HIV-The amazing retrovirus
If one took a step back, a drug user could be forgiven for thinking that the only real health information users seem to receive is regarding what illnesses we may ‘spread’ to others, namely HIV and Hep C, B. In reality though, many long-term drug users could identify numerous life threatening but non-infectious illnesses that are related to IV drug use, yet would consistently discover this type of information hard to find and rarely given out. (BP will continue to pursue these matters).
However, whichever way you look at it, HIV/AIDS has affected almost everyone’s life in one way or another and although there is currently no cure, a huge amount of knowledge has been gathered about HIV and the way it behaves in the body. Unfortunately though , information is seriously lacking for positive drug users. The specialist knowledge needed regarding drug user specific infections, the huge questions surrounding the complex interactions between controlled and illicit drugs with combination therapies, the scarcity of information concerning dual diagnosis (HIV and HCV), and the absence of opportunities for drug users to take part in trials and research – continually paint a very bleak picture for many drug users, not just in the UK but around the world.
This issue, instead of the usual information made available to drug users regarding the principles around not sharing works, BP wanted to expose the inner workings of this extremely clever ‘retrovirus’. By pulling together such words like lymphocytes, T- cells, macrophages, antibodies etc. it may help create a picture of not only the progression of HIV and how it works in the body, but could also give an understanding into why some of the new HIV drug regimes are thought to work.
HIV and AIDS
Even now at the end of the 20th century, we still hear talk of the ‘AIDS virus’ and an ‘AIDS test’ but AIDS (Acquired Immune Deficiency Syndrome) is an acquired condition rather than an inherited one – a syndrome with a number of manifestations rather than a single disease. Most scientists believe that HIV (Human Immuno Deficiency Virus) is the virus that causes AIDS. By attacking and destroying the immune system, the part of the body responsible for fighting off infections and diseased and malignant cells, the human body cannot even fend off the most trivial of illnesses.
Various viruses, bacteria and other micro-organisms seize such an ‘opportunity’ (the reasoning behind the word opportunistic infections) and multiply while the body’s defenses are down. Consequently, a problem that would be easily overcome by a healthy immune system could now become life threatening for someone with a severely depleted immune system. Defects in immunity can also allow certain cancers (malignant cells) to develop.
The Brilliant Workings of a Retro Virus
Viruses are not capable of existing independently. They are tiny parasites and in order to survive, they must find a host cell in which they can reproduce or replicate themselves. All viruses are structured in a similar way. Their outer coat is a protein shell, often wrapped in a fatty envelope, which holds the virus’ inner core. This core (nucleus) is where the virus gets its genetic material (its genes), the blueprint which tells the virus what it is, what it does and how it does it. This genetic material is stored as an individual sequence of small molecules that make up a strand of either DNA (deoxyribonucleic acid) or RNA (ribonucleic acid), sometimes referred to as ‘beads on a necklace’.
Most living organisms, by contrast, have their genetic material stored as DNA. From each particular sequence of molecules, the cells of plants and animals make a mirror image of this genetic material. This copy is called RNA. The RNA contains all the information needed for a cell to survive and do its job. The genetic material of the group of viruses called retroviruses – to which HIV belongs, is made up of RNA rather than our more usual DNA. But this is no copy. ‘Retro’ means backwards and retroviruses are so called because instead of making the usual RNA copy out of its genetic material – its DNA – HIV does the opposite. This means that once it enters a host cell, its RNA will then change dramatically, as the viral RNA makes a DNA copy, thanks to a remarkably versatile enzyme called reverse transcriptase.
Reverse transcriptase is unique to retroviruses and does not occur in human’s cells. Such individuality has become important when designing HIV drugs. The trick being to find some way of knocking out the virus without destroying the human cells in which it lives. (You may have heard of drugs called Reverse Transcriptase Inhibitors such as AZT- obviously inhibiting the role of this enzyme to assist in the RNA conversion).
A popular analogy for HIV replication is the take-over of a factory assembly line (the host immune cell) by new management (HIV), which uses existing machinery (the host cell’s DNA) to manufacture new products (more HIV), which in turn, leave to take over new factories (other immune cells).
However, the DNA copy of this viral chromosome, with continued help from the reverse transcriptase, then goes a step further. It violates the very essence of its victim’s (the host cell) being – by entering the core or nucleus of the cell and inserting itself into the host’s chromosomes. Most retroviruses can only accomplish this feat when a cell is dividing and this is where HIV has a great advantage. It can actually inset copies of itself into the chromosomes of non-dividing cells. This then opens up HIV to whole classes of cells that are normally protected from retroviral invasion. It is the very fact that HIV attacks immune cells, which leads to the immune deficiency seen in AIDS. Most viruses will only enter other body cells leaving the immune system free to respond.
Chemical changes within the cell causes the host cell to refer to its genetic information for clues as to how to deal with this new uninvited intruder – HIV. But of course, HIV has already incorporated its own genetic material into the hosts cell, so when the cell begins reading for information, it will inadvertently read HIV’s DNA. Acting as though it is putting up a form of defense, it is tricked into making many new copies of HIV particles, replicating HIV’s blueprint. It is clear that HIV affects the immune system in a way which allows it to continue to reproduce itself, gaining an advantage.
The way a retrovirus such as HIV works is indeed very complex. We have only discussed one aspect of the whole process here – and scientists are always learning more. The new drugs that have come onto the scene for positive people since 1995 – 96 have indeed seemed to help some people and although we are still unsure of the long term effects of such highly toxic drugs on the body, they have changed the outlook for millions with HIV and saved millions of lives. References are available from BP.