[The cutoff value of small airway dysfunction in children with bronchial asthma]

Objective: To explore the cutoff value for assessing small airway dysfunction in children with asthma. Methods: A total of 364 asthmatic children aged 5 to 14 years, with normal ventilatory function, followed up at the Asthma Clinic of the Children's Hospital of Capital Institute of Pediatrics from January 2017 to January 2018, were selected as the case group. Concurrently, 403 healthy children of the same age range and without any symptoms in the community were chosen as the control group, and pulmonary function tests were conducted. The values of forced expiratory volume in 1 second (FEV1), forced vital capacity (FVC), forced expiratory flow at 50% of FVC (FEF50), forced expiratory flow at 75% of FVC (FEF75) and maximum mid-expiratory flow (MMEF) were compared between case group and control group. Statistical tests such as t-test, χ2 test, or Mann-Whitney U test were used to analyze the differences between the groups. Receiver operating characteristic (ROC) curves were constructed, and the maximum Youden Index was utilized to determine the optimal cutoff values and thresholds for identifying small airway dysfunction in asthmatic children. Results: This study comprised 364 children in the case group (220 boys and 144 girls) and 403 children in the control group (198 boys and 205 girls). The small airway parameters (FEF50%pred, FEF75%pred, MMEF%pred) in the asthmatic group were significantly lower than in the control group (77% (69%, 91%) vs. 95% (83%, 109%), 67% (54%, 82%) vs. 84% (70%, 102%), 76% (66%, 90%) vs. 97% (86%, 113%), Z=12.03, 11.35, 13.66, all P<0.001). The ROC curve area under the curve for FEF50%pred, FEF75%pred, MMEF%pred was 0.75, 0.74, and 0.79, respectively. Using a cutoff value of 80% for FEF50%pred achieved a sensitivity of 56.9% and specificity of 81.4%. A cutoff value of 74% for FEF75%pred resulted in a sensitivity of 67.3% and specificity of 69.2%. Finally, using a cutoff value of 84% for MMEF%pred achieved a sensitivity of 67.9% and specificity of 77.2%. Conclusion: In the presence of normal ventilatory function, utilizing FEF50<80% predicted or MMEF<84% predicted can accurately serve as criteria for identifying small airway dysfunction in children with controlled asthma.

[Efficacy and safety of omalizumab in patients with refractory allergic asthma: a meta-analysis]

Objective: To evaluate the efficacy and safety of omalizumab in patients with refractory allergic asthma using meta-analysis. Methods: We searched databases including PubMed, Web of Science, Embase and the website of ClinicalTrials. gov registry for randomized controlled trials (RCTs), using the search terms: ("anti-IgE" OR "anti-immunoglobulin E" OR "anti-IgE antibody" OR "omalizumab" OR "rhuMAb-E25" OR "Xolair") AND ("allergic asthma"). The time was up to September 19th 2020. Review Manager 5.4 software and Stata16 software were used to calculate pooled RR or WMD, perform heterogeneity test, and assess publication bias. Results: Fifteen RCTs with 6 316 patients in total (omalizumab, n=3 469; placebo, n=2 847) met our selection criteria. Comparing with placebo, omalizumab reduced the risk of asthma exacerbations during both stable-inhaled corticosteroid (ICS) phase (RR=0.69, 95%CI: 0.63-0.75, P<0.001; I²=39.0%, P=0.090) and ICS-reduction phase (RR=0.55, 95%CI: 0.46-0.66, P<0.001; I²=41.0%, P=0.180), reduced emergency visits (RR=0.53, 95%CI: 0.38-0.73, P<0.001; I²=0, P=0.420), made a significant reduction in dosage of ICS (RR=1.35, 95%CI: 1.25-1.45, P<0.001; I²=22.0%, P=0.280) and even withdrew from ICS completely (RR=1.80, 95%CI: 1.41-2.31, P<0.001; I²=57.0%, P=0.070). Omalizumab significantly improved asthma-related quality of life (RR=1.81, 95%CI: 1.51-2.17). The use of rescue bronchodilators was significantly reduced in the omalizumab group (RR=0.78, 95%CI: 0.67-0.92) but there was no significant difference in the dosage of rescue bronchodilators (puff per day) (WMD=-0.32, 95%CI: -0.77-0.13). Patients taking omalizumab did not increase the frequency of any adverse events (RR=1.01, 95%CI: 0.98-1.03) and serious adverse events (RR=0.89, 95%CI: 0.74-1.06). Conclusions: Omalizumab is an ideal adjunctive treatment for refractory allergic asthma with good efficacy and safety. Further randomized controlled trials are needed to determine the appropriate duration of treatment.

[Effect of gMDSCs on natural killer cell functionality in chronic hepatitis C patients treated with direct-acting antiviral agents]

