Assembly and budding of influenza virus.

Influenza viruses are causative agents of an acute febrile respiratory disease called influenza (commonly known as "flu") and belong to the Orthomyxoviridae family. These viruses possess segmented, negative stranded RNA genomes (vRNA) and are enveloped, usually spherical and bud from the plasma membrane (more specifically, the apical plasma membrane of polarized epithelial cells). Complete virus particles, therefore, are not found inside infected cells. Virus particles consist of three major subviral components, namely the viral envelope, matrix protein (M1), and core (viral ribonucleocapsid [vRNP]). The viral envelope surrounding the vRNP consists of a lipid bilayer containing spikes composed of viral glycoproteins (HA, NA, and M2) on the outer side and M1 on the inner side. Viral lipids, derived from the host plasma membrane, are selectively enriched in cholesterol and glycosphingolipids. M1 forms the bridge between the viral envelope and the core. The viral core consists of helical vRNP containing vRNA (minus strand) and NP along with minor amounts of NEP and polymerase complex (PA, PB1, and PB2). For viral morphogenesis to occur, all three viral components, namely the viral envelope (containing lipids and transmembrane proteins), M1, and the vRNP must be brought to the assembly site, i.e. the apical plasma membrane in polarized epithelial cells. Finally, buds must be formed at the assembly site and virus particles released with the closure of buds. Transmembrane viral proteins are transported to the assembly site on the plasma membrane via the exocytic pathway. Both HA and NA possess apical sorting signals and use lipid rafts for cell surface transport and apical sorting. These lipid rafts are enriched in cholesterol, glycosphingolipids and are relatively resistant to neutral detergent extraction at low temperature. M1 is synthesized on free cytosolic polyribosomes. vRNPs are made inside the host nucleus and are exported into the cytoplasm through the nuclear pore with the help of M1 and NEP. How M1 and vRNPs are directed to the assembly site on the plasma membrane remains unclear. The likely possibilities are that they use a piggy-back mechanism on viral glycoproteins or cytoskeletal elements. Alternatively, they may possess apical determinants or diffuse to the assembly site, or a combination of these pathways. Interactions of M1 with M1, M1 with vRNP, and M1 with HA and NA facilitate concentration of viral components and exclusion of host proteins from the budding site. M1 interacts with the cytoplasmic tail (CT) and transmembrane domain (TMD) of glycoproteins, and thereby functions as a bridge between the viral envelope and vRNP. Lipid rafts function as microdomains for concentrating viral glycoproteins and may serve as a platform for virus budding. Virus bud formation requires membrane bending at the budding site. A combination of factors including concentration of and interaction among viral components, increased viscosity and asymmetry of the lipid bilayer of the lipid raft as well as pulling and pushing forces of viral and host components are likely to cause outward curvature of the plasma membrane at the assembly site leading to bud formation. Eventually, virus release requires completion of the bud due to fusion of the apposing membranes, leading to the closure of the bud, separation of the virus particle from the host plasma membrane and release of the virus particle into the extracellular environment. Among the viral components, M1 contains an L domain motif and plays a critical role in budding. Bud completion requires not only viral components but also host components. However, how host components facilitate bud completion remains unclear. In addition to bud completion, influenza virus requires NA to release virus particles from sialic acid residues on the cell surface and spread from cell to cell. Elucidation of both viral and host factors involved in viral morphogenesis and budding may lead to the development of drugs interfering with the steps of viral morphogenesis and in disease progression

Influenza virus morphogenesis and budding.

