T-cell Responses in Individuals Infected with Zika Virus and in Those Vaccinated Against Dengue Virus

Background:

The outbreak of Zika virus (ZIKV) infection in Brazil has raised concerns that infection during pregnancy could cause microcephaly and other severe neurodevelopmental malformations in the fetus. The mechanisms by which ZIKV causes fetal abnormalities are largely unknown. The importance of pre-infection with dengue virus (DENV), or other flaviviruses endemic to Brazil, remains to be investigated. It has been reported that antibodies directed against DENV can increase ZIKV infectivity by antibody dependent enhancement (ADE), suggesting that a history of prior DENV infection might worsen the outcome of ZIKV infection.

Methods:

We used bioinformatics tools to design 18 peptides from the ZIKV envelope containing predicted HLA-I T-cell epitopes and investigated T-cell cross-reactivity between ZIKV-infected individuals and DENV-vaccinated subjects by IFNγ ELISPOT.

Results:

Three peptides induced IFNγ production in both ZIKV-infected subjects and in DENV-vaccinated individuals. Flow cytometry indicated that 1 ZIKV peptide induced a CD4+ T-cell response in DENV-vaccinated subjects.

Conclusions:

We demonstrated that vaccination against DENV induced a T-cell response against ZIKV and identified one such CD4+ T-cell epitope. The ZIKV-reactive CD4+ T cells induced by DENV vaccination and identified in this study could contribute to the appearance of cross-reactive antibodies mediating ADE.

T-cell Responses in Individuals Infected with Zika Virus and in Those Vaccinated Against Dengue Virus

Background: The outbreak of Zika virus (ZIKV) infection in Brazil has raised concerns that infection during pregnancy could cause microcephaly and other severe neurodevelopmental malformations in the fetus. The mechanisms by which ZIKV causes fetal abnormalities are largely unknown. The importance of pre-infection with dengue virus (DENV), or other flaviviruses endemic to Brazil, remains to be investigated. It has been reported that antibodies directed against DENV can increase ZIKV infectivity by antibody dependent enhancement (ADE), suggesting that a history of prior DENV infection might worsen the outcome of ZIKV infection.Methods: We used bioinformatics tools to design 18 peptides from the ZIKV envelope containing predicted HLA-I T-cell epitopes and investigated T-cell cross-reactivity between ZIKV-infected individuals and DENV-vaccinated subjects by IFNg ELISPOT.Results: Three peptides induced IFNg production in both ZIKV-infected subjects and in DENV-vaccinated individuals. Flow cytometry indicated that 1 ZIKV peptide induced a CD4+ T-cell response in DENV-vaccinated subjects.Conclusions: We demonstrated that vaccination against DENV induced a T-cell response against ZIKV and identified one such CD4+ T-cell epitope. The ZIKV-reactive CD4+ T cells induced by DENV vaccination and identified in this study could contribute to the appearance of cross-reactive antibodies mediating ADE.

The contribution of individual TCR signaling components to thymic selection (P4540)

In the thymus, T cell progenitors undergo an extensive selection program that shapes the repertoire of T cell receptors to ensure that mature T cells released into the periphery are tolerant to peptides derived from self proteins but able to recognize foreign peptide antigens. The engagement of the T cell receptor on a developing thymocyte triggers the formation of a proximal signaling complex at the plasma membrane and initiates a calcium signal, which together activate multiple downstream signaling cascades crucial for the thymocyte’s survival and maturation. One of the major signaling pathways initiated is the Ras/MAP kinase cascade, which plays an essential role during the positive selection of thymocytes. As thymic positive selection does not occur efficiently in 2-dimensional co-cultures, we are using a thymic slice preparation that provides the 3-dimensional stromal architecture of the thymus. We aim to study the signaling properties of MHC class I-restricted T cell receptor transgenic CD4+CD8+ thymocytes during positive selection either by flow cytometry or by two-photon laser scanning microscopy. We are using pharmacological inhibitors to understand the contribution of individual T cell receptor signaling components to positive selection. We hope to dissect both their longer-term effect on the thymocytes’ development, as well as their interconnection and potential compensatory mechanisms.

