Biomedical subjects
Publications and source records attributed to C Vilches.
An almost complete and bidirectional association exists between HLA-Cw*17 and the HLA-B antigens B41 and B42. Serological and molecular analysis of an individual in which HLA-B*4101 was identified in the absence of Cw*17 provides experimental evidence to prove a previously proposed hypothesis predicting that alloantisera classified as "B41+B42" are instead specific reagents for HLA-Cw*17.
We present a set of primer mixes for the allele-specific typing of the HLA-B*15 group by PCR-SSP. The set comprises 46 primer mixes which are designed to unequivocally resolve all but two of the 666 possible combinations of the B*15 alleles, B*1501-37 (B*1536 sequence unavailable). A core subset of 34 of the 46 mixes can be used alone to give a high resolution B*15 typing set. This allows for the identification of each B*15 allele when present as the only B*15 allele and the majority of the possible B*15 homozygotic combinations. The method was validated using reference DNA samples and the B*15 allele frequency in 4 distinct ethnic populations was investigated. The results show that these populations contain predominantly mutually exclusive sets of B*15 alleles.
Explore the source record for details and available documents.
Explore the source record for details and available documents.
Genotyping of the HLA-C locus by PCR-SSP has previously shown 100% association of B41 and B42 with a new allelic variant. Partial sequencing studies (exons 2-4) demonstrated that this PCR-SSP variant corresponded to the new allele Cw*1701. In this study we have characterized the whole coding region of Cw*1701 from a Bubi individual of Equatorial Guinea. Our results partially confirm the previously reported sequence and reveal that Cw*1701 has many new polymorphisms at several exons, including a 18-bp insertion in exon 5. Cw*1701 is thus a most unusual HLA-C molecule defining a third allelic lineage of this locus.
The HLA-Cw*1801 specificity, a Cw7/Cw4 hybrid allele, has recently been described in association with B*8101 (formerly B"DT"). In this study, the new Cw*1802 variant, differing from Cw*1801 at exon 5, is found associated with B*5703 in Bubi individuals from Equatorial Guinea. Confirmatory complete coding regions of B*5703 and B*3910 are also reported.
Two previously reported PCR-SSP variants of the HLA-B locus, B51GAC and B45v, were investigated by RT-PCR cloning and nucleotide sequence analysis of their complete coding regions. They have been shown to correspond to the new alleles B*5108 and B*5002, both of which differ from the common B*5101 and B*5001 subtypes, respectively, by amino acid replacements at their alpha-2 domain alpha-helices. The primary structure of B*5002, intermediate between those of B*4501 and B*5001, raises further concern about the current classification of B*45 as a B12 rather than as a B*50 subtype.
Recent evidence indicates that HLA-C molecules are biologically relevant by eliciting T-cell responses and exerting control over NK cell function. In addition, HLA-C is associated with susceptibility to various diseases, notably psoriasis vulgaris. Clarification of the full biological roles for HLA-C has however proved difficult because detection of HLA-C antigens by complement mediated cytotoxicity using alloantisera is inefficient. Up to 50% of individuals in every race have serologically undetectable HLA-C locus antigens due to a combination of relatively low expression, lack of serological reagents and a lack of information about the distribution of the HLA-C blank alleles. Recently, amplification of DNA using sequence-specific primers (PCR-SSP) has proved a reliable, accurate and rapid method for medium resolution HLA-C typing. We have now developed high resolution HLA-C typing by PCR-SSP utilizing allele and group-specific PCR-SSP reactions which can identify all HLA-C alleles (except non-coding change alleles) in most heterozygous combinations. Using this system we have typed 604 unrelated United Kingdom Caucasoids to generate accurate frequency and linkage disequilibrium data. To assess the validity of serology for HLA-C, PCR-SSP typings for 527 out of the 604 individuals were compared to serology. We find that the frequency of many HLA-C antigens has been underestimated by serology and some antigens such as Cw6 are consistently assigned incorrectly by serology. The overall discrepancy rate between serology and SSP was high at 37% (195/527). High-resolution HLA-C typing of 112 International Histocompatibility Workshop cell lines has also been performed.
Explore the source record for details and available documents.
We determined the HLA frequency distribution in a sample of 100 Bubi individuals born on the island of Bioko (Equatorial Guinea). HLA-A, -B and -C typing was performed by serology and PCR-SSP. DRB1/3/4/5, DQB1 and DQA1 alleles were determined by PCR-SSOP. The HLA allele distribution of this population group resembles those found in other Bantu-speaking groups; however, the higher frequency of A30, A32, B44, DRB1*1301 in the Bubi with respect to other Bantu groups and the absence of DR4 deserve special mention. The cloning and sequencing of class I and II genes in this population allowed the description of five new allelic variants: B*4407, Cw*0706, Cw*1801, Cw*1802 and DQB1*0612 and five confirmatory sequences: B*3910, B*5703, B*8101, Cw*1203 and Cw*1701. The following new HLA-C,B haplotypes have been found in Bubi: Cw*08-B*57, Cw*18-B*57, Cw*0302-B*53, Cw*07-B*53 and Cw*1601-B*63. The most frequent seven-locus haplotype is: A*30-Cw*17-B*42-DRB1*1102-DRB3*0202-DQA1*05-DQB1 *0301. In terms of genetic distance, the Bubi are closer to other Bantu groups than to West African populations.
