Alcinda Melo

Instituto de Medicina Molecular, Lisboa, Lisbon, Portugal

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Publications (10)30.73 Total impact

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    ABSTRACT: Venom-specific immunotherapy (VIT) is well recognized by its efficacy and compelling evidence implicates regulatory T cells (Tregs) in the underlying tolerogenic mechanisms. Additionally, hymenoptera venom has for a long time been claimed to modulate immunity. Here we investigated the putative role of Bee venom (Bv) in human FOXP3-expressing Treg homeostasis and differentiation, irrespective of the donors' allergic status. We found that Bv significantly enhanced the differentiation of FOXP3-expressing cells from both conventional naïve CD4 T-cells and mature CD4 thymocytes, a property that may contribute to the VIT's capacity to expand circulating Tregs in allergic individuals. We expect that our data enlightening the Treg-mediated immunomodulatory properties of Bv regardless of TCR specificity, to have application in other allergies, as well as in other clinical settings, such as autoimmunity and transplantation. This article is protected by copyright. All rights reserved. This article is protected by copyright. All rights reserved.
    Allergy 07/2015; DOI:10.1111/all.12691 · 6.00 Impact Factor
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    ABSTRACT: Bronchiectasis are common in Common Variable Immunodeficiency. These patients are prone to infection, leading to progressive lung destruction and accelerated FEV1 decline. 40 year-old man, with recurrent respiratory infections, autoimmunity and diarrhea since age 7. At 17 CVID was diagnosed and IVIgG was started. During the following years, respiratory symptoms progressively worsened and bronchiectasis was found on thoracic computed tomography. Bronchoscopy revealed Pseudomonas aeruginosa in bronchoalveolar lavage and bronchial secretions cultures. Eradication therapy led to clinical improvement. This case report stresses the importance of regular microbiological screening and appropriate antibiotherapy. Early/aggressive treatment may significantly impact on patients' evolution.
    European annals of allergy and clinical immunology 05/2015; 47(3):95-8.
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    ABSTRACT: Severe asthma is a challenging disease, and omalizumab has been an important tool to help clinicians address more efficiently this problem. Besides reduction of free and total serum IgE levels, there are a number of other immunologic effects of omalizumab that may be of relevance in its therapeutic action. We report two mite-allergic severe asthmatic patients successfully treated with omalizumab for one year. Clinically, patients improved gradually, with no further need for systemic steroids or emergency department visits during that treatment period, and with Asthma Control Test (ACT) scores showing controlled disease, although pulmonary function didn't show any significant improvement. Immunologically, we observed marked down-regulation of surface IgE and FcεRI on basophils, plasmacytoid and myeloid dendritic cells, as well as a reduction of basophil activation after specific allergen stimulation. These effects were clearly evident immediately after one month but were enhanced at 3, 6 and 12 months of omalizumab treatment, suggesting an advantage to continuing this therapy, and raising the hypothesis of some markers being useful to assess immunological responses to omalizumab, which could assist in the clinician's decision to stop or to restart this treatment.
    European annals of allergy and clinical immunology 03/2015; 47(2):38-40.
  • Revista Portuguesa de Imunoalergologia 03/2015; 23(1):11-19.
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    ABSTRACT: Purpose B-cell survival and differentiation critically depend on the interaction of BAFF-R and TACI with their ligands, BAFF and APRIL. Mature B-cell defects lead to Common Variable Immunodeficiency (CVID), which is associated with elevated serum levels of BAFF and APRIL. Nevertheless, BAFF-R and TACI expression in CVID and their relationship with ligand availability remain poorly understood. Methods and Results We found that BAFF-R expression was dramatically reduced on B cells of CVID patients, relative to controls. BAFF-R levels inversely correlated with serum BAFF concentration both in CVID and healthy subjects. We also found that recombinant BAFF stimulation reduced BAFF-R expression on B cells without decreasing transcript levels. On the other hand, CVID subjects had increased TACI expression on B cells in direct association with serum BAFF but not APRIL levels. Moreover, splenomegaly was associated with higher TACI expression, suggesting that perturbations of TACI function may underlie lymphoproliferation in CVID. Conclusions Our results indicate that availability of BAFF determines BAFF-R and TACI expression on B cells, and that BAFF-R expression is controlled by BAFF binding. Identification of the factors governing BAFF-R and TACI is crucial to understanding CVID pathogenesis, and B-cell biology in general, as well as to explore their potential as therapeutic targets.
    Journal of Clinical Immunology 07/2014; 34(5). DOI:10.1007/s10875-014-0047-y · 2.65 Impact Factor
  • World Allergy Organization Journal 02/2014; 7(Suppl 1):P11. DOI:10.1186/1939-4551-7-S1-P11
