The role of PA-X C-terminal 20 residues of classical swine influenza virus in its replication and pathogenicity

PA-X is a fusion protein encoded by a +1 frameshifted open reading frame (X-ORF) in PA gene. The X-ORF can be translated in full-length (61 amino acids, aa) or truncated (41 aa) form. However, the role of C-Terminal 20 aa of PA-X in virus function has not yet been fully elucidated. To this end, we constructed the contemporary influenza viruses with full and truncated PA-X by reverse genetics to compare their replication and pathogenicity. The full-length PA-X virus in MDCK and human A549 cells conferred 10- to 100-fold increase in viral replication, and more virulent and caused more severe inflammatory responses in mice relative to corresponding truncated PA-X virus, suggesting that the terminal 20 aa could play a role in enhancing viral replication and contribute to virulence.

Protective efficacy of a bivalent inactivated reassortant H1N1 influenza virus vaccine against European avian-like and classical swine influenza H1N1 viruses in mice

The classical swine (CS) H1N1 swine influenza virus (SIVs) emerged in humans as a reassortant virus that caused the H1N1 influenza virus pandemic in 2009, and the European avian-like (EA) H1N1 SIVs has caused several human infections in European and Asian countries. Development of the influenza vaccines that could provide effective protective efficacy against SIVs remains a challenge. In this study, the bivalent reassortant inactivated vaccine comprised of SH1/PR8 and G11/PR8 arboring the hemagglutinin (HA) and neuraminidase (NA) genes from prevalent CS and EA H1N1 SIVs and six internal genes from the A/Puerto Rico/8/34(PR8) virus was developed. The protective efficacy of this bivalent vaccine was evaluated in mice challenged with the lethal doses of CS and EA H1N1 SIVs. The result showed that univalent inactivated vaccine elicited high-level antibody against homologous H1N1 viruses while cross-reactive antibody responses to heterologous H1N1 viruses were not fully effective. In a mouse model, the bivalent inactivated vaccine conferred complete protection against lethal challenge doses of EA SH1 virus or CS G11 virus, whereas the univalent inactivated vaccine only produced insufficient protection against heterologous SIVs. In conclusion, our data demonstrated that the reassortant bivalent inactivated vaccine comprised of SH1/PR8 and G11/PR8 could provide effective protection against the prevalent EA and CS H1N1 subtype SIVs in mice.

Protective efficacy of a high-growth reassortant H1N1 influenza virus vaccine against the European Avian-like H1N1 swine influenza virus in mice and pigs

Swine influenza A viruses (SIVs) causing outbreaks of acute, highly contagious respiratory disease in pigs also pose a potential threat to public health. European avian-like H1N1 (EA H1N1) SIVs are the predominant circulating viruses in pigs in China and also occasionally cause human infection. In this study, a high-growth reassortant virus (SH1/PR8), with HA and NA genes from a representative EA H1N1 isolate A/Swine/Shanghai/1/2014 (SH1) in China and six internal genes from the high-growth A/Puerto Rico/8/34 (PR8) virus, was generated by plasmid-based reverse genetics and tested as a candidate seed virus for the preparation of inactivated vaccine. The protective efficacy of inactivated SH1/PR8 was evaluated in mice and pigs challenged with wild-type SH1 virus. After primer and boost vaccination, the SH1/PR8 vaccine induced high-level hemagglutination inhibiting (HI) antibodies, IgG antibodies, and neutralization antibodies in mice and pigs. Mice and pigs in the vaccinated group showed less clinical phenomena and pathological changes than those in the unvaccinated group. In conclusion, the inactivated high-growth reassortant vaccine SH1/PR8 could induce high antibody levels and complete protection is expected against SH1 wild type SIV, and protection against heterologous EA H1N1 SIV needs further evaluation.

The PB2-K627E mutation attenuates H3N2 swine influenza virus in cultured cells and in mice

PB2-627K is an important amino acid that determines the virulence of some influenza A viruses. However, it has not been experimentally investigated in the H3N2 swine influenza virus. To explore the potential role of PB2-K627E substitution in H3N2 swine influenza virus, the growth properties and pathogenicity between H3N2 swine influenza virus and its PB2-K627E mutant were compared. For the first time, our results showed that PB2-K627E mutation attenuates H3N2 swine influenza virus in mammalian cells and in mice, suggesting that PB2-627K is required for viral replication and pathogenicity of H3N2 swine influenza virus.

[Rapid detection of alpha-globin gene αααanti-3.7 triplets with droplet digital PCR]

OBJECTIVE

To establish a rapid method for detection of alpha-globin gene ααα^anti-3.7 based on droplet digital PCR (ddPCR) technique.

METHODS

The differential sequence between the X1 and Y1 box of α1 gene was selected as the amplicon of the target gene with β-actin as the reference gene. The specific primers and TaqMan probes were designed, and then a quantitative method for detecting the copy number was established based on ddPCR technique. The sensitivity and accuracy of the method were evaluated by detecting 28 samples of known genotypes and 60 clinical samples.

