HLA genes in Amerindian immigrants to Madrid (Spain): epidemiology and a virtual transplantation waiting list: Amerindians in Madrid (Spain)

HLA-G in Amerindians: Epidemiology and Worldwide Population Comparison

Background:

HLA-G molecules are immunosuppressive and avoid fetal rejection by giving negative signals to maternal immune system from fetal trophoblast cell surface. HLA-G genes have been associated to different pathologies: Spontaneous abortions, autoimmunity, tumor progression, transplant rejection and infection. In addition, different World populations show remarkable different HLA-G allele frequencies in the allele that does not produce a full HLA-G molecule (HLA-G*05N); this allele is almost absent in studied Amerindians.

Objectives:

The aim is to study HLA-A.-B,-DRB1 and –G alleles and extended haplotypes in Amerindians for the first time. This may be useful to asses HLA-G epidemiology, association to disease and Preventive Medicine in Amerindians.

Methods:

HLA-A,-B and -DRB1 have been typed by using standard automatic protocols. HLA-G alleles have been detected by direct HLA-G exon 2, exon 3 and exon 4 DNA sequencing. Computer calculations have been done by specific standard methods.

Results:

HLA-A,-B,-DRB1 and –G extended haplotypes have been calculated in Amerindians for the first time. Also, their HLA-G frequencies have been compared with worldwide populations.

Conclusion:

Low frequencies of null HLA-G*01:05N allele are found in Amerindians. The extended haplotypes with this allele bear other typical Amerindian HLA-DRB1 alleles and its origin is discussed. HLA-G allele frequency profile is closer to that of Europeans than to that of Far East Asians. Our findings are useful to Preventive Medicine and Epidemiology associated to Fertility and HLA-G associated pathology and transplantation.

Characterisation and functional implications of the two new HLA-G alleles found in Amerindian and Caribbean populations

HLA-G polymorphism has been found to be relatively low in all world populations. In the present paper two new HLA-G molecules are described in ancient American natives. A new HLA-G molecule from a Ecuador Amerindian individual (male) showed four codon changes with respect to HLA-G*01:01:01. Silent changes at α1 domain (residue 57, Pro, CCG→CCA) and α2 domain (residue 93, His, CAC→CAT and residue 100, Gly, GGC→GGT) and one productive change in α3 domain (residue 219 changed from Arg to Trp). This α3 change may dramatically alter HLA-G interactions with beta-2 microglobulin, CD8, ILT-2 and ILT-4 ligands present in subsets of T, B, NK, monocytes, macrophages and dentritic cells. Another HLA-G new molecule was found in a woman from Hispaniola Island, Dominican Republic (Sto Domingo): it presented a silent change at α2 domain residue 107, Gly, GGA→GGT and non-silent change at residue 178, Met→Thr (with respect to HLA-G*01:01:01) which is close to class I molecule/clonotypic T cell receptor interaction sites. Functional implications of these findings are discussed.

HLA-DMB in Amerindians: Specific linkage of DMB*01:03:01/DRB1 alleles

BACKGROUND

HLA-DMB proteins are important for intracellular microbial metabolism in order other major histocompatibility complex (MHC) molecules present peptides to lymphocytes. In addition, HLA-DMB alleles have been found linked to diseases in some ethnic groups and HLA-DMB molecules may be important to explain HLA disease association.

OBJECTIVE

To detect HLA-DMB alleles profile in Amerindians for the first time and compare them to other populations. This will establish the bases to study HLA-DMB linkage to disease in Amerindians.

METHOD

A group of 168 voluntary Amerindians have been typed for HLA-DMB alleles. They have been characterized both, by genetic and genealogical bases. Cloning and automated HLA-DMB DNA (exons 2, 3 and 4) sequencing have been performed for allele assignation.

RESULTS

HLA-DMB*01:01:01 and HLA-DMB*01:03:01 show the highest frequencies. These have been compared to other World wide populations. HLA-DMB*01:03:01 is tightly associated to certain specific HLA-DRB1 alleles in Amerindians.

CONCLUSION

The specific Amerindian HLA-DMB allele frequencies and their linkage disequilibrium with other MHC alleles may be crucial to determine HLA-DMB World wide variation, evolution and specific linkage to disease in Amerindians and other populations.

Human leukocyte antigen profiles of latin american populations: differential admixture and its potential impact on hematopoietic stem cell transplantation

The outcome of hematopoietic stem cell transplantation (HSCT) is shaped by both clinical and genetic factors that determine its success. Genetic factors including human leukocyte antigen (HLA) and non-HLA genetic variants are believed to influence the risk of potentially fatal complications after the transplant. Moreover, ethnicity has been proposed as a factor modifying the risk of graft-versus-host disease. The populations of Latin America are a complex array of different admixture processes with varying degrees of ancestral population proportions that came in different migration waves. This complexity makes the study of genetic risks in this region complicated unless the extent of this variation is thoroughly characterized. In this study we compared the HLA-A and HLA-B allele group profiles for 31 Latin American populations and 61 ancestral populations from Iberia, Italy, Sub-Saharan Africa, and America. Results from population genetics comparisons show a wide variation in the HLA profiles from the Latin American populations that correlate with different admixture proportions. Populations in Latin America seem to be organized in at least three groups with (1) strong Amerindian admixture, (2) strong Caucasian component, and (3) a Caucasian-African gradient. These results imply that genetic risk assessment for HSCT in Latin America has to be adapted for different population subgroups rather than as a pan-Hispanic/Latino analysis.

