MicroRNAs (miRNAs) are crucial in the process of host–pathogen interaction. In this study, we established a screening system for miRNAs of target genes to detect the effect of miRNAs on Enterovirus 71 (EV71) replication in rhabdomyosarcoma (RD) cells. A 3’-untranslated region (UTR) dual-luciferase assay was performed to confirm putative miRNA targets in EV71 genome. Firstly, 13 fragments of EV71 genome were inserted into the vector pMIR, and luciferase activities were analyzed to identify the putative miRNAs of target genes. The expression of the reporter protein was significantly downregulated in cells transfected with the vector containing gene VP3. Then we screened for miRNAs that might target to VP3 through online analysis software. In addition, Western blot, real-time PCR, virus titration, and morphological changes were considered to examine the effects of miRNAs on virus replication. The results suggested that miR-18a and miR-452 repress the reproduction of EV71 virus by binding to VP3. Moreover, EV71 infection also affected the expression of endogenous miR-18a and miR-452. In addition, no significant cytotoxic effects were observed. The results from this study suggest that the intracellular miRNAs may play vital roles in the host–virus interaction.

The genome composition of a given avian influenza virus is the primary determinant of its potential for cross-species transmission from birds to humans. Here, we introduce a viral genome-based computational tool that can be used to evaluate the human infectivity of avian isolates of influenza A H7N9 viruses, which can enable prediction of the potential risk of these isolates infecting humans. This tool, which is based on a novel class weight-biased logistic regression (CWBLR) algorithm, uses the sequences of the eight genome segments of an H7N9 strain as the input and gives the probability of this strain infecting humans (reflecting its human infectivity). We examined the replication efficiency and the pathogenicity of several H7N9 avian isolates that were predicted to have very low or high human infectivity by the CWBLR model in cell culture and in mice, and found that the strains with high predicted human infectivity replicated more efficiently in mammalian cells and were more infective in mice than those that were predicted to have low human infectivity. These results demonstrate that our CWBLR model can serve as a powerful tool for predicting the human infectivity and cross-species transmission risks of H7N9 avian strains.

Tick-borne encephalitis virus (TBEV) and louping ill virus (LIV) are members of the tick-borne flaviviruses (TBFVs) in the family Flaviviridae which cause encephalomeningitis and encephalitis in humans and other animals. Although vaccines against TBEV and LIV are available, infection rates are rising due to the low vaccination coverage. To date, no specific therapeutics have been licensed. Several neutralizing monoclonal antibodies (MAbs) show promising effectiveness in the control of TBFVs, but the underlying molecular mechanisms are yet to be characterized. Here, we determined the crystal structures of the LIV envelope (E) protein and report the comparative structural analysis of a TBFV broadly neutralizing murine MAb (MAb 4.2) in complex with either the LIV or TBEV E protein. The structures reveal that MAb 4.2 binds to the lateral ridge of domain III of the E protein (EDIII) of LIV or TBEV, an epitope also reported for other potently neutralizing MAbs against mosquito-borne flaviviruses (MBFVs), but adopts a unique binding orientation. Further structural analysis suggested that MAb 4.2 may neutralize flavivirus infection by preventing the structural rearrangement required for membrane fusion during virus entry. These findings extend our understanding of the vulnerability of TBFVs and other flaviviruses (including MBFVs) and provide an avenue for antibody-based TBFV antiviral development. IMPORTANCE Understanding the mechanism of antibody neutralization/protection against a virus is crucial for antiviral countermeasure development. Tick-borne encephalitis virus (TBEV) and louping ill virus (LIV) are tick-borne flaviviruses (TBFVs) in the family Flaviviridae. They cause encephalomeningitis and encephalitis in humans and other animals. Although vaccines for both viruses are available, infection rates are rising due to low vaccination coverage. In this study, we solved the crystal structures of the LIV envelope protein (E) and a broadly neutralizing/protective TBFV MAb, MAb 4.2, in complex with E from either TBEV or LIV. Key structural features shared by TBFV E proteins were analyzed. The structures of E-antibody complexes showed that MAb 4.2 targets the lateral ridge of both the TBEV and LIV E proteins, a vulnerable site in flaviviruses for other potent neutralizing MAbs. Thus, this site represents a promising target for TBFV antiviral development. Further, these structures provide important information for understanding TBFV antigenicity.

