Biomedical subjects

Camila Macedo

Publications and source records attributed to Camila Macedo.

8 recordsLinked to original sources

PubMed2006

Detection of CD8+ T cells sensitized to BK virus large T antigen in healthy volunteers and kidney transplant recipients.

BK virus (BKV) infections after renal transplantation are increasingly recognized. Development of immune monitoring strategies against BKV requires definition of antigenic epitopes. Hence, T cells from HLA-A02-positive healthy subjects and kidney transplant recipients were stimulated by BKV lysate pulsed on mature autologous dendritic cells and screened against four different T antigen peptides or against BKV lysate. IFN-gamma production was measured by ELISPOT assays. The peptide BKV362-371 (MLTERFNHIL) was naturally processed and recognized by five of six healthy subjects (39 +/- 11 IFN-gamma spots/100,000 cells) and five of seven kidney transplant recipients (21 +/- 12 IFN-gamma spots). Less frequent and weaker CD8+ T-cell responses were detected against three other peptides. Thus, BKV large T antigen is a target for CD8+ T-cell immunity. T-antigen-specific T-cytotoxic cells circulate in healthy blood donors, implying that transient expression of T antigen presumably occurs at sites of viral latency and helps maintain a constant pool of circulating CD8+ T memory cells.

Adult↗

PubMed2005

EBV-specific memory CD8+ T cell phenotype and function in stable solid organ transplant patients.

Immune responses to EBV in immunosuppressed (IS) solid organ transplant (SOTx) recipients have not been well characterized. Here we evaluate the phenotype and function of EBV-specific CD8+ T cells in peripheral blood isolated from "stable" IS SOTx recipients. The EBV-specific CD8+ T cell memory subset distribution in the peripheral blood of patients was examined by flow cytometric analysis using HLA-A2 tetramers incorporating BMLF1 (lytic), and LMP2 and EBNA3A (latent)-derived peptides, in conjunction with mAbs against the CD45RO, CD45RA, and CD62L markers. The ability of CD8+ T cells to produce IFN-gamma in response to the same EBV-derived peptides was measured by ELISPOT assay. Patients and healthy normal donors exhibited similar anti-EBV CD8+ T cell frequencies and specificities against the EBV epitopes evaluated. When compared to healthy normal donors, an overall significant expansion of the CD8+ T cell "effector memory" (CD45RO+/CD62L-) pool, including that of EBV "latent" (LMP2 and EBNA3A)-specific CD8+ T cells was detected in IS SOTx patients. However, the patients' EBV-specific CD8+ T cells showed decreased IFN-gamma production to the EBV-peptide stimulation. These results indicate that the impairment of EBV-specific CD8+ T cell activity is not due to clonal depletion, but is mainly due to impaired functional activation.

Antigens, Viral↗

PubMed2005

Augmentation of type-1 polarizing ability of monocyte-derived dendritic cells from chronically immunosuppressed organ-transplant recipients.

BACKGROUND: Chronic immunosuppressive (IS) therapy impairs normal T-cell immune surveillance and may predispose to opportunistic infections and malignancies that represent life-threatening complication of solid-organ transplantation (SOTx). Our study was designed to ascertain the impact of chronic in vivo administration of IS on the ability of monocyte-derived dendritic cells (MoDC) to differentiate, mature, and function ex vivo. The potential of these cells to be implemented for DC-based adoptive immunotherapy was also considered. METHODS: MoDCs were propagated by conventional procedures, their phenotype was analyzed by flow cytometry, and their function was assessed by mixed leukocyte reaction, enzyme-linked immunoadsorbent assay, and ELISPOT assays. Nuclear translocation of nuclear factor (NF)-kB was analyzed by electrophoretic mobility shift assay. RESULTS: Circulating DC1s in peripheral blood were reduced in SOTx patients. MoDCs generated from patients displayed higher endocytic activity versus normal DCs, indicating their comparative immaturity. Patients' DCs exposed to pro-inflammatory cytokines (tumor necrosis factor-alpha, interleukin [IL]-1beta, and IL-6) were less able to mature, to stimulate recall antigen (Ag)- or allo-Ag-induced proliferation responses, or to secrete IL-12p70. These deficiencies were associated with a decrease in NF-kB translocation. In contrast, combination of pro-inflammatory cytokines and interferon (IFN)-gamma (a Th1-polarizing factor) augmented patients' DC1-type function and IL-12p70 production by way of an NF-kB-independent mechanism. CONCLUSIONS: Chronic IS restrains DC differentiation, maturation, and function at a transcriptional level; however, type-1 polarizing potential of patients' DC1 can be augmented ex vivo by a two-signal stimulation provided by pro-inflammatory cytokines and IFN-gamma. These results may have implications for DC-based immunotherapy of malignancies in the transplantation setting.