Objective: To investigate the changes of natural killer(NK) cell function, and clarify the effect of granulocytic myeloid derived suppressor cells (G-MDSCs) on NK cell functionality in patients with treatment-naive chronic hepatitis C (CHC) who were cured by direct-acting antiviral agents (DAAs). Methods: Thirteen treatment-naive CHC patients and 13 healthy controls were prospectively included in this study from March 2016 to January 2017. They were divided into case group and control group, respectively. The patients of case group,6 males and 7 females aged 21-65 years old with an average of (37±14),were treated with daclatasvir and asunaprevir combination (DCV/ASV) at the Department of Infectious Diseases, Fifth Medical Center of Chinese PLA General Hospital. While 13 healthy individuals, 6 males and 7 females aged 21-57 (36±11) years old, were enrolled as healthy controls(control group). Flow cytometry was used to determine the immunological characteristics of peripheral blood NK cells subset, and detect the frequencies of gMDSCs in peripheral blood of people in two groups. It was specifically notes that CHC patients of case group would be detected before, during and after treatment. The correlations between gMDSCs and each NK cell subset function were also examined. The impact of gMDSCs on NK cell functionalities and the relevant regulatory mechanisms were explored using co-culture experiments of sorted NK cells and gMDSCs in vitro. Results: Compared with healthy controls, the decreased IFN-γ production[M(Q1,Q3)] [3.182 (2.757, 4.237) vs 6.675 (4.476, 8.280),1.434 (1.127, 2.434) vs 3.045 (1.680, 4.856), 2.611 (1.749, 3.498) vs 5.160 (4.232, 7.683)] and increased CD107a degranulation [9.314 (7.838, 13.543) vs 3.480 (2.938, 6.824), 2.544 (1.366, 4.768) vs 0.552 (0.408, 1.560), 10.339 (9.145, 12.534) vs 3.488 (3.117, 5.651)] (all P<0.05) were found on NK cell and its subsets. The frequencies of gMDSCs and plasma concentration of arginase-1 in CHC patients was significantly higher than that in healthy controls [7.050 (4.180, 12.538) vs 1.440 (0.444, 2.261), 114.278 (68.492, 163.724) vs 64.753 (50.809, 93.278)](all P<0.05). The production of IFN-γ was increased and the secretion of CD107a was decreased in NK cell and its subsets after DAAs treatment (P<0.05). The frequencies of gMDSCs and plasma arignase I levels were also decreased in CHC patients treated with DAAs (P<0.05).The results of the study indicated that the frequencies of G-MDSCs were inversely associated with the levels of IFN-γproduction of NK cells and CD56^dim NK cells in CHC patients (r=0.668, -0.750, respectively, both P<0.05). In addition, the frequencies of gMDSCs were positively associated with the expression of CD107a in the CD56^bright NK cell subset (r=0.711, P=0.021). In vitro, the inhibition of gMDSCs on the IFN-γ production of NK cells was demonstrated in the co-culture experiments of sorted NK cells and gMDSCs, and blocking arginase I can significantly increase the ability of NK cells to produce IFN-γ, restore NK cell IFN-γ production. Conclusions: gMDSCs in peripheral blood of CHC patients has been shown to suppress NK cell IFN-γ production in an arginase I-dependent manner. Direct-acting antiviral-mediated clearance of HCV is associated with the normalization of NK cell function and gMDSCs frequency.

Multifaceted p21 in carcinogenesis, stemness of tumor and tumor therapy

Cancer cells possess metabolic properties that are different from those of benign cells. p21, encoded by CDKN1A gene, also named p21^Cip1/WAF1, was first identified as a cyclin-dependent kinase regulator that suppresses cell cycle G1/S phase and retinoblastoma protein phosphorylation. CDKN1A (p21) acts as the downstream target gene of TP53 (p53), and its expression is induced by wild-type p53 and it is not associated with mutant p53. p21 has been characterized as a vital regulator that involves multiple cell functions, including G1/S cell cycle progression, cell growth, DNA damage, and cell stemness. In 1994, p21 was found as a tumor suppressor in brain, lung and colon cancer by targeting p53 and was associated with tumorigenesis and metastasis. Notably, p21 plays a significant role in tumor development through p53-dependent and p53-independent pathways. In addition, expression of p21 is closely related to the resting state or terminal differentiation of cells. p21 is also associated with cancer stem cells and acts as a biomarker for such cells. In cancer therapy, given the importance of p21 in regulating the G1/S and G2 check points, it is not surprising that p21 is implicated in response to many cancer treatments and p21 promotes the effect of oncolytic virotherapy.

Discrete Superconducting Phases in FeSe-Derived Superconductors

A general feature of unconventional superconductors is the existence of a superconducting dome in the phase diagram. Here we report a series of discrete superconducting phases in the simplest iron-based superconductor, FeSe thin flakes, by continuously tuning the carrier concentration through the intercalation of Li and Na ions with a solid ionic gating technique. Such discrete superconducting phases are robust against the substitution of 20% S for Se, but they are vulnerable to the substitution of 2% Cu for Fe, highlighting the importance of the iron site being intact. The superconducting phase diagram for FeSe derivatives is given, which is distinct from that of other unconventional superconductors.

[The significance of different predictive equations for resting energy expenditure in patients receiving invasive mechanical ventilation]

To calculate resting energy expenditure (REE) in patients receiving invasive mechanical ventilation and compare different predictive equations with indirect calorimetry(IC).A total of 60 patients in intensive care unit(ICU) were enrolled. Measure calculating daily REE in the first week included IC, Harris-Benedict formula, Penn State formula and Swinamer formula. Daily REE did not exhibit significant difference in the first week of mechanical ventilation by IC (all P>0.05).All patients' REE values by IC were higher than those by Harris-Benedict formula (all P<0.01). By Penn State formula, REE in day l, 2, and 5 were comparable (all P>0.05) with those by IC, whereas the consistency between the two methods was poor. Similarly, daily REE by Swinamer formula calculation in the first week did not show significant difference (all P>0.05), with acceptable consistency as IC. Resting energy expenditure in patients receiving invasive mechanical ventilation dose not significantly change during the first week. Swinamer formula is more accurate than other equations when IC is considered as the standard method.

