Yep, it sounds like a (semi?)unique structure is required for each target virus.

> A specific combination of nucleotides is first modeled in simulation to be the correct size to handle the target virus

From the article:

> Dietz said the interior of the shells were coated with "antibodies specific for the hepatitis-B virus. You can think of the shells as a generic platform; depending on your selection of inner coatings, you can 'program' them to be specific for a user-defined target virus."

for my understanding its the combination of shell size and coating which does the targeting.

Um, you go ahead and volunteer for cross-species genetic transfer experiments. I'll take the innoculation thanks.