Influenza viruses are enveloped, negative stranded, segmented RNA viruses belonging to Orthomyxoviridae family. Each virion consists of three major sub-viral components, namely (i) a viral envelope decorated with three transmembrane proteins hemagglutinin (HA), neuraminidase (NA) and M2, (ii) an intermediate layer of matrix protein (M1), and (iii) an innermost helical viral ribonucleocapsid [vRNP] core formed by nucleoprotein (NP) and negative strand viral RNA (vRNA). Since complete virus particles are not found inside the cell, the processes of assembly, morphogenesis, budding and release of progeny virus particles at the plasma membrane of the infected cells are critically important for the production of infectious virions and pathogenesis of influenza viruses as well. Morphogenesis and budding require that all virus components must be brought to the budding site which is the apical plasma membrane in polarized epithelial cells whether in vitro cultured cells or in vivo infected animals. HA and NA forming the outer spikes on the viral envelope possess apical sorting signals and use exocytic pathways and lipid rafts for cell surface transport and apical sorting. NP also has apical determinant(s) and is probably transported to the apical budding site similarly via lipid rafts and/or through cortical actin microfilaments. M1 binds the NP and the exposed RNAs of vRNPs, as well as to the cytoplasmic tails (CT) and transmembrane (TM) domains of HA, NA and M2, and is likely brought to the budding site on the piggy-back of vRNP and transmembrane proteins. Budding processes involve bud initiation, bud growth and bud release. The presence of lipid rafts and assembly of viral components at the budding site can cause asymmetry of lipid bilayers and outward membrane bending leading to bud initiation and bud growth. Bud release requires fusion of the apposing viral and cellular membranes and scission of the virus buds from the infected cellular membrane. The processes involved in bud initiation, bud growth and bud scission/release require involvement both viral and host components and can affect bud closing and virus release in both positive and negative ways. Among the viral components, M1, M2 and NA play important roles in bud release and M1, M2 and NA mutations all affect the morphology of buds and released viruses. Disassembly of host cortical actin microfilaments at the pinching-off site appears to facilitate bud fission and release. Bud scission is energy dependent and only a small fraction of virus buds present on the cell surface is released. Discontinuity of M1 layer underneath the lipid bilayer, absence of outer membrane spikes, absence of lipid rafts in the lipid bilayer, as well as possible presence of M2 and disassembly of cortical actin microfilaments at the pinching-off site appear to facilitate bud fission and bud release. We provide our current understanding of these important processes leading to the production of infectious influenza virus particles

Foundations of Migration from the Disaster Consequences Coastal Area of Bangladesh

In Bangladesh the most crucial impact of climate change will result in the migration of the people from coastal areas to all over the country.  Increases in the frequency and severity of chronic environmental hazards and sudden onset disasters are projected to alter the typical migration patterns of different communities. The relationship between climate change and human security is not necessarily direct, but depends on a chain of consequences. This paper deals with the migration patterns of disaster affected coastal areas of Bangladesh. Life of coastal community is experienced with multiple vulnerabilities due to natural disasters. A questionnaire survey was done with 49 randomly selected people to identify the determinants of migration in the study area. Natural disasters were the most frequently cited cause of insecurity in a household survey undertaken for the present study. Other environmental problems such as riverbank erosion and the loss of natural resources were also recorded as significant challenges. The collected data then were analyzed by computer based software SPSS. Findings show that erosion and cyclone are strongly related with migration in the study area where flood, tornado and drought have no strong influence for that so called “ climate change refugees”. Keywords: Climate change, human security, migration pattern, natural disaster, natural resources, climate change refugees

Characterizing Emerging Canine H3 Influenza Viruses.

The continual emergence of novel influenza A strains from non-human hosts requires constant vigilance and the need for ongoing research to identify strains that may pose a human public health risk. Since 1999, canine H3 influenza A viruses (CIVs) have caused many thousands or millions of respiratory infections in dogs in the United States. While no human infections with CIVs have been reported to date, these viruses could pose a zoonotic risk. In these studies, the National Institutes of Allergy and Infectious Diseases (NIAID) Centers of Excellence for Influenza Research and Surveillance (CEIRS) network collaboratively demonstrated that CIVs replicated in some primary human cells and transmitted effectively in mammalian models. While people born after 1970 had little or no pre-existing humoral immunity against CIVs, the viruses were sensitive to existing antivirals and we identified a panel of H3 cross-reactive human monoclonal antibodies (hmAbs) that could have prophylactic and/or therapeutic value. Our data predict these CIVs posed a low risk to humans. Importantly, we showed that the CEIRS network could work together to provide basic research information important for characterizing emerging influenza viruses, although there were valuable lessons learned

