MUC1-specific CTLs are non-functional within a pancreatic tumor microenvironment

Pancreatic cancer is a highly aggressive, treatment refractory disease and is the fourth leading cause of death in the United States. In humans, 90% of pancreatic adenocarcinomas over-express altered forms of a tumor-associated antigen, MUC1 (an epithelial mucin glycoprotein), which is a target for immunotherapy. Using a clinically relevant mouse model of pancreas cancer that demonstrates peripheral and central tolerance to human MUC1 and develops spontaneous tumors of the pancreas, we have previously reported the presence of functionally active, low affinity, MUC1-specific precursor cytotoxic T cells (pCTLs). Hypothesis for this study is that MUC1-based immunization may enhance the low level MUC1-specific immunity that may lead to an effective anti-tumor response. Data demonstrate that MUC1 peptide-based immunization elicits mature MUC1-specific CTLs in the peripheral lymphoid organs. The mature CTLs secrete IFN-gamma and are cytolytic against MUC1-expressing tumor cells in vitro. However, active CTLs that infiltrate the pancreas tumor microenvironment become cytolytically anergic and are tolerized to MUC1 antigen, allowing the tumor to grow. We demonstrate that the CTL tolerance could be reversed at least in vitro with the use of anti-CD40 co-stimulation. The pancreas tumor cells secrete immunosuppressive cytokines, including IL-10 and TGF-beta that are partly responsible for the down-regulation of CTL activity. In addition, they down-regulate their MHC class I molecules to avoid immune recognition. CD4+ CD25+ T regulatory cells, which secrete IL-10, were also found in the tumor environment. Together these data indicate the use of several immune evasion mechanisms by tumor cells to evade CTL killing. Thus altering the tumor microenvironment to make it more conducive to CTL killing may be key in developing a successful anti-cancer immunotherapy.

Carbon monoxide modeling from transportation sources

Street canyon module and gaussian line source module of a regional-scale dispersion model Indic Airviro were used to simulate ambient carbon monoxide (CO) concentrations due to traffic flow at two roadside monitoring locations in Singapore. The fleet average emission factors for each vehicle category was estimated from US EPA MOBILE 5 A guidelines as a function of speed, vehicle deterioration rates and model years. 1-h CO concentrations and worst case 8-h levels have been simulated and compared with measured readings. This study used model-simulated rooftop concentration levels from non-localized sources as background levels at the two sites. The resulting CO concentrations correlate well with actual measured levels and provide a unique approach to predict the impact of CO from transportation.

Normal brain maturation during childhood: developmental trends characterized with diffusion-tensor MR imaging

PURPOSE

To characterize the maturational changes in water diffusion within central gray matter nuclei and central white matter pathways of the human brain by using diffusion-tensor magnetic resonance (MR) imaging.

MATERIALS AND METHODS

Retrospective analysis of normal MR examination findings in 153 subjects (age range, 1 day to 11 years) referred for clinical neuroimaging was performed. All studies included diffusion tensor-encoded echo-planar MR imaging. Isotropic diffusion coefficient (D) and diffusion anisotropy (A(sigma)) were measured in the corpus callosum, internal capsule, caudate nucleus, lentiform nucleus, and thalamus.

RESULTS

exhibited biexponential decay with age in gray and white matter regions, except for monoexponential decay in the genu of the corpus callosum. There was a steep nonlinear increase of A(sigma) in white matter tracts that paralleled the time course of the decline in D. In basal ganglia, only a small linear increase in A(sigma) was observed in patients. A(sigma) changes in the thalamus were intermediate between basal ganglia and white matter structures.

CONCLUSION

Changes in magnitude and anisotropy of water diffusion follow stereotypical time courses during brain development that can be empirically described with multiexponential regression models, which suggests that quantitative scalar parameters derived from diffusion-tensor MR imaging may provide clinically useful developmental milestones for brain maturity.

