Geographical distribution of complement receptor type 1 variants and their associated disease risk

PLoS One. 2017 May 17;12(5):e0175973. doi: 10.1371/journal.pone.0175973. eCollection 2017.

Abstract

Background: Pathogens exert selective pressure which may lead to substantial changes in host immune responses. The human complement receptor type 1 (CR1) is an innate immune recognition glycoprotein that regulates the activation of the complement pathway and removes opsonized immune complexes. CR1 genetic variants in exon 29 have been associated with expression levels, C1q or C3b binding and increased susceptibility to several infectious diseases. Five distinct CR1 nucleotide substitutions determine the Knops blood group phenotypes, namely Kna/b, McCa/b, Sl1/Sl2, Sl4/Sl5 and KCAM+/-.

Methods: CR1 variants were genotyped by direct sequencing in a cohort of 441 healthy individuals from Brazil, Vietnam, India, Republic of Congo and Ghana.

Results: The distribution of the CR1 alleles, genotypes and haplotypes differed significantly among geographical settings (p≤0.001). CR1 variants rs17047660A/G (McCa/b) and rs17047661A/G (Sl1/Sl2) were exclusively observed to be polymorphic in African populations compared to the groups from Asia and South-America, strongly suggesting that these two SNPs may be subjected to selection. This is further substantiated by a high linkage disequilibrium between the two variants in the Congolese and Ghanaian populations. A total of nine CR1 haplotypes were observed. The CR1*AGAATA haplotype was found more frequently among the Brazilian and Vietnamese study groups; the CR1*AGAATG haplotype was frequent in the Indian and Vietnamese populations, while the CR1*AGAGTG haplotype was frequent among Congolese and Ghanaian individuals.

Conclusion: The African populations included in this study might have a selective advantage conferred to immune genes involved in pathogen recognition and signaling, possibly contributing to disease susceptibility or resistance.

MeSH terms

  • Adolescent
  • Adult
  • Brazil
  • Continental Population Groups / genetics*
  • Exons
  • Female
  • Gene Frequency
  • Genetic Predisposition to Disease*
  • Ghana
  • Humans
  • India
  • Linkage Disequilibrium
  • Male
  • Middle Aged
  • Polymorphism, Single Nucleotide*
  • Receptors, Complement 3b / genetics*
  • Selection, Genetic
  • Vietnam

Substances

  • CR1 protein, human
  • Receptors, Complement 3b

Grant support

This work was supported by research grants from CAPES (Coordenação de Aperfeiçoamento de Pessoal Superior) for Thaisa Lucas Sandri and from CNPq (Conselho Nacional de Desenvolvimento Científico e Tecnológico, Brasil) for Iara Jose de Messias Reason. Also, bilateral cooperation support from BMBF to TPV (BMBF BRA11/A33; 01DN11001) for Thirumalaisamy P. Velavan is acknowledged. TPV and FN acknowledge the support from CANTAM (Central Africa Network on Tuberculosis, HIV/AIDS and Malaria), a network of excellence supported by EDCTP. The authors greatly acknowledge the support by the Deutsche Forschungsgemeinschaft (DFG) and Open Access Publishing Fund of Tuebingen University. Other authors received no specific funding for this work. All the funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.