Intracellular Replication of Choleraphage Ê92

The broad host range choleraphage Ê92 contains a linear double-stranded DNA molecule of 68 kilobase (kb) pairs with 3) overhang cohesive ends. Following infection with phage Ê92, the host macromolecular synthesis is shut off within the first 5 min, and synthesis of phage-specific DNA is detectable after 7 min of infection. At early times during infection, phage DNA is replicated in circular form and the synthesis is membrane associated. The closed circular form serves as the precursor for the synthesis of the mature phage DNA which is eventually packaged into the phage head. Pulse labeling of ultraviolet-irradiated infected cells at different times during infection has allowed identification of about 30 phage-specific proteins of which 6 are structural proteins. These proteins appear during the infection cycle in two distinct phases, early and late. Eighteen early and 12 late proteins have been identified

Lipid Raft Disruption by Cholesterol Depletion Enhances Influenza A Virus Budding from MDCK Cells▿

Lipid rafts play critical roles in many aspects of the influenza A virus life cycle. Cholesterol is a critical structural component of lipid rafts, and depletion of cholesterol leads to disorganization of lipid raft microdomains. In this study, we have investigated the effect of cholesterol depletion by methyl-β-cyclodextrin (MβCD) treatment on influenza virus budding. When virus-infected Madin-Darby canine kidney cells were treated with MβCD at the late phase of infection for a short duration, budding of virus particles, as determined by protein analysis and electron microscopy, increased with increasing concentrations and lengths of treatment. However, infectious virus yield varied, depending on the concentration and duration of MβCD treatment. Low concentrations of MβCD increased infectious virus yield throughout the treatment period, but higher concentrations caused an initial increase of infectious virus titer followed by a decrease with a longer duration. Relative infectivity of the released virus particles, on the other hand, decreased with increasing concentrations and durations of MβCD treatment. Loss of infectivity of virus particles is due to multiple effects of MβCD-mediated cholesterol depletion causing disruption of lipid rafts, changes in structural integrity of the viral membrane, leakage of viral proteins, a nick or hole on the viral envelope, and disruption of the virus structure. Exogenous cholesterol increased lipid raft integrity, inhibited particle release, and partially restored the infectivity of the released virus particles. These data show that disruption of lipid rafts by cholesterol depletion caused an enhancement of virus particle release from infected cells and a decrease in the infectivity of virus particles

Probing the mechanical and deformation behaviour of CNT-reinforced AlCoCrFeNi high-entropy alloy – a molecular dynamics approach

This present study investigates the mechanical and deformation behaviour of pristine and carbon nanotube (CNT)-reinforced AlCoCrFeNi high-entropy alloys (HEAs) using molecular dynamics (MD) simulations. The results reveal that an increase in the atomic fraction of Al in pristine AlCoCrFeNi HEAs leads to reduced mechanical behaviour. The mechanical behaviour of the pristine AlCoCrFeNi HEAs notably improves following CNT reinforcement, particularly when using CNT with higher chirality. As the chirality of the CNT increases from (6,6) to (15,15), Young's modulus, yield stress, and toughness of the (15,15) CNT-Al20CoCrFeNi HEA enhance by 17.34%, 29.44%, and 44.44% compared to the (6,6) CNT – Al20CoCrFeNi HEA. HEAs with lower Al fractions experience more substantial stress drops due to rapid structural changes. CNT reinforcement, particularly with higher chirality, decelerates this structural transformation, enhancing yield strength greatly. The analysis of the dislocation evolution revealed that the CNT-reinforced HEA exhibits higher dislocation density compared to the pristine HEA, indicating strain hardening from CNT reinforcement. Furthermore, examination of atomic shear strain reveals confined deformation along shear bands in CNT-reinforced HEAs, leading to the deformation and eventual fracture of CNTs. This study provides valuable insights for enhancing the mechanical behaviour of CNT-reinforced AlCoCrFeNi HEAs, aiding in their design and development.</p

ERIC-PCR based genetic variability and their relationship with pathogenic variability of <em>Xanthomonas campestris</em> pv. <em>Campestris</em> isolates of West Bengal, India

