Susana Almeida

A study of 82 extended HLA haplotypes in HFE -C282Y homozygous hemochromatosis subjects: relationship to the genetic control of CD8+ T-lymphocyte numbers and severity of iron overload

BackgroundIt has been recently demonstrated that CD8+ T-lymphocyte numbers are genetically transmitted in association with the MHC class I region. The present study was designed with the objective of narrowing the region associated with the setting of CD8+ T-lymphocyte numbers in a population of C282Y homozygous hemochromatosis subjects, in whom a high prevalence of abnormally low CD8+ T-lymphocyte counts has been described.MethodsThe study includes 43 C282Y homozygous subjects fully characterized both phenotypically and genotypically. Clinical characterization includes measurements of iron parameters at diagnosis (transferrin saturation and serum ferritin), total body iron stores and T-cell immunophenotyping determined by flow cytometry. Genetic characterization includes HLA class I alleles (A, B and C) and four additional microsatellite markers (D6S265, D6S2222, D6S105 and D6S2239) spanning 5 Megabases in the 6p21.3 region.ResultsEighty-two extended C282Y carrying haplotypes were defined. Single-locus analysis revealed that the HLA-A region was associated with CD8+ T-cell numbers. Multivariate analysis showed that the combinations of the most common HLA-A alleles (HLA-A*03, -A*02 and -A*01) were associated with significantly lower numbers of CD8+ T-lymphocytes (0.30 ± 0.14 × 106/ml), in comparison with subjects carrying only one copy of those alleles (0.46 ± 0.19 × 106/ml) and subjects without any copy of those alleles (0.79 ± 0.15 × 106/ml;p = 0.0001). No differences were observed in CD8+ T-cell counts among control subjects carrying the same combinations of HLA-A alleles (0.47 ± 0.14; 0.45 ± 0.21 and 0.41 ± 0.17 × 106/ml, respectively), therefore not supporting a direct effect of HLA specificity but rather an indirect association with a locus close to HLA-A. Multivariate analysis showed that the combination of the most common HLA-A alleles also have an impact on the clinical expression of HH in terms of iron stores, in males(p = 0.0009).ConclusionThe present study provides evidence supporting an inextricable link between extended HLA haplotypes, CD8+ T-lymphocyte numbers and severity of iron overload in hereditary hemochromatosis(HH). It gives additional information to better define a candidate region involved in the regulation of CD8+ T-lymphocyte numbers. A new evolutionary hypothesis concerning the inheritance of the phenotype of low CD8+ T-lymphocyte numbers associated with particular ancestral HLA haplotypes carrying the C282Y mutation and its implication on the clinical heterogeneity of HH is discussed.

CAT53 and HFE alleles in Alzheimer's disease: a putative protective role of the C282Y HFE mutation.

Alzheimers disease (AD) is a complex disorder, resulting from an interaction between environmental and genetic factors. Several studies addressed the association of AD with MHC class-I polymorphisms without definite conclusions. Considering the remarkable linkage disequilibrium at the MHC region, it is not possible to assume if the reported associations result from a direct effect of the respective genes or result from associations with other closely linked genes transmitted in an extended conserved haplotype. Recent evidence pointed to CAT53, a newly described gene located at the MHC class-I region in the vicinity of HLA-C, as a candidate modifier gene in AD. CAT53 encodes a phosphatase 1 nuclear inhibitor protein and is strongly expressed in brain regions involved in memory and AD. Here we tested the potential association of CAT53 with the risk of developing AD and searched for potential haplotypic associations of CAT53 with two common mutations (H63D, C282Y) in the HFE gene, also located at chromosome 6p21.3. The allele frequencies of these mutations in AD patients were compared to the expected frequencies previously established in the normal Portuguese population. We detected only one polymorphism (G>A) in CAT53, at position 8232, in intron 17. Screening of this polymorphism in 113 AD patients and 82 controls did not show any evidence of association, therefore excluding the hypothetical role of the CAT53 polymorphism as modifier in AD. In contrast, we found a significant negative association of the C282Y HFE mutation with AD, thus supporting a putative protective role of this protein variant in neurodegeneration.

