HIV, also known as the human immunodeficiency virus, is transmitted via contaminated body fluids such as blood, vaginal fluid and semen. This disease destroys the immune system, resulting in acquired immune deficiency syndrome, or AIDS. HIV is not curable, partly due to some characteristics that make this virus different from other, more easily treatable viruses.
Reverse Transcriptase
One of the unique features of HIV is that it stores its genetic material as ribonucleic acid, also known as RNA, as opposed to the DNA or deoxyribonucleic acid, that is found in cells. Although the two types of nucleic acids are similar, HIV must convert its genetic material into DNA in order to incorporate its genes into the host cell. To do this, HIV uses a special protein called reverse transcriptase, the University of Utah explains, which is able to convert RNA into DNA. Reverse transcriptase is the target for many different drugs used to combat HIV, as the enzyme is not found in human cells and is essential for the progression of a HIV infection.
HIV and the Immune System
Another unique characteristic of HIV is that it attacks a specific kind of immune cell, known as CD4-positive T-cells. In order to enter into a human cell, HIV needs to bind to a protein known as CD4, which is only found on certain T-cells, TheBody.com notes. These CD4-positive T-cells are important for the immune system's ability to fight off infections; thus, by attacking these cells, HIV is able to weaken the body's immune system. Paradoxically, the immune system will try to produce more of these cells to fight off a HIV infection, which only gives the virus more cells to infect.
Mutations
HIV is also different from other viruses in that the process that it uses to duplicate its genetic material is error-prone. Because the process is prone to errors, HIV undergoes frequent mutations. Some of these mutations make it easier for the virus to evade treatment and the immune system, a 2001 article in Science Daily titled "Minor Mutations In HIV Virus Have Major Impact" reports. Frequent mutations can mean that over time the virus can develop resistance to certain medications, and it also prevents the manufacturing of an effective vaccine, as small changes in the genes of the virus would render the vaccine useless.