Silencing FKBP38 gene by siRNA induces activation of mTOR signaling in goat fetal fibroblasts

FKBP38 (also known as FKBP8) is a unique member of the FK506-binding protein (FKBP) family, and its role is controversial because it acts as an upstream regulator of the mTOR signaling pathway, which controls cell growth, proliferation, and differentiation. This study aimed to explore the role of FKBP38 in the activation of mTOR signaling in Cashmere goat (Capra hircus) fetal fibroblasts. To construct a Cashmere goat FKBP38 siRNA eukaryotic expression vector that targets FKBP38 mRNA, we designed shRNA based on the gene sequence deposited in GenBank (accession No. JF714970) and synthesized a DNA fragment encoding the shRNA. The DNA fragment was inserted into the pRNAT-U6.1/Neo vector to construct an expression vector of shRNA, which was labeled pRNAT-FKBP38-shRNA. The recombinant plasmid was used to transfect Cashmere goat fetal fibroblasts (GFb) using lipofectamine™2000. We found that cells were successfully transfected with pRNAT-U6.1/Neo-FKBP38-shRNA. Green fluorescence could be observed in cells following 48-h transfection. Proteins were then isolated from GFbs transfected with pRNAT-FKBP38-shRNA and from control cells, and protein expression was analyzed by western blot. Expression of FKBP38 decreased and mTOR signaling was activated, which induced the phosphorylation of mTOR, S6, and 4EBP1. Thus, FKBP38 gene-silencing activates mTOR signaling in goat cells.

Complete eradication of xenograft hepatoma by oncolytic adenovirus ZD55 harboring TRAIL-IETD-Smac gene with broad antitumor effect

Cancer-targeting dual-gene virotherapy (CTGVT-DG) is an important modification of CTGVT, in which two suitable genes are used to obtain an excellent antitumor effect. A key problem is to join the two genes to form one fused gene, and then to clone it into the oncolytic viral vector so that only one investigational new drug application, instead of two, is required for clinical use. Many linkers (e.g., internal ribosome entry site) are used to join two genes together, but they are not all equally efficacious. Here, we describe finding the best linker, that is, sequence encoding the four amino acids IETD, to join the tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) gene and the second mitochondria-derived activator of caspase (Smac) gene to form TRAIL-IETD-Smac and inserting it into oncolytic viral vector ZD55 to construct ZD55-TRAIL-IETD-Smac, which matched ZD55-TRAIL plus ZD55-Smac in completely eliminating xenograft hepatoma. ZD55-TRAIL-IETD-Smac works by quantitative cleavage at IETD↓by inducing caspase-8; activation or inhibition of caspase-8 could up- or downregulate cleavage, respectively. The cleaved product, TRAIL-IETD, does not affect the function of TRAIL. Numerous experiments have shown that the combined use of ZD55-TRAIL plus ZD55-X could completely eradicate many xenograft tumors, and therefore the IETD is potentially a useful linker to construct many antitumor drugs, for example, ZD55-TRAIL-IETD-X, where X has a compensative or synergetic effect on TRAIL. We found that the antitumor effect of ZD55-IL-24-IETD-TRAIL also has an equivalent antitumor effect compared with the combined use of ZD55-IL-24 plus ZD55-TRAIL, because ZD55-IL-24 could also induce caspase-8. This means that IETD, as a two-gene linker, may have broad use.

Structure effects in angle-resolved high-order above-threshold ionization of molecules

We present energy-resolved angular distributions of photoelectrons generated in above-threshold ionization (ATI) of nonaligned diatomic molecules N2 and O2 in high-intensity short laser pulses, with emphasis on the most energetic part of the spectra. The angular distribution for photoelectrons with energy of 10U(p) (U(p): ponderomotive energy), i.e., the plateau cutoff in ATI spectra, is found to be broader in O2 than in N2. Resorting to the analyses from both an S-matrix theory and an intuitive semiclassical model, we attribute the observation to the effect of the ground state molecular orbital structure on high-energy electron emission in strong-field molecular ionization.

Comparative proteomic analysis of colon cancer cells in response to oxaliplatin treatment

Colon cancer is one of the most common malignancies in the world. Oxaliplatin, a third-generation platinum compound, is widely used in clinical chemotherapy of colon cancer. Although the mechanisms of the antitumor effect of Oxaliplatin have been investigated in recent years, the proteomic changes that are associated with the cellular response to this compound are poorly understood. In this study, we performed a comparative proteomic analysis to survey the global changes in protein expression levels after Oxaliplatin treatment in three colon cancer cell lines: HT29, SW620, and LoVo. Two-dimensional gel electrophoresis coupled with MALDI-TOF/TOF mass spectrometry revealed 57, 48, and 53 differentially expressed proteins in the three cell lines (HT29, SW620 and LoVo, respectively) after Oxaliplatin treatment. Of these proteins, 21 overlapped among all three cell lines. These overlapping proteins participate in many cellular processes, such as apoptosis, signal transduction, transcription and translation, cell structural organization, and metabolism. Additionally, the expression levels of ezrin (EZRI), heat-shock protein beta-1 (HSPB1), translationally controlled tumor protein (TCTP), and cell division control protein 2 homolog (CDC2) were confirmed by immunoblotting. This is the first direct proteomic analysis of Oxaliplatin-treated colon cancer cells. Several interesting proteins that we found warrant further investigation owing to their potential significant functions in the antitumor effect of Oxaliplatin.

Combination of cyclooxygenase-2 inhibitor and doxorubicin increases the growth inhibition and apoptosis in human hepatocellular carcinoma cells

Inhibition of cyclooxygenase (COX)-2 elicits therapeutic effects in solid tumors that are coupled with the inhibition of cell proliferation and induction of apoptosis in tumor cells.

