HIV

HIV is a tiny germ.

It can go into the body through blood. Once inside, it looks for special cells. These cells help the body fight off sickness.

The germ enters these cells to make copies of itself. This can make the body's defenses very weak. When the defenses are low, other germs can cause trouble.

Some germs can stay quiet for a long time. They might stay in the body for ten years. During this time, a person might not feel sick at all.

There are two main types of this germ. One type is found all over the world. The other type is mostly in West Africa.

Doctors work hard to help people stay healthy.

It is important to learn how these germs work.

HIV is a tiny germ that attacks the body.

It targets vital parts of the immune system. These include helper T cells, which are cells that help fight sickness. When these cells are lost, the body becomes weak. This can lead to a condition called AIDS.

In this stage, other germs or cancers can cause harm.

There are two main types of HIV. HIV-1 is found all over the world. It is very strong and spreads easily. HIV-2 is mostly found in West Africa. It is less likely to spread to others.

The virus has a clever way of working. Once it enters a cell, it uses a tool called reverse transcriptase. This tool changes the virus's code into a form the cell can read. The virus then hides in the cell's own code. It can stay quiet for up to ten years. During this time, the person may not feel sick. But the virus is still there, waiting to make new copies.

HIV stands for human immunodeficiency virus. It is a tiny germ that targets the human immune system.

This system is what helps our bodies fight off sickness. HIV attacks vital cells like helper T cells, macrophages, and dendritic cells. When these cells are lost, the body cannot protect itself well. This can lead to a condition called AIDS.

In this stage, the body becomes weak against other germs or cancers.

The virus has a very specific way of working inside a cell.

First, the virus uses its outer protein to attach to a target cell. It then fuses with the cell membrane to let its contents inside. Once inside, the virus uses a tool called reverse transcriptase. This enzyme changes the viral RNA into double-stranded DNA.

Next, an enzyme called integrase puts this viral DNA into the cell's own nucleus. The virus can then hide there and stay quiet for up to ten years.

Scientists have identified two main types of this virus.

HIV-1 is the most common type found around the whole world. It is very strong and spreads more easily than the other type. HIV-2 is mostly found in West Africa. It is less likely to spread from person to person. In 2020, experts gave them new scientific names. They are now called Lentivirus humimdef1 and Lentivirus humimdef2.

There are many important facts about how the virus is built.

The virus is a tiny sphere about 120 nanometers wide. This is 100,000 times smaller in volume than a single red blood cell. It carries two copies of single-stranded RNA. This RNA contains nine genes that act like instructions. Some genes help build the virus, while others control how it infects cells. These instructions allow the virus to make new copies of itself.

Understanding HIV helps us see how germs interact with our bodies.

The virus uses special proteins on its surface to find its way. These proteins act like keys that fit into specific locks on our cells. Scientists study these proteins to try and make vaccines. By learning how the virus attaches, they hope to stop it from entering cells. This research is a major part of modern science.

Human immunodeficiency viruses, or HIVs, are a group of viruses that infect humans.

They belong to the genus Lentivirus, which is a subgroup of retroviruses. Lentiviruses are known for causing long-duration illnesses with long incubation periods. Over time, HIV causes acquired immunodeficiency syndrome, also known as AIDS. This is a condition where the immune system fails progressively. When this happens, the body cannot fight off opportunistic infections or certain cancers. Without medical treatment, the average survival time after infection is estimated to be 9 to 11 years. This duration depends on the specific HIV subtype found in the person.

The way HIV works inside a cell is a complex, multi-step process. First, the virus uses its envelope proteins to attach to target cells. Specifically, the gp120 protein interacts with the CD4 molecule on the cell membrane. The virus also uses chemokine co-receptors to enter the cell. Once attached, the viral envelope fuses with the cell membrane. This fusion releases the viral contents into the host cell. Inside, a viral enzyme called reverse transcriptase converts the single-stranded RNA genome into double-stranded DNA.

Next, an enzyme called integrase carries this viral DNA into the cell nucleus. The enzyme then integrates the viral DNA into the host's own DNA.

Once the viral DNA is integrated, the virus can follow different paths. It may become latent, which means it stays dormant or quiet. In this state, the virus and the host cell can avoid detection by the immune system. This dormancy can last for up to ten years after the initial infection. Alternatively, the integrated DNA can be transcribed to produce new RNA genomes and viral proteins. The cell uses its own resources to package these into new virus particles. These new particles are then released to begin the replication cycle in other cells.

Scientists have identified two primary species of HIV.

The first is HIV-1, which was originally called lymphadenopathy associated virus or LAV. It was also known as human T-lymphotropic virus 3, or HTLV-III. HIV-1 is the most common type globally and is highly virulent. It is more infective than the second type. The second species is HIV-2, which is largely confined to West Africa. HIV-2 has a lower capacity for transmission and is less infective. In 2020, the International Committee on Taxonomy of Viruses gave them new names. They are now classified as Lentivirus humimdef1 for HIV-1 and Lentivirus humimdef2 for HIV-2.

The structure of the HIV virion is incredibly small and detailed. It is roughly spherical with a diameter of about 120 nanometers. This makes its volume about 100,000 times smaller than a red blood cell. The virus is composed of two copies of positive-sense single-stranded RNA. This RNA codes for nine essential genes. These genes are enclosed in an ovoidal capsid made of 2,000 copies of the p24 protein. An outer matrix of p17 protein surrounds this capsid. Finally, a lipid bilayer envelope surrounds the entire particle. This envelope is taken from the membrane of the human host cell.

HIV targets specific cells in the immune system to survive. These include helper T cells, specifically CD4+ T cells, as well as macrophages and dendritic cells. The virus can also infect microglial cells in the central nervous system. Different strains of HIV show different patterns of cell targeting, known as viral tropism. M-tropic strains, or R5 viruses, use the CCR5 co-receptor to enter cells. These can replicate in both macrophages and CD4+ T cells. X4 viruses use the CXCR4 co-receptor instead. Some dual-tropic strains can use both receptors. This ability to target different cells helps the virus spread through the body.

The loss of CD4+ T cells is the main reason the immune system fails. HIV reduces these cell numbers through several different mechanisms. It can cause the death of infected cells through direct viral killing. It can also cause the death of uninfected bystander cells through a process called apoptosis. Some infected cells undergo pyroptosis, which is a form of programmed cell death. Additionally, CD8+ cytotoxic lymphocytes may kill the infected CD4+ T cells. When the number of these vital cells drops below a critical level, cell-mediated immunity is lost. This loss makes the body susceptible to the many infections that characterize AIDS.