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Biomedical subjects

A López-Vázquez

Publications and source records attributed to A López-Vázquez.

8 recordsLinked to original sources
PubMed2006

MHC class I chain-related gene B (MICB) is associated with rheumatoid arthritis susceptibility.

OBJECTIVES: Several recent studies have shown that the MHC class III region, located telomeric to HLA-DRB1, contains an additional genetic factor that predisposes to rheumatoid arthritis (RA). In this study, we investigate whether inhibitor of kappaB-like (IkappaBL), MICB or MICA located in the MHC class III region are the second susceptibility gene associated with RA. METHODS: A total of 154 healthy controls and 140 RA patients were genotyped for HLA-DRB1, MICA, MICB and the polymorphism -62 of the IkappaBL gene. RESULTS: A significant increase of HLA-DRB1 shared epitope (SE) alleles was detected in RA patients (61.4 vs 43.5%, P(c) = 0.01, OR = 2.1, 95% CI = 1.3-3.3). Among SE alleles, the HLA-DRB1*0401 (13.5 vs 5.1%, P(c) = 0.04, OR = 3.2, 95% CI = 1.3-8.1) and HLA-DRB1*0404 (6.4 vs 1.2%, P = 0.02, P(c) = NS) showed the most significantly association with RA. No increase of risk was associated with HLA-DRB1*01. Remarkably, the allele MICB*004 was also significantly associated with RA susceptibility (40.7 vs 23.3%, P(c) = 0.01, OR = 2.2, 95% CI = 1.3-3.7). MICB*004 was in linkage disequilibrium with HLA-DRB1*0404 (lambda(s) = 0.33) and HLA-DRB1*0405 (lambda(s) = 0.34). However, MICB*004 was also increased in HLA-DRB1 SE negative patients (37 vs 21.5%, P = 0.04). No significant association between IkappaBL and MICA with RA was found. CONCLUSIONS: MICB*004 allele was associated with RA susceptibility. This allele was in linkage disequilibrium with HLA-DRB1*0404 and DRB1*0405. The association of MICB with RA susceptibility and the functional role of MIC genes in the pathogenesis of RA converts MICB into a candidate to be an additional MHC gene associated with RA susceptibility.

Adaptor Proteins, Signal Transducing↗
PubMed2005

The amino acid at position 97 is involved in folding and surface expression of HLA-B27.

HLA-B27 confers susceptibility to ankylosing spondylitis (AS) but the mechanism linking this association remains unknown. Other properties unrelated to its natural role of antigen presenting function may be important in disease pathogenesis. We determined here the impact of N97D substitution on the folding and expression of HLA-B*2704 transfected in the 721.221 cell line. The mutation at position 97 abolishes the surface expression of non-conformational (HC10) and conformational (ME1) forms. The expression of ME1 forms was found to be absent in B*2704 N97D by immunoprecipitation and flow cytometry of fixed and permeabilized cell experiments with the conformation-sensitive ME1 antibody. However, immunoblotting cell lysates with HC10 revealed the presence of unfolded heavy chain (HC) and HC-dimer forms. The impact of the N97D mutation in the exit from the endoplasmic reticulum (ER) was analysed by western blot after endoglycosidase-H treatment, and it was found that B*2704 N97D was retained and accumulated as unfolded molecules. We tested for mutant association with transporter associated with antigen processing (TAP), calnexin (CNX), calreticulin (CLR) and beta2 microglobulin (beta2m). The wild-type B*2704 and N97D mutants were associated with TAP, CNX and CLR, although HC10 forms of mutant N97D interact more weakly with TAP. Only folded molecules of HLA-B*2704 were associated with beta2m. Surprisingly, the peptide-binding assay demonstrated the ability of unfolded N97D molecules to bind high-affinity peptides. It has been suggested that AS may arise because of aberrant folding of HLA-B27 molecules within the ER. Future work must therefore aim to clarify the functional connection between the unfolded protein response pathway in response to the accumulation of HLA-B27 in the ER. This mutant could be useful as a model for the misfolding of HLA-B27.

Amino Acid Substitution↗
PubMed2005

The HLA-B*5703 allele confers susceptibility to the development of spondylarthropathies in Zambian human immunodeficiency virus-infected patients with slow progression to acquired immunodeficiency syndrome.

