Molecular cloning of two new HLA-C alleles: Cw*1801 and Cw*0706

Treating a Multidrug-Resistant Psoriatic HLA-C*18:01 Allele Carrier with Combination Ustekinumab Apremilast Therapy

BACKGROUND

Nowadays, even though several biologic therapies are available to treat psoriasis, multidrug-resistant disease continues to be a therapeutic challenge. Combination therapy has therefore become increasingly important. In this context, apremilast, according to its safety profile, could easily be combined with biologics in patients with comorbidities and/or recalcitrant multidrug-resistant psoriasis.

OBJECTIVE

Our goal is to share experience from our institution in the observation of a patient with severe chronic plaque psoriasis that was unresponsive to all anti-tumor necrosis factor-α treatment and to an anti-interleukin (IL)-17A drug and only partially responsive to ustekinumab, even in combination with apremilast. The patient carried a rare allele infrequently found in Caucasian people: human leukocyte antigen (HLA)-C*18:01. This allele has been found to be positively associated with psoriasis in Brazilian patients.

METHODS

The patient was typed for the HLA-C locus at high resolution via polymerase chain reaction sequence-specific oligonucleotide probes (PCR-SSOP) using a commercial kit (LAB^®Type, One Lambda Inc., Canoga Park, CA, USA).

RESULTS

Our patient, previously described as having multidrug-resistant psoriasis, commenced ustekinumab and apremilast combination therapy. After 12 weeks, the Psoriasis Area Severity Index score had worsened, and we suspended combination therapy because the patient reported an absence of any benefit and was experiencing side effects from the induction therapy with apremilast.

CONCLUSIONS

Expanding on the previously reported experience with this patient, we conclude that HLA-C*18:01 probably indicates a severe, recalcitrant, multidrug-resistant psoriasis phenotype for which proper therapy remains to be identified.

Advancing allele group-specific amplification of the complete HLA-C gene--isolation of novel alleles from three allele groups (C*04, C*07 and C*08)

A variety of strategies have been designed for sequence-based HLA typing (SBT) and for the isolation of new human leucocyte antigen (HLA) alleles, but unambiguous characterization of complete genomic sequences remains a challenge. We recently reported a simple method for the group-specific amplification (GSA) and sequencing of a full-length C*04 genomic sequence in isolation from the accompanying allele. Here we build on this strategy and present homologous methods that enable the isolation of HLA-C alleles belonging to another two allele groups. Using this approach, which can be applied to sequence-based typing in some clinical settings, we have successfully characterized three novel HLA-C alleles (C*04:128, C*07:01:01:02, and C*08:62).

Characterization of the HLA-C*07:01:01G allele group in European and African-American cohorts

The HLA-C*07:01:01G allele group consists of three nonsynonymous alleles, C*07:01:01, C*07:06 and C*07:18, plus C*07:01:02, which is synonymous to C*07:01:01. All of these alleles have identical exons 2, 3 and 4, but differ in exons 5 or 6. Therefore routine sequence-based typing (SBT) of exons 2 and 3 is unable to resolve these subtypes, resulting in ambiguous typing results in population and disease cohort studies. In the present study, we fully characterized C*07:01:01G subtypes in European and African Americans and examined their relative frequency distributions. In European Americans C*07:01:01G is predominantly represented by C*07:01:01 (94.4%), whereas C*07:01:02 (1.1%) and C*07:18 (4.5%) were detected relatively infrequently. In African Americans C*07:18 (42.4%) showed a high frequency similar to that of C*07:01:01 (44.7%) whereas C*07:06 was detected at a low frequency (4.7%). C*07:06 was found exclusively on B*44:03 carrying haplotypes in both ethnic groups, but C*07:18 showed multiple linkage relationships with HLA-B. These results demonstrate that C*07:01:01G as defined by routine SBT is a heterogeneous group of alleles, especially among individuals of African origin. If C*07:01:01G subtypes prove to bear divergent functional significance, it would be necessary to include these subtypes in routine HLA-C typing for clinical transplantation and disease association studies.

