Mutations in TREM2, a receptor expressed by microglia in the brain, are associated with an increased risk of neurodegeneration, including Alzheimer's disease. Numerous studies support a role for ...TREM2 in sensing damaging stimuli and triggering signaling cascades necessary for neuroprotection. Despite its significant role, ligands and regulators of TREM2 activation, and the mechanisms governing TREM2-dependent responses and its cleavage from the membrane, remain poorly characterized. Here, we present phage display generated antibody single-chain variable fragments (scFvs) to human TREM2 immunoglobulin-like domain. Co-crystal structures revealed the binding of two scFvs to an epitope on the TREM2 domain distal to the putative ligand-binding site. Enhanced functional activity was observed for oligomeric scFv species, which inhibited the production of soluble TREM2 in a HEK293 cell model. We hope that detailed characterization of their epitopes and properties will facilitate the use of these renewable binders as structural and functional biology tools for TREM2 research.
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•scFvs were generated against the immunoglobulin-like domain of the receptor TREM2•Crystal structures revealed scFv binding to epitopes outside the TREM2 CDRs•Oligomeric scFv species reduced levels of shed TREM2 ectodomain in a HEK293 model•The scFvs form renewable structural and functional biology tools for TREM2 research
TREM2 variants are associated with an increased risk of dementia. Szykowska et al. generated scFv antibody fragments to TREM2 immunoglobulin-like domain and solved crystal structures of scFv-TREM2 complexes to reveal their binding modes. Oligomeric scFv species showed enhanced functional activity reducing levels of shed TREM2 ectodomain in a HEK293 model.
Background & Aims:
A previous 4-week trial of telbivudine in patients with chronic hepatitis B indicated marked antiviral effects with good tolerability, leading to the present 1-year phase 2b trial.
...Methods:
This randomized, double-blind, multicenter trial evaluated the efficacy and safety of telbivudine 400 or 600 mg/day and telbivudine 400 or 600 mg/day plus lamivudine 100 mg/day (Comb400 and Comb600) compared with lamivudine 100 mg/day in hepatitis B e antigen (HBeAg)-positive adults with compensated chronic hepatitis B.
Results:
A total of 104 patients were randomized 1:1:1:1:1 among the 5 groups. Median reductions in serum hepatitis B virus (HBV) DNA levels at week 52 (log
10 copies/mL) were as follows: lamivudine, 4.66; telbivudine 400 mg, 6.43; telbivudine 600 mg, 6.09; Comb400, 6.40; and Comb600, 6.05. At week 52, telbivudine monotherapy showed a significantly greater mean reduction in HBV DNA levels (6.01 vs 4.57 log
10 copies/mL;
P < .05), clearance of polymerase chain reaction–detectable HBV DNA (61% vs 32%;
P < .05), and normalization of alanine aminotransferase levels (86% vs 63%;
P < .05) compared with lamivudine monotherapy, with proportionally greater HBeAg seroconversion (31% vs 22%) and less viral breakthrough (4.5% vs 15.8%) (
P = NS for both). Combination treatment was not better than telbivudine alone. All treatments were well tolerated. In exploratory scientific analyses, clinical efficacy at 1 year appeared related to reduction in HBV DNA levels in the first 6 months of treatment.
Conclusions:
Patients with chronic hepatitis B treated with telbivudine exhibited significantly greater virologic and biochemical responses compared with lamivudine. Results with the combination regimens were similar to those obtained with telbivudine alone. These data support the ongoing phase 3 evaluation of telbivudine for treatment of patients with chronic hepatitis B.
Congenital heart defects frequently involve a failure of outflow tract (OFT) formation during development. We analyzed the remodeling of the OFT, using the y96-Myf5-nlacZ-16 transgene, which marks a ...subpopulation of myocardial cells of the pulmonary trunk. Expression analyses of reporter transcript and protein suggest that the myocardial wall of the OFT rotates before and during the formation of the great arteries. Rotational movement was confirmed by Di-I injection experiments with cultured embryos. We subsequently examined the expression of the transgene in mouse models for OFT defects. In hearts with persistent truncus arteriosus (PTA), double outlet right ventricle (DORV), or transposition of the great arteries, rotation of the myocardial wall of the OFT is arrested or fails to initiate. This is observed in Splotch (Pax3) mutants with PTA or DORV and may be a result of defects in neural crest migration, known to affect OFT septation. However, in Pitx2δc mutant embryos, where cardiac neural crest cells are present in the heart, PTA and DORV are again associated with a rotation defect. This is also seen in Pitx2δc mutants, which have transposition of the great arteries. Because Pitx2c is involved in left–right signaling, these results suggest that embryonic laterality affects rotation of the myocardial wall during OFT maturation. We propose that failure of normal rotation of OFT myocardium may underlie major forms of congenital heart disease.
