Structure, Replication, Diagnosis and Treatment of HIV

INTRODUCTION
HIV is short for Human Immunodeficiency Virus, the virus that causes AIDS. HIV is a virus, hence it cannot grow or reproduce by itself. Therefore it needs to infect the cells of a living organism in order to replicate, or make new copies of, itself (Noble 2010).

1. STRUCTURE
1.1 Gross Structure
HIV exists as an aggregate of roughly spherical particles (Noble 2010) when outside of a human cell. The particles, which are called virions, have surfaces studded with numerous little spikes. The size of an HIV particle is around 0.1 microns in diameter, which is roughly about 4 millionths of an inch (Noble 2010).

The particles of an HIV are surrounded with a coat of fatty material known as the viral envelope (Noble 2010), or membrane. Around 72 tiny spikes project outward from this. These spikes are formed from the proteins gp120 and gp41 (Noble 2010).

Located below the viral envelope is the matrix, a layer made from protein p17 (Noble 2010).
The viral core, or capsid, is usually shaped like a bullet and is made from the protein p24 (Noble 2010). There are three types of enzymes contained within the core. These enzymes are required for HIV replication and are named reverse transcriptase, integrase and protease (Noble 2010). The core also holds two identical strands of RNA, which serves as the genetic material of HIV.

1.2 Retrovirus and Lentivirus Characteristics
As a retrovirus, HIV differs from other viruses in that its genes are composed of RNA, or Ribonucleic Acid (Noble 2010), unlike other viruses and most organisms that use long strands of DNA in which they store their genetic material. As RNA is different from DNA, the implication is that the replication process of HIV is a little more complicated than that of other viruses (Noble 2010). At the end of these RNA strands one can find the long terminal repeat (Noble 2010), which is a sequence that helps regulate the replication of HIV.

As a lentivirus, HIV belongs to the same group that includes SIV, FIV, Visna and CAEV, the viruses that infest monkeys, cats, sheep and goats (Noble 2010).

1.3 Genes
On the subject of genes, HIV has just nine genes (Noble 2010) while a bacterium may around 500 and a human being may have as many as 20,000-25,000. The HIV genes have certain designations. Three of these genes  gag, pol and env  contain information needed to make structural proteins for new virus particles (Noble 2010). The other six genes, however, are responsible for coding proteins that command the HIV to infect a cell, produce new copies of virus, or cause disease (Noble 2010).

1.4 Magnification
On the subject of magnification, HIV are too small to be seen through an ordinary microscope (Noble 2010) but are visible with an electron microscope.

2. REPLICATION
The only way for HIV to replicate, or make new copies of itself, is to invade human cells.

2.1. Entry
The beginning of the process is signaled by the contact of the HIV particle with a cell that carries on its surface a special protein called CD4 (Noble 2010). The spikes on the surface of the virus particle attach themselves to the CD4 causing the viral envelope to fuse with the cell membrane (Noble 2010). This is then followed by the release of the contents of the HIV particle into the cell leaving behind the envelope.

2.2 Reverse Transcription and Integration
As soon as the HIV is within the cell, the HIV enzyme reverse transcriptase converts the viral RNA into DNA (Noble 2010). This DNA, which is now compatible with the genetic material of humans, is transported to the nucleus of the cell and spliced into the human DNA (Noble 2010) by another HIV enzyme, integrase. As soon as the process of integration is complete, the HIV DNA, which is now completely integrated into human DNA, is known as provirus (Noble 2010).

2.3 Transcription and Translation
HIV provirus may stay indefinitely inside the human cell for a long time. However, as soon as the cell activates, it treats HIV genes in much the same way as human genes (Noble 2010). The first step is that the cell and the cellular processes within it use human enzymes to convert the HIV genes into messenger RNA. The messenger RNA is then transported outside the nucleus (Noble 2010), and is then translated and used as a blueprint, or template in order to produce new HIV proteins and enzymes (Noble 2010). This step clearly shows that the human cell possesses no ability to recognize the HIV genes of the HIV provirus because they are masked as human DNA. Therefore, instead of the human cell purging the HIV DNA, it actually transcribes it within the nucleus and translates it outside causing it to act as the structural and functional component of the various parts and processes of the human body.

