STD Awareness: Do Sexually Transmitted Diseases Increase HIV Risk?

virion HIVYou might have heard that having an STD like syphilis, herpes, or gonorrhea can make it easier to catch HIV, the virus that causes AIDS. But have you ever wondered if this was true? Maybe it’s just a simple correlation — for example, someone who doesn’t practice safer sex would be more likely to catch HIV along with any other STD. That doesn’t mean that one causes the other, does it?

Common STDs like herpes and trichomoniasis can increase HIV risk.

But it’s not a mere correlation. If you take one person with an STD and one person without an STD and expose them both to HIV through sexual contact, the person with the STD will be at least two to five times more likely to become infected with HIV. Why is that? First, many STDs can make you more susceptible to an HIV infection. Second, the immune response triggered by many sexually transmitted infections can summon the types of immune cells that HIV targets.

Furthermore, if a person with HIV is co-infected with another STD, he or she is more likely to transmit HIV to a partner. In other words, STDs can make a person with HIV more infectious. HIV is more likely to appear in their genital secretions, making it easier to transmit HIV through sexual activity. Continue reading

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