This article is part a series of reviews covering Immunity to Mycobacteria appearing in Volume 301 of Immunological Reviews.

BackgroundLeprosy is a chronic dermato-neurological disease caused by Mycobacterium leprae infection. In 2016, more than 200,000 new cases of leprosy were detected around the world, representing the most frequent cause of infectious irreversible deformities and disabilities.Principal findingsIn the present work, we demonstrate a consistent procoagulant profile on 40 reactional and non-reactional multibacillary leprosy patients. A retrospective analysis in search of signs of coagulation abnormalities among 638 leprosy patients identified 35 leprosy patients (5.48%) which displayed a characteristic lipid-like clot formed between blood clot and serum during serum harvesting, herein named ‘leprosum clot’. Most of these patients (n = 16, 45.7%) belonged to the lepromatous leprosy pole of the disease. In addition, formation of the leprosum clot was directly correlated with increased plasma levels of soluble tissue factor and von Willebrand factor. High performance thin layer chromatography demonstrated a high content of neutral lipids in the leprosum clot, and proteomic analysis demonstrated that the leprosum clot presented in these patients is highly enriched in fibrin. Remarkably, differential 2D-proteomics analysis between leprosum clots and control clots identified two proteins present only in leprosy patients clots: complement component 3 and 4 and inter-alpha-trypsin inhibitor family heavy chain-related protein (IHRP). In agreement with those observations we demonstrated that M. leprae induces hepatocytes release of IHRP in vitro.ConclusionsWe demonstrated that leprosy MB patients develop a procoagulant status due to high levels of plasmatic fibrinogen, anti-cardiolipin antibodies, von Willebrand factor and soluble tissue factor. We propose that some of these components, fibrinogen for example, presents potential as predictive biomarkers of leprosy reactions, generating tools for earlier diagnosis and treatment of these events.

Leprosy is a chronic infectious disease caused by Mycobacterium leprae infection in Schwann cells. Axonopathy is considered a hallmark of leprosy neuropathy and is associated with the irreversible motor and sensory loss seen in infected patients.Although M. leprae is recognized to provoke Schwann cell dedifferentiation, the mechanisms involved in the contribution of this phenomenon to neural damage remain unclear. In the present work, we used live M. leprae to infect the immortalized human Schwann cell line ST8814. The neurotoxicity of infected Schwann cell-conditioned medium (SCCM) was then evaluated in a human neuroblastoma cell lineage and mouse neurons. ST8814 Schwann cells exposed to M. leprae affected neuronal viability by deviating glial 14 C-labeled lactate, important fuel of neuronal central metabolism, to de novo lipid synthesis. The phenolic glycolipid-1 (PGL-1) is a specific M. leprae cell wall antigen proposed to mediate bacterial-Schwann cell interaction. Therefore, we assessed the role of the PGL-1 on Schwann cell phenotype by using transgenic M. bovis (BCG)-expressing the M. leprae PGL-1. We observed that BCG-PGL-1 was able to induce a phenotype similar to M. leprae, unlike the wild-type BCG strain. We next demonstrated that this Schwann cell neurotoxic phenotype, induced by M. leprae PGL-1, occurs through the protein kinase B (Akt) pathway. Interestingly, the pharmacological inhibition of Akt by triciribine significantly reduced free fatty acid content in the SCCM from M. leprae-and BCG-PGL-1-infected Schwann cells and, hence, preventing neuronal death. Overall, these findings provide novel evidence that both M. leprae and PGL-1, induce a toxic Schwann cell phenotype, by modifying the host lipid metabolism, resulting in profound implications for neuronal loss. We consider this metabolic rewiring a new molecular mechanism to be the basis of leprosy neuropathy.

Slippage mutation rates in 15 autosomal short tandem repeat loci for forensic purposes in a Southeastern Brazilian populationWell-defined estimates of mutation rates in highly polymorphic tetranucleotide STR loci are a prerequisite for human identification in genetics laboratory routines useful for civil and criminal investigations. Studying 15 autosomal STR loci of forensic interest (CSF1PO, D2S1338, D3S1358, D5S818, D7S820, D8S1179, D13S317, D16S539, D18S51, D19S433, D21S11, FGA, TH01, TPOX, and vWA), we detected 193 slippage mutations (189 one-step and four two-step mutations) in 148 875 parent-child allelic transfers from 5171 paternity cases with true biological relationship (15 096 individuals; 4754 trios and 417 duos; 9925 meiosis) from the state of São Paulo, a very representative population of Brazil. The overall mutation rate was 1.3 × 10 −3 and the highest rates were observed at loci vWA (2.8 × 10 −3 ), FGA and D18S51 (2.7 × 10 −3 for both), while loci TH01 and TPOX did not present any mutations. The mean slippage mutation rate of paternal origin (1.8 × 10 −3 ) was six times higher than that observed for maternal origin (0.3 × 10 −3 ).

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