1.4. HIV types and characteristics
Types of HIV
The HIV virus belongs to a subgroup of retroviruses known as lentiviruses, or "slow" viruses. This type of virus has no cellular structure, and it doesn’t synthesize protein. The HIV virus can only replicate inside cells of the immune system containing the CD4 receptors on their surface, taking over the cell’s equipment to reproduce.
There are 2 types of HIVs: HIV-1 and HIV-2.
HIV-1 is the main cause of HIV infection and the cause of the pandemic in the world, while HIV-2 circulates locally and is mainly confined to West Africa.
HIV-1 is divided into 3 types: M, N and O. The basic M-type (which originates from the word “main”) is divided into several subtypes designated by the letters (A-K).
Human immunodeficiency virus has certain characteristics:
- High selectivity. It infects only cells of the immune system, and only those that have CD4 receptors: mainly T-lymphocytes as well as monocytes, macrophages and some other cell types.
- The ability of the virus to mutate. Each new viral particle is different from the original. This allows the virus to escape immune detection, which doesn’t happen in time to reproduce antibodies against the virus.
- Self preservation. The virus can be stored in the body without reproduction (inT-lymphocytes) quite a long time.
- Natural immunity to HIV. There are a small number of people (approximately 1%) among Europeans with the CCR5-delta32 mutation that prevents a particular type of HIV-1 (with affinity to co-receptor R5) from joining the CD4 cells.