S. Popov: Another example of a prototype would be an agent, a plague virus, which... which would contain a diphtheria toxin. I mean, not a virus, that wasn't what I meant, a plague bacterium containing a diphtheria toxin. The expectation was that... such... such a plague microbe would have greater virulence, and, interestingly, it turned out that despite the presence of the toxin, the virulence remained elevated, as before. But the agent itself acquired resistance to the vaccine. That is, monkeys that were vaccinated against the plague, couldn't... weren't protected against such a recombinant strain. That is an example, um, of a bacterial agent... as a prototype of a future biological weapon.