What makes HIV such a lethal virus, is the fact that it affects the immune system of the body, leaving you exposed to a number of diseases, with virtually no help of any kind from your immune system. Now, because the immune system of our body is responsible for warding off potential threat to the body, in the form of external threats (such as virus, bacteria and protozoa), therefore a weakened immune system would mean that even medicines would not work. This means that an HIV+ patient has little hope. This is because HIV is still an incurable disease till date; and though we have many scientists claiming to find a cure, we still lack conclusive evidence on their part.
So, how does the Human Immunodeficiency Virus actually affect your immune system? The answer lies in the complex nature of HIV. As it is, HIV is a part of the family of Retroviridae and is an RNA virus. Unlike the human cells, which store information in the form of DNA or deoxyribonucleic acid, HIV stores its information in the form of RNA or ribonucleic acid.
Now, once the virus enters the human body, it performs an unusual function of converting the RNA into DNA. This it does so, by entering a target cell and then converting RNA information into double stranded DNA by way of a reverse transcriptase, which is already present in the virus particle. Once this happens, the contaminated DNA is then integrated into the cellular DNA by way of integrase.
The primary focus of HIV is to infect vital cells in the immune system, such as CD4+ T cells and dendritic cells. This results in lowering of the levels of CD4+ T cells. With the CD4+ T cell count going below a critical level, the immune system of the body of the body weakens and you are vulnerable to a number of diseases and infections.
Now let us see how, does the virus lower your CD4+ T cell count. It does so, in mainly three ways. First, by inflicting direct damage to the cells, secondly, by increasing the rate of apoptosis (the rate of natural death of cells) in infected cells and thirdly, by way of killing infected CD4+ T cells.
A major difficulty in finding a cure for HIV is its genetic variability, which is very high. The main reason for this is variability is the fast replication cycle of the virus, which results in producing as many as with the generation of 109 to 1010 virions per day. Add to this a very high mutation rate and you have a lethal situation leading to the formation of many variants of HIV in a single infected patient in the course of one day. The situation gets more complex, in case if a single cell is simultaneously infected by two or more different strains of HIV.