Virus Structure
In order to understand how this virus attacks the human body, one must understand it's structural properties. It is approximately 120 nm in diameter, 60 times smaller when compared to a red blood cell(3). The genome of this virus is made up of two identical RNA chains, which are held together through hydrogen bonding to form a dimer(3). The RNA strands are about 9749 nucleotides long and are bound to p7 nucleocapsid proteins which are nucleic acid associated proteins(4). They serve two main purposes, one being the fact that they chaperone the conversion of RNA into DNA. As well as, driving the selection and dimerization of RNA during the initial stage of virus assembly(5).
The main genes in the HIV genome are gag, pol and env . The gene gag codes for a group of proteins that make up the “viral core” including p24 which makes up the viral capsid in which the RNA strands are located. The gene pol codes for a number of proteins, but most importantly reverse transcriptase which is vital to its life cycle(5) . This gene also codes for integrase and protease. Integrase is an enzyme that integrates the viral DNA into the target cell’s DNA. Protease is an enzyme that processes proteins from HIV genome so they can be assembled into the new HIV viruses which are produced during the life cycle. The env gene codes for one protein alone called the gp160. This is a glycoprotein (made up of enzymes and complex carbohydrates), after being synthesized this protein travels to the cell surface where protease cleaves into two different proteins which are gp120 and gp41 (3)
Additional genes located on the genome of this virus include tat, rev, nef, vif and vpr (3). Tat gene codes for the tat protein which is an abbreviation for transactivator, this protein binds to cellular factors and allows for their phosphorylation and rapid transcription of HIV genes(3). The tat protein itself is toxic to human cells and large amounts of this in the body worsens the severity of the infection. The rev gene codes for the rev protein which is used to stimulate production of HIV proteins and regulation of gene expression. The vif gene codes for the vif protein which increases the infectivity of the virus, it does this by binding to a cellular protein which is part of the immune response(3). The cellular protein is called APOBEC3G, what this protein usually does is inactivate virus particles, but when the vif protein binds to it, it will become degraded and no longer inactivate virus particles(3).
The RNA dimer is located inside the virus capsid which is made up of p24 proteins, attached to the capsid are the different enzymes; reverse transcriptase, protease and integrase which are all required for the complex life cycle of this retrovirus(3).Then there is the HIV matrix protein made up of p17 which lies between the viral capsid and the lipid envelope. The lipid bilayer is made of phospholipids, which themselves consist of glycerol, two fatty acids, a phosphate group and an R group. These structures are amphillic meaning they are both hydrophobic and hydrophillic. The Long Terminal Repeat is something which is often found in strands of RNA or DNA, the purpose of this sequence is that they are "sticky ends" which the integrase protein uses to insert the HIV cDNA (copied DNA) into the host DNA(5). The matrix protein helps anchor the gp41/gp120 “spikes” to the lipoprotein envelope. Finally the envelope is made up of a lipid bilayer (usually taken from host cells during budding). On the lipid bilayer are “spikes” made up of 3 gp120 and a gp41(3). The gp120 proteins are located on the outside of the virus which are used to bind to CD4 receptors (which are located on T-Cells). The gp41 protein is located on the inside of the virus and anchors the gp120, it is responsible for the membrane fusion process when a host cell attaches to the virus(3).
Additional genes located on the genome of this virus include tat, rev, nef, vif and vpr (3). Tat gene codes for the tat protein which is an abbreviation for transactivator, this protein binds to cellular factors and allows for their phosphorylation and rapid transcription of HIV genes(3). The tat protein itself is toxic to human cells and large amounts of this in the body worsens the severity of the infection. The rev gene codes for the rev protein which is used to stimulate production of HIV proteins and regulation of gene expression. The vif gene codes for the vif protein which increases the infectivity of the virus, it does this by binding to a cellular protein which is part of the immune response(3). The cellular protein is called APOBEC3G, what this protein usually does is inactivate virus particles, but when the vif protein binds to it, it will become degraded and no longer inactivate virus particles(3).
The RNA dimer is located inside the virus capsid which is made up of p24 proteins, attached to the capsid are the different enzymes; reverse transcriptase, protease and integrase which are all required for the complex life cycle of this retrovirus(3).Then there is the HIV matrix protein made up of p17 which lies between the viral capsid and the lipid envelope. The lipid bilayer is made of phospholipids, which themselves consist of glycerol, two fatty acids, a phosphate group and an R group. These structures are amphillic meaning they are both hydrophobic and hydrophillic. The Long Terminal Repeat is something which is often found in strands of RNA or DNA, the purpose of this sequence is that they are "sticky ends" which the integrase protein uses to insert the HIV cDNA (copied DNA) into the host DNA(5). The matrix protein helps anchor the gp41/gp120 “spikes” to the lipoprotein envelope. Finally the envelope is made up of a lipid bilayer (usually taken from host cells during budding). On the lipid bilayer are “spikes” made up of 3 gp120 and a gp41(3). The gp120 proteins are located on the outside of the virus which are used to bind to CD4 receptors (which are located on T-Cells). The gp41 protein is located on the inside of the virus and anchors the gp120, it is responsible for the membrane fusion process when a host cell attaches to the virus(3).