five lesions analysed presented with huge clusters of rod-shaped bacilli but no signs of infiltration.Conclusions/SignificanceResults signify that eight weeks of antibiotic treatment reverses local immunosuppression and leads to an active inflammatory process in different compartments of the skin. Structured leukocyte infiltrates with unique signatures indicative for healing processes developed at the margins of the lesions. It remains to be analysed whether antibiotic resistance of certain strains of M. ulcerans, lacking patient compliance or poor drug quality are responsible for the absent clinical responses in some patients. In future, analysis of local immune responses could serve as a suitable surrogate marker for the efficacy of alternative treatment strategies.

Challenges Associated with Management of Buruli Ulcer/Human Immunodeficiency Virus Coinfection in a Treatment Center in Ghana: A Case Series Study

“…In addition, all samples showed immune infiltration, blood vessel and granuloma formation (Figure 2A, C, and D), as is commonly observed in antibiotic-treated lesions of HIV-negative BU patients. 12 Mixed infiltrates containing large numbers of CD3 positive T cells were found mainly in the dermis and subcutaneous tissue layer. Granulomas and clusters of CD20 positive B cells were embedded in the mixed unstructured infiltrates.…”

“…10,11 Antimicrobial therapy leads to massive leukocyte infiltration, which culminates in the development of ectopic lymphoid structures in the lesions. 12 Some studies have reported paradoxical reactions in BU patients, which is defined as an increase in lesion size of 100% after initial improvement, and/or the appearance of a new lesion(s) following or during antimycobacterial treatment. 13,14 Currently, it is not clear whether immune reconstitution inflammatory syndrome (IRIS)-like mechanisms, secondary infections, 15 or other mechanisms are primarily responsible for impaired wound healing and deterioration of lesions during and after SR treatment in some of the BU patients.…”

IFN-γ–Dependent Activation of Macrophages during Experimental Infections by Mycobacterium ulcerans Is Impaired by the Toxin Mycolactone

“…Our data can also explain the effects observed in patients treated with the combination of Rifampicin and Streptomycin, during which immune activation has been suggested to be required to achieve sterilization. In fact, the antibiotic administration has been shown to increase phagocytosis of bacilli at the infection foci and to promote inflammatory cellular responses (66), associated with an increased production of IFN-g (67), which can be related to the reduction of mycolactone concentrations, allowing macrophage activation and further containment of the infection. Accordingly, it has been reported that after the surgical excision of BU lesions, the IFN-g production is increased (68).…”

Severe Multifocal Form of Buruli Ulcer after Streptomycin and Rifampin Treatment: Comments on Possible Dissemination Mechanisms

“…Several reports have described a similar excessive immune response following effective antimycobacterial therapy. [20][21][22] This phenomenon, called "paradoxical reaction" 22 or "immune reconstitution inflammatory syndrome (IRIS)," has also been described in patients with HIV who are coinfected with other mycobacteria, such as Mycobacterium tuberculosis or Mycobacterium leprae . 23,24 Although our patient was HIV-negative, the IRIS is highly supported by the clinical characteristics (fever, swelling, or abscess) previously described, 20,[24][25][26] the increase in the WBC count, the alpha-1, alpha-2, and gamma globulin values ( Table 2 ), and the histopathologic results.…”