OBJECTIVE: To analyze the HLA distribution in a population of individuals from Zambia in order to establish a possible relationship between the progression of human immunodeficiency virus (HIV) infection and the development of spondylarthropathy (SpA). METHODS: A large epidemiologic analysis of rheumatology patients living in Zambia was performed in order to identify those who had SpA. We selected 64 patients with SpA and found that 54 also had HIV type 1 (HIV-1) infection; only 10 were HIV negative. Additionally, we selected 57 HIV-infected individuals without SpA and 43 healthy controls. Among all of the HIV-1-infected patients, 25 SpA-positive and 24 SpA-negative patients were classified as slow progressors to acquired immunodeficiency syndrome (AIDS), and 8 SpA-positive and 26 SpA-negative patients were classified as rapid progressors. All patients were typed for HLA-B alleles. RESULTS: Of the 64 patients with SpA, HIV infection was observed in 54 (84%). The frequency of B*5703 was increased in patients who were SpA positive and HIV positive compared with patients who were SpA negative and HIV positive (P = 0.0002, odds ratio [OR] 8.28). Among patients who were slow progressors to AIDS, this allele was overrepresented in those with SpA compared with those without SpA (corrected P = 0.001, OR 26.25). CONCLUSION: HLA-B*5703 seems to be a protective allele against the progression of HIV infection but could influence the increased incidence of SpA observed in this population.

Acquired Immunodeficiency Syndrome↗
PubMed2005

Interaction between KIR3DL1 and HLA-B*57 supertype alleles influences the progression of HIV-1 infection in a Zambian population.

KIR and HLA loci are both highly polymorphic, and some HLA class 1 products bind and trigger cell-surface receptors specified by KIR genes. We examined whether KIR genes act in concert with HLA-B locus to control HIV-1 infection in a sample of Zambian patients. DNA samples from 88 Zambian patients with HIV-1 were examined. Patients were classified as either slow progressors (SP; n = 54) or rapid progressors (RP; n = 34) to AIDS. All were typed for HLA-B and KIR genes. Our results reveal an association between B*57 supertype (B*57s, which includes B*57 and B*58 alleles) and delayed progression to AIDS (p = 0.0007 by pc = 0.015; OR = 5.25). We also observed an increase incidence of Bw4-I80 in patients with slow progression (p = 0.001 by pc = 0.003, OR = 5). This increase was found to be secondary to B*57s. The presence of both KIR3DL1 and B*57S has a significant effect on progression to AIDS (p = 0.0008; OR = 5.61). B*57s genotypes with another HLA-B allele different from those in the trans position, which also had a specificity different to Bw4-I80 (Bw4-T80 or Bw6), was also greater in the SP than in the RP group (p = 0.00003; OR = 10.11). The presence of the inhibitory allele KIR3DL1 in combination with the HLA-B*57s alleles that contain the Bw4-I80 epitope, has a highly protective effect against progression to AIDS in Zambian patients.

Acquired Immunodeficiency Syndrome↗
PubMed2004

Diverse clinical presentations of celiac disease in the same family.

We performed a family study to evaluate a total of 34 extended family members (8 siblings, 23 children and nephews, and 3 grandchildren) of an adult patient with celiac disease (CD), a 58- year-old male with severe neurologic involvement manifested as myoclonias. We found 3 other members affected with CD (a 44-year old sister, a 39-year old niece, and a 26-year old nephew). Two of them were completely asymptomatic and all had hypertransaminasemia. All exhibited a villous atrophy pattern of the duodenal mucosa (1 mild, 1 moderate, 1 severe). Overall family involvement was 11.8% (4/14). We wish to emphasize the need to perform extended family studies when diagnosing a case of CD, since risk is not restricted to only first-degree relatives.

Adult↗
PubMed2001

Genetic variability, molecular evolution, and geographic diversity of HLA-B27.

HLA-B27 represents a family of 23 closely related alleles (B*2701-23) that differ at 24 amino acid positions. The pattern of polymorphisms of B27 was studied, with special reference to synonymous (Ks) and nonsynonymous (Ka) divergence among alleles. B27 alleles are characterized by the enhanced rate of nonsynonymous nucleotide substitution in the peptide-binding region (PBR). The percentage of substitutions between each of the B27 pairs ranges from 0.2%-3% in exons 2-3 to 1.8%-20.1% in the PBR. A phylogenetic analysis of all B27 alleles is described in order to identify subtypes with a common evolutionary history. These results, together with the phylogenetic trees obtained from the comparison between exons 2-3 and PBR indicate that polymorphism of B27 is selectively maintained. Most of the differences are clustered in the C/F pocket affecting the specific binding of antigenic peptides. Gene conversion and point mutation are the most important mechanisms responsible for B27 diversification. The interaction of selection, genetic drift, and recombination events is important for generating polymorphism at B27 alleles. We analyzed a large extended B27 positive population from different parts of the world. Our results indicate that B27 subtypes differ in their ethnic distribution, which may be the result of different genetic and geographical origins. Different factors such as genetic drift, bottleneck effect, and admixture among populations could contribute to the genetic constitution of B27. The striking correlation between the structural features of B27 and the ethnic distribution of these subtypes suggests a model of strong directional evolution, in which the subtypes could have arisen from B*2705.

Africa↗