GRB2-mediated recruitment of THEMIS to LAT is essential for thymocyte development

Thymocyte-expressed molecule involved in selection (THEMIS) is a recently identified regulator of thymocyte positive selection. THEMIS's mechanism of action is unknown, and whether it has a role in TCR-proximal signaling is controversial. In this article, we show that THEMIS and the adapter molecule growth factor receptor-bound protein 2 (GRB2) associate constitutively through binding of a conserved PxRPxK motif within the proline-rich region 1 of THEMIS to the C-terminal SH3-domain of GRB2. This association is indispensable for THEMIS recruitment to the immunological synapse via the transmembrane adapter linker for activation of T cells (LAT) and for THEMIS phosphorylation by Lck and ZAP-70. Two major sites of tyrosine phosphorylation were mapped to a YY-motif close to proline-rich region 1. The YY-motif was crucial for GRB2 binding, suggesting that this region of THEMIS might control local phosphorylation-dependent conformational changes important for THEMIS function. Finally, THEMIS binding to GRB2 was required for thymocyte development. Our data firmly assign THEMIS to the TCR-proximal signaling cascade as a participant in the LAT signalosome and suggest that the THEMIS-GRB2 complex might be involved in shaping the nature of Ras signaling, thereby governing thymic selection.

T cell receptor (TCR)-induced tyrosine phosphorylation dynamics identifies THEMIS as a new TCR signalosome component

Stimulation of the T cell antigen receptor (TCR) induces formation of a phosphorylation-dependent signaling network via multiprotein complexes, whose compositions and dynamics are incompletely understood. Using stable isotope labeling by amino acids in cell culture (SILAC)-based quantitative proteomics, we investigated the kinetics of signal propagation after TCR-induced protein tyrosine phosphorylation. We confidently assigned 77 proteins (of 758 identified) as a direct or indirect consequence of tyrosine phosphorylation that proceeds in successive "signaling waves" revealing the temporal pace at which tyrosine kinases activate cellular functions. The first wave includes thymocyte-expressed molecule involved in selection (THEMIS), a protein recently implicated in thymocyte development but whose signaling role is unclear. We found that tyrosine phosphorylation of THEMIS depends on the presence of the scaffold proteins Linker for activation of T cells (LAT) and SH2 domain-containing lymphocyte protein of 76 kDa (SLP-76). THEMIS associates with LAT, presumably via the adapter growth factor receptor-bound protein 2 (Grb2) and with phospholipase Cγ1 (PLC-γ1). RNAi-mediated THEMIS knock-down inhibited TCR-induced IL-2 gene expression due to reduced ERK and nuclear factor of activated T cells (NFAT)/activator protein 1 (AP-1) signaling, whereas JNK, p38, or nuclear factor κB (NF-κB) activation were unaffected. Our study reveals the dynamics of TCR-dependent signaling networks and suggests a specific role for THEMIS in early TCR signalosome function.

Combination of high-dose chemotherapy and monoclonal antibody in breast-cancer patients: a pilot trial to monitor treatment effects on disseminated tumor cells

BACKGROUND

Tumor relapse occurring in high-risk breast cancer patients after high-dose chemotherapy (HDC) and autologous stem-cell transplantation may arise from cells resistant to chemotherapy, as well as from tumor cells reinfused with autologous stem cell grafts. This pilot study was designed to investigate whether ex vivo immunomagnetic purging of PBSC and subsequent immunotherapy with MAb 17-1A is feasible and can reduce the number of disseminated tumor cells in BM.

METHODS

Twelve high-risk breast-cancer patients, seven in Stage II/III and five in Stage IV (UICC breast cancer classification) underwent surgery of the primary tumor and received two cycles of induction chemotherapy, followed by HDC. After each cycle of induction chemotherapy PBSC were collected and incubated with Ab-coated immunomagnetic beads, to remove contaminating tumor cells. Prepared stem-cell grafts were transplanted 24 h after completion of HDC. After recovering from HDC all 12 patients received a total dose of 900 mg MAb 17-1A within 4 months. The effect of in vivo purging with MAb 17-1A after HDC was controlled by examining bone aspirates of the patients with an immunocytochemical assay, allowing the detection of one cytokeratin-positive tumor cell in 10(6) total nucleated cells (TNC).

