Herpesviridae: Viral Cycle, Capsid Transport, and Cancer Treatment

Herpesviridae: Viral Cycle, Capsid Transport, and Cancer Treatment

The nature of a previously described (Stevens, 1966) heat-sensitive step essential to the replication of infectious bovine rhinotracheitis virus deoxyribonucleic acid has been investigated. MT4 cells and peripheral blood mononuclear cells (PBMCs) infected with two different strains (HST and a patient strain GUI) were used. Viruses vary considerably in size and shape. The cytotoxic effect of a phytochemically defined birch bark triterpene extract (TE) as well as different pentacyclic triterpenes was analyzed in cell culture, and revealed a moderate cytotoxicity on RC-37 cells. Our data indicate that the first 8 nucleotides within the RE are critical for replication. Of these viral families, the animal herpes viruses that cause disease are of the Alphaherpesviridae family. Release Hint: At which stage of viral replication does the virus come closest to the host cell’s plasma membrane?

We further demonstrated that berberine significantly reduced HSV-induced NF-κB activation, as well as IκB-α degradation and p65 nuclear translocation. It is thought that more than 50% of adults in the United States have HSV-1, and that nearly 20% have HSV-2 (CDC, 2010). IMPORTANCE Herpesviruses establish and reactivate from lifelong latency in their hosts. The release of IFN-β by 3 h p.i. HSV-1 occasionally spreads to the central nervous system, causing severe encephalitis. All cultures at 39°C were harvested simultaneously 30 h postinoculation (p.i.). acyclovir).

The results of this study are interpreted to indicate that the egress of HSV-1 in Vero cells is directed to virally induced, specialized egress sites that form along specific areas of the cell membrane. Such partially tegumented capsids bind to the host nuclear pore complex (NPC), where the viral DNA is released, a process termed uncoating. Work from Everett and colleagues suggests that ND10s that are detected during stage I of infection represent reformed ND10-like foci that have been recruited to de novo HSV-1 nucleoprotein complexes (23, 27). Release of the herpes simplex virus protease by self- cleavage is required for proper conformation of the portal vertex. The infection then goes into a latent stage, where the infected person is asymptomatic. In the study presented herein, we tested this hypothesis directly by measuring the efficiency of viral replication, viral DNA synthesis, and expression of several viral genes during infections in which Rosco was added after E proteins had already been synthesized. During the latent stage, HSV invades peripheral neurons and remains in the nuclei of these cells (Gupta, 2007).

In case of adenoviruses and Herpesviruses, once the capsid has entered the cytoplasm it migrates to the nucleus where it injects its DNA through a nuclear pore. This methodology increases the frequency (ranging from 40 to 90%, instead of from 4 to 5%) of the homologous recombination between the viral genome and the HSV sequences present in the plasmid. The current study was initiated to refine our understanding of how co-activation of the IFN-α/β- and IFN-γ-signaling pathways prevents HSV-1 replication in vitro. Also, contracting one variant confers some protection against the other, as those infected with HSV-1 are somewhat resistant to HSV-2, while those infected with HSV-2 are resistant to HSV-1 (Gupta, 2007). Regardless of which strain is contracted, the immune system never eradicates the infection. Many viruses manipulate the UP system to favor their replication. ICP8 is a single-strand DNA binding protein essential for HSV-1 DNA replication.

HSV is a DNA based virus; it has a linear, double stranded genome. The protein capsid is in an icosahedral shape approximately 15 nm thick and 125 nm in diameter (Newcomb et al, 1996). There are five conserved proteins that comprise herpes capsids: UL19, which is the major capsid protein that is in all herpes capsids, UL18 and UL38, which are proteins that form triplexes that interact with and help to stabilize adjacent capsids, UL35, which covers all hexons, and UL6, which forms the portal through which the viral genome is injected into the nucleus (Fig 2). The capsid is connected to the membrane envelope via the viral tegument, with which these capsid proteins associate (Mettenleiter, 2006). The envelope gives a somewhat circular appearance to the virus and does not contribute to the symmetry of the nucleocapsid. However, it is unknown exactly what role these cellular proteins play and why they are recruited during replication of virions. Additionally, the TRs are part of a highly structured nucleosome array, which undergoes reorganization in late G1/S phase when replication licensing and initiation occur (46).

The HSV genome is a relatively long genome, with HSV-1 and HSV-2 each encoding at least 74 genes (McGeoch et al, 2006). The herpes genome is linear, and comprised of two main regions, the unique long region (UL), and the unique short region (US). The long region contains 56 genes, while the short region contains 12 genes. Genes in both regions encode for all of the necessary structural components of the virus, including capsid, tegument, and envelope proteins, as well as genes that control viral replication processes and infective ability. Herpes utilizes the RNA Polymerase II of the infected host to transcribe its genes (McGeoch et al, 2006). The genes can be classified into immediate-early, early, and late viral genes. Antibodies.Immunocytochemical staining was performed using antibodies to gB (rabbit polyclonal serum R69; generously provided by R.

