Fig 1. Experimental schedule for repetitive respiratory syncytial virus infections.

Cotton rats were infected with the Long strain (1×10⁶ pfu/rat). Three cotton rats each were sacrificed 4 days after the first, second, third, and fourth infections. The third and fourth infection were analyzed twice. In order to examine immune responses to subgroup A and B, twelve cotton rats were prepared and divided into four groups. Six rats were challenged with RSV/A/Tokyo/2012 or RSV/B/Tokyo/2012 one month after the second infection, and sacrificed the groups of wild-type A-3 and B-3. The other rats were challenged one month after the third infection, and sacrificed. Wild-type A-3, B-3, A-4, and B-4 are showing a third and fourth infection with RSV/A/Tokyo/2012 or RSV/B/Tokyo/2012.