Biomedical subjects

Barbara A Vance

Publications and source records attributed to Barbara A Vance.

7 recordsLinked to original sources

PubMed2006

Immunosurveillance and survivin-specific T-cell immunity in children with high-risk neuroblastoma.

PURPOSE: Tumor immunosurveillance influences oncogenesis and tumor growth, but it remains controversial whether clinical failure of immunosurveillance is a result of lymphocyte dysfunction or tumor escape. In this study, our goal was to characterize the physiology of tumor immunosurveillance in children with high-risk neuroblastoma (HR-NBL). PATIENTS AND METHODS: Immunohistopathologic studies were carried out on 26 tumor samples from a cohort of HR-NBL patients diagnosed at Children's Hospital of Philadelphia for the 2-year period from May 2003 to May 2005. Blood from nine HLA-A2+ patients in this cohort was analyzed for T cells specific for the antiapoptotic protein survivin. RESULTS: Survivin protein was expressed by 26 of 26 tumors. In HLA-A2+ patients, circulating cytotoxic T lymphocytes (CTLs) specific for survivin were detected by peptide/major histocompatibility complex tetramer analysis in the blood of eight of nine children with HR-NBL at the time of diagnosis. Rather than being selectively rendered anergic in vivo, circulating survivin-specific CTLs were highly functional as shown by cytotoxicity and interferon gamma enzyme-linked immunospot assays in six of nine patients. Survivin-specific CD107a mobilization by T cells was found in five of five patients. By immunohistochemistry, tumor-infiltrating T cells were few or absent in 26 of 26 tumors. CONCLUSION: Children with HR-NBL harbor robust cellular immune responses to the universal tumor antigen survivin at the time of diagnosis, but intratumoral T cells are strikingly rare, suggesting a failure of cellular immunosurveillance. Efforts to develop novel therapies that increase T-cell trafficking into tumor nests are warranted.

Adolescent↗

PubMed2005

Human CD69 associates with an N-terminal fragment of calreticulin at the cell surface.

CD69 is thought to be a pluripotent signaling molecule expressed on the surface of a number of activated leukocytes including B, T, and NK cells, monocytes, neutrophils, and platelets. While some advances have been made regarding the mechanisms by which CD69 may participate in such diverse functions as cell aggregation, cellular cytotoxicity, and release of cytokines and inflammatory mediators, the most proximal links of signal initiation have not been identified. Our study has identified, by immunoprecipitation and direct protein sequencing (LC/MS/MS), binding of CD69 to an N-terminal protein fragment of calreticulin expressed on the cell surface of human PBMCs. Given the recently identified roles calreticulin plays in cell adhesion and angiogensis, the identification of CD69 binding directly to calreticulin may provide insights into mechanism(s) by which CD69 or other CD69 family members, i.e., LLT1 and AICL participates in such diverse functions.

Amino Acid Sequence↗

PubMed2005

Age-dependent incidence, time course, and consequences of thymic renewal in adults.

Homeostatic regulation of T cells involves an ongoing balance of new T cell generation, peripheral expansion, and turnover. The recovery of T cells when this balance is disrupted provides insight into the mechanisms that govern homeostasis. In a long-term, single cohort study, we assessed the role of thymic function after autologous transplant in adults, correlating serial computed tomography imaging of thymic size with concurrent measurements of peripheral CD4(+) T cell populations. We established the age-dependent incidence, time course, and duration of thymic enlargement in adults and demonstrated that these changes were correlated with peripheral recovery of naive CD45RA(+)CD62L(+) and signal-joint TCR rearrangement excision circle-bearing CD4(+) populations with broad TCR diversity. Furthermore, we demonstrated that renewed thymopoiesis was critical for the restoration of peripheral CD4(+) T cell populations. This recovery encompassed the recovery of normal CD4(+) T cell numbers, a low ratio of effector to central memory cells, and a broad repertoire of TCR Vbeta diversity among these memory cells. These data define the timeline and consequences of renewal of adult thymopoietic activity at levels able to quantitatively restore peripheral T cell populations. They further suggest that structural thymic regrowth serves as a basis for the regeneration of peripheral T cell populations.

Adult↗

PubMed2004

Minimal residual disease detection in breast cancer: improved sensitivity using cytokeratin 19 and epidermal growth factor receptor RT-PCR.

