Guadalupe Hernández-Pacheco

HLA-DR antigen frequencies in Mexican patients with dengue virus infection: HLA-DR4 as a possible genetic resistance factor for dengue hemorrhagic fever.

The human leukocyte antigen DRB1 locus (HLA-DRB1) was typed in genomic DNA extracted from whole blood samples of 34 Mexican dengue hemorrhagic fever (DHF) patients and 47 dengue fever (DF) patients, by polymerase chain reaction-sequence-specific oligonucleotide reverse dot blot. HLA-DRB1*04 was negatively associated with risk of DHF (OR 0.31, 95% CI 0.11-0.85). HLA-DR4 homozygous individuals were 11.6 times less likely to develop DHF in comparison to DR4 negative persons (OR 0.08, 95% CI 0.01-0.75). After adjusting for gender and infection type by logistic regression, DR4 positive individuals were 3.6 times less likely to develop DHF than DR4 negative persons (OR 0.28, 95% CI 0.12-0.66). A secondary dengue virus infection was also positively linked with DHF risk (OR 2.89, 95% CI 0.92-9.07). This data suggests that genes of the major histocompatibility complex play a major role in the susceptibility and/or resistance to develop DHF. In Mexicans, HLA-DR4 may be a genetic factor that is protective against DHF. Because HLA-DR4 has been positively selected in Latin American populations, these results may apply also to other similar ethnic groups, particularly those with high percentages of admixture with indigenous Amerindian genes.

Tumor necrosis factor-alpha promoter polymorphisms in Mexican patients with rheumatic heart disease

The major histocompatibility genes (MHC) have been associated with the genetic susceptibility to rheumatic heart disease (RHD). Results have been inconsistent and new genes located on the MHC region such as tumor necrosis factor (TNF-alpha) need to be analyzed. TNF-alpha polymorphisms (positions -238 and -308) were determined in 87 RHD Mexican Mestizo patients and 101 healthy controls. Patients were classified into mitral valve damage (MVD) and multivalvular lesion (MVL) categories. TNF-238 G allele and GG genotype were increased in patients when compared to healthy controls (pC=0.001, OR=14.1 and pC=0.003, OR=14.1, respectively). Also, decreased frequencies of TNF-238 A allele (pC=0.001) and AG genotype (pC=0.003) were found. TNF-308 polymorphism analysis showed increased frequencies of T2 (A) allele (pC<10(-3), OR=10.8) and T1T2 (AG) genotype (pC<10(-3), OR=9.85) and decreased frequencies of T1 (G) allele and T1T1 (GG) genotype (pC<10(-3)). When comparing valvular damage to healthy controls, patients with MVD showed increased frequencies of -238 GG (pC=0.03, OR=ND), -308 T1T2 (AG) (pC<10(-3), OR=14) and -308 T2 (A) (pC<10(-3), OR=11.7). Also, this group showed decreased frequencies of T1 (G) allele and T1T1 (GG) genotype (pC<10(-3)). Patients with MVL presented increased frequency of -308 T2 (A) allele (pC=0.0003, OR=8.65) and decreased frequencies of -308 T1 (G) allele and -308 T1T1 (GG) genotype (pC=0.0003 and pC=0.006, respectively). Distribution of -238 and -308 polymorphisms were similar between MVD and MVL. The data demonstrate that RHD is associated with TNF-alpha polymorphisms in the Mexican population; however, these polymorphisms do not have relation with the valve damage.

MHC class II alleles in Mexican patients with rheumatic heart disease.

BACKGROUND Rheumatic heart disease (RHD) is an autoimmune sequel of group A streptococcal infection that has been associated with the presence of some major histocompatibility complex (MHC) genes. Thus, the aim of the present study was to investigate the role of class II alleles in the genetic susceptibility to RHD in Mexican patients and establish the relationship of these alleles with the pattern of valve damage. METHODS HLA-DR, -DQA1 and -DQB1 allele frequencies were determined by PCR-SSO reverse dot blot and PCR-SSP in 98 Mexican Mestizo patients with RHD and 99 healthy controls. Patients were divided into mitral valve damage (n=46), multivalvular lesion (n=49) and aortic damage (n=3). RESULTS RHD patients presented an HLA-DR16 increased frequency (pC=0.009, OR=3.9) and a decreased HLA-DR11 frequency (pC=0.018) when compared to healthy controls. HLA-DR16 subtyping showed that DRB1*1602 was the DR16 allele increased in patients (pC=0.007, OR=5.3). Haplotype analysis showed increased frequency of DR16-DQA1*0501-DQB1*0301 in RHD patients when compared to healthy controls (pC=0.011). HLA-DR16 frequency remained significantly increased on patients with multivalvular lesion (pC=0.004, OR=4.8). CONCLUSIONS Our data suggest an important participation of Amerindian autochthonous HLA-DR16 (DRB1*1602) allele and DR16-DQA1*0501-DQB1*0301 haplotype as markers for RHD genetic susceptibility in the Mexican Mestizo population. HLA-DR16 allele could also play an important role in determining the pattern of valve damage on these patients.