Amerindians show association to obesity with adiponectin gene SNP45 and SNP276: population genetics of a food intake control and "thrifty" gene

Adiponectin gene polymorphisms SNP45 and SNP276 have been related to metabolic syndrome (MS) and related pathologies, including obesity. However results of associations are contradictory depending on which population is studied. In the present study, these adiponectin SNPs are for the first time studied in Amerindians. Allele frequencies are obtained and comparison with obesity and other MS related parameters are performed. Amerindians were also defined by characteristic HLA genes. Our main results are: (1) SNP276 T is associated to low diastolic blood pressure in Amerindians, (2) SNP45 G allele is correlated with obesity in female but not in male Amerindians, (3) SNP45/SNP276 T/G haplotype in total obese/non-obese subjects tends to show a linkage with non-obese Amerindians, (4) SNP45/SNP276 T/T haplotype is linked to obese Amerindian males. Also, a world population study is carried out finding that SNP45 T and SNP276 T alleles are the most frequent in African Blacks and are found significantly in lower frequencies in Europeans and Asians. This together with the fact that there is a linkage of this haplotype to obese Amerindian males suggest that evolutionary forces related to famine (or population density in relation with available food) may have shaped world population adiponectin polymorphism frequencies.

Amerindians show no association of PC-1 gene Gln121 allele and obesity: a thrifty gene population genetics

PC-1 Gln121 gene is a risk factor for type 2 diabetes, obesity and insulin resistance in European/American Caucasoids and Orientals. We have aimed to correlate for the first time this gene in Amerindians with obesity and their corresponding individuals genotypes with obesity in order to establish preventive medicine programs for this population and also studying the evolution of gene frequencies in world populations. Central obesity was diagnosed by waist circumference perimeter and food intake independent HDL-cholesterol plasma levels were measured. HLA genes were determined in order to more objectively ascertain participants Amerindians origin. 321 Amerindian blood donors who were healthy according to the blood doning parameters were studied. No association was found between PC-1 Gln121 variant and obesity. Significant HDL-cholesterol lower values were found in the PC-1 Lys121 bearing gene individuals versus PC-1 Gln121 bearing gene ones (45.1 ± 12.7 vs. 48.7 ± 15.2 mg/dl, p < 0.05). Population analyses showed a world geographical gradient in the PC-1 Gln121 allele frequency: around 9% in Orientals, 15% in European Caucasoids and 76% in Negroids. The conclusions are: (1) No association of PC-1 Gln121 gene is found with obesity in Amerindians when association is well established in Europeans. (2) PC-1 Gln121 gene is associated to higher levels of HDL-cholesterol than the alternative PC-1 Lys121 allele. This may be specific for Amerindians. (3) Amerindians have an intermediate frequency of this possible PC-1 Gln121 thrifty gene when compared with Negroid African Americans (78.5%) or Han Chinese (7.5%, p < 0.0001). Historical details of African and other groups may support the hypothesis that PC-1 Gln121 is indeed a thrifty gene.

Amerindians normalized waist circumference and obesity diagnosis standarized by biochemical and HLA data

Metabolic syndrome (MS) and obesity are principal causes of morbidity all over the World, particularly for their association to cardiovascular risk. Amerindians are often living in countries and remote areas with unavailable sophisticated diagnoses methodologies. However, waist-circumference is a reliable and easy to record parameter of visceral obesity and MS. Waist circumference normal values are not yet established in Amerindians: South Asian and Japanese values have been recommended for Amerindian use. The purpose of this study is to objectively define for the first time the waist circumference measure cut-off points for Amerindians. A total of 303 unrelated Amerindian adults recently immigrated to Madrid were studied; they were healthy, since they were questioned and tested as appropriate for blood donation. Waist-circumference was measured in these voluntary blood donors after written consent. Chosen subjects for study had HLA quasi-specific Amerindian genes and not gained weight since their relatively short time living in Spain. Amerindians with Type I or II diabetes or family antecedents were removed from the study. The biochemical parameter used to define normality for MS was the reliable serum HDL-cholesterol levels, whose values are diet independent. A Receiver Operating Characteristic analysis was used to compare the predictive validity and to find out the optimal cut-off points of waist circumference normal values. Cut-off points were ≤88.5 cm in males and ≤82.5 cm in females; these values were close to the median values (88 and 82.2 cm, respectively). Obtained waist circumference values recorded here in normal Amerindians are different to those previously recommended indirectly (those of South Asian/Japanese populations). These parameters may be of great value for American countries health care in order to predict and control MS and its cardiovascular complications. Other countries having a heavy Amerindian immigration (i.e.: USA, Spain) may also benefit for establishing specific Preventive Medicine programs.