Characterization of the genomic full-length sequence of HLA-Cw*010201, Cw*0706, and Cw*0801 in Chinese individuals

Genomic full-length sequence of human leukocyte antigen (HLA)-Cw*0706, differing from its closet allele Cw*070 101 by six nucleotide exchanges, was detected in two Chinese individuals.

HLA-C polymorphisms and PCR dropout in exons 2 and 3 of the Cw*0706 allele in sequence-based typing for unrelated Chinese marrow donors

To evaluate the accuracy of SBT protocols for HLA-C and to better understand the HLA-C polymorphism in Chinese, 1795 unrelated CMDP donors were typed at exons 2, 3, and 4 of the HLA-C gene using the Atria commercial kit. Of the study subjects, 1768 showed conclusive typing results, whereas the other 27 showed inconclusive results. Subsequent full-length cloning and haplotype sequencing showed that 11 of the 27 inconclusive results could be explained by the presence of nine novel alleles identified: Cw*0130, 0624, 070206, 075602, 0766, 0767, 0820, 0821, and 0827. These novel alleles were generated by a total of 10 coding-region substitutions, eight of them being located in the antigen-binding groove. Cw*0766 and Cw*075602 were detected three and two times, respectively, in the 1795 donors. The other 16 inconclusive samples were retested by SBT using our in-house PCR primers; all of them were found to carry Cw*0706, which dropped out in exons 2 and 3 in the initial PCR using the commercial primers amplifying from 5' UTR to intron 3. Our results showed the importance of the full-length genomic sequence and intronic SNPs for the development of more accurate SBT. The allele distribution and novel alleles detected in this study also provide further insights into the HLA-C polymorphism in the Chinese Han population.

Frequency of HLA-C alleles in differentiated thyroid carcinoma in southeastern Spain

BACKGROUND

The development of thyroid carcinoma may be influenced genetically and has been associated with certain HLA alleles. HLA-C alleles have not been studied in depth, because available serology techniques have not been very reliable in detecting them. However, the development of molecular biology provided an efficient and reliable technique for allele detection. The aims of the current study were to determine whether there is a significant association between any HLA-C allele and differentiated thyroid carcinoma and to establish the possible susceptibility or protection alleles related to these tumors.

METHODS

HLA-C genotyping was performed in 63 patients undergoing surgery for differentiated thyroid carcinoma (57 patients with the papillary subtype and 6 patients with the follicular subtype). A representative sample of 100 nonrelated healthy Caucasians was used as a control group from the same geographic area. The polymerase chain reaction-sequence-specific primer technique was used for HLA-C genotyping. The clinical variables analyzed were age, gender, family history of thyroid pathology, residence in areas of endemic goiter, asymptomatic status, presence of hyperthyroidism, compressive symptoms, presence of an intrathoracic thyroid component, histologic variables of the tumor, and evolution. The chi-square test, the Mantel-Haenszel test, and the Bonferroni correction were used for the statistical analysis.

RESULTS

In the control group, a significant correlation was observed between the lower frequency of the HLA-Cw7 allele and the development of differentiated thyroid carcinoma (P < 0.05). Analysis of the different clinical variables revealed a relation between HLA-C alleles and three clinical situations: cervical lymph node involvement with HLA-Cw7 and HLA-Cw2, vascular involvement with HLA-Cw7 and HLA-Cw1, and cervical carcinoma recurrence with HLA-Cw1. However, after application of the Bonferroni correction, only the association between HLA-Cw7 and lymphatic (P(c) = 0.0483) or vascular involvement (P(c) = 0.0324) persisted.

CONCLUSIONS

The results revealed a relation between HLA-Cw7 and differentiated thyroid carcinoma. In future investigations, HLA-C typing may help to identify patients with a poor prognosis.

