Early stages of HIV infection in human body

When a foreign substance enters our body, similar to how other viruses do, the immune system detects it as "non-self" and initiates an immunological response, which is made up of a variety of cells, tissues, and organs that cooperate to recognise, combat, and eradicate that foreign substance.

The body's immune system is under attack by the human immunodeficiency virus (HIV). It may result in autoimmune deficiency syndrome if untreated (AIDS).

Dendritic cells, which are immune cells that come in contact with the outside world and patrol our bodies in search of pathogens and defending us from illnesses, are where the HIV virus initially enters the body.

The capture and transmission of the virus

The dendritic cells are the ones responsible for processing foreign proteins, molecules or particles, and presenting them to the immune system T-cells, acting as messengers and initiating the immune response.

A critical element that helps the dendritic cells recognize and bind to the virus is a group of membrane proteins that distinguish between self and non-self. One such protein, called Siglec-1, plays a key role in the early stages of HIV infection specifically in the capture and transmission of the virus.

When HIV enters the body, it first encounters the mucosal surfaces and binds to various molecules. Then, dendritic cells expressing Siglec-1 can capture and transmit the virus to other cells, initiating an immune response. But in this transportation journey, HIV-1 viruses can also use the dendritic cells as vehicles to infect the helper T-cells, also known as CD4+cells, spreading the infection further in a process known as trans-infection. This means that, although it can help to initiate the immune response, it can also facilitate the infection.

While previous studies, including those from IrsiCaixa, have identified Siglec-1 as the main receptor on activated dendritic cells that bind to specific molecules of the HIV-1 particles, the specific mechanisms of how this happens are still unknown. Understanding the role of Siglec-1 in the immune response to HIV is critical to developing effective treatments and therapies for people living with HIV/AIDS.