STING-Dependent 2'-5' Oligoadenylate Synthetase-Like Production Is Required for Intracellular Mycobacterium leprae Survival.

Cytosolic detection of nucleic acids elicits a type I interferon (IFN) response and plays a critical role in host defense against intracellular pathogens. Herein, a global gene expression profile of Mycobacterium leprae-infected primary human Schwann cells identified the genes differentially expressed in the type I IFN pathway. Among them, the gene encoding 2'-5' oligoadenylate synthetase-like (OASL) underwent the greatest upregulation and was also shown to be upregulated in M. leprae-infected human macrophage cell lineages, primary monocytes, and skin lesion specimens from patients with a disseminated form of leprosy. OASL knock down was associated with decreased viability of M. leprae that was concomitant with upregulation of either antimicrobial peptide expression or autophagy levels. Downregulation of MCP-1/CCL2 release was also observed during OASL knock down. M. leprae-mediated OASL expression was dependent on cytosolic DNA sensing mediated by stimulator of IFN genes signaling. The addition of M. leprae DNA enhanced nonpathogenic Mycobacterium bovis bacillus Calmette-Guerin intracellular survival, downregulated antimicrobial peptide expression, and increased MCP-1/CCL2 secretion. Thus, our data uncover a promycobacterial role for OASL during M. leprae infection that directs the host immune response toward a niche that permits survival of the pathogen.

STING-Dependent 2'-5' oligoadenylate synthetase-like production is required for intracellular Mycobacterium leprae survival

Cytosolic detection of nucleic acids elicits a type I interferon (IFN) response and plays a critical role in host defense against intracellular pathogens. Herein, a global gene expression profile of Mycobacterium leprae-infected primary human Schwann cells identified the genes differentially expressed in the type I IFN pathway. Among them, the gene encoding 2'-5' oligoadenylate synthetase-like (OASL) underwent the greatest upregulation and was also shown to be upregulated in M. leprae-infected human macrophage cell lineages, primary monocytes, and skin lesion specimens from patients with a disseminated form of leprosy. OASL knock down was associated with decreased viability of M. leprae that was concomitant with upregulation of either antimicrobial peptide expression or autophagy levels. Downregulation of MCP-1/CCL2 release was also observed during OASL knock down. M. leprae-mediated OASL expression was dependent on cytosolic DNA sensing mediated by stimulator of IFN genes signaling. The addition of M. leprae DNA enhanced nonpathogenic Mycobacterium bovis bacillus Calmette-Guerin intracellular survival, downregulated antimicrobial peptide expression, and increased MCP-1/CCL2 secretion. Thus, our data uncover a promycobacterial role for OASL during M. leprae infection that directs the host immune response toward a niche that permits survival of the pathogen.

Distinct patterns of microvasculature in the cutaneous lesions of leprosy

This work is an investigation on the microvasculature of the cutaneous infiltrates of leprosy with the immunohistochemical staining of endothelial cells in cutaneous biopsies. Anti-Factor VIII-related antigen antibody (anti-FVIII-ra) and Ulex Europaeus-1 lectin (UEA-1) binding were utilized as endothelial cell markers. Thirty-nine patients grouped according to the Ridley-Jopling classification (14 borderline tuberculoid, 18 borderline lepromatous, 6 lepromatous, and 1 indeterminate leprosy) were selected for this study. Two microvascular architectural patterns could be clearly distinguished: lepromatous lesions presented a dense and tortuous mesh of microvessels among the Mycobacterium leprae-glutted macrophages; whereas the microvessels in the tuberculoid lesions were restricted to the periphery of the granulomas and were not seen among the central epithelioid cells. We were able to distinguish three basic morphological kinds of infiltrate distribution related to the microvessels: micronodules, cords and macronodules. Intensifications of the FVIII-ra immunoreactivity and UEA-1 binding capacity were observed in the endothelial cells of microvessels involved by the inflammatory infiltrate. A distinct cytokine expression profile at the leprosy poles and the role of mast cells in angiogenesis were speculated as factors contributing to these distinct patterns. Growth of the lesion and systemic dissemination of M. leprae in the bipolar spectrum of leprosy may hypothetically be influenced by the vascular-infiltrate relationship. The detection of angiogenesis in the cutaneous lesions of leprosy may bring about alternate and/or additional strategies for leprosy treatment.

