Liver transplantation in children with sickle-cell disease.

Severe liver disease is an unusual but potentially fatal complication of sickle-cell disease (SCD). Liver transplantation has been complicated by ongoing SCD and thrombosis. We reviewed 214 pediatric transplants done at our institution from 1990 to 2005. Three patients were transplanted for complications of SCD, including intrahepatic cholestasis and viral hepatitis. Overall patient and graft survival was 66%. One patient died after 6 years from a subdural hematoma. There were not any incidences of graft loss, primary nonfunction, or thrombosis. All 3 patients required between 1 and 4 postoperative transfusions to keep hemoglobin (Hgb) >9 g/dL with an S fraction of less than 25%. One patient required a preoperative transfusion for a hemoglobin S (HbS) fraction of 30%. Mean follow-up has been 4.2 years (range, 2.6-5.4 years). All 3 children continued to suffer sequelae from their SCD. One child suffered from recurrent sickle-cell hepatopathy and chronic graft failure. In conclusion, children with SCD can in rare instances develop acute and chronic liver failure. These children can be successfully transplanted with good outcomes. Careful attention must be paid to HbS fraction and hemoglobin level to prevent sickling and vascular thrombosis. Unfortunately, liver transplant cannot alter the natural course of the disease.     

Endovascular stent graft repair of abdominal aortic aneurysms after liver transplantation.

It is estimated that 1.7% of orthotopic liver transplant recipients will develop abdominal aortic aneurysms (AAAs) after transplantation. It has been observed that these aneurysms expand faster in transplant recipients; therefore, aggressive surveillance for AAAs in transplant recipients is required. Endovascular aneurysm repair is rapidly becoming the standard of care, especially in patients with previous abdominal surgery and other significant comorbidities. This article describes our experience with AAAs in orthotopic liver transplant recipients treated successfully by endovascular stent graft repair.     

Preselection Thymocytes Are More Sensitive to T Cell Receptor Stimulation Than Mature T Cells

During T cell development, thymocytes which are tolerant to self-peptides but reactive to foreign peptides are selected. The current model for thymocyte selection proposes that self-peptide–major histocompatibility complex (MHC) complexes that bind the T cell receptor with low affinity will promote positive selection while those with high affinity will result in negative selection. Upon thymocyte maturation, such low affinity self-peptide–MHC ligands no longer provoke a response, but foreign peptides can incidentally be high affinity ligands and can therefore stimulate T cells. For this model to work, thymocytes must be more sensitive to ligand than mature T cells. Contrary to this expectation, several groups have shown that thymocytes are less responsive than mature T cells to anti-T cell receptor for antigen (TCR)/CD3 mAb stimulation. Additionally, the lower TCR levels on thymocytes, compared with T cells, would potentially correlate with decreased thymocyte sensitivity. Here we compared preselection thymocytes and mature T cells for early activation events in response to peptide–MHC ligands. Remarkably, the preselection thymocytes were more responsive than mature T cells when stimulated with low affinity peptide variants, while both populations responded equally well to the antigenic peptide. This directly demonstrates the increased sensitivity of thymocytes compared with T cells for TCR engagement by peptide–MHC complexes.     

Erythematous Bullous Lesions on the Dorsa of the Hands Due to Contact Exposure to Ibutilide Fumarate for Injection

While waiting to observe the response to ibutilide fumarate by a patient with atrial fibrillation, a nurse preparing the intravenous solution inadvertently spilled the drug on the hands of a medical resident. The resident immediately wiped his hands dry with disposable paper towels. Several hours later he sensed tingling and itching over the area, and the next day two erythematous bullous lesions were present on the dorsal surfaces of both hands. A single application of topical steroid was applied to the affected areas. The lesions were kept clean and dry, and healed completely in approximately 10 days. This is an unusual allergic reaction due to contact with ibutilide fumarate.     

Identification of a Thymidylate Synthase Gene within the Genome of Chilo Iridescent Virus

The thymidylate synthase (TS, EC 2.1.1.45) is essential for the de novo synthesis of dTMP in pro- and eucaryotic organisms. Consequently it plays a major role in the replication of the DNA genome of a cell or a DNA virus. The gene encoding the TS of Chilo iridescent virus (CIV) was identified by nucleotide sequence analysis of the viral genome and was mapped within the EcoRI CIV DNA fragments G and R. Computer assisted analysis of the DNA nucleotide sequence between the genome coordinates 0.482 and 0.489 revealed an open reading frame (ORF) of 885 nucleotides. This ORF was found to encode a polypeptide of 295 amino acid residues (33.9 kDa) that showed significant homologies to known TS of different species including mammals, plants, fungi, protozoa, bacteria, and DNA viruses. The highest amino acid homologies were found between the CIV-TS and the TS of herpesvirus ateles (54.0%), Saccharomyces cerevisiae (51.8%), herpesvirus saimiri (51.0%), rhesus monkey rhadinovirus (50.7%), mouse (50.5%), rat (50.2%), varicella-zoster virus (50.2%), equine herpesvirus 2 (50.0%), and the human TS (48.4%). The CIV-TS contains six amino acid domains that are highly conserved in the TS of other species. Within these domains the major amino acid residues are present for which a functional role has been reported. The CIV-TS was found to be more closely related to the TS of eucaryotes than to the TS of procaryotes indicating the phylogenetic origin of the CIV-TS gene. The identification of a TS gene in the genome of CIV is the first report of a viral TS that is not encoded by a herpesvirus or a bacteriophage.     

