Andrea Munguia

Association of narcolepsy-cataplexy with HLA-DRB1 and DQB1 in Mexican patients: A relationship between HLA and gender is suggested

BackgroundNarcolepsy-cataplexy is characterized by excessive daytime sleepiness with recurrent episodes of irresistible sleep, cataplexy, hallucinations and sleep paralysis. Its aetiology is unknown, but it is positively associated with the human leukocyte antigens (HLA) in all studied populations. The purpose of the present study was to investigate the association of HLA class II DRB1/DQB1 alleles with narcolepsy-cataplexy in Mexican Mestizo patients.MethodsThis is a case-control study of consecutive patients and ethnically matched controls. We included 32 patients diagnosed with typical narcolepsy-cataplexy, of the National Institute of Neurology, of the Institute of Psychiatry and at the Center of Narcolepsy at Stanford University. As healthy controls, 203 Mexican Mestizos were included. DRB1 alleles were identified using sequence based typing. A PCR-SSOP reverse dot blot was used for DQB1 typing. Allele frequency was calculated by direct counting and the significance of the differences was assessed using the Yates Chi square. Odds ratio and confidence intervals were evaluated.ResultsHLA-DRB1*1501 (OR = 8.2; pc < 0.0001) and DQB1*0602 (OR = 8.4; pc < 0.0001) were found positively associated with narcolepsy. When deleting DQB1*0602+ patients from the analysis, DQB1*0301 was also found increased (OR = 2.7; p = 0.035; pc = NS). DQB1*0602/DQB1*0301 genotype was present in 15.6% of the cases (OR = 11.5; p = 0.00035), conferring a high risk. DRB1*0407 (OR = 0.2; p = 0.016 pc = NS) and DQB1*0302(OR = 0.4; p = 0.017, pc = NS) were found decreased in the patients. The gender stratification analysis showed a higher risk in females carrying DRB1*1501 (OR = 15.8, pc < 0.0001) and DQB1*0602 (OR = 19.8, pc < 0.0001) than in males (OR = 5.0 for both alleles; p = 0.012, pc = NS for DRB1 & p = 0.0012, pc = 0.017 for DQB1). The susceptibility alleles found in Mexicans with narcolepsy are also present in Japanese and Caucasians; DRB1*04 linked protection has also been shown in Koreans. A stronger HLA association is suggested in females, in accordance with the sexual dimorphism claimed previously.ConclusionThis knowledge may contribute to a better understanding of the disease pathogenesis in different populations. The evaluation of the risk to develop narcolepsy-cataplexy in carriers of the described alleles/genotypes may also be possible. A larger sample should be analysed in Mexican and in other Hispanic patients to confirm these results.

Major histocompatibility complex and strong human leukocyte antigen–DRB1 and gender association with Vogt–Koyanagi–Harada syndrome in Mexican Mestizos

Vogt-Koyanagi-Harada syndrome (VKH) is a multisystem autoimmune disorder mediated by cytotoxic T cells targeting melanocytes antigen(s). A strong major histocompatibility complex (MHC) association with HLA-DRB1*04:05 has been demonstrated in different populations. We investigated the contribution of HLA-A*, -B*, -C*, -DRB1*, and -DQB1* genes, belonging to the human leukocyte antigen (HLA), to the expression of VKH and we analyzed the influence of gender on the HLA association. A total of 76 patients and 256 healthy Mexican Mestizo individuals were included. HLA-A, B, C, and DQB1 typing was performed using the polymerase chain reaction, and hybridization was done using sequence specific probes. DRB1 alleles were defined by means of sequence base typing. The frequency of DRB1*04:05 (odds ratio=2.95) and DRB1*04:04 (odds ratio=2.79) were found to be significantly increased in the patients, conferring a similar risk. Gender stratification analysis showed that these alleles were associated with female gender only. No HLA class I or class II alleles were significantly deviated in males. The frequency of DRB1*04:07 was increased in the whole group, upon withdrawal from analysis the DRB1*04:04 and *04:05 positive patients. A trend of DRB1 alleles contributing to the expression of VKH is suggested: DRB1*04:05=*04:04>*04:07>*01:01>*01:02. Although none of the results were significant after the p value was corrected, the data are consistent with those in numerous other studies, suggesting that several different DRB1* alleles may be involved in the etiopathogenesis of the disease by presenting an overlapping set of ocular peptides to the T cells, which in turn may trigger the autoimmune response that is present in the patients.

Identification of B*9550, a novel B*15 allele, in a Mexican bone marrow donor from Veracruz State.

Human leukocyte antigen-B*9550 is a novel allele identified in a Mexican Mestizo bone marrow donor from Veracruz.

