CCR5Delta32 and susceptibility to HIV infection

The human immunodeficiency virus or HIV is the cause of AIDS or Acquired Immune Deficiency Syndrome, which is characterized by a progressive weakening of the immune system leading to an increased risk of infection. According to the World Health Organization (WHO), HIV remains one of the biggest public health problems in the world, with 38 million people infected by the end of 2019.

It has been observed that some people are more susceptible than others to HIV infection and this may be due to the amount of CCR5, a transmembrane protein found on the surface of immune system cells and modulates its activation.

CCR5 acts as a receptor and interacts with other molecules, triggering a signalling cascade that mainly activates T cells or T lymphocytes, of the CD4+ and CD8+ types. CCR5 binds to chemokines, which are small molecules that are released into the extracellular media and are responsible for directing lymphocytes towards tissues that are inflamed, infected or where an injury has occurred.

The discovery in 1996 that CCR5 was key to the entry of HIV into lymphocytes along with the CD4 receptor was a significant breakthrough in the fight against AIDS. In the same year, a mutation, known as CCR5Delta32, was shown to exist in the CCR5 gene, dramatically reducing the amount of the CCR5 receptor in lymphocytes membrane and demonstrating that it could be a crucial protective factor against HIV infection.

It was not until 2008 that CCR5 became of great public interest. Gero Hütter announced that an HIV-positive patient, known as "the Berlin patient", had been transplanted with bone marrow from a donor with two copies of the CCR5Delta32 mutation and became HIV-negative even though he was off antiretroviral treatment.

The relationship of CCR5Delta32 to infection with various pathogens and the role of CCR5 in the immune response continue to be studied and potential AIDS treatments and therapies developed.

Gene or region studied

  • CCR5
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