Porcine reproductive and respiratory syndrome virus infection triggers HMGB1 release to promote inflammatory cytokine production

AbstractThe high mobility group box 1 (HMGB1) protein is an endogenous damage-associated molecular pattern (DAMP) molecule involved in the pathogenesis of various infectious agents. Based on meta-analysis of all publicly available microarray datasets, HMGB1 has recently been proposed as the most significant immune modulator during the porcine response to porcine reproductive and respiratory syndrome virus (PRRSV) infection. However, the function of HMGB1 in PRRSV pathogenesis is unclear. In this study, we found that PRRSV infection triggers the translocation of HMGB1 from the nucleus to the extracellular milieu in MARC-145 cells and porcine alveolar macrophages. Although HMGB1 has no effect on PRRSV replication, HMGB1 promotes PRRSV-induced NF-κB activation and subsequent expression of inflammatory cytokines through receptors RAGE, TLR2 and TLR4. Our findings show that HMGB1 release, triggered by PRRSV infection, enhances the efficiency of virus-induced inflammatory responses, thereby providing new insights into the pathogenesis of PRRSV infection

Comparative genomic analyses of Mycoplasma hyopneumoniae pathogenic 168 strain and its high-passaged attenuated strain

Background: Mycoplasma hyopneumoniae is the causative agent of porcine enzootic pneumonia (EP), a mild, chronic pneumonia of swine. Despite presenting with low direct mortality, EP is responsible for major economic losses in the pig industry. To identify the virulence-associated determinants of M. hyopneumoniae, we determined the whole genome sequence of M. hyopneumoniae strain 168 and its attenuated high-passage strain 168-L and carried out comparative genomic analyses. Results: We performed the first comprehensive analysis of M. hyopneumoniae strain 168 and its attenuated strain and made a preliminary survey of coding sequences (CDSs) that may be related to virulence. The 168-L genome has a highly similar gene content and order to that of 168, but is 4,483 bp smaller because there are 60 insertions and 43 deletions in 168-L. Besides these indels, 227 single nucleotide variations (SNVs) were identified. We further investigated the variants that affected CDSs, and compared them to reported virulence determinants. Notably, almost all of the reported virulence determinants are included in these variants affected CDSs. In addition to variations previously described in mycoplasma adhesins (P97, P102, P146, P159, P216, and LppT), cell envelope proteins (P95), cell surface antigens (P36), secreted proteins and chaperone protein (DnaK), mutations in genes related to metabolism and growth may also contribute to the attenuated virulence in 168-L. Furthermore, many mutations were located in the previously described repeat motif, which may be of primary importance for virulence. Conclusions: We studied the virulence attenuation mechanism of M. hyopneumoniae by comparative genomic analysis of virulent strain 168 and its attenuated high-passage strain 168-L. Our findings provide a preliminary survey of CDSs that may be related to virulence. While these include reported virulence-related genes, other novel virulence determinants were also detected. This new information will form the foundation of future investigations into the pathogenesis of M. hyopneumoniae and facilitate the design of new vaccines

Enhanced effect of microdystrophin gene transfection by HSV-VP22 mediated intercellular protein transport

Background: Duchenne musclar dystrophy (DMD) is an X-linked recessive disease caused by mutations of dystrophin gene, there is no effective treatment for this disorder at present. Plasmidmediated gene therapy is a promising therapeutical approach for the treatment of DMD. One of the major issues with plasmid-mediated gene therapy for DMD is poor transfection efficiency and distribution. The herpes simplex virus protein VP22 has the capacity to spread from a primary transduced cell to surrounding cells and improve the outcome of gene transfer. To improve the efficiency of plasmid-mediated gene therapy and investigate the utility of the intercellular trafficking properties of VP22-linked protein for the treatment for DMD, expression vectors for C-terminal versions of VP22-microdystrophin fusion protein was constructed and the VP22-mediated shuttle effect was evaluated both in vitro and in vivo. Results: Our results clearly demonstrate that the VP22-microdystrophin fusion protein could transport into C2C12 cells from 3T3 cells, moreover, the VP22-microdystrophin fusion protein enhanced greatly the amount of microdystrophin that accumulated following microdystrophin gene transfer in both transfected 3T3 cells and in the muscles of dystrophin-deficient (mdx) mice. Conclusion: These results highlight the efficiency of the VP22-mediated intercellular protein delivery for potential therapy of DMD and suggested that protein transduction may be a potential and versatile tool to enhance the effects of gene delivery for somatic gene therapy of DMD.National Natural Science Foundation of China (30370510, 30170337); CMB Fund (4209347); the Key Project of the State Ministry of Public Health (2001321); and National Nature Science Foundation of China (30400322)

Comparative Genomics of Mycoplasma: Analysis of Conserved Essential Genes and Diversity of the Pan-Genome

