Ana Rita Couto

Contribution of KIR3DL1/3DS1 to ankylosing spondylitis in human leukocyte antigen-B27 Caucasian populations

Killer cell immunoglobulin-like receptors (KIRs) and humaAn leukocyte antigen (HLA) loci are both highly polymorphic, and some HLA class I molecules bind and trigger cell-surface receptors specified by KIR genes. We examined whether the combination of KIR3DS1/3DL1 genes in concert with HLA-B27 genotypes is associated with susceptibility to ankylosing spondylitis (AS). Two HLA-B27-positive Caucasian populations were selected, one from Spain (71 patients and 105 controls) and another from the Azores (Portugal) (55 patients and 75 controls). All were typed for HLA-B and KIR (3DS1 and 3DL1) genes. Our results show that in addition to B27, the allele 3DS1 is associated with AS compared with B27 controls (p < 0.0001 and p < 0.003 in the Spanish population and Azoreans, respectively). We also observed that the association of KIR3DS1 to AS was found in combination with HLA-B alleles carrying Bw4-I80 in trans position in the Spanish population (30.9% in AS versus 15.2% in B27 controls, p = 0.02, odds ratio (OR) = 2.49) and in Azoreans (27.2% in AS versus 8.7% in B27 controls, p = 0.01, OR = 4.4 in Azoreans). On the other hand, 3DL1 was decreased in patients compared with B27 controls (p < 0.0001 in the Spanish population and p < 0.003 in Azoreans). The presence of this allele in combination with Bw4-I80 had a protective effect against the development of AS in the Spanish population (19.7% in AS, 35.2% in B27 controls; p = 0.03, OR = 0.45). The presence of KIR3DS1 or KIR3DL1 in combination with HLA-B*27s/HLA-B Bw4-I80 genotypes may modulate the development of AS. The susceptibility to AS could be determined by the overall balance of activating and inhibitory composite KIR-HLA genotypes.

A Novel LEMD3 Mutation Common to Patients with Osteopoikilosis With and Without Melorheostosis

Recent studies have reported loss of function mutations in the LEMD3 gene, encoding an inner nuclear membrane protein that influences Smad signaling, as a cause of osteopoikilosis, Buschke-Ollendorff syndrome, and melorheostosis. We investigated LEMD3 in a three-generation family with osteopoikilosis from the Azores, an affected father and daughter from Ireland with osteopoikilosis (the daughter also had melorheostosis), and two other individuals from the UK with isolated melorheostosis. We found a novel C to T substitution at position 2032 bp (cDNA) in exon 8 of LEMD3, resulting in a premature stop codon at amino acid position 678. This mutation co-segregates with the osteopoikilosis phenotype in both the Azorean family and the Irish family. It was not detected in any of the six unaffected family members or in 342 healthy Caucasian individuals. No LEMD3 mutations were detected in the two patients with sporadic melorheostosis. The LEMD3 mutation reported was clearly the cause of osteopoikilosis in the two families but its relationship to melorheostosis in one of the family members is still unclear. Perhaps unsurprisingly in what is a segmental disease, we did not find LEMD3 mutations in peripheral-blood-derived DNA from the two other individuals with sporadic melorheostosis. The nature of the additional genetic and/or environmental influences required for the development of melorheostosis in those with osteopoikilosis requires further investigation.

Role of human leukocyte antigen, killer-cell immunoglobulin-like receptors, and cytokine gene polymorphisms in leptospirosis

Leptospirosis is an emerging zoonotic disease caused by pathogenic species of the genus Leptospira. It has a broad range of clinical presentations in humans. Although progress has been made in the characterization of the host immune system factors that may affect disease progression and outcome, to date few reports have addressed the role of genetic polymorphisms in the susceptibility to leptospirosis. In this work a group of patients with a history of leptospiral infection and a control group were compared for polymorphisms in the human leukocyte antigen (HLA), in killer-cell immunoglobulin-like receptors (KIR), and in cytokine genes. Alleles in the HLA-A and -B loci were associated with susceptibility, as were the class I haplotype A*01-B*08-Cw*07 and the 8.1 ancestral haplotype (A*01-B*08-Cw*07-DRB1*03-DQB1*02). Single nucleotide polymorphisms in the interleukin (IL)-4 and IL-4Ralpha genes also had significantly higher frequencies in the patient group. No association was reported between KIR gene profile and leptospirosis. This work highlights the importance of using genetic polymorphisms to better understand the mechanisms involved in the immune response to leptospirosis.