AIM

This study was designed to investigate the role of COX-2 inhibitor nimesulide in cell growth and apoptosis of the cultured human hepatocellular carcinoma HepG2 cells.

METHODS

We performed the MTT assay, flow cytometric analysis and cell morphology study to evaluate growth inhibition and cell apoptosis upon the action of nimesulide alone or along with doxorubicin, a common agent for the treatment of human hepatocellular carcinoma.

RESULTS

Our results showed that the treatment of HepG2 cells with more than 50 microM of nimesulide suppressed COX-2 enzyme activity because of reduced PGE(2) production, and then induced growth inhibition and cell apoptosis despite no alterations of COX-2 protein expression. Importantly, the combination of 50 microM or 100 microM of nimesulide and low concentrations (5 microM to 20 microM) of doxorubicin resulted in enhanced cell growth inhibition, apoptosis induction and reduced VEGF production.

CONCLUSION

These data suggest synergistic and/or additive effects of COX-2 inhibitors and chemotherapeutic agents, and may provide the rational for clinical studies of COX-2 inhibitors on the treatment or chemoprevention of human hepatocellular carcinoma.

Effects of dietary arsenic levels on serum parameters and trace mineral retentions in growing and finishing pigs

This experiment was conducted to investigate the effect of dietary arsenic (As) levels on growth performance, serum biochemistry, and the retention of iron, copper, and zinc in tissues of growing and finishing pigs. Ninety-six crossbred pigs were randomly allotted to four dietary treatments. The corn-soybean basal diets were supplemented with 0, 10, 20, and 30 mg As/kg. Arsenic trioxide was used as the arsenic source. The feeding experiment lasted for 78 d. The results showed that the high arsenic diet decreased average daily gain (ADG) (p<0.05) and increased feed gain ratio (F/G) (p<0.05). Arsenic intake significantly increased (p<0.05) serum gamma-gultamyltransferase (GGT), glutamic-pyruvic transaminase (GPT), and alkaline phosphatase (ALP) activities, and decreased (p<0.05) total protein, urea nitrogen, creatinine, and triglycerides. Glutamic-oxalacetic transaminase (GOT) activity, albumin, and cholesterol were not affected (p>0.05). Arsenic feeding elevated (p<0.05) liver and kidney copper concentration, but reduced (p<0.05) copper concentration in heart, bile, and lymphaden of intestine mesentery. There were increases in iron levels in liver, bile, spleen, thymus, and pancreas in pigs fed the high As diets (p<0.05), but iron contents in kidney, heart, and serum were decreased by the arsenic treatment (p<0.05). Zinc concentrations were increased (p<0.05) in liver, kidney, and thymus of pigs with arsenic treatment, but decreased (p<0.05) in bile and lymphaden of intestine mesentery. This study suggested that high dietary As levels could alter serum biochemical parameters and the retention of copper, iron, and zinc in the viscera of growing and finishing pigs.

Mutational analysis of the absolutely conserved B8Gly: consequence on foldability and activity of insulin

B8Gly is absolutely conserved in insulins during evolution. Moreover, its corresponding position is always occupied by a Gly residue in other members of insulin superfamily. Previous work showed that Ala replacement of B8Gly significantly decreased both the activity and the foldability of insulin. However, the effects of substitution are complicated, and different replacements sometimes cause significantly different results. To analyze the effects of B8 replacement by different amino acids, three new insulin/single-chain insulin mutants with B8Gly replaced by Ser, Thr or Leu were prepared by protein engineering, and both their foldability and activity were analyzed. In general, replacement of B8Gly by other amino acids causes significant detriment to the foldability of single-chain insulin: the conformations of the three B8 mutants are essentially different from that of wild-type molecules as revealed by circular dichroism; their disulfide stabilities in redox buffer are significantly decreased; their in vitro refolding efficiencies are decreased approximately two folds; the structural stabilities of the mutants with Ser or Thr substitution are decreased significantly, while Leu substitution has little effect as measured by equilibrium guanidine denaturation. As far as biological activity is concerned, Ser replacement of B8Gly has only a moderate effect: its insulin receptor-binding activity is 23% of native insulin. But Thr or Leu replacement produces significant detriment: the receptor-binding potencies of the two mutants are less than 0.2% of native insulin. The present results suggest that Gly is likely the only applicable natural amino acid for the B8 position of insulin where both foldability and activity are concerned.

Replacement of the interchain disulfide bridge-forming amino acids A7 and B7 by glutamate impairs the structure and activity of insulin

Insulin contains three disulfide bonds, one intrachain bond, A6–A11, and two interchain bonds, A7–B7 and A20–B19. Site-directed mutagenesis results (the two cysteine residues of disulfide A7–B7 were replaced by serine) showed that disulfide A7–B7 is crucial to both the structure and activity of insulin. However, chemical modification results showed that the insulin analogs still retained relatively high biological activity when A7Cys and B7Cys were modified by chemical groups with a negative charge. Did the negative charge of the modification groups restore the loss of activity and/or the disturbance of structure of these insulin analogs caused by deletion of disulfide A7–B7? To answer this question, an insulin analog with both A7Cys and B7Cys replaced by Glu, which has a long side-chain and a negative charge, was prepared by protein engineering, and its structure and activity were analyzed. Both the structure and activity of the present analog are very similar to that of the mutant with disulfide A7–B7 replaced by Ser, but significantly different from that of wild-type insulin. The present results suggest that removal of disulfide A7–B7 will result in serious loss of biological activity and the native conformation of insulin, even if the disulfide is replaced by residues with a negative charge.

