Archive for CCR5-Δ32

That Magic Gene…

Posted in Biographical, Covid-19, History, LGBTQ+ with tags , , , , on September 25, 2025 by telescoper

While writing yesterday’s post about the evolution of languages, and the importance of genetic information in reconstructing the story thereof, I was reminded of a post I wrote a while ago about the peculiarities of my own genome, a listing of which I have on a CD-ROM at home. There’s not as much data involved as you might think: it’s effectively only about 800 MB.

Anyway, to cut a long story short, it turns out that I have the CCR5-Δ32 genetic mutation. Not only that, I have it twice over, in that I have two copies (homozygotes). I must therefore have inherited it from both parents. This mutation confers virtually complete immunity from HIV-1 infection.

The above graphic shows that more than 10% of the population in Northern Europe has this mutation in just one allele (i.e. they are heterozygotic). To get an estimate of how many have the form on two alleles (i.e. homozygotic) form you can just square that number, so around 1% or more.

It is thought that the CCR5-Δ32 mutation occurred in a single individual in Scandinavia around 1,000 years ago. When I wrote that post I tacitly assumed that it had propagated passively, i.e. without any particular selection, to the modern era. That it reached 10% of the population starting from just one individual surprised me, but I let it pass.

More recently, I came across a paper about how advances in genetics have impacted epidemiological studies. In the abstract it shows that my assumption was probably incorrect.

Algorithms of molecular evolutionary theory suggested that the CCR5-Δ32 mutation occurred but once in the last millennium and rose by strong selective pressure relatively recently to a ~10% allele frequency in Europeans. 

It goes on to say this:

Several lines of evidence support the hypothesis that CCR5-Δ32 was selected due to its protective influence to resist Yersinia pestis, the agent of the Black Death/bubonic plague of the 14th century.

I didn’t mention in yesterday’s post that evidence of the plague bacillus is found in a significant number of prehistoric human remains and this almost certainly played a role in the ebb and flow of populations. In the context of CCR5-∆32, however it seems that it may have been advantageous to carry it long before the arrival of HIV/AIDS. That might account for it reaching the relatively high level that it did.

Among the downsides, however, as the article explains, are an increased risk for encephalomyelitis and death when infected with the West Nile virus. Hopefully further cohort studies of people with this mutation will help elucidate its effect on other diseases.

By the way, in contrast to most people I know, I have still never had Covid-19…

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Concerning Covid Immunity

Posted in Biographical, Covid-19, Maynooth with tags , , , on June 10, 2022 by telescoper

Over the past few weeks I’ve attended a number of events at which most people were not wearing face coverings, including a recent Open Day at which I took my mask off in order to be heard in a very crowded space. Although I still wear a mask on public transport and in shops, most people now do not.

The first thing I’d note is that that there has been a clear upturn in reported Covid-19 cases, with figures now running at about 700 per day:

(Official figures for Ireland are only issued weekly these days…)

It’s not an alarming increase but hospitalizations and testing positivity are also increasing, though the mortality rate remains low because of the protection afforded by vaccines. Incidentally, it was a year ago on Wednesday (8th June) that I received my second Pfizer dose. One wonders how long vaccine protection will last, though, until further boosters are needed. If cases continue to rise I wonder if any measures will be put in place before the start of next academic year?

A number of my colleagues at home and abroad have attended scientific conferences recently, a number of which have led to mini-outbreaks and some instances of quite serious illness. Although most people seem to think Covid has gone away, it clearly hasn’t. A resurgence is all we need right now.

Anyway, one of my colleagues at work expressed surprise that I didn’t catch Covid during the largely unmasked Open Day at the end of April. Of course I might have done but I certainly didn’t display any symptoms. I’ve actually been quite surprised that I have never shown any sign of SARS-Cov2 at all during the entire period of the pandemic, while many of my colleagues and students in the Department have come down with it.

Coincidentally, a comment appeared yesterday on a blog post I wrote a while ago in which I revealed that I have the  CCR5-Δ32 genetic mutation which confers protection against HIV infection. As a matter of fact I have it twice (i.e. homozygotic). For one thing the commenter pointed out that this mutation may have protected against smallpox, which means some evolutionary selection may have been involved in its propagation. The commenter also drew attention to the evidence – by no means conclusive at this stage – that this mutation may also protect against Covid-19. If you’re interested here are links to some papers:

The last of these is a preprint but the other two are peer-reviewed publications.

Could it be that I’ve yet again been a jammy bastard and inherited immunity to Covid-19 too?

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The Reason I’m Alive

Posted in Biographical, LGBTQ+ with tags , , , on February 27, 2021 by telescoper

For a variety of reasons I’ve always considered myself to have been exceptionally lucky, but last week I got news that increased still further the extent of this sense of good fortune. I hesitated before putting anything about this on here because it is rather personal and there are details I’m going to leave out about how I came by the information.

Over a month ago I posted some thoughts about the TV series It’s A Sin based on my own experiences back in the 1980s. That post ended with this:

… a question that often troubles me returned once again to my mind: why am I still alive, when so many people I knew back then are not?

In response to this a former colleague of mine suggested I get my DNA sequenced to see if I had any innate resistance to HIV infection. I wasn’t sure how to go about doing this but one of the advantages of having worked in several different universities is that I know people in several bioscience and biomedical departments, including people who work on the data science aspects of genetics. After emailing around for advice I eventually ended up talking to a very distinguished scientist in that field to whom I explained the situation.

Since I didn’t really want to have a copy of my entire genome sequence – that’s a lot of data most of which I wouldn’t understand – but just wanted to know the answer to one question it seemed a waste of money to have this done commercially (although at around €1000 it’s not enormously expensive). Instead a plan emerged in which I would offer my (suitably anonymized) DNA as part of a scientific study in return for the small piece of information I wanted.

After a few days I received a kit for taking oral swabs, a medical questionnaire and quite a lot of paperwork to do with ethical considerations and data protection. I sent everything back by return post. Last week the results came back. There was some general info about my genetic make-up – which shows a considerable dollop of Scandinavian ancestry – alongside the answer the question I had asked.

The full DNA sequence of my genome reveals that I have the CCR5-Δ32 genetic mutation. Not just that. I have it twice (i.e. it’s homozygous), which means that I inherited it from both parents.

Of order 1% of the European population has this mutation, which is thought to have arisen in a single Scandinavian individual at some stage during the Viking era and subsequently propagated through mainly Northern Europe where about 10% have one copy, and about 1% have two.

Here is a map of the geographical distribution in Europe (from this paper) :

It’s nowhere near as prevalent in Asia or African populations.

So what does this mean?

Heterozygotic CCR5-Δ32 (i.e. one mutated gene) confers some protection against HIV infection but the homozygotic CCR5-Δ32 mutation involving both copies confers virtually total immunity. I was terrified of AIDS in the 1980s but it turns out I was immune all the time without knowing it. This explains why to my great surprise the HIV test I took in the 1980s came back negative despite my sexual history and behaviour.

As a friend told me when I passed this news on: “you’re a f**king lucky bugger”. Indeed I am. I already considered myself to have been very lucky but this absolutely takes the biscuit.

P.S. My immediate “reward” for having this genetic peculiarity is to take part in further scientific study on it, which I am of course very happy to do.

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