How Does HIV Cause AIDS?

diagram of a human immunodeficiency virus

Last week, we gave a general background of human immunodeficiency virus (HIV), the virus that causes AIDS by destroying the immune system. But how is HIV able to disable our immune systems so effectively, anyway? The answer lies in its structure.

HIV, just like any other virus, is made up of a tiny capsule with a small piece of genetic code inside. While most viruses we’re familiar with store their genes on a molecule called DNA, HIV contains two pieces of RNA, which is another type of gene-storing molecule. The HIV capsules also contain an enzyme called transcriptase, which “translates” the RNA into a strand of DNA that our cells can read. Our cells are then tricked into reading this DNA and producing more copies of the virus — which are then released from the host cell, at which point they are free to infect other cells. In this manner, an HIV infection slowly grows.

HIV targets our immune systems, the very mechanism that evolved to keep us safe from pathogens.

When a virus is introduced into a host’s body, immune cells pick it up and carry it to the lymphoid organs — which are a sort of meeting place for other types of immune cells, including CD4+ T helper cells (also called helper T cells). Helper T cells enlist the help of other immune cells, called killer T cells, which destroy cells infected with viruses. Helper T cells also activate the production of antibodies, molecules that are specialized to attach to a specific pathogen so that it can be destroyed. Normally, this is where the virus meets its end. Unfortunately, HIV is different from run-of-the-mill viruses in that it is specialized to invade helper T cells. Now, instead of coordinating an attack against HIV, the helper T cells have been hijacked — converted into factories for the production of yet more HIV. Continue reading

STD Awareness: HIV and AIDS

Our immune systems are beautiful things, refined through millions of years of evolution. The immune system’s complexity is testament to the “arms race” that has been taking place between our species and the harmful pathogens that surround us. Last century, a virus called human immunodeficiency virus (HIV) emerged, and it found a weak spot in our immune system’s armor. HIV has been exploiting this weakness ever since, and an HIV infection can eventually progress to a disease called AIDS, or acquired immune deficiency syndrome. AIDS is a condition that disables our immune system’s ability to function properly, rendering us vulnerable to a host of opportunistic infections and cancers.

Even if you don’t think you’ve been exposed, HIV testing can be a good idea.

HIV is transmitted via bodily fluids: blood, semen, pre-seminal fluid (which can be present without ejaculation), breast milk, vaginal fluids, and rectal mucus. (It can also be present in bodily fluids like amniotic fluid, cerebrospinal fluid, and synovial fluid, to which health-care workers might be exposed.) The virus is not transmitted by fluids like snot, saliva, sweat, tears, and urine — unless blood is present.

Activities that can bring you into contact with HIV-infected bodily fluids include injection drug use and sexual activities like anal, vaginal, or oral sex. It can also be transmitted to a fetus or baby during pregnancy, childbirth, or breastfeeding. In the early days of HIV, many infections occurred as a result of blood transfusions or organ transplants — though nowadays this is a rarity thanks to tissue screening. Lastly, health-care workers might be exposed to HIV through accidents involving needlesticks or cuts. Continue reading