Synthetic oligosaccharidesbased on SP-3 CPS RUs protect immunized mice against lethal systemicchallenge with SP-3 pneumococci via nonmucosal routes.204 A highly immunogenic SP-3 tetrasaccharide glycoconjugateproved to be immunoprotective against experimental pneumonia causedby transnasal infection with SP-3 strain PN36. Here, SP3 is linked to infection.