Author: Wei Cao (Peking Union Medical College Hospital)
When HIV virus attacks human immune cells CD4 cells, in addition to identifying CD4 cells, it also needs to recognize the receptors on the surface of CD4 cells.
This receptor is like a door lock for the cell. Once it is successfully paired by the virus, the HIV virus can smoothly enter the interior of the CD4 cell through this door.
There are two main door locks on the surface of CD4 cells, one is called CCR5 and the other is called CXCR4.
Image source: Zhanku Hailuo
Most HIV viruses can open the CCR5 door lock to enter, some viruses can open the CXCR4 door lock to enter, and some viruses can open two door locks at the same time, so the survival adaptability is stronger.
The immune cells of the vast majority of people in the world have both CCR5 and CXCR4 door locks, so no matter which kind of unlock function HIV encounters, they are helpless.
However, in a very small number of people, mainly Caucasians, the CCR5 gate-lock structure on their cell surface has been changed during evolution, resulting in a mutation called CCR5-Δ32, As a result, those HIV viruses that specialize in CCR5 fail to recognize and are rejected, resulting in the phenomenon of “immunity” to AIDS.
Image source: Zhanku Hailuo
There are only two patients who have been cured of HIV infection because of the transplantation of CCR5-Δ32 donor stem cells during the treatment of blood diseases.
According to research, the generation of this mutation may be related to some infectious disease pandemics experienced by these ethnic groups in history, and the mutation with Δ32 was more survival advantage at that time, so it was selected to be retained , the mutation rate of this gene does not exceed 10% in Caucasians [1].
It is worth noting, however, that people who are homozygous for CCR5-Δ32 are not immune to HIV that can open CXCR4.
Therefore, natural immunity to AIDS is not absolute.
Image source: Zhanku Hailuo
References:
[1] Barmania F, Pepper MS. C-C chemokine receptor type five (CCR5): An emerging target for the control of HIV infection. Appl Transl Genom. 2013;2:3-16.
*The content of this article is for the popularization of health knowledge and cannot be used as a specific diagnosis and treatment suggestion, nor can it replace the face-to-face consultation of a licensed physician, and is for reference only.
*The copyright of this article belongs to Tencent Medical Dictionary. Unauthorized reprinting by media is prohibited. Illegal reprinting will be investigated for legal responsibility according to law. Individuals are welcome to forward to the circle of friends.