Enterovirus A71（EV-A71） is one of the main causative agents of hand, foot and mouth disease（HFMD） and it also causes severe neurologic complications in infected children. The interactions between some viruses and the host mitochondria are crucial for virus replication and pathogenicity. In this study, it was observed that EV-A71 infection resulted in a perinuclear redistribution of the mitochondria. The mitochondria rearrangement was found to require the microtubule network, the dynein complex and a low cytosolic calcium concentration. Subsequently, the EV-A71 non-structural protein 2 BC was identified as the viral protein capable of inducing mitochondria clustering. The protein was found localized on mitochondria and interacted with the mitochondrial Rho GTPase 1（RHOT1） that is a key protein required for attachment between the mitochondria and the motor proteins, which are responsible for the control of mitochondria movement.Additionally, suppressing mitochondria clustering by treating cells with nocodazole, EHNA, thapsigargin or A23187 consistently inhibited EV-A71 replication, indicating that mitochondria recruitment played a crucial role in the EV-A71 life cycle. This study identified a novel function of the EV-A71 2 BC protein and provided a potential model for the regulation of mitochondrial motility in EV-A71 infection.

Monoclonal antibodies (mAbs) targeting the co-stimulatory molecule 4-1BB are of interest for tumor immunotherapy. We determined the complex structures of human 4-1BB with 4-1BB ligand (4-1BBL) or utomilumab to elucidate the structural basis of 4-1BB activation. The 4-1BB/4-1BBL complex displays a typical TNF/TNFR family binding mode. The structure of utomilumab/4-1BB complex shows that utomilumab binds to dimeric 4-1BB with a distinct but partially overlapping binding area with 4-1BBL. Competitive binding analysis demonstrates that utomilumab blocks the 4-1BB/4-1BBL interaction, indicating the interruption of ligand-mediated signaling. The binding profiles of 4-1BBL and utomilumab to monomeric or dimeric 4-1BB indicate limited cross-linking of 4-1BB molecules. These findings provide mechanistic insight into the binding of 4-1BB with its ligand and its agonist mAb, which may facilitate the future development of anti-4-1BB biologics for tumor immunotherapy.

The Bunyavirales order is one of the largest groups of segmented negative-sense single-stranded RNA viruses, which includes many pathogenic strains that cause severe human diseases. The RNA segments of the bunyavirus genome are separately encapsidated by multiple copies of nucleoprotein (N), and both termini of each N-encapsidated genomic RNA segment bind to one copy of the viral L polymerase protein. The viral genomic RNA, N and L protein together form the ribonucleoprotein (RNP) complex that constitutes the molecular machinery for viral genome replication and transcription. Recently, breakthroughs have been achieved in understanding the architecture of bunyavirus RNPs with the determination of the atomic structures of the N and L proteins from various members of this order. In this review, we discuss the structures and functions of these bunyavirus RNP components, as well as viral genome replication and transcription mechanisms.

The emergence of drug resistance in avian influenza virus (AIV) is a serious concern for public health. Neuraminidase (NA) isolated from a fatal case of avian-origin H10N8 influenza virus infection was found to carry a drug-resistant mutation, NA-Arg292Lys (291 in N8 numbering). In order to understand the full potential of H10N8 drug resistance, the virus was first passaged in the presence of the most commonly used neuraminidase inhibitors (NAIs), oseltamivir and zanamivir. As expected, the Arg292Lys substitution was detected after oseltamivir treatment, however a novel Val116Asp substitution (114 in N8 numbering) was selected by zanamivir treatment. Next generation sequencing (NGS) confirmed that the mutations arose early (after passages 1-3) and became dominant in the presence of the NAI inhibitors. Extensive crystallographic studies revealed that N8-Arg292Lys resistance results mainly from loss of interactions with the inhibitor carboxylate, while rotation of Glu276 was not impaired as observed in the N9-Arg292Lys, a group 2 NA structure. In the case of Val116Asp, the binding mode between oseltamivir and zanamivir is different. Asp151 forms stabilized hydrogen bond to guanidine group of zanamivir, which may compensate the resistance caused by Val116Asp. By contrast, the amino group of oseltamivir is too short to maintain this hydrogen bond, which result in resistant. Moreover, the oseltamivir-zanamivir hybrid inhibitor MS-257 displays higher effectiveness to Val116Asp than oseltamivir, which support this notion. Author Summary Aside from vaccination, NAIs are currently the only alternative for the clinical treatment and prophylaxis of influenza. Understanding the mechanisms of resistance is critical to guide in drug development. In this study, two drug-resistant NA substitutions, Val116Asp and Arg292Lys, were discovered from oseltamivir and zanamivir treatment of H10N8 virus. Crystal structural analyses revealed two distinct mechanisms of these two resistant mutations and provide the explanation for the difference in susceptibility of different NAIs. Zanamivir and laninamivir were more effective against the resistant variants than oseltamivir, and Arg292Lys results in more serious oseltamivir resistance in N9 than N8 subtype. This study is well-correlated to influenza pandemic/epidemic pre-warning, as the discovery of inhibitor resistant viruses will help for new drug preparedness.

