Hi-Virus Host Cell

When we hear the word virus, we usually think of something that makes us sick. A virus is an ultramicroscopic infectious organism that, having no independent metabolic activity, can replicate only within a cell of another host organism. A virus consists of a core of nucleic acid, either RNA or DNA, surrounded by a coating of antigenic protein and sometimes a lipid layer surrounds it as well. The viral genome provides the genetic code for replication, and the host cell provides the necessary energy and raw materials. To fight viruses, we use vaccines. While some may infect a broad range, other viruses can only infect certain kinds of cells. Vaccines are made of inactive, dead or weakened virus cells or protein antigens that can no longer infect

Viruses have also developed methods to prevent the activity of the transporter associated with antigen processing, TAP. The TAP complex consists of two protein subunits; TAP1 and TAP2, and is an ATP-dependant peptide transporter essential for the transport of peptides to the ER and binding of the peptides to MHC class I molecules [11]. Various herpesviruses interfere with antigen presentation through the blocking the activity of TAP. The Herpes simplex virus type I (HSV-1) encodes the protein ICP47, which competes with peptides in the cytoplasm to bind to TAP. As a result fewer viral peptides are transported to the ER for loading onto MHC I molecules. This ICP47 protein consists of 88 amino acid residues, out of which residues 3-34 act as the

Viruses are microscopic particles that invade and take over both eukaryotic and prokaryotic cells. They consist of two structures, which are the nucleic acid and capsid. The nucleic acid contains all genetic material in the form of DNA or RNA, and is enclosed in the capsid, which is the protein coating that helps the virus attach to and penetrate the host cell. In some cases, certain viruses have a membrane surrounding the capsid, called an envelope. This structure allows viruses to become more stealthy and protected. There are two cycles in which a virus can go into: lytic and lysogenic. The lytic cycle consists of the virus attaching to a cell, injecting its DNA, and creating more viruses, which proceed to destroy the host. On the other hand, the lysogenic cycle includes the virus attaching to the cell, injecting its DNA, which combines with the cell’s DNA in order for it to become provirus. Then, the provirus DNA may eventually switch to the lytic cycle and destroy the host.

consists of two types; HSV1 and HSV-2, both of which infect humans and are easily

On encountering a host cell, the retrovirus attaches itself to receptors on the surface of the host cell’s membrane. Once inside the cell, the capsid opens, releasing RNA and reverse transcriptase into the cell’s cytoplasm.

The virus fuses with the cell’s plasma membrane. The capsid proteins are removed, releasing the viral proteins and RNA. Reverse transcriptase catalyzes the synthesis of a DNA strand complementary to the viral RNA. Reverse transcriptase catalyzes the synthesis of a second DNA strand complementary to the first. The double-stranded DNA is incorporated as a provirus into the cell’s DNA. Proviral genes are transcribed into RNA molecules, which serve as genomes for the next viral generation and as mRNAs for translation into viral proteins. The viral proteins include capsid proteins and reverse transcriptase (made in the cytosol) and envelope glycoproteins (made in the ER). Vesicles transport the glycoproteins from the ER to the cell’s plasma membrane. Capsids are assembled around viral genomes and reverse transcriptase molecules. New viruses bud off from the host cell.

CD4 is a glycoprotein found on the surface of immune cells such as T helper cells, monocytes, macrophages, and dendritic cells. HIV infects cells of the immune system called T lymphocytes (T cells) and macrophages. HIV has an envelope and contains two copies of single-stranded RNA as the genome. Within the viral capsid are important viral enzymes called reverse transcriptase, integrase, and protease. The HIV virus has a spike protein that is called gp120, and the host cell receptor is CD4+. HIV belongs to a class of viruses called retroviruses. Retroviruses are RNA viruses, and to replicate or reproduce, they must make a DNA copy of their RNA through transcription and translation. It is the DNA genes that allow the

Hepatitis C virus (HCV) is from the virus family Flaviviridae with an RNA envelope serving as it's genetic material. The genetic material (RNA) is HCV's pathogenic structure. The genome is positive sense single stranded RNA, which is very similar to mRNA and can be translated quickly to the host cell (Bauman 2012). Hepatitis C is an enveloped virus, and the RNA also lacks a proofreading ability after replication, which results in mutations coding for many genotypes within the host. This genetic variability makes it difficult for the host immune system to clear all the HCV infections. As one infection clears, another strain is being produced (Bauman 2012). The HCV antibody detected by ELISA(Wilkinson

HSV-1 is generally transferred from one person to another by kissing.... HSV-2 is usually transferred by vaginal intercourse or anal intercourse. Yet in the same way HSV-1 may invade the genitals and then trigger genital HSV simplex virus, HSV-2 will transfer from a single person's genitals to one other person's lips, leading to oral herpes.