620-626Black rot of cabbage caused by Xanthomonas campestris pv. campestris (Xcc) is one of the most devastating diseases of cabbage causing 10-50% loss consistently. For determining genetic diversity amplification of enterobacterial repetitive intergenic consensus (ERIC-PCR) was reported to be reliable rapid and highly discriminatory. Therefore, current study was undertaken to determine genetic variability of 31 Xcc and five other xanthomonads collected from West Bengal using ERIC-PCR. Based on virulence on cabbage isolate 1.3W and 2.2 were found to be most virulent whereas isolates ND,1,2,6, and 3.1 were least virulent. Based on the ERIC-PCR fingerprints Xcc isolates were clearly distinguish from other xanthomonads. Several bands were identified unique to Xcc or other xanthomonads which can be used as markers for detection at the species and pathovar level. The grouping of the isolates based on ERIC-PCR was in accordance with the virulence of the isolates on cabbage. Genomic fingerprinting with ERIC-PCR revealed groups that did not represent significant relationship between isolates and geographical location isolates and host. However, it did demonstrate existence of genetic differences within the West Bengal X. campestris pv. Campestris population indicating that it is not a similar clonal population of the same genetic background

Assembly and budding of influenza virus.

Influenza viruses are causative agents of an acute febrile respiratory disease called influenza (commonly known as "flu") and belong to the Orthomyxoviridae family. These viruses possess segmented, negative stranded RNA genomes (vRNA) and are enveloped, usually spherical and bud from the plasma membrane (more specifically, the apical plasma membrane of polarized epithelial cells). Complete virus particles, therefore, are not found inside infected cells. Virus particles consist of three major subviral components, namely the viral envelope, matrix protein (M1), and core (viral ribonucleocapsid [vRNP]). The viral envelope surrounding the vRNP consists of a lipid bilayer containing spikes composed of viral glycoproteins (HA, NA, and M2) on the outer side and M1 on the inner side. Viral lipids, derived from the host plasma membrane, are selectively enriched in cholesterol and glycosphingolipids. M1 forms the bridge between the viral envelope and the core. The viral core consists of helical vRNP containing vRNA (minus strand) and NP along with minor amounts of NEP and polymerase complex (PA, PB1, and PB2). For viral morphogenesis to occur, all three viral components, namely the viral envelope (containing lipids and transmembrane proteins), M1, and the vRNP must be brought to the assembly site, i.e. the apical plasma membrane in polarized epithelial cells. Finally, buds must be formed at the assembly site and virus particles released with the closure of buds. Transmembrane viral proteins are transported to the assembly site on the plasma membrane via the exocytic pathway. Both HA and NA possess apical sorting signals and use lipid rafts for cell surface transport and apical sorting. These lipid rafts are enriched in cholesterol, glycosphingolipids and are relatively resistant to neutral detergent extraction at low temperature. M1 is synthesized on free cytosolic polyribosomes. vRNPs are made inside the host nucleus and are exported into the cytoplasm through the nuclear pore with the help of M1 and NEP. How M1 and vRNPs are directed to the assembly site on the plasma membrane remains unclear. The likely possibilities are that they use a piggy-back mechanism on viral glycoproteins or cytoskeletal elements. Alternatively, they may possess apical determinants or diffuse to the assembly site, or a combination of these pathways. Interactions of M1 with M1, M1 with vRNP, and M1 with HA and NA facilitate concentration of viral components and exclusion of host proteins from the budding site. M1 interacts with the cytoplasmic tail (CT) and transmembrane domain (TMD) of glycoproteins, and thereby functions as a bridge between the viral envelope and vRNP. Lipid rafts function as microdomains for concentrating viral glycoproteins and may serve as a platform for virus budding. Virus bud formation requires membrane bending at the budding site. A combination of factors including concentration of and interaction among viral components, increased viscosity and asymmetry of the lipid bilayer of the lipid raft as well as pulling and pushing forces of viral and host components are likely to cause outward curvature of the plasma membrane at the assembly site leading to bud formation. Eventually, virus release requires completion of the bud due to fusion of the apposing membranes, leading to the closure of the bud, separation of the virus particle from the host plasma membrane and release of the virus particle into the extracellular environment. Among the viral components, M1 contains an L domain motif and plays a critical role in budding. Bud completion requires not only viral components but also host components. However, how host components facilitate bud completion remains unclear. In addition to bud completion, influenza virus requires NA to release virus particles from sialic acid residues on the cell surface and spread from cell to cell. Elucidation of both viral and host factors involved in viral morphogenesis and budding may lead to the development of drugs interfering with the steps of viral morphogenesis and in disease progression