Spontaneous adenocarcinoma mouse models for immunotherapy

Recent discoveries regarding the identification of tumor-associated antigens and antigen presentation have made successful immunotherapy strategies possible with little, if any, toxicity. Here, we describe transgenic mammary, pancreas, prostate, stomach and lung adenocarcinoma animal models that can be used to study various immunotherapeutic strategies. The challenge in developing a tumor vaccine is effective antigen presentation that elicits anti-tumor immune responses without precipitating autoimmunity. Clinical trials must be preceded by appropriate animal studies to demonstrate that the concepts can be translated into efficacious therapy for cancer. Although many xenograph or transplantable tumor models have been used, the most effective studies are in spontaneous tumor models. These models are clinically relevant, as tumors arise in an appropriate tissue background and in a host conditioned by the physiological events of neoplastic progression and tumorigenesis and in the context of a viable immune system.

Gene expression profiling of the tau mutant (P301L) transgenic mouse brain

To provide a global analysis of the influence of Tau neuropathology at molecular level, we used cDNA arrays representing 8832 genes to determine the mRNA expression profile in transgenic mice expressing the most common frontotemporal dementia and parkinsonism linked to chromosome 17 (FTDP-17) Tau mutation (P301L) (Nat. Genet. (2000) 402). Genes whose expression is associated with development of neurofibrillary tangles and neuron loss in P301L mice with motor and behavioral deficits were identified. The data suggest that a major mechanism underlying P301LTau neurodegeneration primarily involved altered expression of genes contributing to inhibition of apoptosis and intracellular transport. We propose that the expression of mutated P301L may lead to select altered expression of genes which may cause neurodegeneration in FTDP-17.

Efficient presentation of both cytosolic and endogenous transmembrane protein antigens on MHC class II is dependent on cytoplasmic proteolysis

Peptides from extracellular proteins presented on MHC class II are mostly generated and loaded in endolysosomal compartments, but the major pathways responsible for loading peptides from APC-endogenous sources on MHC class II are as yet unclear. In this study, we show that MHC class II molecules present peptides from proteins such as OVA or conalbumin introduced into the cytoplasm by hyperosmotic pinosome lysis, with efficiencies comparable to their presentation via extracellular fluid-phase endocytosis. This cytosolic presentation pathway is sensitive to proteasomal inhibitors, whereas the presentation of exogenous Ags taken up by endocytosis is not. Inhibitors of nonproteasomal cytosolic proteases can also inhibit MHC class II-restricted presentation of cytosolically delivered protein, without inhibiting MHC class I-restricted presentation from the same protein. Cytosolic processing of a soluble fusion protein containing the peptide epitope I-Ealpha(52-68) yields an epitope that is similar to the one generated during constitutive presentation of I-Ealpha as an endogenous transmembrane protein, but is subtly different from the one generated in the exogenous pathway. Constitutive MHC class II-mediated presentation of the endogenous transmembrane protein I-Ealpha is also specifically inhibited over time by inhibitors of cytosolic proteolysis. Thus, Ag processing in the cytoplasm appears to be essential for the efficient presentation of endogenous proteins, even transmembrane ones, on MHC class II, and the proteolytic pathways involved may differ from those used for MHC class I-mediated presentation.

Non-steroidal anti-inflammatory drugs protect against chondrocyte apoptotic death