The open circles (○) represent the kinetics of growth at the permissive temperature, whereas the filled triangles (▴) indicate the yields of infectious particles reached at 30 h postinfection when the infected culture was first kept at 33°C for the shown period of time (▴) and then shifted to 39°C (shift kinetics). In Results and Discussion section, we report the results of applying these scoring schemes to predict the locations of replication origins for 39 fully sequenced herpesviruses, and compare the prediction accuracies in terms of sensitivity and positive predictive value. It is important to examine the process of viral release in a variety of cell types to fully understand the mechanism of HSV-1 egress. Prior to infection, cells were washed one time with 30 ml per roller bottle MEM with 1% FBS, l-glutamine, and antibiotics. BAY 57-1293 (N-[5-(aminosulfonyl)-4-methyl-1,3-thiazol-2-yl]-N-methyl-2-[4-(2-pyridinyl)phenyl]acetamide) was obtained from Gerald Kleymann (Bayer Pharmaceuticals; Wuppertal, Germany) (36). Yang K, and Joel D Baines. The presence of gD and gHL are indicated during leaflet mixing and hemifusion, while gB is present during full fusion and mixing of viral and cellular contents.

A sequential model has been proposed for glycoprotein involvement in envelope fusion, with gD being necessary for Phase I as the glycoprotein that is recognized by cell surface receptors, gHL being necessary for Phase II leaflet mixing, and gB being necessary for full fusion and pore formation. All four proteins are necessary for HSV to be infectious, for without any one of the glycoproteins no cellular invasion occurs (Subramanian, 2007). On the other hand, DNA-containing naked icosahedral viruses that mature in the nucleus do not reach the cell surface as rapidly, and are released when the cells undergo autolysis. The tegument remains attached to the capsid, and makes its way to the nucleus by using the cytoskeleton proteins of the infected cell (Zaichick, 2013). Cells were incubated for 1 hour with a 1:20,000 dilution of rabbit anti-HSV-1 (Dako Cytomation, Carpinteria, CA) and a 1:1000 dilution of mouse monoclonal antibodies against ICP0, ICP4, ICP6, gC, or gD (Rumbaugh Goodwin Institute, Plantation, FL). This injection is done through the capsid portal, created by the formation of a twelve units of the capsid protein pUL6 (Trus et al, 2004). There is but a single portal per capsid, and it is assembled at one of the capsid’s vertices (Cardone et al, 2007).

The estimation of the viroplasms’ size was carried out as reported previously (7). HSV-1 induced TERRA in a dose-dependent manner that peaks at ~1 MOI (Figure S2G). The protein that controls this process is the UL41 gene product protein, VHS, which is a tegument protein (Matis, 2001). The activities of VHS affects multiple cellular functions, including shutoff of host protein synthesis, degradation of host mRNA. VHS remains in the cytoplasm to carry out these functions, while the viral capsid travels directly to the nucleus to inject the viral genome (Taddeo, 2006). VHS is an example of an immediate-early protein that is present in the infected cell immediately upon infection. After the assembly is complete, the virions are ready to be released into the environment (Figure 2 ).

This seems counter-intuitive, but is important because VHS does not differentiate between cellular and viral mRNA (Taddeo, 2006). The insoluble fraction (nuclear pellet) was suspended in 21 ml nuclear pellet solubilization buffer (10 mM Tris-HCl [pH 8.0], 140 mM NaCl, 1 mM DTT, protease inhibitor cocktail, 1% Triton X-100, 0.1% Na deoxycholate), homogenized, and sonicated. This circularization is able to occur without protein synthesis. Evidence found in cell lines where circularization is inhibited is that circularization is required for viral DNA replication (Boehmer, 1997). This circularization allows for origin-dependent replication. There are three reported sites of origin for DNA replication within the HSV genome; oriL, which is located between the UL29 and UL30 genes, and two copies of oriS, which are located near either end of US (Boehmer, 1997). Interestingly, not all of these genes are required for replication, as deletions of either allow for viral replication.

