Precore and basal core promoter mutations in Asian American patients with hepatitis B e antigen-positive chronic hepatitis B

BACKGROUND

Prior studies have shown that precore mutations abolish and basal core promoter (BCP) mutations down-regulate hepatitis B e antigen (HBeAg) production. Thus, the presence of precore and BCP mutations in HBeAg-positive patients indicates an infection with a mixed viral population of wild-type and precore and/or BCP mutant hepatitis B virus (HBV). To date, there has been limited study of the prevalence and clinical significance of precore and BCP mutations in patients with HBeAg-positive chronic hepatitis B.

AIM

To determine the prevalence, predictors and clinical characteristics of mixed wild-type and precore/BCP HBV infection, through a cross-sectional study, in a US cohort of patients with chronic hepatitis B.

METHODS

We conducted a retrospective study of 828 chronic hepatitis B patients with HBV genotype and mutation panel testing seen at three US gastroenterology and liver clinics from June 2005 to September 2009.

RESULTS

A majority of our patients (92.3%) were either Vietnamese or Chinese American. In the HBeAg-positive cohort, 17% of patients had precore mutations only, 28% had BCP mutations only and 5% had both BCP and precore mutations. On multivariate analyses, HBV genotype C, increasing age, lower HBV DNA level and an ALT quotient >2 were independent predictors for the presence of precore and/or BCP mutations.

CONCLUSIONS

The current distinction and management recommendations for HBeAg-positive vs. HBeAg-negative patients with chronic hepatitis B should be reassessed. Additional biomarkers and treatment endpoints should be studied for their usefulness in predicting continued viral suppression after treatment discontinuation.

SU-E-T-254: Quantitative Evaluation of Three Mathematical Models for Radiation-Induced Secondary Cancer Risk for Lung in Stereotactic Body Radiotherapy

PURPOSE

Several mathematical models exist to predict secondary cancer risks from radiotherapy treatment. In this study, we aimed to compare three dosimetry-based models in the application of stereotactic body radiotherapy (SBRT) of early-stage non-small cell lung cancer (NSCLC) with three radiotherapy treatment modalities.

METHODS

Ten patients who received definitive SBRT for early-stage NSCLC were retrospectively selected. for each patient, a helical tomotherapy (HT) plan, a three-dimensional conformal radiotherapy (3D-CRT) plan, and a volumetric modulated arc therapy (VMAT) plan were generated to deliver 50 Gy to the planning target volume in five fractions. The excess absolute risk (EAR) for secondary lung cancer occurrence was calculated using three risk models: the linear-exponential model, the plateau model, and the linear model. The sensitivity of the EAR to the prescription dose was evaluated by varying the prescription dose in the range of 40 to 60 Gy.

RESULTS

Based on the linear-exponential model, the average EAR's (in occurrences per 10,000 patients per year) were 8.4+/-2.7, 8.3+/-2.1, and 8.4+/-1.9 for the HT plans, 3D-CRT plans, and VMAT plans respectively with 40 Gy prescription dose, and 9.4+/-2.5, 9.0+/-2.1, and 9.3+/-1.8 with 60 Gy. Based on the plateau model, the average EAR's were 10.7+/-3.9, 10.6+/-3.0, and 10.9+/-2.8 with 40 Gy, and 12.9+/-4.2, 12.6+/-3.4, 12.9+/-3.1 with 60 Gy. Based on the linear model, the average EAR's were 29.1+/-13.4, 29.4+/-11.4, and 30.0+/-11.1 with 40 Gy, and 43.8+/-20.1, 44.0+/-11.0, 45.1+/-16.6 with 60 Gy. The difference in EAR's were not statistically significant among the HT, 3D-CRT, and VMAT plans.

CONCLUSIONS

Three secondary cancer risk models, as well as three SBRT treatment modalities, were compared. There was no significant difference in secondary lung cancer risks among the three treatment modalities in this study.