Recent evidence suggests that the degradation of cartilage in osteoarthritis is characterized by chondrocyte apoptosis, but little is known about the molecular mechanisms involved or potential protective measures. In the present study, we used an immortalized chondrocyte cell line to explore the mechanisms of apoptotic chondrocyte cell death. We found that staurosporine-mediated chondrocyte death depended on the concentration and time of incubation, and coincided with increased Bax:Bcl-X mRNA expression, cytochrome C release, and activation of caspase-3. Pre-treatment of the cultures with nimesulide, a preferential cyclooxygenase (COX)-2 inhibitor, or with ibuprofen, a non-selective COX-1/COX-2 inhibitor, protected the chondrocytes against the staurosporine-mediated nuclear damage and cell death in a concentration-dependent manner (10(-12) to 10(-6) M). Cell protection coincided with inhibition of the staurosporine-mediated induction of caspase-3 activation. Notably, the selective COX-2 inhibitor NS-398 (10(-6) M, 24 hr pre-treatment) did not protect the cells against staurosporine-mediated apoptotic death. The data suggest that nimesulide and ibuprofen, in addition to their anti-inflammatory and analgesic benefits, may also have a protective effect in osteoarthritis through the inhibition of apoptosis in chondrocytes.

Evaluating pediatric brain tumor cellularity with diffusion-tensor imaging

OBJECTIVE

MR imaging of central nervous system (CNS) malignancies falls short of a definitive evaluation. Tissue diagnosis remains the gold standard. Diffusion-tensor MR imaging measures the apparent diffusion coefficient and diffusion anisotropy of water in tissue. The purpose of this study was to test the hypothesis that the apparent diffusion coefficient may improve the MR imaging evaluation of newly diagnosed CNS neoplasms. We examined the relationship between the apparent diffusion coefficient, anisotropy, and tumor cellularity in 12 pediatric patients.

MATERIALS AND METHODS

On the basis of histopathologic evaluation, tumors in this case series were segregated into three types: low-grade gliomas, embryonal tumors, and nonembryonal high-grade tumors. Mean apparent diffusion coefficient and anisotropy values obtained from the solid components of each tumor were compared with cellularity, total cellular area, and total nuclear area derived from biopsy material.

RESULTS

The apparent diffusion coefficient ratio (tumor to normal brain) correlated well with tumor classification (p = 0.001). Anisotropy was decreased similarly in all tumor classifications. The absolute apparent diffusion coefficient correlated well with cellularity (p = 0.014) and total nuclear area (p = 0.005) per high-power field. The correlation between apparent diffusion coefficient and total cellular area per high-power field was not statistically significant.

CONCLUSION

The apparent diffusion coefficient may be predictive of tumor classification and may be a useful tool in characterizing tumor cellularity and total nuclear area. These parameters are not available in standard MR imaging. Therefore, diffusion-tensor imaging may enhance the diagnostic process in pediatric CNS malignancies.

Reversible posterior leukoencephalopathy syndrome: evaluation with diffusion-tensor MR imaging

PURPOSE

To characterize the changes in brain water diffusion caused by reversible posterior leukoencephalopathy syndrome (RPLS).

MATERIALS AND METHODS

Twelve patients with the clinical features and conventional magnetic resonance (MR) imaging findings of RPLS underwent diffusion-tensor echo-planar MR imaging. The isotropic diffusion coefficient (D) and diffusion anisotropy (A(sigma)) were measured in posterior regions of diffusion abnormality and in anterior areas of normal-appearing brain.

RESULTS

Across all 12 subjects, the mean D of (1.09 +/- 0.13 [SD]) x 10(-3) mm(2)/sec in affected posterior regions was 26% greater than its value of (0.87 +/- 0.07) x 10(-3) mm(2)/sec in normal-appearing anterior regions. The mean A(sigma) of 0.15 +/- 0.03 in posterior regions was 35% less than its value of 0.23 +/- 0.02 in anterior regions (t(11) = 9.58; P <.001). There was a significant inverse correlation between D and A(sigma) in posterior regions (r = -0.67; P <.018) but not in anterior regions (r = -0.12; P =.719). A follow-up study performed in one patient after resolution of symptoms documented reversal of elevated isotropic diffusion and at least partial recovery of anisotropy loss.

CONCLUSION

The increased magnitude of brain water diffusion characteristic of RPLS is accompanied by reduced A(sigma). The magnitudes of these two effects are correlated and may be reversible. These observations support the proposal that vasogenic edema due to cerebrovascular autoregulatory dysfunction is the underlying pathophysiologic mechanism in uncomplicated RPLS.