Influenza virus neuraminidase (NA) drug resistance is one of the challenges to preparedness against epidemic and pandemic influenza virus infections. NA N1- and N2-containing influenza viruses are the primary cause of seasonal epidemics and past pandemics. The structural and functional basis underlying drug resistance of the influenza virus N1 NA is well characterized. Yet drug resistance of the N2 strain is not well understood. Here, we confirm that replacement of N2 E119 or I222 results in multidrug resistance, and when the replacements occur together, the sensitivity to NA inhibitors (NAI) is reduced severely. Using crystallographic studies, we showed that E119 replacement results in a loss of hydrogen bonding to oseltamivir and zanamivir, whereas I222 replacement results in a change in the hydrophobic environment that is critical for oseltamivir binding. Moreover, we found that MS-257, a zanamivir-oseltamivir hybrid inhibitor, is less susceptible to drug resistance. The binding mode of MS-257 shows that increased hydrogen bonding interactions between the inhibitor and NA active site anchor the inhibitor within the active site and allow adjustments in response to active-site modifications. Such stability is likely responsible for the observed reduced susceptibility to drug resistance. MS-257 serves as a next-generation anti-influenza virus drug candidate and serves also as a scaffold for further design of NAIs.IMPORTANCEOseltamivir and zanamivir are the two major antiviral drugs available for the treatment of influenza virus infections. However, multidrug-resistant viruses have emerged in clinical cases, which pose a challenge for the development of new drugs. N1 and N2 subtypes exist in the viruses which cause seasonal epidemics and past pandemics. Although N1 drug resistance is well characterized, the molecular mechanisms underlying N2 drug resistance are unknown. A previous report showed that an N2 E119V/I222L dual mutant conferred drug resistance to seasonal influenza virus. Here, we confirm that these substitutions result in multidrug resistance and dramatically reduced sensitivity to NAI. We further elucidate the molecular mechanism underlying N2 drug resistance by solving crystal structures of the N2 E119V and I222L mutants and the dual mutant. Most importantly, we found that a novel oseltamivir-zanamivir hybrid inhibitor, MS-257, remains more effective against drug-resistant N2 and is a promising candidate as a next-generation anti-influenza virus drug.

The non-pathogenic Human Pegivirus (HPgV, formerly GBV-C/HGV), the most prevalent RNA virus worldwide, is known to be associated with reduced morbidity and mortality in HIV-infected individuals. Although previous studies documented its ubiquity and important role in HIV-infected individuals, little is known about the underlying genetic mechanisms that maintain high genetic diversity of HPgV within the HIV-infected individuals. To assess the within-host genetic diversity of HPgV and forces that maintain such diversity within the co-infected hosts, we performed phylogenetic analyses taking into account 229 HPgV partial E1-E2 clonal sequences representing 15 male and 8 female co-infected HIV patients from Hubei province of central China. Our results revealed the presence of eleven strongly supported clades. While nine clades belonged to genotype 3, two clades belonged to genotype 2. Additionally, four clades that belonged to genotype 3 exhibited inter-clade recombination events. The presence of clonal sequences representing multiple clades within the HIV-infected individual provided the evidence of co-circulation of HPgV strains across the region. Of the 23 patients, six patients (i.e., five males and one female) were detected to have HPgV recombinant sequences. Our results also revealed that while male patients shared the viral strains with other patients, viral strains from the female patients had restricted dispersal. Taken together, the present study revealed that multiple infections with divergent HPgV viral strains may have caused within-host genetic recombination, predominantly in male patients, and therefore, could be the major driver in shaping genetic diversity of HPgV.

