H9N2 avian influenza viruses circulate worldwide in poultry and have sporadically infected humans, raising concern whether H9N2 viruses have pandemic potential. Here, we use a guinea pig model to examine whether serial passage results in adaptive viral changes that confer a transmissible phenotype to a wild-type H9N2 virus. After nine serial passages of an H9N2 virus through guinea pigs, productive transmission by direct contact occurred in 2/3 guinea pig pairs. The efficiency of transmission by direct contact increased following the fifteenth passage and occurred in 3/3 guinea pig pairs. In contrast, airborne transmission of the passaged virus was less efficient and occurred in 1/6 guinea pig pairs and 0/6 ferret pairs after the fifteenth passage. Three amino acid substitutions, HA1-Q227P, HA2-D46E, and NP-E434K, were sufficient for contact transmission in guinea pigs (2/3 pairs). The two HA amino acid substitutions enhanced receptor binding to α2,3-linked sialic acid receptors. Additionally, the HA2-D46E substitution increased virus thermostability whereas the NP-E434K mutation enhanced viral RNA polymerase activity in vitro. Our findings suggest that adaptive changes that enhance viral receptor binding, thermostability, and replicative capacity in mammalian cells can collectively enhance the transmissibility of H9N2 AIVs by direct contact in the guinea pig model.
() type 2 is an extremely important Gram-positive bacterial pathogen that can cause human or swine endocarditis, meningitis, bronchopneumonia, arthritis and sepsis. Catabolite control protein A (CcpA) is a major transcriptional regulator in type 2 that functions in catabolite control, specifically during growth on glucose or galactose. The regulation of central metabolism can affect the virulence of bacteria. In the present study, a metabolomics approach was used along with principal components analysis (PCA) and partial least-squares-discriminant analysis (PLS-DA) models and 37 metabolites were found that differed substantially between native and a mutant lacking CcpA. These results showed that CcpA is an important protein in type 2 for studying bacterial protein function.
Abstract.Catabolite control protein A (CcpA) serves a key function in the catabolism of Streptococcus suis serotype 2 (S. suis 2) by affecting the biological function and metabolic regulatory mechanisms of this bacterium. The aim of the present study was to identify variations in CcpA expression in S. suis 2 using gene expression profile analysis. Using sequencing and functional analysis, CcpA was demonstrated to play a regulatory role in the expression and regulation of virulence genes, carbon metabolism and immunoregulation in S. suis 2. Gene Ontology and Kyto Encyclopedia of Genes and Genomes analyses indicated that CcpA in S. suis 2 is involved in the regulation of multiple metabolic processes. Furthermore, combined analysis of the transcriptome and metabolite data suggested that metabolites varied due to the modulation of gene expression levels under the influence of CcpA regulation. In addition, metabolic network analysis indicated that CcpA impacted carbon metabolism to a certain extent. Therefore, the present study has provided a more comprehensive analysis of the role of CcpA in the metabolic regulation of S. suis 2, which may facilitate future investigation into this mechanism. Furthermore, the results of the present study provide a foundation for further research into the regulatory function of CcpA and associated metabolic pathways in S. suis 2.
The catabolite control protein A (ccpA) regulates the carbon metabolism in Streptococcus suis type 2 and has pleiotropic regulatory functions in bacterial virulence and transcription. The present study systematically investigated ccpA activity in Streptococcus suis type 2 using isobaric tag for relative and absolute quantification (iTRAQ) liquid chromatography‑tandem mass spectrometry‑based proteomics. Gene Ontology and Kyoto Encyclopedia of Genes and Genomes analyses demonstrated that ccpA is an important protein for the regulation of metabolism, virulence and immune pathways in Streptococcus suis type 2. The present study therefore expanded the current understanding of the effects of ccpA on virulence, metabolic regulation and transcription in Streptococcus suis type 2 and other important pathogens.
Abstract. In this paper the failure sets and symptom sets of the problem for a 1000MW unit were determined. On the basis of distinguishing the precipitous decline and slow decline of vacuum, the calculation model of the state quantization value of every symptom parameter was established and the fault characteristic vector of the lower vacuum of the condenser was obtained by the simulation test of the unit. Based on BP neural network, the fault diagnosis model of condenser was established, and the low vacuum fault of the unit was diagnosed. The results show that the fault diagnosis of condensers can be used in the actual unit operation according to the fault theory domain feature vector of 1000MW unit.
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