A little HIV knowledge

A few months ago, I gave you a short primer on the immunology of vaccines. It’s time now for another short, oversimplified primer, this time on the immunology of HIV. This was originally up on the old blog, but it will provide some necessary background for upcoming posts (I think).

HIV denialists form a persistent little cult, and one of their newest leaders is Gary Null. Despite their small size and dearth of academic heavy-weights, they are quite loud, and can affect health policy.

Let’s delve into the immunology, and, once again, please forgive the over-simplification.

HIV—nasty non-critter

HIV is a retrovirus. Like all viruses, it is not a living organism as such, but a hunk of nucleic acids (in this case, RNA) and proteins that requires a living cell in order to reproduce. Take it away from a human body, and it rapidly becomes a useless hunk of chemicals.

HIV is a particularly successful virus for a variety of reasons. It has a very long latency period — that is, a person can be infected for years without symptoms, giving ample opportunity to spread the virus. It also reproduces quickly and in vast numbers, allowing for many random mutations which help it evade both the immune system and medications. While the mutations are random, the results are not. Introduce a selective pressure, such as a new anti-retroviral drug, and resistant variants will reproduce more successfully than non-resistant ones (it’s called “evolution”—deal with it). But all that happens after a person becomes infected. Let’s go back a step.

HIV—opening act

After entering a persons body, via sexual contact, dirty needles, and occasionally other blood and body fluid exposures (although those are the big ones), the virus is eaten up by local immune cells (macrophages) like any other virus. This leads to the viral parts being displayed on the outside of the cell for all to see, and T-cells come by to start the body’s specific immune response (you may want to reference my earlier article). Most viruses have a preference for one or another type of cell. Unfortunately for us, in the case of HIV, its preference is immune cells, especially a type of T-cell (CD4+ T-helper cells). Still, the body mounts a vigorous immune response (with flu-like symptoms), and despite an early and rapid spread of the virus to all parts of the body, the virus count in the blood rapidly drops. For now.


hiv-timecourse.pngSo your immune system did a nice job. It got the virus out of your blood. Unfortunately, the virus is very comfortable in the immune cells of the lymph nodes, and hangs out there, slowly reproducing. At that point, there is some mild depression of the immune system, with perhaps some additional risk of pneumonia and other diseases, but really, there isn’t much in the way of outward signs of disease. Your immune system, however, is being devastated. T-cells are serving as little HIV factories, but these factories burn down after a successful run. Your T-cell count is slowly dropping. After about ten years feeling generally OK, but then…


As the years pass, the number of T-cells has steadily dropped. The ability of the body to discover new invaders, control old invaders, and activate a strong immune response has been decimated. Pneumocystis, an organism that normally lives peacefully in the lungs, no longer has T-cells to hold down its numbers. The same goes for TB. These diseases can quickly overwhelm someone with HIV.

Cancers that are rare in healthy people take advantage of decreased immunity. Lymphoma of the brain, which is caused by a viral infection, can pop up. So can Kaposi’s sarcoma, a rare cancer of the blood vessels, also caused by a virus.

Without treatment, AIDS is fatal in a matter of months.

I can haz gud nuz?

The study of HIV spurred a generation of research in the biomedical fields. Anti-HIV drugs became available about five or six years after the identification of the epidemic. Unfortunately, resistance to these drugs developed quickly, via the evolutionary mechanisms described above. Research showed that the virus had to be fought on multiple fronts at once to reduce resistance.

I was a medical student when one class of drugs, the protease inhibitors, came out. We went from full inpatient AIDS wards, to empty beds in a matter of months. HIV became a disease treated in the office. I now take care of elderly HIV patients—not for their HIV, but for the usual diseases that affect older adults, and for some of the side-effects of HIV meds, such has high cholesterol.

HIV is a great example of how science can actually work to produce good results. Of course, we have a long way to go in prevention and treatment, especially in developing countries. A vaccine is also a long way off.

If the HIV denialists have their way, you won’t have to worry about any advances in treatment of HIV, since they don’t believe it causes AIDS. Their foolishness is one of our greatest enemies, and must be battled daily.


13 responses to “A little HIV knowledge”

  1. Deepsix

    So, what’s the driving force behind HIV denialists? What’s “in it” for them?

  2. I had a thought. Now, remember that I’m an undergrad who’s majoring in neuroscience who’s had general biology but has never taken a microbiology class – I’ve read enough about viruses to know more than most people, but I am not a microbiologist or a physician.

    Could it be possible that, since viruses contain DNA and RNA, viruses diverged from a sort of ‘pre-life’ lineage of nucleic acids before the first real cells formed?

  3. synapse

    @Katharine: Viruses are dependent on living cells for replication. That makes it hard to imagine viruses existing before cells.