2.4 Further Replication
Instead of human genetic material, the one transcribed and translate are actually complete copies of HIV genetic material (Noble 2010). These twin processes of transcription and translation further form new viral particles (Noble 2010) and the intracellular process repeats. It is also at this point that the HIV enzyme protease chops up long strands of protein into smaller pieces which are used to construct mature viral cores that are ready to infect another cell and begin the replication process all over again (Noble 2010).

3. DIAGNOSIS

3.1 Preliminary Tests
Before any diagnostic procedures are conducted, there is a need for a preliminary self-examination of ones health habits and lifestyle to be done by the patient himself. A test is imperative if one has had unprotected vaginal, anal or oral sex with men who have sex with men, multiple partners, or anonymous partners (Centers for Disease Control and Prevention n.d.). Other symptoms that predispose one to HIV would be a previous diagnosis and treatment for hepatitis, tuberculosis, or a sexually transmitted disease (CDC n.d.).

3.2 HIV Tests
Mostly, HIV tests are antibody tests that measure the antibodies your body makes against HIV and it is expected that most people will develop detectable antibodies within 2 to 8 weeks with the average falling at 25 days. This is called the window period (CDC  n.d.).

3.21 Oral Fluid Tests
This particular HIV test uses oral fluid, not saliva, which is collected from the mouth using a special collection device (CDC n.d.). One particular example of oral test is the OraSure HIV antibody test that uses oral mucus obtained with a specially treated cotton pad that is placed between the cheek and lower gum for two minutes (San Francisco AIDS Foundation 2010).

3.22 Urine Test
Although this is not as accurate as a blood test, it also yields substantial results.

3.23 Rapid Test
Within 20 minutes, one can produce very quick results with a rapid test. This particular HIV test uses blood from a vein or from a finger stick (CDC n.d.).

3.24 RNA Test
RNA tests are used to look for genetic material of the virus (CDC n.d.) using the blood and used in cases where antibody tests are unable to detect antibodies to HIV. (CDC n.d.). Another name for the RNA test is NAT or NAAT test, which stands for nucleic acid amplification test, and serves to detect the presence of genetic material specific to HIV (SFAF 2010).

3.25 Home HIV Antibody Test
This particular HIV test, of which one U.S.-based company in the name of Home Access is approved to conduct, uses a blood sample from a finger prick (SFAF 2010). The sample is then sent to a certified medical laboratory for testing and analysis.

4. TREATMENT
Until the early 1980s during the start of the AIDS outbreak, drugs were scarce and treatment was rare thus people with AIDS were not likely to live longer than a few years (National Institute of Allergy and Infectious Diseases 2009). The treatment for HIV or AIDS actually does not cure the patient but rather they suppress the virus. If the amount of virus in the body is suppressed, AIDS patients can lead longer lives but they can still infect others with the virus.

4.1. Performance of Antiretroviral Drugs
Nowadays, with 31 antiretroviral drugs sold in the market to treat HIV infection, 73 percent of AIDS patients had been treated with the leading drug AZT or zidovudine at one time or another (NIAID 2009).

4.2. Classes of Antiretroviral Drugs
The various antiretroviral drugs are classified into Reverse Transcriptase (RT) Inhibitors that interfere with the reverse transcription process of converting HIV RNA to HIV DNA, Protease Inhibitors that blocks the action of the protease enzyme in producing infectious viral particles, and FusionEntry Inhibitors that prevents HIV from fusing with the cell membrane, thereby blocking entry into the host cell (NIAID 2009). Moreover, two other antiretroviral drugs include Integrase Inhibitors that block the action of the enzyme integrase in integrating HIV genetic material into the human cell, and Multidrug Combination Products that combine any of the previously mentioned drugs in order to produce a more potent inhibitor against HIV (NIAID 2009).

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