Dermal extracellular matrix in cutaneous leprosy lesions

Thirty-eight biopsies of cutaneous lesions from leprosy patients [borderline tuberculoid (BT) 14, borderline lepromatous (BL) 18, lepromatous (LL) 6] were processed for staining of some extracellular matrix (ECM) components (collagen, proteoglycans, elastic fibers and fibronectin). Specific histological staining and the indirect immunofluorescence method with antibodies to collagen and fibronectin were utilized. The ECM of the normal dermis was strikingly modified in the inflammatory infiltrate. By Gomori's reticulin and anti-fibronectin immunostaining, replacement of the dense interlaced collagen fibers with a reticular mesh was observed in the infiltrate. The immunoreactivity obtained with anti-type I and anti-type III collagens showed positive fibrils and a lumpy pattern in the lepromatous and tuberculoid lesions with a higher amount in the lepromatous lesions. The lack of clear-cut boundaries between the normal dermis and the inflammatory infiltrate in the lepromatous (BL, LL) lesions was correlated with the blurred limits of the clinical lesions of this pole of the leprosy spectrum. Absence of elastic fibers in the infiltrate was a constant finding, and fuchsin-positive microfibrils were found in some infiltrates. The clear zone of lepromatous lesions was devoid of oxytalan fibers. Elaunin fiber rings around sweat gland acini were present even when the leprosy infiltrate was seen enveloping them. The original ECM is replaced by a newly assembled one, which is suited for the dynamic nature of the inflammatory process. The trophic effects of the ECM upon the cutaneous epithelial structures are modified so that atrophy and late degeneration ensues. These ECM modifications contribute, therefore, to the biological alterations of the skin functions in leprosy.

Estudo imuno-histoquímico e ultra-estrutural da inervação de lesões cutâneas de hanseníase em fase inicial / ?

A inervação cutanea das lesões da hanseníase em fase inicial foi estudada através da expressão imuno-histoquímica das proteinas neuronais NGER ("nerve growth factor receptor"). PGP 9.5 ("protein gene product 9.5") ENE (enolase neurônio-específica") e também através do estudo ultra-estrutural com microscopia eletronica de transmissão. Observamos uma redução do numero de fibras nervosas PGP 9.5- e ENE-positivas não estava relacionada topograficamente com o infiltrado inflamatório. No estudo ultra-estrutural, a maioria dos nervos examinados mostrava-se sem envolvimento inflamatório e sem alterações morfológicas. O infiltrado inflamatório estava presente em sete nervos e em seis deles, situava-se em torno do perincuro. Em apenas um nervo permeava as lamelas perineurais e invadia o endoneuro. Mesmo alcançando o endoneuro, as células inflamatórias não mostravam interação de contacto com a fibra nervosa. Não encontramos alterações morfológicas das fibras ocasionadas pela inflamação. A existência de redução do número de fibras nervosas e de fibrose endoneural independentes do evento inflamatorio foi suspeitada. Existe portanto, nas fases iniciais da hanseniase, uma alteração seletiva na expressão de proteinas neuronais não relacionada com o incipiente infiltrado específico. A nivel ultra-estrutural, não detectamos lesões das fibras nervosas diretamente causadas pelo infiltrado inflamatório, este comprometia mais o componente mesenquimatoso do nervo (perineuro). O infiltrado hanseniano inicial não deve ser implicado como o unico responsavel pelos distúrbios neurológicos exibidos pelos pacientes hansenianos. A existência de um processo patogênico distinto da inflamação e intrinseco à fibra nervosa, foi cogitada para explicar os mecanismos de lesão neural da neuropatia hanseniana.