One theory is that not all that origin points are used simulatenously, that some may e active during the lytic phase while the rest are active during the reactivation from the latent infection (Boehmer, 1997). Biotinylated infected cells were treated three times with freshly prepared glutathione (GSH) at 60 mg/ml for 20 min at 4°C to remove any biotin remaining at the cell surface. 4B). The score of a window in the genome is simply the total of the scores of all the palindromes occurring in this window. Ultrathin sections (70 to 80 nm) prepared on a Leica Ultracut UCT ultramicrotome using a Diatome diamond knife were collected on 200-mesh copper grids and contrast stained with lead citrate and uranyl acetate as described previously (39). Prior to grouping images, a calibration image was used to find the optimal contrast for each individual color. Images were arranged using Adobe Photoshop, version 7.0, Adobe Illustrator, and Zeiss LSM 510 image viewer software.
Herpesviridae: Viral Cycle, Capsid Transport, and Cancer Treatment

17. The closed, spherical capsid is an unstable conformation, but it is a more open form than the icosahedral capsid (Newcomb et al, 1996). A conserved capsid-associated protein, UL25, is thought to play a role in envelope formation by being part of the tegument that joins the capsid to the envelope, and that it helps selectively to selectively form envelopes around capsids that contain viral DNA (as opposed to an empty capsid) (Mettenleiter and Minson, 2006). After nucleocapsid formation, the capsid must exit the nucleus. The capsid moves towards the inner membrane of the nucleus just before the formation of the primary virion envelope. Movement of the capsid within the nucleus is facilitated by the microfilament protein actin, and contact with the inner nuclear membrane is enabled by two viral proteins, UL31 and UL34 (Mettenleiter and Minson, 2006). Treatment with 200 U/ml IFN-β or IFN-γ alone delayed the detection of viral DNA synthesis by approximately 3 hours and slightly decreased the rate (slope) of viral DNA synthesis between 15 and 24 hours p.i.

This allows the nucleocapsids to cross through the inner membrane layer. The movement of the capsid across the outer nuclear membrane into the cytoplasm is achieved by fusion of the primary capsid envelope with the outer nuclear membrane. The effect of the proteasome inhibitor MG132 on protein synthesis is reversed by addition of nonessential amino acids, but the effect on the yield of progeny virus is not. These observations suggested that the E3 ligase activity of ICP0 plays a role in TERRA activation. The tegument is actually formed at two sites, both at the capsid and at the envelope (Mettenleiter and Minson, 2006). These two subassembly sites utilize two different sets of proteins in their functions. At the capsid site, the tegument is assembled by proteins that are encoded by UL36 and UL37, as well as proteins encoded by UL25 and US3 (Mettenleiter and Minson, 2006).

At the envelope formation site, which is part of the trans-Golgi complex, glycoproteins are assembled with tegument proteins. The tegument proteins are encoded by the genes UL46, UL47, and UL49. Also key are the glycoprotein M (gM) and the protein encoded by UL11 (Mettenleiter and Minson, 2006). The chromatin was precleared for 30 min at 4°C with 75 μl protein A/G agarose beads and 0.4 mg/ml salmon sperm DNA. Once these subassemblies are joined, a mature virion is formed within a cellular vesicle. This vesicle then migrates to the cellular membrane and fuses with it to release the mature virion (Fig 3). An interesting facet of secondary envelopment is that these envelopes may be formed without a capsid (Mettenleiter, 2006).

Though these steps describe the process of HSV replication, the basic mechanisms are appear to be conserved across the Herpesviridae family (Mettenleiter, 2006). One of the key traits of the herpes virus family is the ability to infect the host with a latent infection and remain in host cells for the life of the host. This ability is dependent on two factors; first, the virus must be able to evade the immune response of the host, and second the virus must be able to halt the lytic cycle. Infected cell culture supernatants were harvested at different times postinfection and, after low-speed centrifugation to clear the supernatants, extracellular virions were titrated on Vero cells. HSV achieves this interference through an immediate-early protein called ICP47. Finally, rows that are not shaded denote those viruses whose origins of replication are not known, as far as we know. The virus-containing pellets were dissolved in 100 μl 1× SDS-PAGE sample buffer, and an approximately equal amount of virus normalized to VP5 was loaded into an SDS-PAGE gel for Western blot analyses.

Native labeling.Cells were grown in eight-well chambered cover glasses to 75% confluence. Stage IIIb foci on the other hand are seen in cells infected in the presence of PAA and contain all seven viral replication proteins as well as several cellular proteins (7, 68). The virus invades the nucleus of the neuron, where it maintains its genome in a circular form. This circular formation is associated with nucleosomes in a chromatin configuration (Pinnoji et al, 2007). Viral genes are deactivated during latency, to prevent the lytic cycle from activating in the neuron. Neuronal factors are involved in the repression of HSV gene expression during the latent phase of the infection. One such factor is Repressor Element Silencing Transcription Factor/Neuronal Restrictive Silencer Factor (REST/NRSF) (Pinnoji et al, 2007).