Rapid identification of female carriers of DMD/BMD by quantitative real-time PCR

Recently developed PCR systems offer online-monitoring of amplification and allow simple and reliable DNA quantification. We have used the LightCycler system to develop a simple and rapid method for direct identification of female carriers of deletions and duplications in the dystrophin gene. The challenge resides in the ability to identify the presence of a deleted or duplicated allele over the background contributed by the normal allele. Quantification is based on the determination of the ratio between potentially deleted/duplicated dystrophin exons and non-deleted/-duplicated reference exons using the unspecific dsDNA-dye SYBRgreen I. In a retrospective study, we evaluated our method in female relatives of DMD/BMD patients with known carrier status by comparative analysis of deleted or duplicated versus non-deleted/-duplicated exons. Carrier status was accurately attributed in 100% of cases, the mean ratios being 0.52+/-0.12 for deletion carriers (expected value: 0.5) and 1.56+/-0.18 for duplication carriers (expected value: 1.5) vs. 1.022+/-0.17 for non-carriers (expected value: 1.0). The method proved to be simple, rapid, reliable, and cost-effective. It may be used for direct determination of deletions/duplications in potential DMD/BMD carriers and may easily be adapted for other genetic conditions involving deletions and duplications.     

The hemodynamics of oddball processing during single-tone and two-tone target detection tasks

Event-related potential (ERP) studies have shown that the neural systems engaged during performance of oddball tasks are sensitive to contextual manipulations, such as the number of stimulus classes. Some ERP components (i.e., N1) are modulated by the number of stimulus types, while others (i.e., P3) are not greatly affected. However, little is known about how these contextual manipulations affect the hemodynamics underlying oddball processing. The purpose of this study was to examine the hemodynamic correlates of target stimulus processing in single-tone (targets alone) and two-tone (targets and standard tones) auditory oddball tasks. The primary hypothesis was that processing of salient stimuli in both contextual conditions would engage the same spatially distributed cortical and subcortical networks observed in previous oddball fMRI studies. Results were consistent with this hypothesis and suggest that the brain engages many potentially useful brain regions during salient stimulus processing despite the low probability that said regions are necessary for task performance, which likely reflects a form of “adaptive reflexive processing”. Results were also consistent with ERP data that shows that the N1 is larger for single-tone tasks by showing greater amplitude of hemodynamic response for single-tone targets, relative to two-tone targets, in bilateral temporal cortex and bilateral inferior lateral frontal cortex. The results are discussed as they relate to the understanding of neurocognitive function pertaining to contextual manipulations in general, and orienting processes in particular.     

High responsiveness of HLA-B57-restricted Gag-specific CD8+ T cells in vitro may contribute to the protective effect of HLA-B57 in HIV-infection

HLA-B57 has been shown to be associated with long-term asymptomatic HIV-1 infection. To investigate the biological mechanism by which the HLA-B57 allele could protect from HIV-1 disease, we studied both the number of CD8(+) T cells as well as CD8(+) T cell responsiveness directed to different HIV-1 Gag peptides presented by HLA-A2, -B8 or -B57. T cells specific for the HLA-B57 peptide KAFSPEVIPMF responded more readily and to a higher extend to antigenic stimulation in vitro than T cells specific for the HLA-A2 peptide SLYNTVATL or the HLA-B8 peptide EIYKRWII. This phenomenon was reproducible with T cells from individuals expressing HLA-B57 in combination with one or both of the other alleles and was persistent during long-term follow-up. Lower reactivity of A2- and B8-restricted T cells was not explained by mutations in the B8- or A2-restricted Gag-peptides. Moreover, no correlation between peptide mutation frequency and IFN-gamma production by the corresponding Gag-specific T cells was observed. In conclusion, functional differences were observed between T cells specific for HIV epitopes derived from the same protein presented by different HLA molecules. B57-restricted KAFSPEVIPMF-specific CD8(+) T cells have relatively high responsiveness, which could contribute to the protective effect of HLA-B57 in HIV infection.     

LcrV plague vaccine with altered immunomodulatory properties

Yersinia pestis, the causative agent of plague, secretes LcrV (low-calcium-response V or V antigen) during infection. LcrV triggers the release of interleukin 10 (IL-10) by host immune cells and suppresses proinflammatory cytokines such as tumor necrosis factor alpha and gamma interferon as well as innate defense mechanisms required to combat the pathogenesis of plague. Although immunization of animals with LcrV elicits protective immunity, the associated suppression of host defense mechanisms may preclude the use of LcrV as a human vaccine. Here we show that short deletions within LcrV can reduce its immune modulatory properties. An LcrV variant lacking amino acid residues 271 to 300 (rV10) elicited immune responses that protected mice against a lethal challenge with Y. pestis. Compared to full-length LcrV, rV10 displayed a reduced ability to release IL-10 from mouse and human macrophages. Furthermore, the lipopolysaccharide-stimulated release of proinflammatory cytokines by human or mouse macrophages was inhibited by full-length LcrV but not by the rV10 variant. Thus, it appears that LcrV variants with reduced immune modulatory properties could be used as a human vaccine to generate protective immunity against plague.