Complement anaphylatoxin C5a neuroprotects through mitogen-activated protein kinase-dependent inhibition of caspase 3

We previously reported that pretreatment of murine cortico-hippocampal neuronal cultures with the complement-derived anaphylatoxin C5a, protects against glutamate neurotoxicity. In this study we explored the potential mechanisms involved in C5a-mediated neuroprotection. We found that C5a neuroprotects in vitro through inhibition of apoptotic death because pretreatment with human recombinant (hr)C5a prevented nuclear DNA fragmentation coincidental to inhibition of the pro-apoptotic caspase 3 activity mediated by glutamate treatment. Also, hrC5a-mediated responses appeared to be receptor-mediated because pretreatment of cultures with the specific C5a receptor antagonist C177, prevented hrC5a-mediated neuroprotection. Based on this evidence, we further explored possible signaling pathways involved in hrC5a inhibition of caspase 3 activation and apoptotic neuronal death. We found that treatment of cultures with the mitogen-activated protein kinase (MAPK) pathway inhibitor PD98059 prevented hrC5a-mediated inhibition of caspase 3 and apoptotic neuron death. MAPK pathways, whose activation by hrC5a is inhibited by PD98059 and C177, include the extracellular signal-regulated kinase (ERK)2 and, to a lesser extent, ERK1. The study suggests that C5a may protect against glutamate-induced apoptosis in neurons through MAPK-mediated regulation of caspase cascades.

N -butyldeoxynojirimycin reduces growth and ganglioside content of experimental mouse brain tumours

Abnormalities in glycosphingolipid (GSL) biosynthesis have been implicated in the oncogenesis and malignancy of brain tumours. GSLs comprise the gangliosides and the neutral GSLs and are major components of the cell surface glycocalyx. N -butyldeoxynojirimycin (N B-DNJ) is an imino sugar that inhibits the glucosyltransferase catalysing the first step in GSL biosynthesis. The influence of N B-DNJ was studied on the growth and ganglioside composition of two 20-methylcholanthrene-induced experimental mouse brain tumours, EPEN and CT-2A, which were grown in vitro and in vivo. N B-DNJ (200 microM) inhibited the proliferation of the EPEN and CT-2A cells by 50%, but did not reduce cell viability. The drug, administered in the diet (2400 mg kg(-1)) to adult syngeneic C57BL/6 mice, reduced the growth and ganglioside content of subcutaneous and intracerebral EPEN and CT-2A tumours by at least 50% compared to the untreated controls. N B-DNJ treatment also shifted the relative distribution of tumour gangliosides in accordance with the depletion of metabolic substrates. Side effects of N B-DNJ treatment were generally mild and included reductions in body and spleen weights and intestinal distension. We conclude that N B-DNJ may inhibit tumour growth through an effect on ganglioside biosynthesis and may be useful as a new chemotherapy for brain tumours.

MUC1-specific cytotoxic T lymphocytes eradicate tumors when adoptively transferred in vivo

We have reported previously that MUC1 transgenic mice with spontaneous tumors of the pancreas (designated MET) naturally develop MHC class I-restricted, MUC1-specific CTLs as tumors progress (P. Mukherjee et al., J. Immunol., 165: 3451-3460, 2000). From these MET mice, we have isolated, expanded, and cloned naturally occurring MUC1-specific CTLs in vitro. In this report, we show that the CTL line is predominantly CD8+ T cells and expresses T-cell receptor Vbeta chains 5.1/5.2, 11, 13, and 2 and Valpha chains 2, 8.3, 3.2, and 11.1/11.2. These CTLs recognize several epitopes on the MUC1 tandem repeat with highest affinity to APGSTAPPA. The CTL clone, on the other hand, is 100% CD8+ cells and expresses a single Vbeta chain of 5.1/5.2 and Valpha2. It recognizes only the H-2Db class I-restricted epitope of MUC1, APGSTAPPA. When adoptively transferred, the CTLs were effective in eradicating MUC1-expressing injected tumor cells including mammary gland cells (C57mg) and B16 melanomas. These results suggest that MUC1-specific CTLs are capable of possibly preventing, or at least substantially delaying, MUC1-expressing tumor formation. To our knowledge, this is the first evidence that demonstrates that the naturally occurring MUC1-specific CTLs isolated from one tumor model has antitumor effects on other MUC1-expressing tumors in vivo. Therefore, our data confirm that MUC1 is an important tumor rejection antigen and can serve as a target for immunotherapy.