Peptide models of four possible insulin folding intermediates with two disulfides

The single-chain insulin (PIP) can spontaneously fold into native structure through preferred kinetic intermediates. During refolding, pairing of the first disulfide A20-B19 is highly specific, whereas pairing of the second disulfide is likely random because two two-disulfide intermediates have been trapped. To get more details of pairing property of the second disulfide, four model peptides of possible folding intermediates with two disulfides were prepared by protein engineering, and their properties were analyzed. The four model peptides were named [A20-B19, A7-B7]PIP, [A20-B19, A6-B7]PIP, [A20-B19, A6-A11]PIP, and [A20-B19, A7-A11]PIP according to their remaining disulfides. The four model peptides all adopt partially folded structure with moderate conformational differences. In redox buffer, the disulfides of the model peptides are more easily reduced than those of the wild-type PIP. During in vitro refolding, the reduced model peptides share similar relative folding rates but different folding yields: The refolding efficiency of the reduced [A20-B19, A7-A11]PIP is about threefold lower than that of the other three peptides. The present results indicate that the folding intermediates corresponding to the present model peptides all adopt partially folded conformation, and can be formed during PIP refolding, but the chance of forming the intermediate with disulfide [A20-B19, A7-A11] is much lower than that of forming the other three intermediates.

[Study of protective effect of leech, radix Salviae miltiorrhizae and its composite recipe on vascular endothelial cells in rats with blood stasis syndrome]

OBJECTIVE

To study the protective effect for Chinese medicine of promoting blood circulation and removing blood stasis (PBCRBS) on vascular endothelial cells (VEC) in rats, aiming at further research on the mechanism of blood stasis syndrome and PBCRBS.

METHOD

Establishing a model of blood stasis with endothelial damage by means of giving rats an injection of adrenalin and making it swim in ice-cold water, then measuring the number of circulating endothelial cells (CEC) in whole blood and rheology. Moreover observing the change of the above indexes after the rats have taken Leech, Radix salviae miltrorrhizae (RSM) and its composite recipe for 5 days or 10 days.

RESULT

It could increase the number of CEC accompanied by whole blood viscosity, fibrinogen and hematocrit in rats with blood stasis. But for groups taking Chinese medicine, the number of CEC was decreased distinctively and blood rheology was improved.

CONCLUSION

The rat with blood stasis syndrome suffered from obvious injury of VEC. The Leech, RSM and its composite recipe could protect VEC.

Genetic analysis of West Nile New York 1999 encephalitis virus

Analysis of the genome of the flavivirus responsible for the 1999 New York City encephalitis epidemic cloned from human brain by reverse-transcription polymerase chain reaction Indicates its identity as a lineage I West Nile virus (WNV; WNV-NY1999) closely related to WNVs previously isolated In the Middle East.

Identification of a Kunjin/West Nile-like flavivirus in brains of patients with New York encephalitis

Molecular analysis of brains from patients of the recent New York City encephalitis outbreak reveals the presence of a flavivirus not previously described in the Americas.

Hepatitis A virus capsid protein VP1 has a heterogeneous C terminus

Hepatitis A virus (HAV) encodes a single polyprotein which is posttranslationally processed into the functional structural and nonstructural proteins. Only one protease, viral protease 3C, has been implicated in the nine protein scissions. Processing of the capsid protein precursor region generates a unique intermediate, PX (VP1-2A), which accumulates in infected cells and is assumed to serve as precursor to VP1 found in virions, although the details of this reaction have not been determined. Coexpression in transfected cells of a variety of P1 precursor proteins with viral protease 3C demonstrated efficient production of PX, as well as VP0 and VP3; however, no mature VP1 protein was detected. To identify the C-terminal amino acid residue of HAV VP1, we performed peptide sequence analysis by protease-catalyzed [18O]H2O incorporation followed by liquid chromatography ion-trap microspray tandem mass spectrometry of HAV VP1 isolated from purified virions. Two different cell culture-adapted isolates of HAV, strains HM175pE and HM175p35, were used for these analyses. VP1 preparations from both virus isolates contained heterogeneous C termini. The predominant C-terminal amino acid in both virus preparations was VP1-Ser274, which is located N terminal to a methionine residue in VP1-2A. In addition, the analysis of HM175pE recovered smaller amounts of amino acids VP1-Glu273 and VP1-Thr272. In the case of HM175p35, which contains valine at amino acid position VP1-273, VP1-Thr272 was found in addition to VP1-Ser274. The data suggest that HAV 3C is not the protease responsible for generation of the VP1 C terminus. We propose the involvement of host cell protease(s) in the production of HAV VP1.

trans-encapsidation of a poliovirus replicon by different picornavirus capsid proteins

A trans-encapsidation assay was established to study the specificity of picornavirus RNA encapsidation. A poliovirus replicon with the luciferase gene replacing the capsid protein-coding region was coexpressed in transfected HeLa cells with capsid proteins from homologous or heterologous virus. Successful trans-encapsidation resulted in assembly and production of virions whose replication, upon subsequent infection of HeLa cells, was accompanied by expression of luciferase activity. The amount of luciferase activity was proportional to the amount of trans-encapsidated virus produced from the cotransfection. When poliovirus capsid proteins were supplied in trans, >2 x 10(6) infectious particles/ml were produced. When coxsackievirus B3, human rhinovirus 14, mengovirus, or hepatitis A virus (HAV) capsid proteins were supplied in trans, all but HAV showed some encapsidation of the replicon. The overall encapsidation efficiency of the replicon RNA by heterologous capsid proteins was significantly lower than when poliovirus capsid was used. trans-encapsidated particles could be completely neutralized with specific antisera against each of the donor virus capsids. The results indicate that encapsidation is regulated by specific viral nucleic acid and protein sequences.