Mycoplasma, the smallest self-replicating organism with a minimal metabolism and little genomic redundancy, is expected to be a close approximation to the minimal set of genes needed to sustain bacterial life. This study employs comparative evolutionary analysis of twenty Mycoplasma genomes to gain an improved understanding of essential genes. By analyzing the core genome of mycoplasmas, we finally revealed the conserved essential genes set for mycoplasma survival. Further analysis showed that the core genome set has many characteristics in common with experimentally identified essential genes. Several key genes, which are related to DNA replication and repair and can be disrupted in transposon mutagenesis studies, may be critical for bacteria survival especially over long period natural selection. Phylogenomic reconstructions based on 3,355 homologous groups allowed robust estimation of phylogenetic relatedness among mycoplasma strains. To obtain deeper insight into the relative roles of molecular evolution in pathogen adaptation to their hosts, we also analyzed the positive selection pressures on particular sites and lineages. There appears to be an approximate correlation between the divergence of species and the level of positive selection detected in corresponding lineages

Understanding Streptococcus suis serotype 2 infection in pigs through a transcriptional approach

<p>Abstract</p> <p>Background</p> <p><it>Streptococcus suis </it>serotype 2 (<it>S. suis </it>2) is an important pathogen of pigs. <it>S suis 2 </it>infections have high mortality rates and are characterized by meningitis, septicemia and pneumonia. <it>S. suis </it>2 is also an emerging zoonotic agent and can infect humans that are exposed to pigs or their by-products. To increase our knowledge of the pathogenesis of meningitis, septicemia and pneumonia in pigs caused by <it>S. suis </it>2, we profiled the response of peripheral blood mononuclear cells <b>(</b>PBMC), brain and lung tissues to infection with <it>S. suis </it>2 strain SC19 using the Affymetrix Porcine Genome Array.</p> <p>Results</p> <p>A total of 3,002 differentially expressed transcripts were identified in the three tissues, including 417 unique genes in brain, 210 in lung and 213 in PBMC. These genes showed differential expression (DE) patterns on analysis by visualization and integrated discovery (DAVID). The DE genes involved in the immune response included genes related to the inflammatory response (CD163), the innate immune response (TLR2, TLR4, MYD88, TIRAP), cell adhesion (CD34, SELE, SELL, SELP, ICAM-1, ICAM-2, VCAM-1), antigen processing and presentation (MHC protein complex) and angiogenesis (VEGF), together with genes encoding cytokines (interleukins). Five selected genes were validated by qRT-PCR analysis.</p> <p>Conclusions</p> <p>We studied the response to infection with <it>S. suis </it>2 strain SC19 by microarray analysis. Our findings confirmed some genes identified in previous studies and discovered numerous additional genes that potentially function in <it>S. suis </it>2 infections in vivo. This new information will form the foundation of future investigations into the pathogenesis of <it>S. suis</it>.</p

Functions of Coronavirus Accessory Proteins: Overview of the State of the Art

Coronavirus accessory proteins are a unique set of proteins whose genes are interspersed among or within the genes encoding structural proteins. Different coronavirus genera, or even different species within the same coronavirus genus, encode varying amounts of accessory proteins, leading to genus- or species-specificity. Though accessory proteins are dispensable for the replication of coronavirus in vitro, they play important roles in regulating innate immunity, viral proliferation, and pathogenicity. The function of accessory proteins on virus infection and pathogenesis is an area of particular interest. In this review, we summarize the current knowledge on accessory proteins of several representative coronaviruses that infect humans or animals, including the emerging severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), with an emphasis on their roles in interaction between virus and host, mainly involving stress response, innate immunity, autophagy, and apoptosis. The cross-talking among these pathways is also discussed

DEAD-Box RNA Helicase 21 (DDX21) Positively Regulates the Replication of Porcine Reproductive and Respiratory Syndrome Virus via Multiple Mechanisms

The porcine reproductive and respiratory syndrome virus (PRRSV) remains a persistent hazard in the global pig industry. DEAD (Glu-Asp-Ala-Glu) box helicase 21 (DDX21) is a member of the DDX family. In addition to its function of regulating cellular RNA metabolism, DDX21 also regulates innate immunity and is involved in the replication cycle of some viruses. However, the relationship between DDX21 and PRRSV has not yet been explored. Here, we found that a DDX21 overexpression promoted PRRSV replication, whereas knockdown of DDX21 reduced PRRSV proliferation. Mechanistically, DDX21 promoted PRRSV replication independently of its ATPase, RNA helicase, and foldase activities. Furthermore, overexpression of DDX21 stabilized the expressions of PRRSV nsp1&alpha;, nsp1&beta;, and nucleocapsid proteins, three known antagonists of interferon &beta; (IFN-&beta;). Knockdown of DDX21 activated the IFN-&beta; signaling pathway in PRRSV-infected cells, suggesting that the effect of DDX21 on PRRSV-encoded IFN-&beta; antagonists may be a driving factor for its contribution to viral proliferation. We also found that PRRSV infection enhanced DDX21 expression and promoted its nucleus-to-cytoplasm translocation. Screening PRRSV-encoded proteins showed that nsp1&beta; interacted with the C-terminus of DDX21 and enhanced the expression of DDX21. Taken together, these findings reveal that DDX21 plays an important role in regulating PRRSV proliferation through multiple mechanisms