  4. synapse, I know modern viruses are dependent on living cells for replication, though could there have been a point where they weren’t? I know there’s also a hypothesis that DNA viruses are rogue DNA from cells, and this makes me think that they’re probably at least somewhat remotely similar to prions in that they’re bits of cellular and organismic stuff which are somewhat nuts and the viruses have somehow formed a capsid while prions are nutty proteins. Is there a phenomenon similar to the amyloid fold in prions which might have caused nucleic acid to become viruses – something with one of the DNA enzymes or histone? Anything epigenetic ?

  5. Deepsix, that is a good question on which I hope someone can give us some insight. Contrarians and conspiracy theorists are odd. A lot of them only get satisfaction from believing they figured-out something that few others can understand. Some few don’t want to believe they have a serious (asymptomatic) infection that requires drastic lifestyle changes (e.g., using condoms, inability to nurse a baby, the need to take medicine).

  6. I personally would like to know how anyone can look at this disease and think that scientists made it deliberately to target a specific group (see the comments of Jeremiah Wright). My question is, are we even capable of making such a sly and deadly virus, especially considering that at this point there is no cure? I know that we use viruses as vectors for specific bits of DNA (such as for knockouts in specific brain regions in neuroscience research), but could we be capable of creating the HIV virus in the first place? My instinct says no, but I’m afraid that I don’t really know. Regardless, I cannot believe that we could create such a thing and release it upon the world.

  7. What’s “in it” for AIDS denialists? Depends on why they believe against it.

    Many would rather believe that AIDS is caused by god, to punish the “sinful”. If it’s caused by something as mundane as HIV, then there goes their “lightning strike from god” theory.

    I have no problem with them exersising their freedom of religion, until they actively try to step in the way of scientific research, and the saving of lives. At that point, theirs is no longer a victimless crime.

  8. [Sorry about the “Anonymous”. I’m signed in TypeKey as TheNerd, but this old computer has problems retaining information.]

  9. mayhempix

    It would appear that the Seed sites are no longer connecting to RSS feeds.

    I haven’t recieved any feeds in 3 days.

  10. > What’s “in it” for AIDS denialists?

    I have noticed the pattern that AIDS denialism is quickly followed by condom effectiveness denialism.

    The people who are most interested in indulging in condom free sex with multiple casual partners are also very interested to give credence to AIDS denialism.

  11. Snout

    There are several different motivations of AIDS denialists. Some are actual scientists who are disappointed with the trajectory of their careers and cannot believe that the world has failed to recognize their ability and achievements and present them with the Nobel Prize they so richly deserve (in their own self estimation).

    Some are people who have received an HIV diagnosis. The normal response to this includes a phase of grieving and fear, and according to some theorists of grief, ?denial? is actually a normal part of this process. Unfortunately, some people get stuck here, especially if they find a subculture which reinforces this position.

    Some are half educated graduates of postmodernist influenced humanities departments who have failed to recognize that skepticism does not mean permanently deferring taking a position for action. Some people have a philosophical objection to being overwhelmed by evidence. The real world doesn?t work that way.

    HIV particularly affects groups who may see themselves as disenfranchised from mainstream society, particularly those parts of society that exercise power, including mainstream medicine. The very real stigma associated with an HIV diagnosis reinforces this. Mainstream thinking about HIV therefore becomes associated with stigmatizing minorities. The fact that HIV does, in fact, disproportionately affect minorities in Western countries, reinforces latent irrational prejudices, both amongst the marginalised and also some who associate themselves with the mainstream.

    HIV has provide rich pickings for quacks, who traditionally exploit the gap between fear and knowledge, and for many years between disease and effective amelioration. The long latency, unpredictable course, complex presentations of disease, and often hidden shame around its acquisition make HIV a quack?s dream. It?s an immune system disease, and most people know very little about how the immune system works. It?s very easy for a quack to present a bogus but superficially plausible scientific sounding spiel ? very few people can pick the faults in what are often complex arguments with a smidgeon of arcane actual science for believability.

  12. Dr. Duke

    HIV denialists are by no means a unique phenomena. There are more people who deny that evolution is the driving force that created diverse life forms on Earth. There are people who deny that cancer can’t be cured or prevented with woo.

    Humans are not rational by design. Many find it impossible to comprehend that “gut instincts” can in fact be very wrong. Common sense works so well for most things, that it is understandably difficult for some people to comprehend that some things defy it.

    I myself still find it exceedingly difficult to comprehend problems that require more than 3 dimensions. I can look at an XYZ plot and get a grip on the meaning. When a computer scientist tells me about searching for peaks and valleys in an 8 or 45-dimensional space, I find it a bit mind-boggling.

    I have no beef with people who believe strange things, or fail to believe rather common things. I do have a large problem with the people who deliberately tell lies, know that they are lying, and know that their lies are responsible for killing people. There is a significant difference between ignorance and evil, even if both are equally harmful.

  13. Ethan Romero

    I think that the period from exposure to symptoms is called the incubation period not the latent period, which is the period from exposure to infectiousness. At least that’s what I remember from my infectious epi courses.

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