RESULTS

The ddPCR-based method accurately identified the genotypes of all the 28 samples with known genotypes and detected 5 cases of αα/ααα^anti-3.7 from the 60 clinical samples, and the results were verified by MLPA. The sensitivity and accuracy of this method were both 100% for detecting alpha-globin gene ααα^anti-3.7.

CONCLUSION

This ddPCR-based method for detecting ααα^anti-3.7 triplet can be applied for population screening and in routine clinical molecular diagnosis with simple operation, rapid analysis and accurate results.

Novel triple-reassortant H1N1 swine influenza viruses in pigs in Tianjin, Northern China

Pigs are susceptible to both human and avian influenza viruses and therefore have been proposed to be mixing vessels for the generation of pandemic influenza viruses through reassortment. In this study, for the first time, we report the isolation and genetic analyses of three novel triple-reassortant H1N1 swine influenza viruses from pigs in Tianjin, Northern China. Phylogenetic analysis showed that these novel viruses contained genes from the 2009 pandemic H1N1 (PB2, PB1, PA and NP), Eurasian swine (HA, NA and M) and triple-reassortant swine (NS) lineages. This indicated that the reassortment among the 2009 pandemic H1N1, Eurasian swine and triple-reassortant swine influenza viruses had taken place in pigs in Tianjin and resulted in the generation of new viruses. Furthermore, three human-like H1N1, two classical swine H1N1 and two Eurasian swine H1N1 viruses were also isolated during the swine influenza virus surveillance from 2009 to 2013, which indicated that multiple genetic lineages of swine H1N1 viruses were co-circulating in the swine population in Tianjin, China. The emergence of novel triple-reassortant H1N1 swine influenza viruses may be a potential threat to human health and emphasizes the importance of further continuous surveillance.

Size selectivity between gap junction channels composed of different connexins

Gap junction channels are traditionally viewed as large, nonspecific pores connecting cells. Recently the diversity in the connexin family has drawn more attention to their permeability characteristics. Several studies have shown that both size and charge contribute to the permeability of gap junctional channels. We have used a graded series of neutral polyethylene glycol probes (PEGs), which eliminate charge contribution completely, to specifically assess the physical exclusion limits of gap junction channels formed by different connexins. Cx 26, 32 and 37 were expressed in paired Xenopus oocytes to form homotypic gap junctional channels. PEG probes were perfused intracellularly into one side of the oocyte pair. A reversible drop in conductance of the gap juctional channels indicated that the probe was small enough to enter the pore and hinder ion flux. Our data suggest that Cx32 channels have a size cut-off between PEG 400 (11.2 A) and PEG 300 (9.6 A) despite their relatively small single channel conductance (approximately 55 pS). Cx26 channels (approximately 130 pS single channel conductance) have a size exclusion limit around PEG 200 (8.0 A), while Cx37 channels show the most restricted size cut-off between PEG 200 (8.0 A) and TriEG (6.8 A), despite having the largest unitary conductance (approximately 300 pS).

Epidermal growth factor receptor vIII enhances tumorigenicity in human breast cancer

Epidermal growth factor receptor vIII (EGFRvIII) is a tumor-specific, ligand-independent, constitutively active variant of the EGFR. Its expression has been detected in gliomas and various other human malignancies. To more fully characterize the function and potential biological role of EGFRvIII in regulating cell proliferation and in tumorigenesis, we transfected EGFRvIII cDNA into a nontumorigenic, interleukin 3 (IL-3)-dependent murine hematopoietic cell line (32D cells). We observed 32D cells expressing high levels of EGFRvIII (32D/EGFRvIII P5) to be capable of abrogating the IL-3-dependent pathway in the absence of ligands. In contrast, the parental cells, 32D/EGFR, 32D/ErbB-4, and 32D/ErbB-2+ErbB-3 cells, all depended on IL-3 or EGF-like ligands for growth. 32D/EGFRvIII P5 cells subjected to long-term culture conditions in the absence of IL-3 revealed further elevation of EGFRvIII expression levels. These results suggested that the IL-3-independent phenotype is mediated by EGFRvIII. The level of expression is a critical driving force for the IL-3-independent phenotype. Dose-response analysis revealed 32D/EGFRvIII cells to require 500-fold higher concentrations (50 ng/ml) of EGF to further stimulate the EGF-mediated proliferation than in the 32D/EGFR cells (100 pg/ml). Similar effects were also observed in beta-cellulin-mediated proliferation. Moreover, 32D cells expressing high levels of EGFRvIII formed large tumors in nude mice, even when no exogenous EGF ligand was administered. In contrast, no tumors grew in mice injected with 32D/EGFR, 32D/ErbB-4, and 32D/ErbB-2+ErbB-3 cells or low-expressing clone 32D/EGFRvIII C2 cells or the parental 32D cells. The changes of the ligand specificity support the notion for an altered conformation of EGFRvIII to reveal an activated ligand-independent oncoprotein with tumorigenic activity analogous to v-erbB. These studies clearly demonstrate that EGFRvIII is capable of transforming a nontumorigenic, IL-3-dependent murine hematopoietic cell line (32D cells) into an IL-3-independent and ligand-independent malignant phenotype in vitro and in vivo. To delineate the biological significance of EGFRvIII in human breast cancer, we expressed EGFRvIII in the MCF-7 human breast cancer cell line. Expression of EGFRvIII in MCF-7 cells produced a constitutively activated EGFRvIII receptor. Expression of EGFRvIII in MCF-7 cells also elevated ErbB-2 phosphorylation, presumably through heterodimerization and cross-talk. These MCF-7/EGFRvIII transfectants exhibited an approximately 3-fold increase in colony formation in 1% serum with no significant effect observed at higher percentages of serum. A similar result was also seen in anchorage-dependent assays. Furthermore, EGFRvIII expression significantly enhanced tumorigenicity of MCF-7 cells in athymic nude mice with P < 0.001. Collectively, these results provide the first evidence that EGFRvIII could play a pivotal role in human breast cancer progression.

