Reverse transcriptase:

Why we cannot beat HIV AIDS

Dr. M. W. N. Dharmawardene

DISEASE: "The world has been unconsciously slow. About 17 million women are now infected and it is especially disappointing to see the world's lack of movement in fighting the spread of HIV in women and girls," lamented Koffi Annan, Secretary General, UN.

He was addressing a special session of the UN General Assembly on HIV/AIDS recently. HIV is the acronym for Human Immuno Deficiency Virus.

The disease is given the acronym AIDS, for Acquired Immuno Deficiency Syndrome.

When an infection is caused by a microorganism, it is the white blood cells or lymphocytes that coordinate and control our defense (immune) response to invaders of our body. These cells respond to invading microorganisms by mass proliferation, communicating with other cells of the immune system and producing molecular missiles that subdue the invaders.

HIV directly attacks the white blood cells of our immune system which is the defense mechanism in our body that fights invading microbes. HIV gradually overruns the white blood cells, making the system weak and deficient. When immune system gets weak and deficient, one becomes vulnerable immediately to even the common germs as the body is unable to fight the invading microbes including HIV.

At this stage, victim dies either of full-blown AIDS or some other common infection such as a common cold. It is for this reason the virus is called Human Immuno Deficiency Virus or HIV because it makes your immune system deficient. As the virus is always acquired from another person who has the disease, it is called Acquired Immuno Deficiency Syndrome or AIDS.

No doubt, the Secretary General of the UN had reasons to express his concerns and disappointments at the 'apparent inactivity' of the world community in tackling the AIDS virus which seemed to be galloping unchecked across the globe.

"These shortcomings are deadly" he went on to say showing his anxiety over the mounting problem. He knew from the information on the global spread of the disease, that the deadly disease would certain to create havoc in every nation if HIV is allowed to have its own way.

However, he was probably unaware that it was not only him that was frustrated at the apparent inability of modern science to crack the HIV paradox.

Senior research scientists who had grappled with HIV over a decade in the most modern laboratories and at human clinical trials in trying to outwit this deadly enemy were equally exasperated for they were now at their wits end with the super bug HIV.

However, unlike the Secretary General, scientists had the satisfaction of knowing that they were fighting one of the most unusual virus, ever seen in the medical history, a marvel of biological evolution, a fighting machine which has the ability to nullify an array of missiles, by changing itself within a very short period of time.

Furthermore, they had the pleasure of unraveling one of the most unusual secrets of natural evolution in the form of HIV. It has now become a mind boggling scientific challenge of enormous magnitude in the history of life sciences, especially to molecular biologists and the geneticists.

For, this virus has evolved novel mechanisms that enabled it to have an evolutionary edge over drugs and vaccines that were thrown at it for well over a decade.

All other viruses would get simply wiped out by those drugs but HIV. It has learnt simply to ignore them. Moreover, it has learnt to frustrate all the known weapons of the human immune system as well, by having a master craftsman called Reverse transcriptase in its cells. It is this most unusual enzyme that has given the HIV, its super powers.

The AIDS causing Human Immunodeficiency Virus or HIV is the most intensively investigated and most talked about virus in the medical history. All over the world millions of dollars are being spent in various laboratories undertaking very sophisticated experiments under the guidance of expert scientists to find a cure to overrun the virus.

But each time a drug is discovered, AIDS virus finds a way out to beat the drug in no time! Upto now, AIDS virus has managed to keep its evolutionary edge one step ahead of the drugs discovered by scientists and also to outrun our immune system.

This success of HIV, to beat the efforts of scientists has brought misery to millions of people all over the world who got infected with it annually. As of today, there is not a single country in the world, which is free of this deadly disease. It is still spreading and infecting millions of more people every year. Last year alone, 4.1 million people worldwide were infected and at least 2.8 million died of the disease.

It is said that highest number of AIDS victims are found in India, but this of course in a population of one billion people and as a percentage it is less than one per cent which fades into insignificance when compared it with that of Sub-Saharan Africa. In Swaziland, it is said that one in every three adults is infected.

Today, almost 40 million people live with AIDS and millions of them are sure to die from full-blown disease. The situation in Sri Lanka, although has not yet reached epidemic levels, statistics show that nearly three HIV positive cases are reported each day.

However, research scientists are now thinking of a different approach. They want to use the mechanism used by AIDS virus itself, namely error prone copying of its DNA by reverse transcriptase which gives the evolutionary edge, for its success, to spell its own doom. Scientists want to increase the number of errors in each viral DNA.

Instead of few errors as presently done by reverse transcriptase, they want it to introduce more errors in one go. Their reasoning is that if we can increase the number of errors in each copy of viral DNA beyond a given threshold, then the organisms thus produced would become unstable. Such a population of AIDS virus would become very sluggish.

This may give the human immune system the advantage it needs to overrun the virus. If scientists could figure out how to make this happen, then we could trick the AIDS virus to spell its own doom. It seems that one has to set a thief to catch a thief!