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    ABSTRACT: Common variable immunodeficiency disorders (CVID), the most frequent cause of symptomatic primary immunodeficiency, are defined by impaired antibody production. Notwithstanding, T cell activation and granulomatous manifestations represent the main causes of CVID morbidity even in patients receiving immunoglobulin (Ig) G replacement therapy. Additionally, gut pathology is a frequent feature of CVID. In this study, we investigated monocyte imbalances and their possible relationship with increased microbial translocation in CVID patients. Monocyte subsets were defined according to CD14 and CD16 expression levels and evaluated in terms of human leucocyte antigen D-related (HLA-DR), CD86 and programmed death-1 molecule ligand 1 (PD-L1) expression by flow cytometry, in parallel with the quantification of plasma lipopolysaccharide (LPS) and serum levels of soluble CD14 (sCD14), LPS-binding protein (LBP) and anti-LPS antibodies. CVID patients (n=31) featured significantly increased levels of serum sCD14 and an expansion of CD14(bright) CD16(+) monocytes in direct correlation with T cell and B cell activation, the latter illustrated by the frequency of the CD21(low) CD38(low) subset. Such alterations were not observed in patients lacking B cells due to congenital agammaglobulinaemia (n=4). Moreover, we found no significant increase in circulating LPS or LBP levels in CVID patients, together with a relative preservation of serum anti-LPS antibodies, in agreement with their presence in commercial IgG preparations. In conclusion, CVID was associated with monocyte imbalances that correlated directly with T cell activation markers and with B cell imbalances, without an association with plasma LPS levels. The heightened monocyte activated state observed in CVID may represent an important target for complementary therapeutic strategies.
    Clinical & Experimental Immunology 09/2012; 169(3):263-72. DOI:10.1111/j.1365-2249.2012.04620.x · 3.28 Impact Factor
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    ABSTRACT: IL-17 is a pro-inflammatory cytokine implicated in autoimmune and inflammatory conditions. The development/survival of IL-17-producing CD4 T cells (Th17) share critical cues with B-cell differentiation and the circulating follicular T helper subset was recently shown to be enriched in Th17 cells able to help B-cell differentiation. We investigated a putative link between Th17-cell homeostasis and B cells by studying the Th17-cell compartment in primary B-cell immunodeficiencies. Common Variable Immunodeficiency Disorders (CVID), defined by defects in B-cell differentiation into plasma and memory B cells, are frequently associated with autoimmune and inflammatory manifestations but we found no relationship between these and Th17-cell frequency. In fact, CVID patients showed a decrease in Th17-cell frequency in parallel with the expansion of activated non-differentiated B cells (CD21(low)CD38(low)). Moreover, Congenital Agammaglobulinemia patients, lacking B cells due to impaired early B-cell development, had a severe reduction of circulating Th17 cells. Finally, we found a direct correlation in healthy individuals between circulating Th17-cell frequency and both switched-memory B cells and serum BAFF levels, a crucial cytokine for B-cell survival. Overall, our data support a relationship between Th17-cell homeostasis and B-cell maturation, with implications for the understanding of the pathogenesis of inflammatory/autoimmune diseases and the physiology of B-cell depleting therapies.
    PLoS ONE 08/2011; 6(8):e22848. DOI:10.1371/journal.pone.0022848 · 3.23 Impact Factor
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    ABSTRACT: Venom immunotherapy (VIT) induces long-lasting immune tolerance to hymenoptera venom antigens, but the underlying mechanisms are not yet clarified. Regulatory T cells are thought to play an important role in allergic diseases and tolerance induction during specific immunotherapy. Characterize longitudinally the impact of VIT on the pool of circulating regulatory T cells. Fourteen hymenoptera venom-allergic patients with severe reactions (grades III-IV) were studied before, 6 and 12 months after starting ultra-rush VIT. Freshly isolated peripheral blood mononuclear cells were surface stained with a panel of markers of T cell differentiation and intracellularly for CTLA-4 and Foxp3 and analysed by flow cytometry. foxp3 mRNA was quantified by real-time PCR. VIT responses were assessed by measuring specific IgG4 and IgE levels. Eleven individuals with no history of insect venom allergy were studied as controls. VIT induces a significant progressive increase in both the proportion and the absolute numbers of regulatory T cells defined as CD25bright and/or Foxp3+ CD4+ T cells. These changes are not related to alterations in the expression of activation markers or imbalances in the naïve/memory T cell compartments. foxp3 mRNA levels also increased significantly during VIT. Of note, the increase in circulating regulatory T cell counts significantly correlates with the venom-specific IgG4/IgE ratio shift. VIT is associated with a progressive expansion of circulating regulatory T cells, supporting a role for these cells in tolerance induction.
    Clinical & Experimental Allergy 03/2008; 38(2):291-7. DOI:10.1111/j.1365-2222.2007.02887.x · 4.32 Impact Factor
  • Journal of Allergy and Clinical Immunology 02/2008; 121(2). DOI:10.1016/j.jaci.2007.12.710 · 11.25 Impact Factor