I was recently asked my thoughts on whether there was any truth in certain blood groups being resistant to HIV. My immediate response (in my head) was nonsense – it is not true! It’s as silly as the diets that espouse eating based on blood group (yes indeed such a diet exists, but has been debunked). Then two thoughts came into my mind in rapid succession when I considered the biochemistry (a subject which I have studied). It is possible and there are people who have an extremely rare genetic trait that makes them resistant to HIV infection but it is not related to ABO blood groups. My second thought was stories like this often get misconstrued, misinterpreted and then people erroneously think they are immune to HIV such as in discordant (mixed HIV status) couples.
In order to debunk the myth, I did research on the internet to make sure as I was talking from a credible science base. Credibility of information is important, not everything you find on the internet is accurate, reliable, valid or true. When I did a search of blood groups and HIV, the first sites that I came across were dodgy Wikianswer sites, where anyone can put in their two cents and random blogs in India. This confirmed to me that people can easily be misled.
The most useful guide was probably a very technical site 23andme.com. This company provides genetic testing i.e. individuals can pay to have their genetic code tested to determine whether they are likely to be immune to HIV.
A short dally into the biology of HIV infection. HIV is a virus, a tiny tiny “thing”. In order for it to survive it enters white blood cells (specifically CD4+ cells). HIV only infects CD4+ cells because these cells have specific markers. Think of the human body as a city, blood vessels are roads and cells are cars. HIV knows which cells to infect because CD4 cells – cars carry a specific number plate called CCR5. People who are immune to HIV do not have this number plate. What determines whether CD4 cells carry this number plate is information inside the car – genes, genes inside the car make the number plates. In some people the genes that make the special number plate are faulty so cars don’t make the special number plate, CCR5, and hence are immune to HIV.
23andme tests whether individuals have faulty genes or information and hence don’t make the CCR5 number plate, which would then make one immune to HIV. On a side, there is another group of very special and again rare people who make cells or army tankers that kill off HIV, but that is another story.
What if anything have blood groups got to do with HIV infection? Absolutely nothing…whether your blood group A,B,O or AB does not confer immunity. Where did the blood group myth come from? A scientific paper published in 2009 announced if cells/cars produce a lot of a specific number plate called Pk, individuals could also be immune to HIV. Pk is a way of typing or classifying blood but is not related to the ABO blood group system. So once again no connection to ABO blood groups and HIV resistance.
What influences immunity i.e. ability to not make CCR5 or to make a lot of Pk? Scientists are trying to find out, if they can find the answers that could lead to cures and vaccines.
Ps….I hope I did not lose you in my car and number plate analogy.