Explore the source record for details and available documents.
Explore the source record for details and available documents.
A novel HLA-Cw*15, B7 haplotype has been found in Caucasians. Molecular cloning studies demonstrate that this haplotype is constituted by the new alleles Cw*15052 and B*0706, which seem to be intermediate steps in the diversification of their respective allelic families. A pathway for the evolution of Cw*15 alleles is proposed.
A novel HLA-DQB1 allele was detected by oligotyping in the Bubi population of Equatorial Guinea. In order to characterize the new allelic variant, a RT-PCR method which permitted the cloning of its complete coding region was designed. With this method, we have determined the nucleotide sequence of the new DQB1*0612 allele, related to *0604 and *0609 but differing from them at polymorphic codon 70. A proposal for the improvement of the sequencing strategies of HLA class II alleles is made.
Recent evidence indicates that HLA-C molecules are biologically relevant by eliciting T-cell responses and exerting control over NK cell function. In addition, HLA-C is associated with susceptibility to various diseases, notably psoriasis vulgaris. Clarification of the full biological roles for HLA-C has however proved difficult because detection of HLA-C antigens by complement mediated cytotoxicity using alloantisera is inefficient. Up to 50% of individuals in every race have serologically undetectable HLA-C locus antigens due to a combination of relatively low expression, lack of serological reagents and a lack of information about the distribution of the HLA-C blank alleles. Recently, amplification of DNA using sequence-specific primers (PCR-SSP) has proved a reliable, accurate and rapid method for medium resolution HLA-C typing. We have now developed high resolution HLA-C typing by PCR-SSP utilizing allele and group-specific PCR-SSP reactions which can identify all HLA-C alleles (except non-coding change alleles) in most heterozygous combinations. Using this system we have typed 604 unrelated United Kingdom Caucasoids to generate accurate frequency and linkage disequilibrium data. To assess the validity of serology for HLA-C, PCR-SSP typings for 527 out of the 604 individuals were compared to serology. We find that the frequency of many HLA-C antigens has been underestimated by serology and some antigens such as Cw6 are consistently assigned incorrectly by serology. The overall discrepancy rate between serology and SSP was high at 37% (195/527). High-resolution HLA-C typing of 112 International Histocompatibility Workshop cell lines has also been performed.
Nucleotide sequence analysis of the HLA-C alleles of the GB92 cell line, heterozygous for B*8101 and B*4407, revealed the existence of two new allelic variants: Cw*1801 and Cw*0706. The former allele, initially detected as a PCR-SSP variant, displays a hybrid aspect, sharing sequence motifs with Cw*07 at exons 1 and 2, and with Cw*04 at distal exons. In serological assays, Cw*1801 is only recognized by some cross-reactive sera. Cw*0706 shows a primary structure closely related to previously known Cw7 alleles, but carries new sequence motifs at its 3'-end. Preliminary data indicate that Cw*1801 is associated to B*8101 and that Cw*0706, B*4407 could account for a part of the Cw7, B44 haplotypes observed in African populations.
BACKGROUND: We have recently described the association between the IgE antibody response to Ole e I (the major antigen from olive tree pollen) and the DR7-DQ2 haplotype in a Spanish population. OBJECTIVE AND METHODS: Due to the linkage disequilibrium between DR7 and DQ2, and thus the difficult distinction between the role of these two antigens in the T-cell activation response, we decided to solve this question by two approaches: 1. The study of another ethnic group, individuals of Arabic origin, with a presumably distinct disequilibrium linkage between DR and DQ antigens. Genomic DNA typing was performed in 46 subjects (allergic and non-allergic) by Restriction Fragment Length Polymorphism (RFLP) and results showed that patients with specific IgE antibodies alpha-Ole e I, were DR7 and/or DQ2. These data show a similar restriction pattern to those previously described for Spanish patients. The phenotypic frequency of DR7 antigen is significantly greater than in the non-allergic population, with a corrected P (Pc) value of 0.03. 2. The analysis of the genetic requirements of Ole e I response, using T-cell lines specific for this antigen. This was first carried out by blocking the proliferative response of these T-cell lines with specific anti-human HLA class II antibodies and then testing the genetic restriction of this response using a panel of histocompatible and histoincompatible Antigen Presenting Cells (APCs). Both experiments corroborate the hypothesis that DR7 and DQ2 are implicated in the recognition of Ole e I.
The novel HLA-Cw*0704 allele, previously detected as the PCR-SSP variant Cw7/8v, has been cloned and sequenced from the homozygous typing cell KRO3/4 after amplification by anchored PCR. The nucleotide sequence of Cw*0704 is closely related to those of other Cw*07 alleles, but carries specific changes in exon 3 consistent with its serological behavior-a short Cw7 cross-reactive with antibodies directed against HLA-Cw8. Some of the substitutions of Cw*0704 have not been previously described for HLA-C but are found in HLA-B alleles and in published C sequences of non-human primates. The new allele carries a novel polymorphism in its 5' untranslated region (5' ut) that could be shared by all Cw*07 alleles. By PCR-SSP, Cw*0704 is a relatively common allele in English Caucasoids at a frequency of 4.6%. It is most often observed on HLA-B44 haplotypes previously described as HLA-C "blank", although linkage disequilibria with other HLA-B specificities have been found.