Replication of hepatitis A viruses with chimeric 5' nontranslated regions

The role of the 5' nontranslated region in the replication of hepatitis A virus (HAV) was studied by analyzing the translation and replication of chimeric RNAs containing the encephalomyocarditis virus (EMCV) internal ribosome entry segment (IRES) and various lengths (237, 151, or 98 nucleotides [nt]) of the 5'-terminal HAV sequence. Translation of all chimeric RNAs, truncated to encode only capsid protein sequences, occurred with equal efficiency in rabbit reticulocyte lysates and was much enhanced over that exhibited by the HAV IRES. Transfection of FRhK-4 cells with the parental HAV RNA and with chimeric RNA generated a viable virus which was stable over continuous passage; however, more than 151 nt from the 5' terminus of HAV were required to support virus replication. Single-step growth curves of the recovered viruses from the parental RNA transfection and from transfection of RNA containing the EMCV IRES downstream of the first 237 nt of HAV demonstrated replication with similar kinetics and similar yields. When FRhK-4 cells infected with recombinant vaccinia virus producing SP6 RNA polymerase to amplify HAV RNA were transfected with plasmids coding for these viral RNAs or with subclones containing only HAV capsid coding sequences downstream of the parental or chimeric 5' nontranslated region, viral capsid antigens were synthesized from the HAV IRES with an efficiency equal to or greater than that achieved with the EMCV IRES. These data suggest that the inherent translation efficiency of the HAV IRES may not be the major limiting determinant of the slow-growth phenotype of HAV.

Antibodies against viral nonstructural proteins in response to infection with poliovirus

Sera from recent and past cases of poliomyelitis as well as from healthy subjects vaccinated with live attenuated poliovirus, all contain antibodies to poliovirus nonstructural proteins. Reactivity of these antisera with nonstructural protein antigens present in virus-infected HeLa cells or translated from cDNA transcripts in rabbit reticulocyte lysates was sometimes sensitive to denaturation of the antigens. The finding of antibodies to nonstructural proteins of poliovirus and other viruses should have applications in the development of diagnostic assays for virus infection and may have implications for future vaccine design.

Expression of hepatitis A virus precursor protein P3 in vivo and in vitro: polyprotein processing of the 3CD cleavage site

Hepatitis A virus (HAV) cDNAs encoding the P3 region proteins were expressed in vivo and in vitro to characterize the HAV 3D protein and to identify the cleavage site between 3C and 3D. Protein coding sequences were placed under control of a T7 promoter and an EMCV translational initiation signal. T7 RNA polymerase was provided by simultaneous infection of transfected BS-C-1 cells with a recombinant vaccinia virus vTF7-3 (T. R. Fuerst et al., Proc. Natl. Acad. Sci. USA 83, 8122-8126, 1986). Efficient synthesis and processing of P3 proteins occurred to yield 3CD (78 kDa), 3D (54 kDa), 3ABC (33 kDa), 3BC (25 kDa), and 3C (23 kDa). Similar products were produced by translation of T7 transcripts in a rabbit reticulocyte lysate in vitro. The 3C/D cleavage site was mapped by comparing the mobility of 3D in SDS-PAGE with 3D proteins engineered to begin at each of the two proposed cleavage sites; in addition, direct N-terminal sequencing of radiolabeled 3D protein from translation in vitro was performed. The results showed that 3D was formed by cleavage at the glutamine-arginine (Q/R) pair at position 1738 and 1739 of the HAV polyprotein. HAV 3D protein produced by autocatalytic cleavage of P3 precursor proteins in BS-C-1 cells is virtually completely insoluble and sediments after low-speed centrifugation. This is in contrast to the poliovirus 3D protein, produced from a similar construct, a significant portion of which remains soluble. Extracts containing the poliovirus 3D protein manifested high levels of RNA-dependent RNA polymerase activity, whereas those containing the HAV 3D protein showed no detectable activity by the same assay.

Analysis of a potential myristoylation site in hepatitis A virus capsid protein VP4

The VP4 capsid protein of several picornaviruses has been shown to be myristoylated at an N-terminal glycine residue. Myristoylation occurs after removal of an initial methionine residue or a leader peptide, resulting in the exposure of an N-terminal eight amino acid myristoylation signal including a consensus G-x-x-x-T/S motif. Analysis of the amino acid sequence of hepatitis A virus (HAV) capsid protein reveals a potential myristoylation site beginning at position 5 of the VP4 sequence. To assess the significance of this apparent myristoylation signal, mutations were engineered (G to A; T to N) to alter the consensus sequence as well as the potential cleavage site that would be required to remove the short leader. An additional mutant was constructed in which the proposed leader was deleted. Expression of these HAV sequences in BS-C-1 cells showed that leader cleavage did not occur in the wild-type or mutant proteins, although the threonine to asparagine mutation resulted in reduced translation and processing efficiency. Transfection of BS-C-1 or FRhK-4 cells with transcripts derived from the wild-type or mutagenized cDNA clones gave rise to infectious virus, with no detectable incorporation of myristate. The results indicate that HAV does not require leader cleavage and myristoylation of VP4 for growth in cultured cells.

