Are you immune to HIV and smallpox?

ypestis.jpgThe CCR5 gene encodes a chemokine receptor (a long name for a protein that sits in the walls of our cells). When the body has been invaded by a pathogen such as a cold virus, CCR5 plays an important role in fighting that virus. Smart viruses such as HIV-1, however, hijack the CCR5 protein and use it to sneak into CD4+ T cells & macrophages.

In some populations the CCR5 gene has experienced a mutation that deleted 32 basepairs in the gene sequence. The mutation prevents the expression of the protein on the cell surface. As a result, people with this mutation show some degree of protection from certain viruses. In fact, homozygosity of the CCR5-D32 allele (meaning BOTH copies of the gene are mutated) leads to “nearly complete resistance to HIV-1 infection.” People with only 1 copy are as much as 70% resistant! Surprisingly, homozygotes do not show any other problems as a result of the mutation.

The CCR5-D32 allele is absent among Amerindians and East Asians but is found in some African populations. The allele is found in high concentration among Eurasians. Indeed, the average frequency of the allele among European populations is 10%. The fact that the allele is found in such a high percentage in one population and not at all in another suggests that there was a strong selective pressure in favor of that allele. The source of that genetic pressure is still being debated by scientists. The early favorite was the Black Death, the Bubonic plague that swept through Europe in the Fourteenth century. The picture above is of Yersinia pestis, the bacterium that causes the plague.

Other researchers have hypothesized that the period of selective pressure created by the Bubonic plague, roughly 400 years, was not long enough for the overwhelming presence of the gene to appear. These researchers suggest that smallpox, which has killed as many people as the plague over a much longer time period, could have provided sufficient selective pressure. To support this conclusion it is proposed that the continued presence of the mutated gene in the face of lowered genetic fitness is due to the fact that smallpox was only eradicated recently while the plague hasn’t been a serious problem in 250 years. Indeed, a cousin of the smallpox virus has been shown to use CCR5 to enter host cells. Thus, CCR5-D32 may provide resistance to smallpox.

So what does this have to do with genetic genealogy? Family Tree DNA offers CCR5 testing through their advanced test options (meaning you have to already have your DNA stored at the company). If a person is tested and has one or two copies of the CCR5-D32 allele, it is very likely that the person has European ancestry.

I would caution that CCR5 testing should NOT be used as a diagnostic test for medical conditions. In my opinion the CCR5 test should be only be used to explore one’s ancestry. The presence of the CCR5-D32 allele implies that a person has European ancestry, NOT that they have a license to engage in risky behavior!

23 Responses

  1. suzanne 21 August 2007 / 10:02 pm

    I possibly have the Delta 32 allele gene. Having barely survived what I think was staph pneumonia in the late eighties, (a friend my age positively diagnosed died and we cought the same flu at work,) and having an ancestor purported to be a Montpesson although I have no idea how she was related to Eyam. Are there any DNA studies near me I could volunteer for? Let’s say at Yale or in New York City. I can’t afford to be tested out of pocket.

  2. suzanne 21 August 2007 / 10:21 pm

    PS – The year my friend and co-worker died I travelled Europe coughing but didn’t see a doctor. My friend wound up in an iron lung until her heart collapsed.

    I also went home from a local street fair a few years later without a trace of upset stomach having eaten the same rotten fajitas that sent over 230 people to the hospital with salmonella poisining. I thought it was just bad spices but ate the whole overpriced portion anyway and should have been very sick.

    I do indeed get sick. Sometimes. But not for long compared to the guy next to me.

    So, I do think someone should run a DNA test on me.

  3. Tony 30 August 2007 / 12:56 am

    Where I can test my DNA for the CCR5 Delta 32 gene?How much does it cost (I’m UK based)?

  4. Josh 8 December 2007 / 3:33 am

    Tony, you can purchase a test for the CCR5 Delta 32 mutation from

    HIVGene will ship internationally.

  5. Wil 7 July 2009 / 11:38 pm

    I would like to get tested for CCR5. I have had too numberous to count exposres and remain serology and pcr negative.

  6. drravi 16 July 2009 / 10:31 am

    hi instead of vaccinating the ppl with this gene.. why can’t we delete that gene itself by zinc finger nucleases!