Angiotensin-Converting Enzyme Gene (ACE) Insertion/Deletion Polymorphism in Mexican Populations

The angiotensin-converting enzyme gene (ACE) insertion/deletion polymorphism was determined in 211 Mexican healthy individuals belonging to different Mexican ethnic groups (98 Mestizos, 64 Teenek, and 49 Nahuas). ACE polymorphism differed among Mexicans with a high frequency of the D allele and the D/D genotype in Mexican Mestizos. The D/D genotype was absent in Teenek and present in only one Nahua individual (2.0%). When comparisons were made, we observed that Caucasian, African, and Asian populations presented the highest frequencies of the D allele, whereas Amerindian (Teenek and Pima) and Australian Aboriginals showed the highest frequencies of the I allele. The distribution of I/D genotype was heterogeneous in all populations: Australian Aboriginals presented the lowest frequency (4.9%), whereas Nahuas presented the highest (73.4%). The present study shows the frequencies of a polymorphism not analyzed previously in Mexican populations and establishes that this polymorphism distinguishes the Amerindian populations of other groups. On the other hand, since ACE alleles have been associated with genetic susceptibility to developing cardiovascular diseases and hypertension, knowledge of the distribution of these alleles could help to define the true significance of ACE polymorphism as a genetic susceptibility marker in the Amerindian populations.

Distribution of HLA-B alleles in Mexican Amerindian populations

In the present study we analyzed by PCR-SSO technique the HLA-B gene frequencies in 281 healthy individuals from four Mexican Amerindian populations (66 Mayos, 90 Mazatecans, 72 Nahuas and 53 Teenek). The most frequent alleles in all studied populations were HLA-B35, HLA-B39, and HLA-B40; however, some differences were observed between populations. The HLA-B35 allele was the most frequent in three of the four populations studied (Mayos, Nahuas and Teenek), whereas in Mazatecans the most frequent allele was HLA-B39. HLA-B40 presented frequencies higher than 10% in all groups. On the other hand, only Mayos presented an HLA-B51 gene frequency higher than 10%. When comparisons were made, important differences between groups were observed. The Teenek group presented an increased frequency of HLA-B35 when compared to Mazatecans and the HLA-B52 allele was increased in Nahuas and Teenek when compared to Mayos. An increased frequency of HLA-B39 was observed in Mazatecans when compared to Nahuas, Mayos and Teenek. Also, an increased frequency of HLA-B51 was observed in Mayos when compared to Mazatecans and Nahuas. These data corroborate the restricted polymorphism of HLA-B alleles and the high frequency of HLA-B35, HLA-B39 and HLA-B40 alleles in autochthonous American populations. In spite of the restriction in this polymorphism, differences in frequencies of HLA-B alleles could be helpful in distinguishing each of these populations.

HLA-DR4 allele frequencies on Indian and Mestizo population from Mexico

Using PCR-SSOP and sequencing, we examined DRB1*04 nucleotide polymorphism in 137 DR4-positive Mexican healthy individuals (46 Mexican Mestizos, 64 Mazatecans, and 27 Nahuas), carrying a total of 147 DR4 haplotypes. Eleven different DRB1*04 alleles were detected in Mexican Mestizo population, whereas, in the two Indian groups a restricted polymorphism was observed (5 variants in Mazatecans and 4 in Nahuas). DRB1*0407 was the most frequent allele (gf = 0.106 in Mexican Mestizos, gf = 0.281 in Mazatecans, and gf = 0.189 in Nahuas). In spite of the restriction in polymorphism, there were differences on DRB1*04 alleles found in Mexicans mainly between Mazatecan and Nahua populations. DRB1*0403 was characteristic allele in Nahua ethnic group, whereas, 0404 and 0411 were predominant alleles in Mazatecans. This data corroborates the restricted polymorphism of DRB1*04 alleles in American populations. In spite of the restriction in this polymorphism, differences in frequencies of DRB1*04 alleles could help distinguish each population.