Antibody response to nonstructural proteins of hepatitis A virus following infection

The nonstructural proteins of hepatitis A virus (HAV), produced during active virus replication, are alternative antigens that could be used to differentiate disease from inactivated vaccine-induced antibodies. An assay based on immune precipitation of proteins translated from transcripts of the P2 region of viral cDNA was used to evaluate the development of antibodies after natural infection or vaccination. Antibodies against P2 proteins were found in all sera from clinical cases of hepatitis A following the acute phase. Chimpanzees vaccinated with inactivated or cell-adapted HAV had no detectable antibodies against P2 products, either before or after wild type virus challenge. A serosurvey of sera positive for total anti-HAV (HAVAB, Abbott Laboratories, North Chicago) suggested that some individuals had no detectable antibodies to the P2 antigen by immune precipitation. These results were attributed to the lower sensitivity of the immunoprecipitation assay, since antibodies to capsid proteins, as measured by immunoprecipitation, were also not detected in most of these sera.

Identification of the hepatitis A virus internal ribosome entry site: in vivo and in vitro analysis of bicistronic RNAs containing the HAV 5' noncoding region

Hepatitis A virus (HAV), a RNA virus of positive polarity, contains a long 5' noncoding region (5'NCR) that lacks the characteristic m7GpppN cap group of most eukaryotic messages. By creating bicistronic constructs that contain the bacterial chloramphenicol acetyltransferase gene followed by the HAV 5'NCR and the luciferase gene we have demonstrated by assaying in vitro and in vivo that ribosome entry for translation initiation occurs via binding to sequences within the HAV 5'NCR. Using mutations created within this region we have identified that the HAV internal ribosome entry site (IRES) is located downstream of nucleotide 45 and including sequences up to nucleotide 734 of the HAV 5'NCR. Translation of a number of mutant constructs both in vitro in a rabbit reticulocyte lysate and in vivo by transfection of the cDNAs into BS-C-1 cells in the presence of the recombinant vaccinia virus, vTF7-3, gave similar results. However, a 4-nucleotide insertion at base 628 showed an increased activity over wild-type when transfected into BS-C-1 cells that was not seen in vitro. This increase in activity correlated with an increase in luciferase gene product as assayed by immunoprecipitations of [35S]methionine radiolabeled cells. Comparison of mono- and bicistronic RNAs that were synthesized with or without a m7GpppG cap group showed a competition for ribosome binding when translated in a rabbit reticulocyte lysate system. The presence of the cap group on the RNA 5'terminus of the RNA led to a greater ability of this RNA to translate than the RNA containing the HAV IRES.

Primary cleavage of the HAV capsid protein precursor in the middle of the proposed 2A coding region

Portions of the P1 and P2 hepatitis A virus (HAV) polyprotein were generated by in vitro translation of cDNA transcripts and analyzed for a primary cleavage reaction that would release the capsid protein precursor. No autocatalytic activity was observed on either side of the 2A coding sequence. Incubation of these proteins with an extract containing active HAV 3C protease, however, resulted in cleavage at a position approximately 40 amino acids downstream of the previously proposed P1-2A junction. This cleavage site likely accounts for the VP1-containing proteins of approximately 38-40 kDa observed in HAV-infected cells.

Polyprotein processing in cis and in trans by hepatitis A virus 3C protease cloned and expressed in Escherichia coli

To determine the P3 region protein-processing sites cleaved by the hepatitis A virus 3C protease, a nested set of constructs containing a portion of 3A (3A* [the asterisk denotes an incomplete protein]), 3B and 3C and various amounts of 3D, fused in frame to Escherichia coli TrpE-coding sequences under control of the tryptophan promoter, was made. Additional plasmids that encoded a portion of 2C (2C*) and the P3 proteins, including complete or incomplete 3D sequences, were constructed. After induction, E. coli containing these recombinant plasmids produced high levels of fusion proteins as insoluble aggregates. 3C-mediated cleavage products were identified by comparison of expression with a matching set of plasmids, containing an engineered mutation in 3C. Cleavage products were detected by immunoblot analyses by using antisera against the TrpE protein, against 3D*, and against 3CD*. Scissile bonds were determined by N-terminal amino acid sequencing of the proteins formed by cleavage. The results showed that when a portion of 2C was present, the primary cleavage by the 3C protease was between 2C and 3A, and the cleavage site was QG, as predicted by J. I. Cohen, J. R. Ticehurst, R. H. Purcell, A. Buckler-White, and B. M. Baroudy, J. Virol. 61:50-59, 1987. Very little further cleavage of the released P3 protein was detected. When the fusion protein contained no 2C and included only 3A*-to-3D sequences, efficient cleavage occurred between 3B and 3C, at the QS pair, also as predicted by Cohen et al. (J. Virol. 61:50-59, 1987). The latter proteins were also cleaved between 3C and 3D, but less efficiently than between 3B and 3C. Extracts of bacteria expressing proteins from 3A* to 3D also cleaved a radiolabelled hepatitis A virus substrate containing VP1*2ABC* sequences in trans.