T cells in mice expressing a transgenic human TCR beta chain get positively selected but cannot be activated in the periphery by signaling through TCR

TCR-CD3 complex-mediated signaling is crucial for both developmental selection and antigenic activation of T cells. We report that mice expressing a recombined human TCRbeta chain (Tg), which have normal development of T cells, mounted very weak responses to immunization with protein antigens as well as the HA307-319 peptide recognized by the human T cell clone HA1.7 from which the transgene is derived. An anti-CD3epsilon mAb triggered equivalent proliferation from Tg and non-Tg T cells, but an anti-human TCRbeta mAb induced proliferation poorly in Tg T cells in contrast to human T cells or HA1.7. In Tg mice, T cells expressing endogenous TCR were CD44(high), whereas most transgene-expressing T cells remained CD44(low), suggesting that transgene-expressing cells are not activated in the periphery to participate in immune responses. However, anti-human TCRbeta could induce some activation markers on T cells and cross-linking of the Tg TCR by plate-coated anti-human TCRbeta efficiently induced T cell proliferation. Human TCRbeta-mediated Tg T cell activation could be rescued by exogenous IL-2, as well as by the calcium ionophore A23187, but not by phorbol esters. Thus, this human TCRbeta chain functions efficiently for positive selection of mouse T cells, but not for their peripheral activation, probably because of a lack of oligomerization leading to defects in signaling for calcium flux and IL-2 induction. The data thus suggest an early point of separation of signaling pathways between positive selection and peripheral activation of T cells.

Mice with spontaneous pancreatic cancer naturally develop MUC-1-specific CTLs that eradicate tumors when adoptively transferred

Pancreatic cancer is a highly aggressive, treatment refractory cancer and is the fourth leading cause of death in the United States. In humans, 90% of pancreatic adenocarcinomas overexpress altered forms of a tumor-specific Ag, mucin 1 (MUC1; an epithelial mucin glycoprotein), which is a potential target for immunotherapy. We have established a clinically relevant animal model for pancreatic cancer by developing a double transgenic mouse model (called MET) that expresses human MUC1 as self molecule and develops spontaneous tumors of the pancreas. These mice exhibit acinar cell dysplasia at birth, which progresses to microadenomas and acinar cell carcinomas. The tumors express large amounts of underglycosylated MUC1 similar to humans. Tumor-bearing MET mice develop low affinity MUC1-specific CTLs that have no effect on the spontaneously occurring pancreatic tumors in vivo. However, adoptive transfer of these CTLs was able to completely eradicate MUC1-expressing injectable tumors in MUC1 transgenic mice, and these mice developed long-term immunity. These CTLs were MHC class I restricted and recognized peptide epitopes in the immunodominant tandem repeat region of MUC1. The MET mice appropriately mimic the human condition and are an excellent model with which to elucidate the native immune responses that develop during tumor progression and to develop effective antitumor vaccine strategies.