RESULTS

Tumor cells were found in 5/12 BM aspirates prior to chemotherapy and even after HDC. Further monitoring of BM aspirates for cancer cells during Ab therapy showed a consistent reduction of tumor cells in four out of these five patients. After a median clinical follow-up of 41 (32-48) months all four patients are alive. These results are different from those of a historical control group of six patients with breast cancer treated with the same chemotherapy schedule, but without 17/1A consolidation. In comparison with the patients from the study group, all patients of this control group revealed a significantly increased number of tumor cells in BM (p < 0.01) after HDC during follow-up of 5 (3-7) months. These preliminary results indicate that induction chemotherapy, followed by HDC, may reduce disseminated tumor cells in BM.

DISCUSSION

Immunotherapy with MAb 17-1A after HDC may further eliminate residual disease without severe toxicity.

Distribution of cell adhesion molecules (ICAM-1, VCAM-1, ELAM-1) in renal tissue during allograft rejection

The tissue distribution of cellular adhesion molecules (CAMs) was studied in specimens from 10 normal human kidneys and in 52 biopsies from kidney allografts with cell-mediated rejection. In addition to the vascular presence of ICAM-1, a common finding in normal kidneys, expression of ICAM-1 on tubular cells was observed in 22 graft biopsies. Compared with normal kidneys, where VCAM-1 was present on Bowman's capsules and few proximal tubular cells, a markedly enhanced expression of VCAM-1 in numerous tubuli (including distal tubular segments) was observed in 51 graft biopsies. In 41 graft specimens VCAM-1 appeared also in variable numbers of peritubular capillaries. Infiltrating leukocytes carrying VCAM-1 were observed in 7 grafts. ELAM-1 could not be found in normal kidneys but was restricted to some peritubular capillaries in 29 grafts. Comparable results were obtained with cultured renal tubular cells when stimulated by TNF-alpha. That the induced appearance of adhesion molecules was in fact related to actual cellular synthesis was demonstrated by Northern blot analysis. Thus, little ICAM-1 specific mRNA of 3.4-kb length could be detected in unstimulated cultured renal tubular cells, but hybridization was markedly increased after stimulation with TNF-alpha. A substantial amount of VCAM-1 specific mRNA of 3.2-kb length was present already in unstimulated renal tubular cells. Likewise, synthesis of VCAM-1 mRNA was enhanced by stimulation with TNF-alpha. TNF-stimulated endothelial cells also showed weak synthesis of VCAM-1 mRNA. The results provide further evidence that constitutive and inducible expression of cell adhesion molecules contributes to the process of allograft rejection.

Detection of antineutrophil cytoplasmatic antibodies (ANCA) and their association with other autoantibodies in patients with hepatobiliary disorders

Sera from 35 out of 655 patients with suspected or confirmed hepatobiliary diseases were positive for anti-neutrophil antibodies with a perinuclear staining pattern (p-ANCA). Nineteen of these sera did not react with myeloperoxidase (MPO), Cathepsin G or Elastase, the three proposed antigens of p-ANCAs. No distinct antigen for these sera could be characterized by western blot techniques with fractionated granulocyte proteins.

Vascular deposition of complement-split products in kidney allografts with cell-mediated rejection

Complement activation in 73 renal transplant biopsies was investigated by indirect immunoperoxidase staining using MoAbs reactive with complement-split products. Intense deposition of complement fragments C4d and C3d in peritubular capillaries, indicating activation of the classical pathway, could be detected in the majority of transplanted kidneys with cell-mediated rejections. Abundant deposition of complement-split products was observed in 22 early biopsies from patients with high 'immunological risk' (i.e. previous, rejected transplants and/or circulating antibodies against HLA-antigens). Despite negative results in the crossmatch before transplantation and paucity of immunoglobulins in transplant biopsies, antibodies directed against endothelial cell antigens should be considered as a possible cause of classical complement activation.

Secretory differentiation of human fetal bronchial epithelial cells in culture. A study by histochemistry and electron microscopy

Human fetal bronchial epithelial (HFBE) cells at 6-8 passages were cultivated on a collagen gel for 10 days. A basal differentiative medium (BDM), consisting of RPMI 1640 supplemented with hormones and growth factors, was employed. Histochemistry, scanning electron microscopy and transmission electron microscopy revealed that HFBE cells developed secretory granules when cultivated on collagen gel in BDM. They were electron-dense and stained positive for PAS but negative for alcian blue. On additional treatment with 8 micrograms/ml vitamin A (VA), the number of secretory granules was increased. Moreover, the HFBE cells lost their surface microvilli, and dilation of rough endoplasmic reticulum was more marked than in culture without VA.