  7. Keith 12 January 2010 / 12:48 pm

    ZFor over 3 years I have searching the internet to try and find a lab/company where I can get a CCR-5 Delta 32 gene test by mail (swab culture ?). The few sites that have info on this all say “test not available at this time”. Several people mentioned a site they got the test from called “” but this is not a company; it is just a list of other websites and I could find nothing on any of them either. Does anyone know of a specific place (ie – a company or lab) that offers this test at a resonable price to the general public ? Keith

  8. Jeanne 3 March 2010 / 3:10 pm

    I am considering taking a test or I would like to know if there are any studies being conducted to test for this. The reason why I would like to know is because I already know I am HIV negative and never got smallpox. I also have a particular lineage that has been traced in my family and it goes back to as far as the year 1245 in Lancashire England and I can pinpoint which one of my particular ancestors came out of the bubonic plague unaffected by it. I usually don’t get sick and when I do I recover fast. My husband had meningitis too and I miraculously never got it because it was very contagious. So I am curious

  9. james 26 July 2010 / 10:36 pm

    i have been in a long term sexual relationship with an HIV female for 13 years we have had sex like rabbits oral and vaginal iwe have never used protection and i am still HIV neg i would love to be tested and find out if i could help her we both are O+ blood type and i heard about the bone marrow transplant that cured that guy in germany

  10. curious 5 May 2011 / 9:34 pm

    i have also been trying to get tested for the ccr5 mutation for a number of years because i remain hiv negative despite some high risk exposures in the past.

    sadly the powers-that-be seem to think that people should be treated like sheep, unable to make informed decisions, so now it has become virtually impossible to find a company to do the test, even for a fee. doesnt seem to offer it if you are hiv negative it and directs you to a google ad.

    it seems technological advances just spawn more repressive legislation because self-styled experts think they hold the moral high ground.
    this is the same mentality which believes it’s better to advocate abstinence among teenage girls than to vaccinate them against papillomavirus.

  11. owen willison 7 June 2011 / 5:12 am

    I was one of about 600 males given the smallpox immunisation ‘scratch’ whilst in the UK military. It reacted in a large lump and I was told to return for a 2nd attempt in a fortnights time. I did and it reacted the same. The conclusion by the doctors was that I was naturally immune. I was only ever immunised against Polio as a child and have always recovered from rare infections with remarkable speed, even colds can last as little as hours. My ancestry is English as far back as there are records with red hair being a common feature each generation.

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  13. al 23 January 2012 / 1:20 pm

    the polio vaccines were contaminated with a monkey virus sv-40. being i got the shots in 58-59 and also the oral sabin’s which were likely contaminated ,i checked in with the tech geneticist at stanford univ med school .they confirmed that sv-40 could change into siv or hiv . i still test hiv neg at 59 y old . i also had a small pox shot as a kid but bear no scar . next i had the test done for ccr5 delta 32 mutation and it said negative for the mutation . i don’t quite understand whats up here . i did have nonhodgkins lymphoma . this problem arose at about age 17,never being much bothered by it ,i didn’t finally have to have this left axillary node out until 1995 . it was only then confirmed low stage nhl by biopsy . any insights would be appreciated .

  14. J. 19 August 2012 / 4:51 pm

    I also would like to get tested for the CCR5 Delta 32 mutation and I can’t find any info about how to get tested for it.

    I did go to a seminar about genetic testing and I asked the woman who was a geneticist and she said how her genetic testing company did not even test for this gene mutation.

  15. Rubi 7 December 2012 / 5:45 pm

    I was tested in 2005 and have the homogenous version of the mutation. I was married to a man and had 2 children with him when we found out he was HIV+. He died in 1994 and we are all HIV- after almost two decades. The mutation literally saved my life…

    My ancestry is heavily European, with American Indian.

    I’ve tried my best to donate my stem cells. Anyone with HIV that needs a bone marrow transplant anyway should get delta32 CCR5 stem cells. The only cure of HIV was from this exact procedure.

    I also seem to be immune to chicken pox. …and don’t have any reaction to bug bites? CCr5 controls some immune system responses. It is interesting to know that I have it. I wish I could help someone…

  16. Valerie 7 January 2013 / 7:17 am

    I too was desperately searching for the ccr5 delta 32 testing and finally found a reliable website

    I purchased my kit just two days ago and can’t wait to get the results. I’ve had several risky relationships over the past 8 years and with both sexes and remained hiv negative. I’m very curious to know. I can’t wait for my results! These findings are astonishing.

  17. Brianna 18 January 2013 / 6:58 pm

    I find what Rubi had to say quite interesting. We have the same ancestry and while I can not be sure I’m immune to chicken pox I suspect I am. When I was young my mom did not want me to get vaccinated because of the media so she had me play with kids who had chicken pox because she wanted me to get it when I was younger so it wouldn’t be as bad. I never got it though so I ended up getting vaccinated. Anyways years later I got tested for a bunch of different viruses and the test showed that I had not antibodies to chicken pox so I’m not sure if this means anything. Not really sure why I even commented on this but whatever.

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