Influence of the Apolipoprotein E Polymorphism on Plasma Lipoproteins in a Mexican Population

Abstract The influence of apolipoprotein E (APOE) genotypes on plasma lipid levels was determined in 278 Mexican individuals. The most frequent genotype was E3/3 (80.5%) followed by E3/4 (12.5%), E2/3 (5.0%), E2/4 (1.4%), and E4/4 (0.3%). Our data are similar to those previously described for Mexican-American and American Indian populations, which show the highest frequency worldwide of the APOE*3 and the E3/3 genotype. Compared to female carriers of the E3/3 genotype, women with the E3/4 genotype presented increased low-density lipoprotein cholesterol (117 ± 28.0 mg/dL vs. 134.0 ± 31.7 mg/dL, p < 0.05), and total cholesterol (179.4 ± 33.4 mg/dL vs. 197.5 ± 35.4 mg/dL, p < 0.01). Also, we detected increased high-density lipoprotein concentrations in women with the E2/3 genotype (53.7 ± 19.5 mg/dL) when compared to women with the E3/3 genotype (45.2 ± 12.0 mg/dL) (p < 0.032). Our data suggest that genetic variation at the APOE locus in the Mexican population is a genetic factor that influences plasma lipid levels. This effect was observed only in the female population. Additional studies attempting to correlate APOE polymorphism with plasma lipid profile in a large number of individuals would be helpful in establishing the true significance of this polymorphism in the Mexican population.

HLA-DRB and HLA-DQB loci in the genetic susceptibility to develop glaucoma in Mexicans.

PURPOSE Glaucoma is a clinically heterogeneous disease with a pathophysiology that may include genetic susceptibility, possibly associated with an immunologic disorder. The aim of this study was to determine whether the DNA polymorphisms located in the HLA-DRB1 and HLA-DQB1 genes show a specific association pattern in Mexican mestizo patients with primary open-angle glaucoma. METHODS This was a cross-sectional, case-control, multicenter study. We analyzed the HLA-DRB1 and DQB1 loci of 81 Mexican mestizo nonrelated patients with primary open-angle glaucoma and 98 healthy ethnic matched control subjects. Patients were diagnosed clinically and by visual fields examination. HLA typing was performed by PCR-SSO reverse dot blot. RESULTS We documented increased frequencies of HLA-DRB1*0301, DRB1*1101, DRB1*0701, DRB1*1402, DQB1*0302, and DQB1*0301; however, none of them were significantly different from normal control subjects. Haplotype analysis showed that the HLA-DRB1*0407-DQB1*0302 haplotype is significantly increased in patients compared with control subjects (P = .0001). CONCLUSIONS The haplotype HLA-DRB1*0407-DQB1*0302 is common among Mexican mestizo (haplotype frequency = 0.102), and it was increased in our patients (haplotype frequency = 0.259, P = .0001). This may reflect an independent association of this haplotype with the disease as the result of linkage disequilibrium or the influence of a neighboring gene. The pathophysiology of this illness is uncertain, and further studies are needed regarding the genetic susceptibility to develop primary open-angle glaucoma.

Polymorphism and distribution of HLA-DR2 alleles in Mexican populations.

DRB1*15/16 nucleotide polymorphism was analyzed in 68 DR2 positive individuals (18 Mexican Mestizos, 30 Mazatecans and 20 Nahuas), carrying a total of 75 DR2 haplotypes. HLA-DR2 was one of the most frequent specificities detected in Mazatecans and Nahuas with gene frequency (gf) of 0.232 and 0.141, respectively. In these populations DRB1*16 was the most frequent DR2 split (gf = 0.183 in Mazatecans and gf = 0.135 in Nahuas), whereas in Mexican Mestizos the most frequent was DRB1*15 (gf = 0.065). Four DRB1-DQB1 combinations in Mexican Mestizos, two in Mazatecans and one in Nahuas were in linkage disequilibrium. In spite of the restricted polymorphism, there were differences on DRB1*15/16 alleles found in Mexicans. DRB1*1501 a Caucasian allele was predominant in Mexican Mestizos, whereas DRB1*1602 an Amerindian allele was characteristic on Indian populations. An important difference was detected among the Amerindian populations studied since DRB1*1502 was only present in Mazatecans. This data corroborates the restricted polymorphism of DRB1*15/16 and the high frequency of DRB1*16 subtype in autochthonous American populations and suggest that the differences in gene frequencies of DRB1*15/16 alleles could be helpful in distinguishing each of these population.

Matrix γ-Carboxyglutamic Acid Protein (MGP) G-7A and T-138C Gene Polymorphisms in Indian (Mayo and Teenek) and Mestizo Populations from Mexico

Matrix γ-carboxyglutamic acid protein (MGP) genotypes (G-7A and T-138C) were determined in 266 individuals from three Mexican populations. Mexicans showed increased frequencies of the G-7A G allele and the G7-A GG genotype compared to Europeans. For the T-138C genotype, we found differences among the Mexicans. This study could help to define the significance of MGP polymorphisms as genetic markers in Amerindian populations.