Cutting edge: a Toll-like receptor 2 polymorphism that is associated with lepromatous leprosy is unable to mediate mycobacterial signaling.

Toll-like receptors (TLRs) are key mediators of the innate immune response to microbial pathogens. We investigated the role of TLRs in the recognition of Mycobacterium leprae and the significance of TLR2Arg(677)Trp, a recently discovered human polymorphism that is associated with lepromatous leprosy. In mice, TNF-alpha production in response to M. leprae was essentially absent in TLR2-deficient macrophages. Similarly, human TLR2 mediated M. leprae-dependent activation of NF-kappaB in transfected Chinese hamster ovary and human embryonic kidney 293 cells, with enhancement of this signaling in the presence of CD14. In contrast, activation of NF-kappaB by human TLR2Arg(677)Trp was abolished in response to M. leprae and Mycobacterium tuberculosis. The impaired function of this TLR2 variant provides a molecular mechanism for the poor cellular immune response associated with lepromatous leprosy and may have important implications for understanding the pathogenesis of other mycobacterial infections.

Toll-like receptor 2 (TLR2) polymorphisms are associated with reversal reaction in leprosy.

BACKGROUND: Leprosy is characterized by a spectrum of clinical manifestations that depend on the type of immune response against the pathogen. Patients may undergo immunological changes known as "reactional states" (reversal reaction and erythema nodosum leprosum) that result in major clinical deterioration. The goal of the present study was to assess the effect of Toll-like receptor 2 (TLR2) polymorphisms on susceptibility to and clinical presentation of leprosy. METHODS: Three polymorphisms in TLR2 (597C-->T, 1350T-->C, and a microsatellite marker) were analyzed in 431 Ethiopian patients with leprosy and 187 control subjects. The polymorphism-associated risk of developing leprosy, lepromatous (vs. tuberculoid) leprosy, and leprosy reactions was assessed by multivariate logistic regression models. RESULTS: The microsatellite and the 597C-->T polymorphisms both influenced susceptibility to reversal reaction. Although the 597T allele had a protective effect (odds ratio [OR], 0.34 [95% confidence interval {CI}, 0.17-0.68]; P= .002 under the dominant model), homozygosity for the 280-bp allelic length of the microsatellite strongly increased the risk of reversal reaction (OR, 5.83 [95% CI, 1.98-17.15]; P= .001 under the recessive model). These associations were consistent among 3 different ethnic groups. CONCLUSIONS: These data suggest a significant role for TLR-2 in the occurrence of leprosy reversal reaction and provide new insights into the immunogenetics of the disease.

Polymorphisms in Toll-like receptor 4 (TLR4) are associated with protection against leprosy.

Accumulating evidence suggests that polymorphisms in Toll-like receptors (TLRs) influence the pathogenesis of mycobacterial infections, including leprosy, a disease whose manifestations depend on host immune responses. Polymorphisms in TLR2 are associated with an increased risk of reversal reaction, but not susceptibility to leprosy itself. We examined whether polymorphisms in TLR4 are associated with susceptibility to leprosy in a cohort of 441 Ethiopian leprosy patients and 197 healthy controls. We found that two single nucleotide polymorphisms (SNPs) in TLR4 (896G>A [D299G] and 1196C>T [T399I]) were associated with a protective effect against the disease. The 896GG, GA and AA genotypes were found in 91.7, 7.8 and 0.5% of leprosy cases versus 79.9, 19.1 and 1.0% of controls, respectively (odds ratio [OR] = 0.34, 95% confidence interval [CI] 0.20-0.57, P < 0.001, additive model). Similarly, the 1196CC, CT and TT genotypes were found in 98.1, 1.9 and 0% of leprosy cases versus 91.8, 7.7 and 0.5% of controls, respectively (OR = 0.16, 95% CI 0.06--.40, P < 0.001, dominant model). We found that Mycobacterium leprae stimulation of monocytes partially inhibited their subsequent response to lipopolysaccharide (LPS) stimulation. Our data suggest that TLR4 polymorphisms are associated with susceptibility to leprosy and that this effect may be mediated at the cellular level by the modulation of TLR4 signalling by M. leprae.

Genome-wide re-sequencing of multidrug-resistant Mycobacterium leprae Airaku-3.

Genotyping and molecular characterization of drug resistance mechanisms in Mycobacterium leprae enables disease transmission and drug resistance trends to be monitored. In the present study, we performed genome-wide analysis of Airaku-3, a multidrug-resistant strain with an unknown mechanism of resistance to rifampicin. We identified 12 unique non-synonymous single-nucleotide polymorphisms (SNPs) including two in the transporter-encoding ctpC and ctpI genes. In addition, two SNPs were found that improve the resolution of SNP-based genotyping, particularly for Venezuelan and South East Asian strains of M. leprae.

History of biological warfare and bioterrorism.

Bioterrorism literally means using microorganisms or infected samples to cause terror and panic in populations. Bioterrorism had already started 14 centuries before Christ, when the Hittites sent infected rams to their enemies. However, apart from some rare well-documented events, it is often very difficult for historians and microbiologists to differentiate natural epidemics from alleged biological attacks, because: (i) little information is available for times before the advent of modern microbiology; (ii) truth may be manipulated for political reasons, especially for a hot topic such as a biological attack; and (iii) the passage of time may also have distorted the reality of the past. Nevertheless, we have tried to provide to clinical microbiologists an overview of some likely biological warfare that occurred before the 18th century and that included the intentional spread of epidemic diseases such as tularaemia, plague, malaria, smallpox, yellow fever, and leprosy. We also summarize the main events that occurred during the modern microbiology era, from World War I to the recent 'anthrax letters' that followed the World Trade Center attack of September 2001. Again, the political polemic surrounding the use of infectious agents as a weapon may distort the truth. This is nicely exemplified by the Sverdlovsk accident, which was initially attributed by the authorities to a natural foodborne outbreak, and was officially recognized as having a military cause only 13 years later.

Comparative genomic and phylogeographic analysis of Mycobacterium leprae.

Reductive evolution and massive pseudogene formation have shaped the 3.31-Mb genome of Mycobacterium leprae, an unculturable obligate pathogen that causes leprosy in humans. The complete genome sequence of M. leprae strain Br4923 from Brazil was obtained by conventional methods (6x coverage), and Illumina resequencing technology was used to obtain the sequences of strains Thai53 (38x coverage) and NHDP63 (46x coverage) from Thailand and the United States, respectively. Whole-genome comparisons with the previously sequenced TN strain from India revealed that the four strains share 99.995% sequence identity and differ only in 215 polymorphic sites, mainly SNPs, and by 5 pseudogenes. Sixteen interrelated SNP subtypes were defined by genotyping both extant and extinct strains of M. leprae from around the world. The 16 SNP subtypes showed a strong geographical association that reflects the migration patterns of early humans and trade routes, with the Silk Road linking Europe to China having contributed to the spread of leprosy.