Viral intra-host evolutionary dynamics revealed via serial passage of Japanese encephalitis virus in vitro.

Analyses of viral inter- and intra-host mutations could better guide the prevention and control of infectious diseases. For a long time, studies on viral evolution have focused on viral inter-host variations. Next-generation sequencing has accelerated the investigations of viral intra-host diversity. However, the theoretical basis and dynamic characteristics of viral intra-host mutations remain unknown. Here, using serial passages of the SA14-14-2 vaccine strain of Japanese encephalitis virus (JEV) as the in vitro model, the distribution characteristics of 1,788 detected intra-host single-nucleotide variations (iSNVs) and their mutated frequencies from 477 deep-sequenced samples were analyzed. Our results revealed that in adaptive (baby hamster kidney (BHK)) cells, JEV is under a nearly neutral selection pressure, and both non-synonymous and synonymous mutations represent an S-shaped growth trend over time. A higher positive selection pressure was observed in the nonadaptive (C6/36) cells, and logarithmic growth in non-synonymous iSNVs and linear growth in synonymous iSNVs were observed over time. Moreover, the mutation rates of the NS4B protein and the untranslated region (UTR) of the JEV are significantly different between BHK and C6/36 cells, suggesting that viral selection pressure is regulated by different cellular environments. In addition, no significant difference was detected in the distribution of mutated frequencies of iSNVs between BHK and C6/36 cells.

Genomic epidemiological characteristics of dengue fever in Guangdong province, China from 2013 to 2017.

Dengue fever, a mosquito-borne viral disease in humans, has been endemic in many Southeast Asian countries. Since its first outbreak in 1978 in Foshan, Guangdong province, China, dengue has been continually epidemic in recent years in Guangdong, which raised the concern whether dengue infection is endemic in Guangdong. In this study, we performed phylogenetic, recombinant, and nucleotide variation analyses of 114 complete genome sequences of dengue virus serotypes 1-4 (DENV1-4) collected from 2013 to 2017 in 18 of 21 cities of Guangdong. Phylogenetic analyses revealed that DENV sequences did not form a single cluster, indicating that dengue fever was not endemic in Guangdong, although DENV1-4 co-circulated in Guangdong. Twenty intra-serotype recombinant isolates involving DENV1-4 were detected, but no inter-serotype recombinant events were identified in this study. Additionally, the most recombinant events were detected simultaneously in the gene NS3 of DENV1-4. Nucleotide variation analyses showed that no significant intra-serotype differences were observed, whereas more significant inter-subtype differences were discovered in non-structural genes than in structural genes. Our investigation will facilitate the understanding of the current prevalent status of dengue fever in Guangdong and contribute to designing more effective preventive and control strategies for dengue infection.

Host Src controls gallid alpha herpesvirus 1 intercellular spread in a cellular fatty acid metabolism-dependent manner.

Viral spread is considered a promising target for antiviral therapeutics, but the associated mechanisms remain unclear for gallid alpha herpesvirus 1 (ILTV). We previously identified proto-oncogene tyrosine-protein kinase Src (Src) as a crucial host determinant of ILTV infection. The present study revealed accelerated spread of ILTV upon Src inhibition. This phenomenon was independent of either viral replication or the proliferation of infected cells and could not be compromised by neutralizing antibody. Neither extracellular vesicles nor the direct cytosol-to-cytosol connections between adjacent cells contributed to the enhanced spread of ILTV upon Src inhibition. Further genome-wide transcriptional profile analyses in combination with functional validation identified fatty acid metabolism as an essential molecular event during modulation of the intercellular spread and subsequent cytopathic effect of ILTV by Src. Overall, these data suggest that Src controls the cell-to-cell spread of ILTV in a cellular fatty acid metabolism-dependent manner, which determines the virus's cytopathic effect.

Phylogeography, Transmission, and Viral Proteins of Nipah Virus.

