HIV/Aids

03 November 2006

A day in the life of the HI Virus

We know HIV causes AIDS. It was first recognised in 1981 - yes, it's been with us for the last 20 years!

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We know HIV causes AIDS. It was first recognised in 1981 - yes, it's been with us for the last 20 years!

HIV positive means you have been infected with the virus and AIDS means that you have a syndrome of immune deficiency that may eventually lead to death. Once HIV positive, there is no cure. Up till now there are no proven cases of people that have recovered completely.

It may take seven to ten years for a HIV positive person to develop AIDS. People with AIDS survive for one to three years on average, but there are people that have had AIDS (not HIV) for more than five years. HIV positive people are normal people like you and me and pose no threat to anyone as long as you don't make love to them without a condom. HIV can also be spread from mother to child via the placenta (vertical transmission) and breast milk, and by receiving infected blood through blood transfusions, shared needles, etc. (horiontal transmission).

What do you need to know?

The body recognises the virus and tries to kill it by producing antibodies within three to six months after the infection. This is the time where the ELISA (Enzyme-linked immunosorbent assay) and Western blot tests are negative and is called the window period. During this time the PCR (polymerase chain reaction) test will be able to tell if you have been infected by detecting viral nucleic acid. The ELISA and Western blot tests are 99.9% accurate.

If you have a HIV positive blood test, it means that you have antibodies against the HI virus. There are people who test negative for HIV antibodies, but are PCR positive for years. Yes, you've guessed it; these are the people every trashy magazine in the world focuses on. What they forget to tell you is that these people are as scarce as hen's teeth and that they are 400 times less infective than other HIV positive people.

The Aids virus infects, replicates in and destroys cells like B-lymphocytes, macrophages, microglial cells of the brain and dendritic cells in the skin, but it mainly targets CD4 lymphocytes. CD4 lymphocytes direct the other cells in the immune network when an immune reaction takes place and are also known as CD4 helper-inducer lymphocytes. It stands to reason then that if the CD4 lymphocytes don't work properly, the whole immune mechanism suffers. This is also why the CD4 count is a good marker of how far the disease has progressed.

Still with me?

The HI virus consists of viral RNA (ribonucleic acid or viral genetic material) surrounded by a protein coat. HIV locator spikes (glycoprotein or GP120) protrude through this layer. It has a unique enzyme called reverse transcriptase that enables it to replicate in DNA (deoxyribonucleic acid) host cells. Some of the AIDS treatments target this enzyme to stop replication of the virus and in that way slow down the progression of the disease.Ok, if you are still reading this, you really do want to know how the virus operates in the body. What follows is a simplified version of the life cycle of the HI virus:

1. The GP120 spikes attach to the receptor proteinson the wall of the CD4 cell.
2. The virus penetrates the CD4 cell and sheds its protein coat.
3. The virus releases its genetic material (RNA) along withthe reverse transcriptase enzyme.
4. The reverse transcriptase enzyme uses the single-strand RNA as atemplate to form a double strand DNA copy.
5. This new viral DNA now enters the cell nucleus andjoins with the cell's own DNA.
6. It now hijacks and reprograms the DNA toproduce more viral RNA.
7. The cell can no longer carry out its normal functions, but instead has become a virus factory with its hijacked DNA sending outmany strands of new viral RNA to construct new HIVs.
8. The new HIVs erupt from the cell and often cause cell death.
9. These new HIVs now infect many more CD4 cells and leadto the crippling of the patient's immune cells.
10. This eventually leads to AIDS.So there you go; HIV in a nutshell.

Now that you have a better understanding of HIV and AIDS, I hope that you will stop fearing HIV positive people and treat them like the normal people they are.

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Ask the Expert

HIV/Aids expert

Dr Sindisiwe van Zyl qualified at the University of Pretoria before working for an HIV/AIDS NPO in Soweto for many years. She was named one of the Mail & Guardian's Top 200 Young South Africans in 2012.

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