Host antibody response to viral structural and nonstructural proteins after hepatitis A virus infection

Subgenomic hepatitis A virus (HAV) RNA sequences were translated in vitro to produce proteins representing the structural (P1) and nonstructural (P2 and P3) domains of the viral polyprotein. These proteins were used as antigens to detect the presence of antibodies in sera from acute and convalescent humans and an experimentally infected chimpanzee. All infected individuals tested had antibodies that recognized uncleaved P1 proteins as well as nonstructural proteins. Antibodies in sera from infected individuals recognized conformation-dependent epitopes that were sensitive to SDS and heat treatment. Time-course studies of the experimentally infected chimpanzee showed that antibodies to the HAV proteins were detectable between 24 and 31 days after infection and persisted for greater than 6 months. Human sera remained positive for antibodies to both structural and nonstructural antigens for at least 2 1/2 years. The data suggest that HAV nonstructural proteins could be used as serologic markers for HAV diagnosis and for evaluating field trials of inactivated vaccines.

Serological approaches to distinguish immune response to hepatitis A vaccine and natural infection

Currently, the immune status of an individual exposed to hepatitis A virus (HAV) is determined by assays which measure antibodies against the capsid proteins. These assays indicate exposure to the viral capsid that could result from either infection or from vaccination. Recent data indicate that proteins from the non-structural genome region of the virus (P2 or P3), which are only produced during active virus replication, generate antibodies after clinical disease. A sub-genomic cDNA segment of HAV corresponding to the P2 region was used for in vitro transcription-translation followed by immune precipitation of the translated products under non-denaturing conditions. Serial serum specimens from experimentally infected chimpanzees and humans naturally infected with hepatitis A verified the development of antibodies to P2 proteins following infection. A serosurvey of individuals positive for antibodies to the HAV capsid (HAV AB assay, Abbott Laboratories) revealed that 50-60% of children and 16-32% of adults had no detectable antibodies to the P2 antigen by immune precipitation. These results may reflect subclinical infections resulting in a lower level of antibodies against the non-structural antigens or may represent a greater sensitivity of the competitive assay (HAV AB) used to detect capsid antibodies compared to the immunoprecipitation assay used to detect non-structural antigens.

Translation of hepatitis A virus RNA in vitro: aberrant internal initiations influenced by 5' noncoding region

Hepatitis A virus (HAV) RNAs were translated in vitro in rabbit reticulocyte lysates. The pattern of proteins synthesized from full-length HAV RNA was highly complex, consisting of a continuous spectrum of polypeptides ranging from less than 20,000 to greater than 200,000 Da. The pattern was not significantly altered by varying incubation times, ion, or other reaction parameters, or by the addition of HeLa or BS-C-1 cell extracts to the translation reactions. Plasmids engineered with mutations in the 3C coding region produced transcripts which directed the synthesis of the same overall pattern of polypeptide products as those transcribed from wild-type sequences, suggesting that protein processing by 3C did not generate the complex set of protein products. Translation of RNA containing only the P3 coding region of HAV, directly adjacent to the HAV 5' noncoding region, generated a set of protein products which precisely matched a subset of those synthesized from full-length HAV RNA. The translation products of P3 RNA, full-length RNA, and mutant 3C-containing RNAs were analyzed by immunoprecipitation with antisera specific for 3D, VP1, and 2C sequences; several products were subjected to N-terminal sequence analysis. All together, the results demonstrate that translation of HAV RNA in rabbit reticulocyte lysates initiates predominantly at a large number of internal AUG codons, especially those in the P3 coding region. A minor population of products is initiated from sites in the P1 and P2 regions. The latter proteins undergo some proteolytic processing, at unidentified sites, catalyzed by 3C protein sequences. Replacement of the HAV 5' noncoding region with encephalomyocarditis virus 5' end sequences increased initiation at the correct polyprotein start site and both reduced and altered the products generated by internal initiation.

Proteolytic activity of hepatitis A virus 3C protein

Although the genome organization and overall structure of hepatitis A virus are similar to those of other picornaviruses, nothing is known about the protein-processing pathways used by this virus to generate its capsid and nonstructural proteins from the polyprotein precursor. RNA transcripts of cloned hepatitis A virus cDNAs representing parts of the P2 and P3 regions of the genome were translated in rabbit reticulocyte lysates in vitro, and the translation products were analyzed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis before and after immunoprecipitation with specific antisera. Pulse-chase experiments demonstrated rapid cleavage at the P2-P3 junction, followed by further but incomplete processing at the 3C-3D junction. Mutation of the 3C coding sequence eliminated all cleavages. Efforts to demonstrate intermolecular cutting of the P2-P3 cleavage site by active 3C or 3CD sequences were unsuccessful; thus, it is likely that this cleavage occurs by intramolecular reaction, in cis.

Crystal-Structures of 2 3-Substituted 10,11-Dimethoxy-1,2,3,4,5,6-Hexahydro-7,9-etheno-3-benzazecine Derivatives

The title compounds are 3-aza[6](1,7)-naphthalenophanes with 3-Me and 3-CO2Me substituents, C18H23NO2 and C19H23NO4; in the former the chemical shift of the naphthalene hydrogen enclosed by the medium nitrogen-containing ring is the highest yet observed in a derivative of this type ( σ 9.33). In order to examine the environment of this hydrogen atom and the expected associated naphthalene ring distortions in both compounds, single-crystal X-ray structure determinations have been carried out at 295 K showing the transannular H…N distance in the methyl derivative to be remarkably short at 2.08(2) � . Crystals are triclinic, P1, a 11.683(3), b 10.846(3), c 6.729(2) �, α 90.08(2), β 93.33(2), γ 112.88 Z 2; R was 0.041 for 1378 'observed' reflections. Crystals of the 3-CO2Me derivative are also triclinic, P1, a 12.587(9), b 10.650(4), c 6.758(3) � , a 91.91(3), β 100.51(4), γ 104.74(5)° Z 2; R 0.067 for 1267 'observed' reflections.