Modeling mobile source emissions in presence of stationary sources

The impact of oxides of nitrogen (NO(x)) emissions from motor vehicles to the air quality in city-state Singapore is analyzed using AIRVIRO, a regional scale dispersion model developed by the Swedish Meteorological and Hydrological Institute. In a predominantly urban location like Singapore, it is difficult to separate out the contribution of pollutants from mobile and point sources at different locations. In this work, a new approach is used by first modeling only the impact of point and area sources and then overlaying the traffic impact on air quality at different locations. Monthly scenario simulations are run with point, area and traffic sources of emissions for the Gaussian model validation. Street Canyon modeling is used for street segments surrounded by buildings on either side. A simplified photochemical model, which takes into account NO(x) undergoing chemical transformations in the urban atmosphere, is used to account for variations in NO(x) and ozone levels with respect to traffic data. The diurnal variation of NO(x) concentration levels is studied as a function of ozone levels at site, hourly traffic counts and meteorological parameters. The impact on ambient air quality within the breathing zone of the public from mobile sources, is found to be about 40% at urban stations although overall emissions from mobile sources is only 24%. The proposed approach appears to predict the variations in NO(x) as a function of traffic and meteorological conditions.

Dietary protection by iron against clastogenic effects of short-term exposure to arsenic in mice in vivo

Iron, as freshly prepared aqueous solution of ferrous sulfate, was administered by gavage to laboratory bred Swiss albino mice. The concentration used was 152 mg/kg body weight (1/10 of the LD(50)). While screening for protection against arsenic, in one set of experiment exposure to iron was followed after 2 hr by gavaging with 2.5 mg/kg body weight (1/10 of the LD(50)) of arsenic as sodium (III) meta arsenite in distilled water. In another set, equal amounts (1:1) of ferrous sulfate and sodium arsenite were administered simultaneously. Control sets were given sodium m-arsenite alone and distilled water (vehicle). After exposure for 24 hr in all experiments, mice were sacrificed and chromosome preparations were made from bone marrow according to a colchicine-hypotonic-fixation-air-drying-Giemsa schedule. Cytogenetic endpoints screened were chromosome aberrations and divisional frequencies. Sodium arsenite alone was highly clastogenic. Ferrous sulfate, whether given together with or before exposure to sodium arsenite, reduced the clastogenic effects of the latter to a significant extent.

Synergistic cell killing by combination therapy of retinoic acid and hyperthermia in human epidermoid laryngeal carcinoma cells in culture

In vitro monolayer culture and clonogenic assay were used to investigate the individual and combined effect of temperature and retinoic acid (RA) on cellular morphology and colony forming ability of human epidermoid laryngeal carcinoma (HEp-2) cells. 20 micromol. RA alone inhibited multilayer formation and induced cell flattening. Hyperthermia (42 degrees C) individually caused formation of cytoplasmic processes and irregularities in cellular shape and size. Combined effect of hyperthermia (42 degrees C) and 20 micromol. RA treatment caused bleb formation on cell surfaces and lysis of cytoplasmic and nuclear membrane. RA treatment also caused dose-dependent reduction of colony growth. Heat-induced cell killing was only observed at lethal temperatures of 43 degrees C and above. RA in combination with heat synergistically inhibited colony formation even at non lethal temperatures of 41 and 42 degrees C. These results indicate that RA in combination with hyperthermia may facilitate the therapy of human epidermoid larynx carcinoma.

The role of complement anaphylatoxin C5a in neurodegeneration: implications in Alzheimer's disease