The role of microvascular permeability in the mechanism for stunned myocardium in rats

The microvascular permeability of stunned myocardium in rats in vivo was studied with FITC-labeled albumin (FITC-BSA). It was found that 15 and 20 min of myocardial ischemia followed by 1 hr of reperfusion resulted in myocardial stunning. The concentrations of FITC-BSA in myocardial tissue were 240.6 +/- 7.8 (IS15) and 267.4 +/- 7.9 (IS20) micrograms/g myocardium in ischemic groups, respectively, which were significantly higher than those in the control group (166.0 +/- 7.9 micrograms/g myocardium; P < 0.01). In stunned groups, the concentrations were 224.8 +/- 11.8 (MS15) and 241.7 +/- 6.0 (MS20) micrograms/g myocardium, decreased from those in ischemic groups but still higher than those in control group by 35.4 and 45.6%, respectively. The more significant the concentration of FITC-BSA, the more serious the myocardial stunning. Electron microscopy revealed no significant vascular injury. The results suggest that the increase in microvascular permeability resulting from transient ischemia is functional and is involved in the pathogenesis of stunned myocardium.

Effect of glucocorticoid receptor (GR) blockade on endotoxemia in rats

To study the clinical significance of the decrease of glucocorticoid receptor (GR) in stress and shock, GR was blocked about 80% by mifepristone (RU38486), and the effects of the blockade on the pathological changes of endotoxemia were studied in rats. The results revealed that GR blockade may exacerbate the pathological and pathophysiological changes of endotoxemia: (1) the more rapid drop in arterial blood pressure, (2) the more severe pathological changes involving multiple organs, especially the lung and small intestine, (3) the increase of leukocyte adherence in venules and more pronounced rheological changes in the mesenteric microcirculation, and (4) the striking elevation of serum acid phosphatase (ACP), phospholipase A2 (PLA2) activity, and lipoperoxide (LPO). The changes of serum ACP, PLA2, and LPO in the rats with 80% GR blockade were more marked than in those with 50% GR blockade. Based on these findings, we propose that the decrease in GR during stress and shock might be a contributing factor in the pathogenesis of shock and multiple organ failure (MOF). The possible mechanisms of the above noted findings are discussed.

Effects of platelet-activating factor on rat mesenteric microcirculation

The actions of platelet-activating factor (PAF) on rat mesenteric microcirculation were studied by laser Doppler microscopy in vivo. PAF 0.2 -0.6 micrograms/kg iv produced a dose-related decrease in the blood flow velocity and an increase in the diameters of the mesenteric arterioles and venules. These responses were completely reversed by pretreatment with PAF receptor antagonist SRI 63441. The results suggest that PAF may be a mediator of microcirculatory disturbances in the disease conditions associated with excessive PAF release.

Triazine monomers and their adhesion to dentin

A series of 4,6-dichloro-1,3,5-triazines [e.g., 2-allylamino-(ADT), diallylamino-(DADT), 2-N-p-allyloxyphenylamino-, 2-N-allyl-N-phenylamino-, and 2-N-allyl-N-p-tolylamino-4,6-dichloro-1,3,5-triazine] was synthesized and characterized by IR, NMR, and mass spectrometry. These monomers have chlorine atoms that can react with NH2 or OH groups and double bonds capable of copolymerization. Aniline reacted readily with ADT and DADT, ethanol reacted with ADT, but acetone, H2O, and DMF did not react with either triazine. It appears that ADT or DADT will react with dentinal collagen through NH2 or OH groups in the peptide side-chains. An aprotic solvent should be used for ADT or DADT, but absolute dryness in clinical usage is not essential because of the slow hydrolysis of ADT and DADT. Stability of the N-di-substituted amino derivative (DADT) is greater than that of the mono-substituted compound (ADT), which may isomerize. ADT and methyl methacrylate were copolymerized at 37 degrees C with amine-peroxide. ADT solutions enhanced the adhesive strength of restorative resin to dentin. Thus, monomers such as ADT and DADT appear to be promising dentin-bonding agents.