Hepatitis B virus (HBV) infects more than 300 million people worldwide, contributing to debilitating illness and death.
1
Until recently, the only antiviral drug for the treatment of hepatitis B was ...interferon.
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–
4
In preliminary studies of patients with chronic hepatitis B, lamivudine, an oral nucleoside analogue,
5
was well tolerated and suppressed serum levels of HBV DNA profoundly.
6
–
9
We therefore conducted a one-year study of the efficacy of lamivudine in patients with chronic hepatitis B. After our data on patients had been collected, Lai et al.
10
reported the results of a placebo-controlled study in which they found histologic, biochemical, and . . .
Malformations of the septum, outflow tract and aortic arch are the most common congenital cardiovascular defects and occur in mice lacking Cited2, a transcriptional coactivator of TFAP2. Here we show ...that Cited2(-/-) mice also develop laterality defects, including right isomerism, abnormal cardiac looping and hyposplenia, which are suppressed on a mixed genetic background. Cited2(-/-) mice lack expression of the Nodal target genes Pitx2c, Nodal and Ebaf in the left lateral plate mesoderm, where they are required for establishing laterality and cardiovascular development. CITED2 and TFAP2 were detected at the Pitx2c promoter in embryonic hearts, and they activate Pitx2c transcription in transient transfection assays. We propose that an abnormal Nodal-Pitx2c pathway represents a unifying mechanism for the cardiovascular malformations observed in Cited2(-/-) mice, and that such malformations may be the sole manifestation of a laterality defect.
Celotno besedilo
Dostopno za:
DOBA, IJS, IZUM, KILJ, NUK, PILJ, PNG, SAZU, UILJ, UKNU, UL, UM, UPUK
Background & Aims: Chronic hepatitis B is a leading cause of death worldwide. To identify patients who might require urgent liver transplantation despite antiviral therapy, we investigated the ...determinants of early mortality in a large cohort of patients with decompensated chronic hepatitis B treated with lamivudine. Methods: One hundred fifty-four North American patients with decompensated chronic hepatitis B received lamivudine for a median of 16 months. Univariate and multivariate Cox regression modeling was used to develop a model of 6-month mortality. Results: A biphasic survival pattern was observed, with most deaths occurring within the first 6 months of treatment (25 of 32, 78%) because of complications of liver failure. The estimated actuarial 3-year survival of patients who survived at least 6 months was 88% on continued treatment. In multivariate modeling, elevated pretreatment serum bilirubin and creatinine levels as well as the presence of detectable hepatitis B virus (HBV) DNA (by the bDNA assay) pretreatment were significantly associated with 6-month mortality. An equation approximating the probability of early mortality was developed from these variables. Conclusions: Our data demonstrate a distinct alteration in the slope of the survival curve after 6 months of lamivudine treatment for decompensated chronic hepatitis B. An equation consisting of 3 widely available pretreatment laboratory parameters was developed that can be used to predict the likelihood of early death in patients receiving lamivudine for decompensated chronic hepatitis B. These observations may help identify patients who can be stabilized with suppressive antiviral therapy vs. those who require urgent liver transplantation.
GASTROENTEROLOGY 2002;123:719-727
Elevated alanine transaminase (ALT) levels and low serum hepatitis B virus (HBV) DNA predict a higher likelihood of hepatitis B e antigen (HBeAg) loss in patients with chronic hepatitis B treated ...with interferon. Predictors of HBeAg loss in patients treated with lamivudine are not known. The objective of this analysis of 4 lamivudine-controlled Phase III trials was to determine patient-dependent or laboratory variables that predict HBeAg loss. Predictors of HBeAg loss in patients treated with interferon, lamivudine plus interferon, or placebo are also described. A total of 805 adults with chronic hepatitis B were treated either with lamivudine (n = 406), matching placebo (n = 196), interferon (n = 68), or the combination of lamivudine plus interferon (n = 135). Demographic and baseline disease characteristics were used in stepwise multivariate analyses to identify features that were predictive of lamivudine-induced HBeAg loss. HBeAg loss correlated with increased pretreatment ALT levels in all groups. The rate of HBeAg loss was highest among patients with pretreatment ALT levels greater than 5 times the upper limit of normal (ULN) and was most pronounced in the lamivudine group (56%). Multivariate modeling indicated that elevated baseline ALT levels (
P < .001) and histologic activity index (HAI) score (
P < .001) were important predictors of HBeAg loss in response to lamivudine. The effect of pretreatment ALT levels on HBeAg loss was similar for Asians and Caucasians. In conclusion, elevated pretreatment ALT levels and/or active histologic disease were the most important predictors of lamivudine-induced HBeAg loss. Asians and Caucasians had similar rates of response to lamivudine at comparable ALT levels. (H
EPATOLOGY 2002;36:186-194.)