This factor acts on the viral gene ICP4, which is a key transactivator of HSV genes involved in the lytic cycle. Cells infected with an ICP4− virus expressed 5 times as much ICP0 as KOS-infected cells treated with IFN-β and IFN-γ. The mechanisms that trigger reactivation of the virus are not understood. The mechanism by which capsids are transported to the nucleus from the cell membrane is through the usage of the cell’s own cytoskeleton. Altogether, these results indicate that proteasome activity is required for efficient viral and cellular protein synthesis and for efficient rotavirus replication. Single stranded G-rich telomere DNA can be measured by native in-gel hybridization without alkaline denaturation of DNA strands, a method that also measures telomeric 3’ G-overhang signal. The difference between the two is their direction of motion; kinesins move from the negative to the positive end of the microtubule, while dyneins move in the opposite direction.

Current research has shown that herpesvirus tegument proteins attach to dyneins and promote retrograde motion towards the nucleus (Zaichick, 2013). The tegument protein that performs this action was determined to be viral protein 1/2 (VP1/2), also known as UL36, using the neuroinvasive herpesvirus, pseudorabies virus (PRV). UL36 interacts with the tegument protein UL25 for functional activation. This complex tethers the capsid to the dynein through a protein-protein interaction with a proline-rich sequence in UL36, which then carries the capsid to the nucleus for injection of the viral genome. Data from this experiment showed that mutant variants of PRV with the proline-rich sequence deletion were not as virulent as wild-type PRV, and movement of the capsid to the nucleus was impaired.As shown in Figure 4, cells were infected with fluorescent-labelled PRV, consisting of wild-type PRV and a strain with mutated UL36. The replication efficiency for each plasmid was determined by comparing the intensity of the replicated DNA band with that of the corresponding input band from two or three independent assays. HSV has been an object of interest into research and development as a treatment vector for cancer.

HSV has many traits that make it desirable as a treatment vector; HSV can infect a wide variety of cell types, the normal replication cycle of HSV causes cells to lyse (killing cancerous cells), The HSV genome has many genes that are non-essential to replication that can be replaced with therapeutic genes, there are already many pharmaceutical options that can be used to control against unwanted replication of the virus, and the viral genome remains as an intact plasmid within the cell nucleus which protects against unwanted insertion of viral DNA into the host genome (Varghese, 2002). HSV viruses were re-engineered to express cytotoxic genes or genes to stimulate immune response. The effectiveness of HSV as a treatment vector increased when used in conjunction with other cancer therapies such as radiation treatment and chemotherapy. Three strains of re-engineered HSV, designated G207, 1716, and NV1020, were put through Phase I clinical trials in 2002. There were no negative effects attributed to the virus. Vero cells were cotransfected with the KgBct-GFP infectious viral DNA and the linearized plasmids pgBY889A or pgBLL871AA. (Varghese, 2002).

We use BWSm(Local) to represent the local version of BWS of order m. Note that, unlike infected cells, the cell membrane is closely apposed to the coverslip edge. A reduction in the number of nuclear capsids was interpreted as antibody interference with the capsid’s ability to interact with the nuclear pore, indicating a role for the protein in the binding process. have suggested that PML-containing foci are recruited to viral genomes (27, 28). Simultaneously, development of HSV as a treatment vector for cancer is a promising development that could one day allow for more precise treatment of cancer than the brute force methods of chemotherapy and radiation treatment that are still used for many cancers today. Hill, A., Jugovic, P., York, I., Russ, G., Bennink, J., Yewdell, J., . .

. Johnson, D. (1995). Studies in IFN receptor knockout mice corroborate the functional relevance of this interaction in vivo (Luker et al., 2003, Vollstedt et al., 2004). Nature, 375(6530), 411-415. Taddeo, B., & Roizman, B. In contrast, in H38.5 cells, which are ts20b cells stably transfected with the wild-type human E1 ubiquitin-activating enzyme gene (9), the yield of rotavirus progeny was unaffected at the restrictive temperature ().

At later times, excess ICP8 foci accumulated at additional sites outside of telomeric foci. Journal of Virology, 80(18), 9341-9345. Trus, B. L., Cheng, N., Newcomb, W. W., Homa, F. L., Brown, J. C., & Steven, A.

To further define critical bases within the RE, we constructed four additional mutants, REm1-4-LBS1/2, REm5-8-LBS1/2, REm9-12-LBS1/2, and REm13-16-LBS1/2, each with a 4-nt substitution (Fig. (2004). Structure and polymorphism of the UL6 portal protein of herpes simplex virus type 1. Journal of Virology, 78(22), 12668-12671.

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