The virus on entering the body will target specific cells such as those of the liver, immune system and the endothelial lining of the blood vessels.

HSV-1, the prototype α-herpesvirus, is a highly contagious infection known to cause several diseases ranging from painful skin lesions to keratitis and encephalitis. The virus, which is common and endemic throughout the world, causes a lifelong infection for which there is no cure, although treatment can reduce symptoms. During lytic infection, one of the first proteins to be expressed by HSV-1 is ICP27, a 63kDa, 512-amino acid protein that is post-translationally modified by phosphorylation and arginine methylation, modifications that also regulate some of its functional interactions. ICP27 is a highly conserved regulatory protein that assumes different roles throughout the course of infection. One major role of ICP27 is as the primary

Some viruses also have an outer bag of lipo-protein called an envelope. After a virus attaches to a living cell, it either enters the cell to release the genetic information, or, the virus injects the information through the cells outer lining. Thus changing the cells natural functions and forcing the cell to spend its energy to create copies of the virus. The cell will go on making copies of the virus until the cell is used up and dies. The virus then leaves the dead cell and invades a nearby cell and the process starts all over. There are five types of human herpes virus: Varicella zoster which causes chickenpox, Epstein Barr virus which causes infectious mononucleosis, cytomegalovirus which can cause cytomegalic inclusion disease in infants, and herpes simplex viruses 1 and 2.

The influenza virus usually has a round shape; it can be elongated or even have an irregular shape at times. In addition, it has a layer of spikes on its exterior. Note that there are two different types of these spikes. Each spike has its own protein, one is the hemagglutinin (HA) protein and the other is the neuraminidase (NA) protein. The HA protein lets the virus to attach to a cell, so it can enter into a host cell and start the infection process (every virus must enter cells in order to make more copies of themselves). The NA protein is needed for the virus to leave the host cell, so that new viruses that were made inside the host cell can infect more cells. Because these proteins are present on the surface of the virus, they are visible to the human immune system. Inside the layer of spikes, are eight pieces of RNA that contain the genetic information for making new copies of the virus. Each segment contains instructions to make one or more proteins of the virus.

There is no difference in the pathogenicity between subtypes because cross immunity exists among them due to universal presence of the “a” determinant (Ganen, 1996). Antibody to “a” determinant is used in the diagnostic assay kit for HBsAg detection (Caan, 1996). The complete virus or Dane particles are the infectious viron of HBV (Ganen, 1996). Its outer shell is a lipoprotein envelope containing the viral surface glycoprotein. The inner core particle (hepatitis B core antigen) or nucleocapsid has a diameter of 25 – 27nm and its major structural protein is the C protein (Adabara et al., 2012) within the core is the viral DNA, a protein kinase and a polymerise known to be centrally involved in genomic replication. The core also contains non particulate soluble antigen (HBeAg) derived from HBcAg by proteoltic self-cleavage. The viral DNA is a double stranded circular molecule. This molecule has an unusual structure such that its two DNA are not perfectly symmetrical. Replication of HBV occurs predominantly in liver but also occurs in lymphocytes, spleen, kidney and pancreas. HBsAg is a product of S gene of the HBV genome and the prime constituent hepatitis B particle forms. It is manufactured in the cytoplasm of infected hepatocytes in high quantities, the excess that did not combine with DNA to produce viral

The protective capsid helps the virus escape detection and destruction during the invasion of the host. When the virus reaches the target cell, biochemical reactions between the capsid and cell wall allow the virus to latch on and inject its genome into the cell’s interior. Once inside, the viral genetic material insinuates itself into the host’s DNA or RNA. In an efficient feat of natural bioengineering, the host cell’s genetic machinery now does the rest of the work for the virus. The cell, which had already been making copies of its own genome, now also replicates that of the virus. Coded within the viral material is the blueprint for making more copies of the viral genome. Further instructions command the production of capsids and directions for assembly of new viruses. After the host cell becomes engorged with viruses, it explodes, sending the new