ADAP Regulates the Stability and Movement of SLP-76 Microclusters (178.10)

The adaptor molecule ADAP and its paralog, PRAM-1, are expressed in mononuclear cells, lymphocytes, and granulocytes. ADAP plays a crucial role in T cell receptor-induced integrin activation, conjugate formation, NF-kB activation, IL-2 production, and T cell proliferation. However, it is not clear how ADAP exerts its profound effects on T cell activation. Here, we demonstrate that endogenous ADAP is an integral component of TCR-induced SLP-76 microclusters, and is essential for their persistence and movement. Our live cell imaging studies show that when we break the ADAP-SLP-76 interaction ADAP is not recruited into SLP-76 MC and SLP-76 MC are immobile and non-persistent. Consequently, T cell adhesion via the TCR is severely impaired, indicating a novel role for ADAP in adhesion to TCR ligands. Phosphorylation of highly conserved, SLP-76-interacting tyrosines within the ADAP C-terminus is necessary for ADAP to enter SLP-76 MC, and associations mediated by the N-terminus are required to stabilize ADAP within SLP-76 MC. These data demonstrate that ADAP could participate in TCR-mediated adhesion to antigen in vivo. Consequently, ADAP and PRAM-1 could be therapeutically relevant targets for modulating TCR- and FcR-dependent signals in clinical settings.

The SKAP55 dimer stabilizes TCR-induced SLP-76 microclusters (121.27)

The adapter molecule SKAP55 enables the formation of T-cell:APC conjugates, facilitates T-cell cytokine production, and is required for optimal T cell proliferation in response to antigen. However, the molecular basis for the involvement of SKAP55 in these events remains unclear. Here, we demonstrate that both endogenous SKAP55 and exogenous SKAP55 chimeras enter T cell receptor (TCR)-induced signaling microclusters containing the adapter protein SLP-76. Using a SKAP55-deficient Jurkat T cell line, we demonstrate that SKAP55 is required for both the persistence and the movement of SLP-76 microclusters. Furthermore, the recruitment of SKAP55 into microclusters requires the presence of both SLP-76 and ADAP, an intermediary adapter protein capable of interacting with both SLP-76 and SKAP55. In addition, we show that SKAP55 homodimerizes via an N-terminal dimerization motif (DM). Our structure-function analyses indicate that the dimerization domain and the ADAP-interacting Src-homology domain 3 (SH3) domain of SKAP55 are both required for the recruitment of SKAP55 into SLP-76 microclusters, and for the stabilization of SLP-76 microclusters. Importantly, an artificial tandem dimer composed of two functional SH3 domains joined by a flexible linker was sufficient for entry into, and stabilization of these signaling complexes. This data indicates that SKAP55 could contribute to T-cell activation by increasing the overall avidity and stability of TCR-induced SLP-76 microclusters.

Depressive symptoms in mild cognitive impairment predict greater atrophy in Alzheimer's disease-related regions

BACKGROUND

Depression has been associated with higher conversion rates from mild cognitive impairment (MCI) to Alzheimer's disease (AD) and may be a marker of prodromal AD that can be used to identify individuals with MCI who are most likely to progress to AD. Thus, we examined the neuroanatomical changes associated with depressive symptoms in MCI.

METHODS

Two-hundred forty-three MCI subjects from the Alzheimer's Disease Neuroimaging Initiative who had brain magnetic resonance imaging scans at baseline and 2-year follow-up were classified into depressed (n = 44), nondepressed with other neuropsychiatric symptoms (n = 93), and no-symptom (NOSYMP; n = 106) groups based on the Neuropsychiatric Inventory Questionnaire. Tensor-based morphometry was used to create individual three-dimensional maps of 2-year brain changes that were compared between groups.

RESULTS

Depressed subjects had more frontal (p = .024), parietal (p = .030), and temporal (p = .038) white matter atrophy than NOSYMP subjects. Those whose depressive symptoms persisted over 2 years also had higher conversion to AD and more decline on measures of global cognition, language, and executive functioning compared with stable NOSYMP subjects. Nondepressed with other neuropsychiatric symptoms and NOSYMP groups exhibited no differences in rates of atrophy.

CONCLUSIONS

Depressive symptoms were associated with greater atrophy in AD-affected regions, increased cognitive decline, and higher rates of conversion to AD. Depression in individuals with MCI may be associated with underlying neuropathological changes, including prodromal AD, and may be a potentially useful clinical marker in identifying MCI patients who are most likely to progress to AD.

Detection of atomic and molecular mega-electron-volt projectiles using an x-ray charged coupled device camera

We show that an x-ray charge coupled device (CCD) may be used as a particle detector for atomic and molecular mega-electron-volt (MeV) projectiles of around a few hundred keV per atomic mass unit. For atomic species, spectroscopic properties in kinetic energy measurements (i.e., linearity and energy resolution) are found to be close to those currently obtained with implanted or surface barrier silicon particle detectors. For molecular species, in order to increase the maximum kinetic energy detection limit, we propose to put a thin foil in front of the CCD. This foil breaks up the molecules into atoms and spreads the charges over many CCD pixels and therefore avoiding saturation effects. This opens new perspectives in high velocity molecular dissociation studies with accelerator facilities.