ABSTRACT To survive and replicate within a host, many viruses have evolved strategies that target crucial components within the apoptotic cascade, leading to either inhibition or induction of cell apoptosis. Enterovirus 71 (EV71) infections have been demonstrated to impact the mitochondrial apoptotic pathway and induce apoptosis in many cell lines. However, the detailed mechanism of EV71-induced apoptosis remains to be elucidated. In this study, we report that EV71 2B protein (2B) localized to the mitochondria and induced cell apoptosis by interacting directly with and activating the proapoptotic protein Bax. 2B recruited Bax to the mitochondria and induced Bax conformational activation. In addition, mitochondria isolated from 2B-expressing cells that were treated with a recombinant Bax showed increased Bax interaction and cytochrome c (Cyt c) release. Importantly, apoptosis in cells with either EV71 infection or 2B expression was dramatically reduced in Bax knockdown cells but not in Bak knockdown cells, suggesting that Bax played a pivotal role in EV71- or 2B-induced apoptosis. Further studies indicate that a hydrophobic region of 18 amino acids (aa) in the C-terminal region of 2B (aa 63 to 80) was responsible for the location of 2B in the mitochondria. A hydrophilic region of 14 aa in the N-terminal region of 2B was functional in Bax interaction and its subsequent activation. Moreover, overexpression of the antiapoptotic protein Bcl-XL abrogates 2B-induced release of Cyt c and caspase activation. Therefore, this study provides direct evidence that EV71 2B induces cell apoptosis and impacts the mitochondrial apoptotic pathway by directly modulating the redistribution and activation of proapoptotic protein Bax. IMPORTANCE EV71 infections are usually accompanied by severe neurological complications. It has also been postulated that the induction of cell apoptosis resulting from tissue damage is a possible process of EV71-related pathogenesis. In this study, we report that EV71 2B protein (2B) localized to the mitochondria and induced cell apoptosis by interacting directly with and activating the proapoptotic protein Bax. This study provides evidence that EV71 induces cell apoptosis by modulating Bax activation and reveals important clues regarding the mechanism of Cyt c release and mitochondrial permeabilization during EV71 infection.

39 To survive and replicate within a host, many viruses have evolved strategies that target crucial 40 components within the apoptotic cascade, leading to either an inhibition or induction of cell 41 apoptosis. Enterovirus 71 (EV71) infections have been demonstrated to impact the mitochondrial 42 apoptotic pathway and induce apoptosis in many cell lines. However, the detailed mechanism of 43 EV71-induced apoptosis remains to be elucidated. In this study, we report that EV71 2B protein 44 (2B) localized to the mitochondria and induced cell apoptosis by interacting directly with and 45 activating the pro-apoptotic protein Bax. 2B recruited Bax to the mitochondria and induced Bax 46 conformational activation. In addition, mitochondria isolated from 2B expressing cells that were 47 treated with a recombinant Bax showed increased Bax interaction and Cyt c release. Importantly, 48 apoptosis in cells with either EV71 infection or 2B expression was dramatically reduced in Bax 49 but not in Bak knockdown cells, suggesting that Bax played a pivotal role in EV71 or 2B-induced 50 apoptosis. Further studies indicate that a hydrophobic region of 18 amino acids (aa) in the 51 C-terminal (63-80) region of 2B was responsible for the location of 2B in the mitochondria. A 52 hydrophilic region of 14 aa in the N-terminal region of 2B was functional in Bax interaction and 53 its subsequent activation. Moreover, over-expression of the anti-apoptotic protein Bcl-XL 54 abrogates 2B-induced release of Cyt c and caspase activation. Therefore, this study provides direct 55 evidence that EV71 2B induces cell apoptosis and impacts the mitochondrial apoptotic pathway 56 by directly modulating the redistribution and activation of pro-apoptotic protein Bax. 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 on O cber 4, 2017 by gest http/jvi.asm .rg/ D ow nladed fom

A series of adamantine substituted imidazo[1,2-a]pyridine derivatives were developed through a one-pot multi-component Groebke–Blackburn–Bienaymé reaction, among them several compounds were identified to be the potent inhibitors against HIV-1 cells.