Genetic involvement of bacterial sensor molecules in Japanese leprosy

Association of CD209 (DC-SIGN) rs735240 SNV with paucibacillary leprosy in the Brazilian population and its functional effects

BACKGROUND

Leprosy, caused by Mycobacterium leprae, is a public health problem in Brazil that affects peripheral nerves, resulting in physical disabilities. During host-pathogen interactions, the immune response determines leprosy outcomes from a localised (paucibacillary) form to a disseminated (multibacillary) form. The recognition of M. leprae involves the DC-SIGN receptor, which is present on the dendritic cells (DCs) and participates in immune activation.

OBJECTIVES

To evaluate the association of polymorphisms in the promoter region of the gene encoding DC-SIGN (CD209) and the clinical form of leprosy, and to investigate its functional effects.

METHODS

The study population included 406 leprosy patients from an endemic area in Brazil [310 multibacillary (MB); 96 paucibacillary (PB)]. A functional evaluation based on the effects of the single nucleotide variant (SNV) associated with PB leprosy on the specific immune response was also performed.

RESULTS

The GA genotype and the presence of the A allele of rs735240 (-939G>A) were associated with PB leprosy [OR: 2.09 (1.18-3.69) and 1.84 (1.07-3.14), respectively]. Carriers of the A allele showed reduced expression of CD209 and TGF-β1 in leprosy lesions in comparison with individuals with GG genotype, in addition to a higher response to the Mitsuda test.

CONCLUSION

These data suggest that rs735240 influences the immune response against M. leprae and clinical presentation of leprosy.

[Leprosy, a pillar of human genetics of infectious diseases]

Despite a natural reservoir of Mycobacterium leprae limited to humans and free availability of an effective antibiotic treatment, more than 200,000 people develop leprosy each year. This disease remains a major cause of disability and social stigma worldwide. The cause of this constant incidence is currently unknown and indicates that important aspects of the complex relationship between the pathogen and its human host remain to be discovered. An important contribution of host genetics to susceptibility to leprosy has long been suggested to account for the considerable variability between individuals sustainably exposed to M. leprae. Given the inability to cultivate M. leprae in vitro and in the absence of relevant animal model, genetic epidemiology is the main strategy used to identify the genes and, consequently, the immunological pathways involved in protective immunity to M. leprae. Recent genome-wide studies have identified new pathophysiological pathways which importance is only beginning to be understood. In addition, the prism of human genetics placed leprosy at the crossroads of other common diseases such as Crohn's disease, asthma or myocardial infarction. Therefore, novel lights on the pathogenesis of many common diseases could eventually emerge from the detailed understanding of a disease of the shadows.