Increased T cell immunosenescence and accelerated maturation phenotypes in older kidney transplant recipients.

Older kidney transplant recipients experience increased rates of infection and death, and less rejection, compared with younger patients. However, little is known about immune dysfunction in older compared with younger kidney transplant recipients and whether it is associated with infection. We evaluated T cell phenotypes including maturation, immune senescence, and exhaustion in a novel investigation into differences in older compared with younger patients receiving identical immune suppression regimens. We evaluated PBMC from 60 kidney transplant recipients (23 older and 37 matched younger patients) by multiparameter immune phenotyping. Older kidney transplant recipients demonstrated decreased frequency of naïve CD4+ and CD8+ T cells, and increased frequency of terminally differentiated, immune senescent, and NK T cells expressing KLRG1. There was a trend towards increased frequency of T cell immune senescence in patients experiencing infection in the first year after transplantation, which reached statistical significance in a multivariate analysis. This pilot study reveals immune dysfunction in older compared with younger transplant recipients, and suggests a likely mechanism for increased vulnerability to infection. The ability to assess T cell maturation and immune senescence in transplant recipients offers the potential for risk stratification and customization of immune suppression to prevent infection and rejection after transplantation.

A case report of CMV lymphadenitis in an adult kidney transplant recipient.

Cytomegalovirus (CMV) infection following kidney transplantation is associated with increased morbidity and mortality. In this case report we describe a case of a 23-year-old woman with an unusual presentation of diffuse CMV lymphadenitis following kidney transplantation that did not respond to gangiclovir therapy. This case highlights the atypical presentation of CMV disease in a kidney transplant recipient, the importance of CMV hypergammaglobulin in the treatment of CMV infection post kidney transplantation, and the difficulties in transitioning care from pediatric to adult transplant programs.

Trends in invasive disease due to Candida species following heart and lung transplantation.

Although invasive candidiasis (IC) causes significant morbidity and mortality in patients who undergo heart, lung, or heart-lung transplantation, a systematic study in a large cohort of thoracic organ transplant recipients has not been reported to date. Clinical and microbiological data were reviewed for 1305 patients who underwent thoracic organ transplantation at Stanford University Medical Center between 1980 and 2004. We identified and analyzed 76 episodes of IC in 68 patients (overall incidence 5.2% per patient).The incidence of IC was higher in lung (LTx) and heart-lung transplant (HLTx) recipients as compared with heart transplant (HTx) recipients (risk ratio [RR] 1.7, 95% confidence interval [CI] 1.1-2.7).The incidence of IC decreased over time in all thoracic organ transplant recipients, decreasing from 6.1% in the 1980-1986 time period to 2.1% in the 2001-2004 era in the HTx recipients, and from 20% in the 1980-1986 period to 1.8% in the 2001-2004 period in the LTx and HLTx recipients.The most common site of infection differed between the HTx and LTx cohorts, with bloodstream or disseminated disease in the former and tracheobronchitis in the latter. IC in the first year after transplant was significantly associated with death in both HTx (RR 2.9, 95% CI 1.8-4.6, P=0.001) and LTx and HLTx patients (RR 3.0, 95% CI 1.9-4.6, P<0.001). The attributable mortality from IC decreased during the 25-year period of observation, from 36% to 20% in the HTx recipients and from 39% to 15% in the LTx and HLTx recipients. There were a significant number of cases caused by non-albicans Candida species in all patients, with a trend toward higher mortality in the HTx group. In conclusion, the incidence and attributable mortality of IC in thoracic organ transplant recipients has significantly declined over the past 25 years.The use of newer antifungal agents for prophylaxis and treatment, the decrease in the incidence of cytomegalovirus disease, and the use of more selective immunosuppression, among other factors, may have been responsible for this change.

Identification and characterization of an Entamoeba histolytica upstream regulatory element 3 sequence-specific DNA-binding protein containing EF-hand motifs.

The hgl5 gene of Entamoeba histolytica is negatively regulated through the upstream regulatory element 3 (URE3) DNA motif TATTCTATT. This motif is also present and significant in the function of the E. histolytica fdx gene promoter. A yeast one-hybrid screen was used to identify an E. histolytica cDNA encoding a protein (URE3-BP) that recognized this DNA motif. Analysis of the predicted amino acid sequence demonstrated the presence of two EF-hand motifs but identified no canonical DNA binding motifs. URE3-BP, expressed in bacteria, demonstrated Ca(2+)-dependent and sequence-specific recognition of the URE3 DNA sequence as assessed by electrophoretic mobility shift assays. Antibodies raised against URE3-BP blocked the formation of the URE3 DNA-protein complex by native nuclear extracts. The URE3-BP protein was present in the E. histolytica nucleus and cytoplasm with an apparent molecular mass of 22.6 kDa. Our results represent the first use of a yeast genetic screen to identify, on the basis of function, a DNA-binding protein of an early branching eukaryote. Since the URE3 DNA can modulate gene expression in both a positive and negative manner, this protein may have more than one mechanism of interaction with transcriptional machinery. Characterization of URE3-BP should provide insight into transcription regulation and virulence control in this parasite.

Identification of two Entamoeba histolytica sequence-specific URE4 enhancer-binding proteins with homology to the RNA-binding motif RRM.

To study transcriptional regulation in the lower branching eukaryote Entamoeba histolytica, we have identified two sequence-specific DNA-binding proteins that recognize the upstream regulatory element URE4, an enhancer that regulates expression of the Gal/GalNAc lectin heavy subunit gene hgl5. A chromatographic purification of E. histolytica nuclear extracts by gel filtration, cation exchange, and sequence-specific DNA affinity chromatography led to a 700-fold increase in URE4 binding activity and the appearance of two dominant protein species with molecular masses of 28 and 18 kDa. These proteins, termed E. histolytica enhancer-binding proteins 1 and 2 (EhEBP1 and EhEBP2), were sequenced by tandem mass spectroscopy and their corresponding cDNA clones identified. Recombinant EhEBP1 and EhEBP2 were able to bind double-stranded oligonucleotides bearing the URE4 motif in a sequence-specific manner, and antibodies raised against EhEBP1 were able to interfere with the formation of URE4-protein complexes in crude nuclear extracts. Overexpression of EhEBP1 in E. histolytica trophozoites resulted in a 7-fold drop in promoter activity in transiently transfected reporter gene constructs when the URE4 motif was present, confirming its ability to specifically recognize the URE4 motif and suggesting that additional cofactors may be required for transcriptional activation by URE4. Further characterization and identification of binding partners for EhEBP1 and EhEBP2, the first proteins with demonstrated sequence-specific DNA binding activity to be identified in E. histolytica, should provide new insights into transcriptional regulation in this protozoan parasite.