One of the reasons why we still do not have a cure for HIV infection yet is that the virus infects cells of the immune system that activate the response that should stop infection. In concrete terms, the main HIV targets are a sort of white cells named CD4 T lymphocytes, so called because they have the protein CD4 on their membrane.
While we have more than 20 different drugs available today in the market, all of them act blocking the cycle that HIV follows to infect those CD4 T lymphocytes, but do not cure because they do not manage to eliminate all the viruses from the organism. One of the possible explanations for that fact is that the available treatments do not fully act on another kind of immune cells, called dendritic cells, where HIV also penetrates and remains almost fully infectious. Dendritic cells are responsible for activating the immune response, but when they do it, they also infect CD4 T lymphocytes in parallel. Therefore, the proliferation of the infection is more efficient when dendritic cells harboring viruses are around.
Now, scientists from the AIDS Research Institute IrsiCaixa, funded by “la Caixa” Foundation and the Health Department of the Generalitat de Catalunya (the autonomous catalan government), have identified the entry door that HIV uses to hide into dendritic cells, an enigma that the scientific community had been trying to solve for years. The work has just been published in the international scientific journal PLoS Biology, and it has been supported by the HIVACAT Program for the research and development of a vaccine against AIDS.
Siglec-1 is the molecule that can be found on the surface of dendritic cells that allows the entry of HIV into cells. It acts as a gateway for HIV to mature dendritic cells when are joined by the gangliosides of the virus, functioning as a key. Thus, dendritic cells accumulate large amounts of virus inside and become Trojan horses, allowing the infection of the CD4 + T cells, the main target of HIV, and contributing to spread HIV through the body.