Vav1-mediated scaffolding interactions stabilize SLP-76 microclusters and contribute to antigen-dependent T cell responses

The guanine nucleotide exchange factor (GEF) Vav1 synergizes with the adaptor protein SLP-76 (Src homology 2 domain--containing leukocyte phosphoprotein of 76 kD) to support T cell development and activation. In response to ligation of the T cell receptor (TCR), SLP-76 is assembled into microclusters that provide an essential platform for the signaling events that drive T cell activation. We found that Vav1 selectively entered SLP-76 microclusters, rather than TCR microclusters, influencing their stability and function. The carboxyl terminus of Vav1, which consists of Src homology domains, was both necessary and sufficient for the entry of Vav1 into SLP-76 microclusters; however, this fragment of Vav1 was insufficient to stabilize the microclusters, and it potently suppressed T cell activation. This indicated that the amino terminus of Vav1, which has the GEF domain, also contributed to the integrity of SLP-76 microclusters and thereby to T cell activation. These microcluster-stabilizing functions were independent of the GEF activity in the amino terminus of Vav1 and were unaffected if the GEF function of Vav1 was either inactivated or constitutively activated by mutation. In contrast, Vav1 deletion mutants lacking either the calponin homology domain or the catalytic core of the GEF exhibited mild scaffolding defects, but they differentially affected TCR-dependent calcium ion (Ca²+) responses. We conclude that multiple GEF-independent scaffolding functions distributed throughout the amino terminus of Vav1 contribute to the activation of T cells by acting synergistically to increase the stability and function of SLP-76 microclusters.

Synthesis and mechanical properties of interconnected carbon nanofiber network reinforced polydimethylsiloxane composites

Carbon nanofiber (CNF) reinforced elastomer composites with light weight, sustainability of large deformation, chemical stability, corrosion and fatigue resistance, and vibration and noise reduction capability can have positive impact on a wide range of applications. However, this type of composite is still a under studied research area due to the difficulties in material handling and processing. To improve processing control and reproducibility for large scale engineering applications, cost effective carbon nanofibers (CNFs) in form of interconnected porous network structure were used as nanofillers. Processing, microstructure and mechanical properties of carbon nanofibers reinforced polydimethylsiloxane (PDMS) have been studied. Mechanical measurements on the composites show that the CNF-PDMS interfacial bonding can be until failure, interfacial debonding happens in the CNF-PDMS composites and the resulted permanent deformation stabilizes with increasing load-unload cycles with significant energy dissipation.

Response to pegylated interferon and ribavirin in Asian American patients with chronic hepatitis C genotypes 1 vs 2/3 vs 6

Chronic hepatitis C is generally underappreciated in Asian Americans, and most pivotal studies were conducted in western countries and only included a small numbers of Asian patients. Our goal was to examine and compare treatment outcomes in these patients with genotypes 1 vs 2/3 vs 6. We performed a retrospective cohort study of 167 consecutive treatment-naïve Asian American patients treated with pegylated interferon (PEG IFN) plus ribavirin (RBV) at two community clinics in Northern California from 12/00 to 1/08. Primary outcome was sustained virological response rate by intention-to-treat analysis. The overall completion rate was 76%, and treatment adherence (completion of ≥ 75-80% PEG IFN + RBV dose for ≥ 75-80% of intended duration) was 74%. Significant depression was noted in only 4% of patients. Sustained virologic response in patients with genotype 6 treated for 48 weeks was similar to that seen in those with genotype 2/3 (74%vs 75%, P = 0.89) and significantly higher than those with genotype 1 (74%vs 49%, P = 0.016). On multivariate analysis inclusive of sex, age, body mass index (≤ 25 vs > 25) and viral load, only treatment adherence and genotype (2/3 and 6 treated for 48 weeks) were found to be significant predictors of sustained virologic response. We conclude that significant depression is rare in Asian American patients (4%). Patients with genotype 6 treated for 48 weeks appear to have a similar treatment response rate as patients with genotype 2/3 and a significantly higher response rate than those with genotype 1.