Background
: Activation of hepatic stellate cells is the earliest step in fibrogenesis. Alpha-smooth muscle actin (α-SMA), expressed by activated hepatic stellate cells, and C-terminal procollagen ...α1(III) propeptide (PIIICP) are early markers of fibrogenesis and should precede fibrosis.
Aim
: Determine if suppression of hepatitis B virus replication with lamivudine would decrease fibrogenesis as measured by immunohistochemical markers.
Methods
: Paired liver biopsies from patients with hepatitis B before and after therapy with lamivudine (
n=47) or placebo (
n=33) were studied. α-SMA and PIIICP were detected in paraffin-embedded tissue by immunohistochemistry and quantified in a blinded manner by video imaging analysis.
Results
: Liver biopsies from patients treated with lamivudine showed a significant decrease in α-SMA expression (1.06±0.23 vs. 0.58±0.11, pre vs. post,
P<0.05). Placebo recipients had increased levels of α-SMA (0.82±0.14 vs. 1.32±0.21,
P<0.05). PIIICP was similarly decreased after lamivudine. Among subjects whose Histologic Activity Index fibrosis score was unchanged or worsened, the mean change in α-SMA expression was significantly decreased in the lamivudine group compared with placebo.
Conclusions
: Lamivudine decreased markers of hepatic stellate cell activation and collagen synthesis. Immunohistochemical techniques are sensitive for assessing fibrogenesis and will be useful in trials of antiviral and antifibrotic agents.
Orthotopic liver transplantation for end-stage hepatitis-B-virus (HBV) infection is commonly complicated by recurrence of HBV. Lamivudine, a cytosine nucleoside analogue, has been shown to suppress ...HBV infection. We report the development of resistance to lamivudine in three patients who underwent transplantation for end-stage liver disease secondary to hepatitis B.
Two of the patients received lamivudine for recurrent HBV infection after transplantation, whereas the third patient began treatment 1 month before transplantation in an attempt to prevent HBV recurrence after transplantation. The three patients initially responded well to treatment, but viral recurrence occurred after 9–10 months of treatment in all patients. HBV DNA was amplified from serum and sequenced through a conserved polymerase domain—the tyrosine, methionine, aspartate, aspartate (YMDD) locus. We assessed the susceptibility of HBV to lamivudine by infecting primary human hepatocytes with serum taken before the start of treatment and after recurrence in varying concentrations of lamivudine.
DNA sequencing showed a common mutation within the YMDD locus of the HBV polymerase gene in all patients during lamivudine treatment. In hepatocyte cultures infected with pretreatment serum, HBV DNA concentrations were reduced to less than 6% of those in control cultures by addition of lamivudine in concentrations as low as 0·03 μol/ L. By contrast, in cultures treated with serum taken after recurrence, HBV DNA concentrations did not fall below 20% of control values, even with lamivudine at 30 μmol/ L.
Resistance to lamivudine has been reported in HIV patients with mutations in the YMDD locus of the polymerase gene. Our findings indicate a common mechanism of lamivudine resistance for HIV and HBV that involves similar point mutations in homologous domains of the viral polymerases.
Background/Aims: Lamivudine is effective in treatment-naive patients with chronic hepatitis B, but its role in interferon nonresponders has not been described. We assessed lamivudine treatment, with ...or without added interferon, in patients with hepatitis B e antigen (HBeAg)-positive chronic hepatitis B who had failed interferon therapy previously.
Methods: Patients were randomized to lamivudine (100 mg) or placebo for 52 weeks or to a 24-week regimen of lamivudine plus interferon. Primary treatment comparisons were at week 52, with a 16-week posttreatment follow-up period. Measurements included histology (primary endpoint), HBeAg response, normalization of alanine aminotransferase, reduction of hepatitis B virus (HBV) DNA, and safety.
Results: Among 238 patients, histologic response was significantly more common in patients treated with lamivudine (52 versus placebo 25%,
P=0.002) or the combination regimen (32%,
P=0.01). HBeAg loss was also more common with lamivudine (33 versus 13 versus 21%), as were virologic and alanine aminotransferase responses. Among 28 subjects with HBeAg loss/seroconversion, 71% had durable responses 16 weeks posttreatment.
Conclusions: Lamivudine for 52 weeks is as effective in interferon nonresponders as in previously reported treatment-naive patients; however, a combination of lamivudine for 24 weeks and interferon for 16 weeks was not effective in this population.
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