Breast cancer cells pose a difficult target for detection due to their lack of tumor specific markers. Small numbers of metastatic cells circulate through the blood and reach target organs, but current methods are presently not sensitive enough to allow for early detection. Our goal is to develop a method for specific and sensitive detection for breast cancer tumor cells by using cell enrichment coupled to RT-PCR with selective primer pairs. Fifty million normal donor mononuclear cells (NDMNC) were spiked with serial dilutions of a breast cancer cell line, positively selected for surface expression of the epithelial cell adhesion molecule (EPCAM) with anti-Ber-EP4 mAb. Total RNA was isolated and the cDNA was transcribed and measured by quantitative PCR for cytokeratin 19 (CK19), epidermal growth factor receptor (EGF-R), and beta-2-microglobulin (beta2M) transcripts using specific hybridization probes with the LightCycler System. A sensitivity of 1 tumor cell in 5 million NDMNC was consistently achieved with a metastatic breast cancer cell line with target primer sets for CK19 and EGF-R. Less, but appreciable sensitivity was achieved by spiking NDMNC with other breast cancer cells. Detection of both gene targets ranged between 1 in 5,000 to 5 million cells. The method described, a cell enrichment procedure and RT-PCR using specific hybridization probes (spanning introns and hybridizing to areas that discriminate transcribed pseudogenes), results in increased sensitivity while decreasing false positives above those methods previously reported. This general approach may have wide applicability to increasing sensitivity of minimal residual disease detection in other cancers.

Biomarkers, Tumor↗

PubMed2003

RNA-transfected CD40-activated B cells induce functional T-cell responses against viral and tumor antigen targets: implications for pediatric immunotherapy.

Vaccination with antigen-presenting cells (APCs) engineered to mimic mechanisms of immune stimulation represents a promising approach for cancer immunotherapy. Dendritic cell vaccines have entered phase 3 testing in adult malignancies, but such vaccines in children have been limited. We demonstrate that CD40-activated B cells (CD40-B) transfected with RNA may serve as an alternative vaccine that can be generated from small blood volumes regardless of patient age. CD40-B from pediatric patients are efficient APCs and can be loaded with RNA as an antigenic payload, permitting simultaneous targeting of multiple antigenic epitopes without the necessity of HLA matching. For viral and tumor antigens, CD40-B/RNA technology induced cytotoxic T lymphocytes (CTLs) from adults and children, which could be identified with peptide/major histocompatibility complex (MHC) tetramers. These CTLs secreted interferon-gamma (IFN-gamma) and killed targets in an MHC-restricted fashion. For pooled neuroblastoma RNA and autologous neuroblastoma RNA, CTLs that lysed neuroblastoma cell lines, including CTLs specific against the widely expressed tumor-antigen survivin, were generated. These findings support a novel platform for tumor-specific vaccine or adoptive immunotherapies in pediatric malignancies.

Adult↗

PubMed2003

Proliferation kinetics of subpopulations of human marrow cells determined by quantifying in vivo incorporation of [2H2]-glucose into DNA of S-phase cells.

This report investigated in vivo turnover kinetics of marrow hematopoietic progenitors and precursors using a recently developed stable isotope-mass spectrometric technique (SIMST). Human subjects were administered a 2-day infusion of 6,6-[2H2]-glucose, a nontoxic stable isotope-labeled form of glucose, which becomes incorporated into DNA of all S-phase cells. The percent [2H2]-glucose incorporated into DNA in the form of [2H2]-deoxyadenosine (%[2H2]-dA enrichment) was determined by gas chromatography-mass spectrometry. The rate constant of replacement of unlabeled by labeled DNA strands (labeling kinetics) was used to calculate population turnover kinetics of CD34+ cells, CD133+ cells, and CD133-CD34+ cells. The observed mean replacement half-life (t1/2) was 2.6 days for CD34+ cells, 2.5 days for CD133-CD34+ cells, and 6.2 days for CD133+ cells. Results from the estimated rate constant of replacement of labeled by unlabeled DNA (delabeling kinetics) also demonstrated slower turnover rates for CD133+ cells than for CD133-CD34+ cells. Although there was a relatively rapid initial decrease in the %[2H2]-dA enrichment, low levels of labeled DNA persisted in CD34+ cells for at least 4 weeks. The results indicate the presence of subpopulations of CD34+ cells with relatively rapid turnover rates and subpopulations with a slower t1/2 of 28 days. Results also demonstrate that in vivo [2H2]-glucose-SIMST is sensitive enough to detect differences in turnover kinetics between erythroid and megakaryocyte lineage cells. These studies are the first to demonstrate the use of in vivo [2H2]-glucose-SIMST to measure in vivo turnover kinetics of subpopulations of CD34+ cells and precursors in healthy human subjects.

AC133 Antigen↗

PubMed2002

A potential role for CD69 in thymocyte emigration.

The early activation marker, CD69, is transiently expressed on activated mature T cells and on thymocytes that are undergoing positive or negative selection in the thymus. CD69 is a member of the NK gene complex family of C-type lectin-like signaling receptors; however, its function is unknown. In this report, we describe the characterization of mice that constitutively express high levels of surface CD69 on immature and mature T cells throughout development. Constitutive surface expression of CD69 did not affect T cell maturation, signaling through the TCR or thymocyte selection. However, phenotypically and functionally mature thymocytes accumulated in the medulla of CD69 transgenic mice and failed to be exported from the thymus. The retention of mature thymocytes correlated with transgene dose and CD69 surface levels. These results identify a potential role for CD69 in controlling thymocyte export, and suggest that the transient expression of CD69 on thymocytes and T cells may function to regulate thymocyte and T cell trafficking.

Animals↗