Investigation of a potential cotumorigenic effect of the dioxides of nitrogen and sulfur, and of diesel-engine exhaust, on the respiratory tract of Syrian golden hamsters

Syrian golden hamsters (480 males and 480 females) allocated into 24 groups were exposed 19 hours per day and 5 days per week for 6, 10.5, 15, or 18 months to total diesel exhaust, diesel exhaust without particles, a mixture of nitrogen dioxide (5 parts per million [ppm]2) and sulfur dioxide (10 ppm), or clean air. Two exposure groups from each test atmosphere were also treated by a single subcutaneous injection of either 3 mg or 6 mg of diethylnitrosamine/kg of body weight to evaluate an enhancing effect of diethylnitrosamine on exposure-related changes. Morphological evaluation was done by histopathology. Minor changes of the larynx and trachea were investigated by scanning electron microscopy, which showed a loss of ciliated cells in all exhaust-exposed groups. After exposure to diesel exhaust with or without particles, focal metaplasia and dysplasia of the respiratory epithelium were seen in the oldest animals by scanning electron microscopy. In the same specimens, attached mucous droplets indicated changes in mucous cells and mucous viscosity. Only the exposure to total diesel exhaust significantly increased the tumor rate in the upper respiratory tract of male hamsters treated with 6 mg of diethylnitrosamine per kg of body weight. At the lower diethylnitrosamine dose, no exposure-related effects on the tumor rates could be observed. The results from this study and from our other inhalation experiments appear to be insufficiently conclusive to demonstrate that diesel-engine exhaust should be classified as a cocarcinogen or enhancer for the test system used.

An improved embedding method for obtaining semithin and ultrathin sections from critical-point dried trachea specimens

Critical-point dried trachea specimens were rinsed for 48 h in dimethylsulphoxide before being embedded in Epon 812 to obtain semithin and ultrathin sections. Compared with methods hitherto published, this treatment leads to better resin infiltration of the specimens and better preservation of intracellular structures.

Light and scanning electron microscopic investigation of the laryngeal mucosa of Syrian golden hamsters

The laryngeal epithelium of Syrian golden hamsters (SGH) at 8, 12.5 and 17 months was studied by scanning electron microscopy (SEM) and light microscopy (LM). Stratified squamous epithelium, covered with shallow microvilli or microplicae, was observed covering the upper two-thirds of the laryngeal epiglottis, the false folds, the vocal cords and the luminal protrusions of the arytenoid cartilages. Pseudostratified respiratory epithelium, characterized by mucus producing cells with microvilli and ciliated cells, covered the base of the epiglottis and the entire subglottis. Transitional zones between squamous and respiratory epithelium were composed of stratified cuboidal epithelium. Towards the base of the epiglottis cuboidal cells with a relatively large surface area were present which displayed short surface microvilli, while cells with a small surface area were covered with long microvilli. Age related changes were not observed. Degenerative changes of submucosal glands or cartilages occurred in almost every animal, but no epithelial lesions were found. The findings confirm a low incidence of spontaneous metaplasia in the laryngeal epithelium of the SGH.

Spontaneous lesions in the respiratory epithelium of the Syrian golden hamster as seen by scanning electron microscopy

The respiratory epithelium of 8, 12.5 and 17.5-month-old Syrian golden hamsters was investigated by scanning electron microscopy (SEM) and routine light microscopy (LM) of paraplast sections. In selected cases, SEM-specimens were embedded in Epon after SEM evaluation. The samples were cut in semithin sections and examined by light microscopy. The density of ciliated cells in the respiratory epithelium differs from hamster to hamster. Care must, therefore, be taken when diagnosing simple metaplasia by SEM alone unless a sufficient number of damaged cilia are present. Only 1 animal (8 months old) exhibited squamous metaplasia of the tracheal mucosa. However, surface polymorphism resembling squamous metaplasia was seen in almost every specimen. The polymorphism was caused by either submucosal calcifications or by cystic changes of hypertrophic submucosal glands. In addition, variously formed aggregations of mucus were seen protruding from duct openings of hypertrophic submucosal glands. To avoid false positive or negative diagnosis which can occur when screening is done by SEM alone, light-microscopical examination of sections cut from SEM identified lesions appears necessary.