Active Transport, Cell Nucleus↗

PubMed2005

Carcinoma of donor origin after liver-intestine transplantation in a child.

Tumor-related complications after intestinal transplantation in children have been principally EBV driven post-transplant disorders. We describe the clinical course of a child, with a diagnosis of microvillus inclusion disease who received a liver and intestine allograft at the age of 9 months. His postoperative course was significant for multiple episodes of acute intestinal allograft rejection and eventually the development of post-transplant lymphoproliferative disorder (PTLD), which resolved. At 8 yr post-transplant he presented with masses in the intestine allograft mesentery and in the right lobe of the allograft liver, biopsy of which revealed a relatively undifferentiated tumor, suggestive of a carcinoma. In situ hybridization for X and Y chromosomes, revealed his tumor to be of donor origin. Treatment included debulking of the mesenteric mass with segmental enterectomy of the intestinal allograft, and stopping his immunosuppression for a period of 4 months; this resulted in complete resolution of his malignancy. Immunosuppression with tacrolimus and steroids was restarted because of intestinal allograft rejection; he died suddenly of unknown causes at 17 months post-diagnosis of carcinoma. The severely immunosuppressed state produced in this patient allowed for the development of an unusual donor derived carcinoma, which resolved spontaneously with withdrawal of immunosuppression. The mechanism of such regression of tumor may be related to restitution of immunologic competence, but is yet to be determined.

Child↗

PubMed2005

Sclerosing peritonitis after intestinal transplantation in children.

Long-term graft dysfunction and/or graft loss after intestinal transplantation (ITx) is a significant concern. Sclerosing peritonitis (SP) is a manifestation of chronic allograft failure and its presence may also include classic arterial obliterative arteriopathy (OA) as in chronic rejection. We describe the clinical presentation and management of SP occurring after ITx in children. Case records of 121 children undergoing ITx from 1990 to 2003 were reviewed. Three children (2.4%) presented with SP of the intestine allograft at a mean time of 6.6 yr following ITx as follows: age at Tx (yr) 8.2, and 3.7, with indication for ITx being gastroschisis in two and midgut volvulus in one patient. Type of ITx was isolated intestine in one and liver/intestine in two patients. Gross findings of SP included fibrosis/strictures; microscopically SP showed fibrosis/serositis, and fibrous adhesions; one patient had evidence of chronic allograft vasculopathy. All patients presented with clinical signs and symptoms of bowel obstruction and gastrointestinal contrast studies confirmed distal ileal obstruction (DIO). Operative findings confirmed SP and DIO in all patients; all patients were initially treated with distal segmental intestine allograft resection and lysis of the fibrous peel. All three patients recovered, although two required repeat laparotomy, there is only one long-term survival. SP after ITx may be a different manifestation of long-term intestine allograft degeneration. Surgical resection appears to offer palliation.

Child↗

PubMed2005

Intestinal transplantation under tacrolimus monotherapy after perioperative lymphoid depletion with rabbit anti-thymocyte globulin (thymoglobulin).