Evaluation of two methods for computational HLA haplotypes inference using a real dataset

BackgroundHLA haplotype analysis has been used in population genetics and in the investigation of disease-susceptibility locus, due to its high polymorphism. Several methods for inferring haplotype genotypic data have been proposed, but it is unclear how accurate each of the methods is or which method is superior. The accuracy of two of the leading methods of computational haplotype inference – Expectation-Maximization algorithm based (implemented in Arlequin V3.0) and Bayesian algorithm based (implemented in PHASE V2.1.1) – was compared using a set of 122 HLA haplotypes (A-B-Cw-DQB1-DRB1) determined through direct counting. The accuracy was measured with the Mean Squared Error (MSE), Similarity Index (IF) and Haplotype Identification Index (IH).ResultsNone of the methods inferred all of the known haplotypes and some differences were observed in the accuracy of the two methods in terms of both haplotype determination and haplotype frequencies estimation. Working with haplotypes composed by low polymorphic sites, present in more than one individual, increased the confidence in the assignment of haplotypes and in the estimation of the haplotype frequencies generated by both programs.ConclusionThe PHASE v2.1.1 implemented method had the best overall performance both in haplotype construction and frequency calculation, although the differences between the two methods were insubstantial. To our knowledge this was the first work aiming to test statistical methods using real haplotypic data from the HLA region.

Characterisation of human papillomavirus (HPV) genotypes in the Azorean population, Terceira island

BackgroundHuman papillomavirus detection is very important for the evaluation of prevention strategies in cervical cancer. In the Azorean population, the virus prevalence has never been studied, and there is no data available to preview a successful outcome with HPV vaccination. In this article, our objective is to characterise the HPV genotypes in Terceira Island, contributing for the epidemiological knowledge on the virus infection.ResultsCervical samples were collected from 289 women aged 16–81 in the Gynaecological Outpatient Clinic of the Hospital de Santo Espírito de Angra do Heroísmo (HSEAH). HPV DNA was amplified by Polymerase Chain Reaction using the general consensus primers PGMYO9/PGMY11. Commercially available Papillomavirus Clinical Arrays® kits (Genomica) were used to perform HPV genotyping. 30 women were HPV positive, with a median age of 41 years old. Our results show that the overall HPV prevalence was 10.49%. Seventeen genotypes were identified, including 58.82% high risk, 17.65% low risk and 23.53% undetermined risk.ConclusionUnlike other epidemiological studies, HPV31 was the most frequent type (26.67%) in Terceira Island, followed by HPV16 (10.00%), HPV51, HPV53, HPV70 and HPV82 (6.67%). Further studies are needed to investigate if the HPV types found in our population are associated with the risk of progression to high-grade squamous intraepithelial lesions or cervical cancer.

Linkage disequilibrium between S65C HFE mutation and HLA A29-B44 haplotype in Terceira Island, Azores

Our objective was to investigate the frequency of HFE gene mutations and to study linkage disequilibrium (LD) between HLA-Class I alleles and these mutations in the population of Terceira Island, Azores, Portugal. A total of 218 unrelated individuals were investigated. Three HFE mutations--C282Y, H63D, and S65C--were identified by restriction endonuclease digestion of polymerase chain reaction (PCR)-amplified genomic DNA. HLA-Class I alleles were typed by PCR-single-strand polymorphism. Gene frequencies and LD were estimated using Arlequin V 1.1. Six genotypes were found in the population: WT/WT (58.3%), H63D/WT (31.2%), H63D/H63D (2.3%), H63D/C282Y (0.9%), S65C/WT (4.1%), and C282Y/WT (3.2%). No cases of C282Y or S65C homozygosity were identified. HLA haplotype A3-B7 was in LD with C282Y; HLA alleles A29, B44, and HLA haplotype A29-B44 were in LD with S65C mutation. HFE gene frequencies in this population are similar to those in other European populations; HFE S65C mutation was found in LD with the alleles A29, B44, and with A29-B44 HLA haplotype.

