Assessing HLA imputation accuracy in a West African population

Area of Science:

• Genetics
• Immunogenetics
• Population Genetics

Background:

• The Human Leukocyte Antigen (HLA) region is vital for immune responses and disease susceptibility.
• High polymorphism in the HLA region complicates accurate imputation, especially in understudied populations.
• West African populations exhibit significant genetic diversity, necessitating tailored imputation strategies.

Purpose of the Study:

• To evaluate Human Leukocyte Antigen (HLA) imputation accuracy in a West African population.
• To compare the performance of different genotyping arrays, imputation tools, and reference panels for HLA imputation.
• To identify optimal methods for improving HLA imputation in genetically diverse populations.

Main Methods:

• Utilized whole-genome sequence data from 315 Gambian individuals.
• Assessed Illumina Omni 2.5 and H3Africa genotyping arrays.
• Tested imputation tools (HIBAG, SNP2HLA, CookHLA, Minimac4) with various reference panels (1000 Genomes, H3Africa, HLA Multi-ethnic).
• Concordance rate was the primary metric for assessing imputation accuracy.

Main Results:

• HIBAG demonstrated the highest overall concordance rate (0.84).
• The H3Africa reference panel yielded the best performance (0.62 concordance).
• Minimac4 improved HLA-B imputation accuracy (0.75) compared to other tools.
• Genotyping array type had minimal impact on imputation accuracy in this population.

Conclusions:

• Employing a larger, population-specific reference panel is key to enhancing HLA imputation accuracy.
• The HIBAG tool is recommended for optimal HLA imputation in West African populations.
• Accurate HLA imputation is essential for genetic studies of autoimmune and infectious diseases in diverse populations.