EV-D68 (as discussed in the main post) is a virus in the same family as the polio virus and coxsackievirus (which can cause meningitis). The innate immune system is critical in preventing viral infections from getting out of control and talking with the adaptive immune system if they do get out of hand. Let’s say you were given pictures of a villain and a superhero, but you don’t recognize either of them. Chances are that based off of clues in the expressions on their faces, physical features, or background colors you would be able to pick who was good and who was bad.
Cells of the innate immune system recognize viruses and bacteria using similar mechanisms. They see very broad features that are common to lots of different types of viruses or lots of different types of bacteria. These broad features are called Pathogen Associated Molecular Patterns (PAMPs) and are recognized by innate immune cells using Pattern Recognition Receptors (PRR). For enterovirus, the PAMP is double stranded RNA (dsRNA). RNA is in our own cells as well and is used to make proteins, but we don’t generally have it in this double stranded form so it’s seen as foreign. Innate immune cells recognize this RNA with a PRR molecule called TLR3. Binding of dsRNA to TLR3 starts a series of actions that tells cells to go into anti-viral mode partly through telling the cell to make the cytokine called Interferon. (This cytokine was also discussed in the nerd boost about Ebola). EV-D68 interrupts these events from occurring by cutting up one of the “signaling molecules” that allows the cell to go from recognizing the danger to producing the Interferon. This disruption prevents the anti-viral mode from going into full action.
Luckily this virus hasn’t proven to be deadly and only causes a few days of cold-like symptoms. This is an indication that most likely the immune system adjusts and the T cells and B cells of the adaptive immune system are able to eventually take over and get rid of the virus.