There is evidence that the complement system, a major component of inflammatory responses, may play an important role in neurodegenerative conditions such as Alzheimer's disease (AD). Work from our lab demonstrated that mice genetically deficient in the complement component C5 are more susceptible to hippocampal excitotoxic lesions (Pasinetti et al., 1996) and that the C5-derived ana;hylatoxin C5a may protect against excitotoxicity in vitro and in vivo (Osaka et al., 1999). Potential mechanisms identified in C5a-mediated neuroprotection include activation of mitogen activated protein (MAP)-kinase (Osaka et al., 1998; Osaka et al., 1999). This novel neuroprotective role of C5a complicates current theories that complement proteins augment beta-amyloid (Abeta) toxicity in AD. In view of the fact that the complement system represents a target for therapeutic interventions in AD, further characterization of the complex role of complement proteins is essential. Towards this aim, we have characterized a transgenic C5a receptor (C5aR) knockout (KO) mouse. Recent studies in the lab using C5aR-KO mice show that disruption of C5aR alters calcium calmodulin kinase (CaM-KII) signal transduction in brain cells. We are presently using C5aR-KO mice to study the role of C5a in caspase mediated apoptotic neuronal death. In this review we will attempt to delineate possible neuroprotective roles for C5a in mechanisms of neurotoxicity pertaining to AD.

Differences between gray matter and white matter water diffusion in stroke: diffusion-tensor MR imaging in 12 patients

PURPOSE

To investigate differences in water diffusion between white matter and gray matter in acute to early subacute stroke with diffusion-tensor magnetic resonance (MR) imaging.

MATERIALS AND METHODS

Twelve patients with unilateral middle cerebral arterial infarcts were examined with diffusion tensor-encoded echo-planar MR imaging 17 hours to 5 days after stroke onset. Isotropic diffusion coefficient (D) and diffusion anisotropy (A(sigma)) images were computed. (D) values were measured in ischemic and contralateral gray matter and white matter by using A(sigma) images to differentiate white matter from gray matter. (D) images were compared with unidirectional and directionally averaged diffusion-weighted images.

RESULTS

In all patients, (D) images showed two distinct levels of diffusion reduction in the infarct; more severe reduction occurred exclusively in white matter. (D) values were significantly less in infarcted white matter than in infarcted gray matter, whereas (D) values in the contralateral white matter and gray matter were not significantly different. Relative to the contralateral side, (D) values in the infarct were reduced by 46% in white matter and by 31% in gray matter (P <.001). Diffusion-weighted imaging caused underestimation of the magnitude and, in some cases, the spatial extent of the white matter diffusion abnormality.

CONCLUSION

Isotropic diffusion is more reduced in white matter than in gray matter in acute to early subacute middle cerebral arterial stroke. Diffusion-tensor imaging may be more sensitive than diffusion-weighted imaging to white matter ischemia.

An unusual case of double outlet right ventricle

A 17-year-old unmarried girl was admitted with the complaints of breathlessness on exertion, swelling of upper and lower limbs and intermittent fever for last 21 days. Past history revealed bluish discolouration of nails and tongue since birth along with recurrent dyspnoea. After thorough general and cardiovascular examination, a provisional diagnosis of tetralogy of Fallot was made. Chest x-ray revealed cardiomegaly and absent main pulmonary artery segment. ECG revealed gross right axis deviation and right ventricular hypertrophy. Echocardiogram showed features of double outlet right ventricle.

Disruption of T cell tolerance to self-immunoglobulin causes polyclonal B cell stimulation followed by inactivation of responding autoreactive T cells

Scavenger receptor (SR)-specific delivery by maleylation of a ubiquitous self-protein, Ig, to SR-bearing APCs results in self-limiting induction of autoimmune effects in vivo. Immunization with maleyl-Ig breaks T cell tolerance to self-Ig and causes hypergammaglobulinemia, with increases in spleen weight and cellularity. The majority of splenic B cells show an activated phenotype upon maleyl-Ig immunization, leading to large-scale conversion to a CD138+ phenotype and to significant increases in CD138-expressing splenic plasma cells. The polyclonal B cell activation, hypergammaglobulinemia, and autoreactive Ig-specific T cell responses decline over a 2-mo period postimmunization. Following adoptive transfer, T cells from maleyl-Ig-immune mice taken at 2 wk postimmunization can induce hypergammaglobulinemia in the recipients, but those taken at 10 wk postimmunization cannot. Hypergammaglobulinemia in the adoptive transfer recipients is also transient and is followed by an inability to respond to fresh maleyl-Ig immunization, suggesting that the autoreactive Ig-specific T cells are inactivated peripherally following disruption of tolerance. Thus, although autoreactive T cell responses to a ubiquitous self-Ag, Ig, are induced by SR-mediated delivery to professional APCs in vivo resulting in autoimmune pathophysiological effects, they are effectively and rapidly turned off by inactivation of these activated Ig-specific T cells in vivo.