Modifications in the timing and dosage of immunosuppression can ameliorate the morbidity and mortality that has prevented widespread use of intestinal transplantation (ITx) in children. Thirty-six patients receiving ITx, aged 5 months to 20 years were given 2-3 mg(kg of rabbit anti-thymocyte globulin (rATG, thymoglobulin) just before ITx, and 2-3 mg(kg postoperatively (total 5 mg(kg). Twice daily doses of tacrolimus (TAC) were begun enterally within 24 h after graft reperfusion with reduction of dose quantity or frequency after 3 months. Prednisone or other agents were given to treat breakthrough rejection. After 8-28 months follow-up (mean 15.8 +/- 5.3), 1- and 2-year patient and graft survival is 100% and 94%, respectively. Despite a 44% incidence of acute rejection in the first month, 16 of the 34 (47%) survivors are on TAC (n = 14) or sirolimus (n = 2) monotherapy; 15 receive TAC plus low dose prednisone; one each receive TAC plus sirolimus, TAC plus azathioprine and TAC plus sirolimus and prednisone. There was a low incidence of immunosuppression-related complications. This strategy of immunosuppression minimized maintenance TAC exposure, facilitated the long-term control of rejection, decreased the incidence of opportunistic infections, and resulted in a high rate of patient and graft survival.

Adolescent↗

PubMed2004

Graft versus host disease in intestinal transplantation.

Our aim was to analyze the clinical course and outcome of patients with graft vs. host disease (GVHD) after intestinal transplantation (ITx). All patients receiving ITx between May, 1990 and December, 2003 were retrospectively reviewed for evidence of GVHD. Two hundred and fifty patients underwent ITx during the study period. Graft vs. host disease was suspected clinically in 23 patients on the clinical basis of presentation such as skin rash, ulceration of oral mucosa, diarrhea, lymphadenopathy, or native liver dysfunction. Fourteen (eight children and six adults) patients (5.6% of total patient population) had GVHD confirmed by histopathological criteria including keratinocyte necrosis (n = 9), epithelial apoptosis of the native gastrointestinal tract (n = 4), and epithelial cell necrosis of oral mucosa (n = 1). Donor-cell tissue infiltration or extensive peripheral blood donor-cell chimerism was documented on seven occasions. The majority of cases of GVHD resolved with steroid administration and optimization of tacrolimus immunosuppression. The incidence of histologically proven GVHD after clinical intestinal transplantation is 6.5% (8/122) in children and 4.7% (6/128) in adults. Successful clinical management requires a high index of suspicion to minimize morbidity and mortality. Diagnostic and treatment strategies based on this experience are proposed.

Adolescent↗

PubMed2003

Ex vivo priming of naïve T cells into EBV-specific Th1/Tc1 effector cells by mature autologous DC loaded with apoptotic/necrotic LCL.

Posttransplant lymphoproliferative disorders (PTLDs) represent life-threatening complications of bone marrow and solid organ transplantation (SOTx). These are B-cell malignancies triggered by Epstein-Barr Virus (EBV) infection in chronically immunosuppressed (IS) recipients. Immunosuppressed EBV seronegative (EBV(-)) organ recipients are at highest risk of developing PTLD owing to the lack of anti-EBV memory T cells to control subsequent EBV challenges. Our aim is to establish effective anti-EBV T-cell generation protocols for prevention or treatment of PTLD encountered in SOTx. We have used autologous dendritic cells (DCs) loaded with apoptotic/necrotic lymphoblastoid cell lines (LCLs) to evaluate the ability of such an approach to activate naïve T cells in vitro. In EBV(-) individuals, both CD8+ and CD4+ T-cell responses were amplified by this approach, as detected by IFN-gamma ELISPOT and cytotoxicity assays. The CD8+ T cells were poly-specific anti-EBNA3 A, -LMP2 and -BMLF1, with uniform reversion to a CD45RO+/RA-phenotype, decreased CD62L expression, and up-regulation of the activation markers CD28 and CD69. Addition of rhIL-12 improved anti-viral T-cell responses and reduced the functional differences observed between EBV(+) and EBV(-) responders. In conclusion, the DC/LCL method promotes cross-presentation of EBV-associated epitopes and may serve as an effective protocol for the adoptive immunotherapy of PTLD in EBV(-) SOTx patients.

Antigen Presentation↗