Nipah virus (NiV), a zoonotic paramyxovirus belonging to the genus Henipavirus, is classified as a Biosafety Level-4 pathogen based on its high pathogenicity in humans and the lack of available vaccines or therapeutics. Since its initial emergence in 1998 in Malaysia, this virus has become a great threat to domestic animals and humans. Sporadic outbreaks and person-to-person transmission over the past two decades have resulted in hundreds of human fatalities. Epidemiological surveys have shown that NiV is distributed in Asia, Africa, and the South Pacific Ocean, and is transmitted by its natural reservoir, Pteropid bats. Numerous efforts have been made to analyze viral protein function and structure to develop feasible strategies for drug design. Increasing surveillance and preventative measures for the viral infectious disease are urgently needed.

Gallid Herpesvirus 1 Initiates Apoptosis in Uninfected Cells through Paracrine Repression of p53.

Apoptosis is a common innate defense mechanism of host cells against viral infection and is therefore suppressed by many viruses, including herpes simplex virus (HSV), via various strategies. A recent in vivo study reported the apoptosis of remote uninfected cells during Gallid herpesvirus 1 (GaHV-1) infection, yet little is known about this previously unknown aspect of herpesvirus-host interactions. The aim of the present study was to investigate the apoptosis of uninfected host cells during GaHV-1 infection. The present study used in vitro and in ovo models, which avoided potential interference by host antiviral immunity, and demonstrated that this GaHV-1-host interaction is independent of host immune responses and important for both the pathological effect of viral infection and early viral dissemination from the primary infection site to distant tissues. Further, we revealed that GaHV-1 infection triggers this process in a paracrine-regulated manner. Using genome-wide transcriptome analyses in combination with a set of functional studies, we found that this paracrine-regulated effect requires the repression of p53 activity in uninfected cells. In contrast, the activation of p53 not only prevented the apoptosis of remote uninfected cells and subsequent pathological damage induced by GaHV-1 infection but also delayed viral dissemination significantly. Moreover, p53 activation repressed viral replication both in vitro and in ovo, suggesting that dual cell-intrinsic mechanisms underlie the suppression of GaHV-1 infection by p53 activation. This study uncovers the mechanism underlying the herpesvirus-triggered apoptosis of remote host cells and extends our understanding of both herpesvirus-host interactions and the roles of p53 in viral infection.IMPORTANCE It is well accepted that herpesviruses suppress the apoptosis of host cells via various strategies to ensure sustained viral replication during infection. However, a recent in vivo study reported the apoptosis of remote uninfected cells during GaHV-1 infection. The mechanism and the biological meaning of this unexpected herpesvirus-host interaction are unclear. This study uncovers the mechanisms of herpesvirus-triggered apoptosis in uninfected cells and may also contribute to a mechanistic illustration of paracrine-regulated apoptosis induced by other viruses in uninfected host cells.

Integrated High Throughput Analysis Identifies GSK3 as a Crucial Determinant of p53-Mediated Apoptosis in Lung Cancer Cells.

BACKGROUND/AIMS: p53 dysfunction is frequently observed in lung cancer. Although restoring the tumour suppressor function of p53 is recently approved as a putative strategy for combating cancers, the lack of understanding of the molecular mechanism underlying p53-mediated lung cancer suppression has limited the application of p53-based therapies in lung cancer. METHODS AND RESULTS: Using RNA sequencing, we determined the transcriptional profile of human non-small cell lung carcinoma A549 cells after treatment with two p53-activating chemical compounds, nutlin and RITA, which could induce A549 cell cycle arrest and apoptosis, respectively. Bioinformatics analysis of genome-wide gene expression data showed that distinct transcription profiles were induced by nutlin and RITA and 66 pathways were differentially regulated by these two compounds. However, only two of these pathways, 'Adherens junction' and 'Axon guidance', were found to be synthetic lethal with p53 re-activation, as determined via integrated analysis of genome-wide gene expression profile and short hairpin RNA (shRNA) screening. Further functional protein association analysis of significantly regulated genes associated with these two synthetic lethal pathways indicated that GSK3 played a key role in p53-mediated A549 cell apoptosis, and then gene function study was performed, which revealed that GSK3 inhibition promoted p53-mediated A549 cell apoptosis in a p53 post-translational activity-dependent manner. CONCLUSION: Our findings provide us with new insights regarding the mechanism by which p53 mediates A549 apoptosis and may cast light on the development of more efficient p53-based strategies for treating lung cancer.