Adeno-associated virus 2-mediated transduction and erythroid lineage-restricted expression from parvovirus B19p6 promoter in primary human hematopoietic progenitor cells

Human parvovirus B19 gene expression from the viral p6 promoter (B19p6) is restricted to primary human hematopoietic cells undergoing erythroid differentiation. We have demonstrated that expression from this promoter does not occur in established human erythroid cell lines in the context of a recombinant parvovirus genome (Ponnazhagan et al. J Virol 69:8096-8101, 1995). However, abundant expression from this promoter can be readily detected in primary human bone marrow cells (Wang et al. Proc Natl Acad Sci USA 92:12416-12420, 1995; Ponnazhagan et al. J Gen Virol 77:1111-1122, 1996). In the present studies, we investigated the pattern of expression from the B19p6 promoter in primary human bone marrow-derived CD34+ HPC undergoing differentiation into myeloid and erythroid lineages. CD34+ cells were transduced with recombinant adeno-associated virus 2 (AAV) vectors containing the beta-galactosidase (lacZ) gene under the control of the following promoters/enhancers: the cytomegalovirus promoter (vCMVp-lacZ), B19p6 promoter (vB19p6-lacZ), B19p6 promoter with an upstream erythroid cell-specific enhancer element (HS-2) from the locus control region (LCR) from the human beta-globin gene cluster (vHS2-B19p6-lacZ), and the human beta-globin gene promoter with the HS-2 enhancer (vHS2-beta p-lacZ). Transgene expression was evaluated either 48 h after infection or following erythroid differentiation in vitro for 3 weeks. Whereas high-level expression from the CMV promoter 48 h after infection diminished with time, low-level expression from the B19p6 and the beta-globin promoters increased significantly following erythroid differentiation. Furthermore, in HPC assays, there was no significant difference in the level of expression from the CMV promoter in myeloid or erythroid cell-derived colonies. Expression from the B19p6 and the beta-globin promoters, on the other hand, was restricted to erythroid cell colonies. These data further corroborate that the B19p6 promoter is erythroid cell-specific and suggest that the recombinant AAV-B19 hybrid vectors may prove useful in gene therapy of human hemoglobinopathies in general and sickle cell anemia and beta-thalassemia in particular.

Improving high-resolution MR bold venographic imaging using a T1 reducing contrast agent

Recently, a new imaging method was proposed by Reichenbach et al (Radiology 1997;204:272-277) to image small cerebral venous vessels specifically. This method, referred to as high-resolution blood oxygen level-dependent venography (HRBV), relies on the susceptibility difference between the veins and the brain parenchyma. The resulting phase difference between the vessels and the brain parenchyma leads to signal losses over and above the usual T2* effect. At 1.5 T, a rather long TE (roughly 40 msec) is required for this cancellation to become significant, leading to enhanced susceptibility artifacts and a long data acquisition time. In this study, we examine the utility of incorporating a clinically available T1 reducing contrast agent, Omniscan (Sanofi Winthrop Pharmaceuticals, NY, NY), with the HRBV imaging approach to reduce susceptibility artifacts and imaging time while maintaining the visibility of cerebral veins. Using a double-dose injection of Omniscan, we were able to reduce TE from 40 to 25 msec. This led to a decrease in TR from 57 to 42 msec, allowing a 26% reduction in data acquisition time while maintaining the visibility of cerebral venous vessels and reducing susceptibility artifacts. J. Magn. Reson. Imaging 1999;10:118-123, 1999.