HLA and susceptibility to leprosy.

Area of Science:

• Immunogenetics
• Infectious Disease Epidemiology
• Human Genetics

Background:

• Leprosy, caused by Mycobacterium leprae, exhibits variable host immune responses.
• The human leukocyte antigen (HLA) complex plays a crucial role in immune regulation and is implicated in infectious disease susceptibility.
• Understanding genetic factors, including HLA, is vital for elucidating leprosy pathogenesis.

Purpose of the Study:

• To review evidence linking MHC-associated factors, specifically HLA, to host immune responses in leprosy.
• To analyze HLA studies in sporadic and familial leprosy cases.
• To discuss potential HLA-related immunological mechanisms determining leprosy outcomes.

Main Methods:

• Systematic review of published HLA studies in leprosy.
• Collating data from sporadic and multiple-case leprosy families.
• Formal linkage analysis of HLA haplotype segregation in 109 families.

Main Results:

• Linkage between the HLA complex and a leprosy susceptibility locus was observed under a three-allele recessive model (recombination fraction of 20%).
• This linkage significance was primarily noted in families with at least two tuberculoid leprosy offspring and unaffected parents.
• In families with an affected parent, HLA linkage was inconclusive, suggesting an additional, non-HLA linked susceptibility locus.

Conclusions:

• The human leukocyte antigen (HLA) complex is significantly associated with leprosy susceptibility, particularly for tuberculoid leprosy.
• The findings support a genetic model for leprosy susceptibility involving both HLA-linked and non-HLA-linked factors.
• Further research into the interplay of genetic loci is warranted to fully understand leprosy's complex etiology.