A putative gene located at the MHC class I region around the D6S105 marker contributes to the setting of CD8+ T-lymphocyte numbers in humans

Significant associations between human leucocyte antigen (HLA)‐A and ‐B alleles and CD8+ T‐lymphocyte numbers have been reported in the literature in both healthy populations and in HFE‐haemochromatosis patients. In order to address whether HLA alleles themselves or alleles at linked genes are responsible for these associations, several genetic markers at the MHC class I region were typed on a population of 147 apparently healthy unrelated subjects phenotypically characterized for their CD8+ and CD4+ T‐lymphocyte numbers. By using a machine learning approach, a set of rules was generated that predict the number of CD8+ T‐lymphocyte numbers on the basis of the information of the D6S105 microsatellite alleles only. We demonstrate that the previously reported associations with HLA‐A and ‐B alleles are due to the presence of common long (up to 4 megabases long) haplotypes that increased in frequency recently due to positive selection and that encompass a region where a putative gene contributing to the setting of CD8+ T lymphocytes is located, in the neighbourhood of microsatellite locus D6S105, in the 6p21.3 region.

Low serum levels of prohepcidin, but not hepcidin-25, are related to anemia in familial amyloidosis TTR V30M

Familial amyloidosis TTR V30M (FAP-I) usually presents as a sensorimotor and autonomic neuropathy. Anemia was first described in this disease more than 20 years ago and classified as an anemia of chronic disease. However, so far no studies have addressed the role of inflammatory proteins in this disease. The anemia affects 24.8% of symptomatic FAP-I Portuguese patients, and is associated with low serum erythropoietin levels, independently of the presence of clinical nephropathy. In this study we evaluate the role of systemic inflammation on the erythropoietin production and anemia genesis in FAP-I. Data from 24 FAP-I patients (50% with anemia) and 33 healthy controls were analysed. Laboratory data included hemoglobin, hematocrit, ferritin, transferrin saturation, soluble transferrin receptors (sTR), prohepcidin, hepcidin-25, C-reactive protein (CRP), interleukin-6 and erythropoietin levels. In general, FAP-I patients presented significantly lower hemoglobin, hematocrit and observed/expected erythropoietin levels. Mean sTR was lower in FAP-I patients than in controls (2.36+/-1.3 vs 2.96+/-0.8 mg/l, P=0.055) correlating with hemoglobin and hematocrit. As expected, sTR were positively correlated with erythropoietin both in controls and in FAP-I patients. No significant differences on CRP, interleukin-6, transferrin saturation, ferritin and hepcidin-25 were found between anemic and non-anemic FAP-I patients and between non-anemic FAP-I patients and healthy controls. In all groups, a positive correlation was observed between hepcidin-25 and ferritin. Surprisingly, significantly lower prohepcidin levels were found in FAP-I patients, with or without anemia, not correlated with serum hepcidin-25 levels. In general, the decreased observed/expected EPO levels in FAP-I correlated with the prohepcidin levels, therefore raising the possibility that a common defect in these two hormones may be somehow involved in the genesis of the disease.

Pazopanib-Induced Cutaneous Leukocytoclastic Vasculitis: An Exclusion Diagnosis of a Multidisciplinary Approach

In phase II/III trials, cutaneous side effects of pazopanib were reported in less than 20% of patients, with only 1–3% being grade 3/4. We present a case of a 66-year-old man with a previous history of left nephrectomy for a stage II clear cell renal carcinoma. Approximately 18 months later, recurrent disease in the lungs, mediastinum, and left psoas and bulky abdominal/pelvic nodal metastasis were documented. He was initially treated with pazopanib 800 mg q.d. and 1 week after starting this therapy, the patient presented with palpable purpura on his ankles. These lesions regressed within 2 weeks off pazopanib, but had recurred 4 weeks after he resumed medication at 400 mg q.d. Biopsy of the lesions revealed leukocytoclastic vasculitis. Despite tumour response to therapy, pazopanib was discontinued with total resolution of this skin toxicity within 2 weeks of his cutaneous toxicity. To the best of our knowledge, we report a rare yet significant cutaneous adverse reaction to pazopanib.