Identification of A*29:47, previously typed as A*29:19, in a Mexican bone marrow donor from the state of Hidalgo, Mexico

The A*29:47 allele was identified in a Mexican Mestizo unrelated bone marrow donor from the state of Hidalgo.

Identification of A*02:336 in a Mexican Mestizo acute lymphoblastic leukemia patient from the state of Veracruz

A*02:336 was identified in a Mexican Mestizo ALL patient, born in the State of Veracruz.

DRB1*1532, a new DR15 allele, identified in a Mexican unrelated donor from Veracruz, Mexico

DRB1*1532 allele was identified in a Mexican unrelated marrow donor from the Gulf of Mexico.

Identification of HLA-B*14:41N in a NMDP Hispanic donor, selected for a patient of The Unrelated Mexican Donor Registry-DONORMO program in Mexico.

The B*14:41N allele was identified in a The National Marrow Donor Program (NMDP) Hispanic donor typed by our Mexican Registry-DONORMO.

HLA-B*35:233, a novel B*35 allele found in a volunteer of the DONORMO - The Mexican Bone Marrow Registry of Unrelated Donors

Several new human leukocyte antigen (HLA) alleles have been published by us recently, corresponding to the very diverse antigen groups (1, 2). As of June 2013, 2934 alleles encoding 2211 proteins have been described for the HLA-B gene. The HLA-B*35 group is highly polymorphic, with 309 alleles, described nowadays (IMGT/HLA database) (3). A new B*35 allele, B*35:233 was found in a 22-year-old Mexican Mestizo male, born and living in the state of Puebla, Mexico. During a routine HLA-B typing for the Mexican Bone Marrow Registry of Unrelated Donors (DONORMO), the analysis software showed a perfect match with the combination B*39:48 , B*35:04/09/12 . The typing was performed using Luminex technology with the Lifecodes HLA-B typing kit (Gen-Probe Transplant Diagnostics Inc., Stamford, CT). DNA extracted from whole blood cells was used as template for the polymerase chain reaction (PCR) reaction. As B*39:48 is a rare allele, according to the Allele frequencies database (4), HLA-B sequence-based typing was performed on this sample to confirm the results. HLA-B exons 2, 3 and 4 were sequenced in both directions using the AlleleSEQR HLA-B kit (Celera, Alameda, CA) and an ABI Prism 310 Genetic Analyzer (Applied Biosystems, Alameda, CA). The sequence analysis was performed with the assign 3.5+ software (ConexioGenomics, Applecross, Western Australia, Australia). No exact match was found for the consensus sequence of the sample. The closest typing was B*35:12:01 , B*39:05 with one mismatch at nucleotide 583, exon 3 corresponding to codon 171.1. At this position, the consensus of the sample showed Y (C and T) but only T was expected for a perfect match with the mentioned allele pair, suggesting the presence of a new allele. B*35 and B*39 alleles were amplified and sequenced separately for exons 2–4, using two group-specific PCR primers: S4B7 (specific for B*35 , *48:02 , *51 , *52 , *53 , *56:06 , *58 , *78 ) and S4B8 (specific for B*14 , *38 , *39 , *67:01 , Protrans , Ketsch, Germany). An exact match for B*39:05:01 was found for the PCR product obtained with primer S4B8. However, for the S4B7 PCR product, the consensus sequence of the sample showed one mismatch with B*35:12:01 at nucleotide 583, exon 3 (Figure 1). This substitution affects aminoacid 171 that changes from the polar non charged Y, present in most of the B*35 alleles, to the positively charged H (codon 171 TAC→CAC). This substitution possibly does not affect the stability of the encoded B molecule, as histidine is found at this position, in most of the B*14 and B*18 alleles and in some B*15 and B*35 alleles. A point mutation occurring on B*35:12:01 , a very frequent B*35 allele in Mexican population (5), is the most probable mechanism that generated this new B*35 allele. B*35:233 was submitted to the GenBank; the accession number is KF032077. The name B*35:233 has been officially assigned by the World Health Organization (WHO) Nomenclature Committee in May 2013. This follows the agreed policy that, subject to the condition stated in the most recent Nomenclature Report (6), names will be assigned to new sequences as they are identified. Lists of such new names will be published in the following WHO Nomenclature Report. The complete HLA typing of this individual was A*02 , A*68 B*39:05:01 , B*35:233 , C*04 , C*07 , DRB1*04:07 , DRB1*04:07 , DQB1*03:02 , DQB1*03:02 . We were unable to set the gametic phase, however, as B*35-C*04 and B*39C*07 are typically in linkage disequilibrium. Therefore, we suggest that the new allele is part of the haplotype B*35:233C*04-DRB1*04:07-DQB1*03:02 . These demonstrate the importance of further confirming any HLA typing involving rare or less frequent alleles, using a different methodology, even when ‘a perfect match’ message seems to be clear from the software analysis.