Strong association between HLA-Cw*0706 and HLA-B*44032 in the Bubi population from Equatorial Guinea

Unrelated Bubi, native to the island of Bioko (Equatorial Guinea), were previously typed by low-resolution polymerase chain reaction using sequence-specific primers (PCR-SSP) and serology for HLA-A, -B and -C. HLA-B*44 was found frequently and associated with Cw*07. We have studied the HLA subtypes of 20 B*44pos/Cw*07pos Bubi individuals. HLA-B and -C were typed by sequencing exons 2 and 3. To distinguish the alleles Cw*1701/02/03, Cw*07011/012/06 and Cw*1801/02 additional sequencing of exon 1 or 5 was performed. All 20 B*44pos/Cw*07pos individuals of the Bubi population were typed Cw*0706 positive. Nineteen of them carried the B*44032 allele and one B*4407. In addition, 19 B*44neg/ Cw*07pos Bubi individuals were typed for HLA-C and none of them proved Cw*0706 positive. To determine whether the association between Cw*0706 and B*44032 was limited to the Bubi, 19 individuals from Dutch Caucasian families were typed in which B44 and Cw7 segregated on one haplotype. None of these individuals showed the presence of B*44032 or Cw*0706. The haplotypes found in the Dutch Caucasians were B*4402-Cw*0704, B*44031-Cw*07011 and B*44031-Cw*0702. The present observation indicates a strong association between B*44032 and Cw*0706 in the Bubi population.

Sequence of four new HLA-Cw alleles: a possible role of interallelic recombination

In order to extend our current understanding of HLA-C polymorphism, four new alleles have been cloned and sequenced: Cw*1801 in a donor of mixed origin, Cw*02024 in a Senegalese individual, Cw*1205 and Cw*1604 in European Caucasoid blood donors. HLA-Cw*1801, which most likely results from an interallelic recombination between Cw*0704 and 0401 alleles, was not associated with B*8101, but with either B*4403 or B18. The Cw*02024 allele differs from Cw*02022 by a silent mutation in exon 3. Both Cw*1801 and Cw*02024 appear to be rather frequent in populations of African origin but have not yet been detected in Caucasoids. HLA-Cw*1604 differs from Cw*1601 by two nucleotides at codon 156 leading to a Gln to Trp substitution. This new Cw16 subtype was subsequently identified in three additional unrelated families, all of South-European origin, and presented an unusual association with B*4402 in all cases. HLA-Cw*1205 is a composite allele with the alpha1 domain of Cw*1602 and the alpha2 domain of Cw*1203. It appears to be rare, at least in European Caucasoids. Three of these four alleles may have resulted from gene conversion-like or interallelic recombination events.

HLA-Cw*1602: a new susceptibility marker of Behçet's disease in southern Spain

Genotyping of the HLA-C locus by PCR-SSP in Behçet's disease patients from southern Spain reveals a statistically significant association with Cw*1602 (OR 20.15, corrected p < 0.05). This is an uncommon allele absent from the healthy control group, which seems to confer higher relative risk than B51 in this study (OR 1.85). Stratified frequencies do not show statistically significant differences but suggest that the Cw*1602-B51 haplotype could be the main HLA marker of Behçet's disease in the analyzed population.

HLA class I and class II allele distribution in the Bubi population from the island of Bioko (Equatorial Guinea)

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.

The novel HLA-Cw*1802 allele is associated with B*5703 in the Bubi population from Equatorial Guinea

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.

The complete primary structure of Cw*1701 reveals a highly divergent HLA class I molecule

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.

Characterization of an HIV-1 p24gag epitope recognized by a CD8+ cytotoxic T-cell clone

A CD8+ cytotoxic T-cell clone that recognized HIV p24gag was isolated from an infected individual. The minimal epitope was localized to amino acids 308-316 (QASQEVKNW). Using allogeneic target cells, we found that lysis was restricted by the HLA-Cw0401 molecule. We observed that C1R cells, that express the HLA-Cw0401 allele are able to present the peptide to the cytotoxic clone, but with reduced efficiency. Other B-cell lines, that have been genotyped as HLA-Cw0401+ were unable to present the peptide to the clone, suggesting the existence of other variants of HLA-Cw0401 or a loss of cell surface expression of this molecule.