Novel ANKH amino terminus mutation (Pro5Ser) associated with early-onset calcium pyrophosphate disease with associated phosphaturia.

AbstractThis report describes a 32-year-old woman presenting since childhood with progressive calcium pyrophosphate disease (CPPD), characterized by severe arthropathy and chondrocalcinosis involving multiple peripheral joints and intervertebral disks. Because ANKH mutations have been previously described in familial CPPD, the proband’s DNA was assessed at this locus by direct sequencing of promoter and coding regions and revealed 3 sequence variants in ANKH. Sequences of exon 1 revealed a novel isolated nonsynonymous mutation (c.13 C>T), altering amino acid in codon 5 from proline to serine (CCG>TCG). Sequencing of parental DNA revealed an identical mutation in the proband’s father but not the mother. Subsequent clinical evaluation demonstrated extensive chondrocalcinosis and degenerative arthropathy in the proband’s father. In summary, we report a novel mutation, not previously described, in ANKH exon 1, wherein serine replaces proline, in a case of early-onset severe CPPD associated with metabolic abnormalities, with similar findings in the proband’s father.

HLA Class‐I Diversity in Cameroon: Evidence for a North‐South Structure of Genetic Variation and Relationships with African Populations

HLA class I diversity (loci A, B and C) was analysed in four populations, two from North Cameroon (Podokwo and Uldeme) and two from South Cameroon (Ewondo and Bamileke). Northern and southern Cameroon populations show a substantial genetic diversity in terms of haplotype sharing and genetic distances, even despite the low percentage of variance due to differences among populations evidenced by analysis of molecular variance. The signals of differentiation among populations are consistent with their linguistic affiliation, and support previous evidence, based on autosomal microsatellites and protein loci, which has shown that the complex pattern of genetic variation of Cameroon can in part be described by contrasting the northern and southern part of the country. Looking at our results in the more general framework of HLA diversity in sub‐Saharan Africa, it turns out that the Podokwo and Uldeme show some genetic links to populations of the southern western branch of the Sahel corridor, while their high frequency of A*02 and C*04 alleles is congruent with previously hypothesised introgression of non‐sub‐Saharan alleles. On the other hand, signals of shared ancestry between the Bamileke and Ewondo and the Bantu speakers from central and southern Africa were detected.

The coexistence of ankylosing spondylitis and diffuse idiopathic skeletal hyperostosis--a postmortem diagnosis.

A 72-year-old male was diagnosed as having ankylosing spondylitis, mainly according to radiological findings, confirmed as HLA-B27-negative. Postmortem examination of the skeleton raised doubts on the initial diagnosis, since spinal findings pointed out also to diffuse idiopathic skeletal hyperostosis. The authors discuss the differential diagnosis and enhance the postmortem findings which allowed the diagnosis of the two clinical entities in the same patient.

HLA-E, HLA-F and HLA-G — The Non-Classical Side of the MHC Cluster

Traditionally, the MHC is divided into the classes containing groups of genes with related functions; the MHC class I and II genes encode for human leukocyte antigens (HLA), proteins that are displayed on the cell surface. In humans, MHC class I molecules com‐ prise the classical (class I-a) HLA-A, -B, and -C, and the non-classical (class I-b) HLA-E, F, -G and – H (HFE) molecules (Pietra et al., 2009). Both categories are similar in their mechanisms of peptide binding and presentation and in the induced T-cell responses (Rodgers and Cook, 2005). The most remarkable feature of MHC class I-b molecules is their highly conserved nature (van Hall et al., 2010). In contrast with class Ia molecules they have been under a distinct selective pressure, exhibiting very low levels of allelic polymor‐ phism (Strong et al., 2003). Classical MHC class I gene transcription is mediated by several cis-acting regulatory elements, in the proximal promoter region (Gobin and van den Elsen, 2000). Those elements determine the constitutive and cytokine induced expression levels of the molecule (Gobin and van den Elsen, 2000).