Human Immunodeficiency Virus (HIV) is very simple in its structure and the way that it infects cells and replicates. Ironically, it is this very simplicity that makes HIV so difficult to treat. With a genome of only 9 genes that code for around 20 different proteins and processes, there is a very limited number of targets to attack. To complicate matters further the virus is usually hidden inside the human cells and is therefore protected from the immune system. Viruses outside the cells are covered in an outer layer called the envelope, this is actually part of the host cell membrane which the virus uses to cloak itself when it bursts from the cell.
HIV is a virus, which means that it is not alive. So how do you ‘kill’ something that is non-living. Well much like defending yourself in a zombie apocalypse you need a very specific and targeted method; a headshot in the case of zombies. However, in the case of HIV the ‘headshot’ treatment needs to destroy the virus while leaving the human host unharmed.
Sounds simple enough, doesn’t it? Humans and viruses look nothing alike; it should be easy to tell the difference between them. It’s like that age-old adage of distinguishing between apples and oranges. But the story on a molecular level is completely different. Most of the genetic material and enzymes that make up HIV are basically the same as those found in humans. So, if you develop a drug that, for example, destroys HIV enzymes and administer it to a patient, the drug will not be able to distinguish between the viral and human enzymes and will destroy both leading to the death of the patient as well as the virus.
There are 6 main categories of HIV treatment. They either target viral enzymes and the way that they work, or they prevent the virus from attaching to and entering the human cell. HIV can develop resistance to these drugs with a single genetic mutation. When human DNA is copied there is an intricate system in place to ensure that the copy is an exact replica of the original. However, in a rapidly replicating virus as simple as HIV mutations take place all the time. Think of making a photocopy of a photocopy of a photocopy, with each successive copy looking less like the original. In the case of HIV sooner or later the change in one of the copies will make it drug resistant. This copy or mutant of the virus will then flourish unaffected by the drugs being administered to the human host.
The solution… drug cocktails containing different treatments. To develop resistance to a drug cocktail HIV would need to mutate resistance to multiple drugs simultaneously. Infected patients being treated are continuously monitored and when viral load increases the drug cocktail is changed.
Sadly the treatments currently available for HIV can only prevent the virus from replicating and infecting new cells, but cannot cure cells that have already been infected. The aim of treatment is to allow the body’s immune system to recover, to prevent transmission of the virus and to improve the length and quality of life of the patient.
HIV is here to stay, and it is unlikely that a cure will be developed within our lifetimes. Perhaps the key to defeating this disease is not in developing a cure but in preventing infection in the first place, this will be the topic of my next article.
