A fast immune priming that confers a complete infection resistance on silkworm (Bombyx mori)

I have previously reported an immune priming in silkworm triggered by peptidoglycans (bacterial cell wall components), which took more than six hours to fully confer a complete infection resistance to otherwise lethal bacterial infections. Nevertheless, such a peptidoglycan-inducible pathway seemed not to be a front-line defense system because of the long lag time. Here I report a faster immune priming, which can be triggered by an injection of gelatin, that confers a complete infection resistance to silkworms within two hours. Gelatin-injected silkworms showed 100% viability in a lethal dose of a Gram-negative bacterial infection. The effect became apparent within two hours after the gelatin injection. Whereas, an injection of non-gelatin protein (bovine serum albumin) solution did not induce such reaction. These results suggest that the silkworm possesses a fast and gelatin-inducible pathway that confers infection resistance to Gram-negative bacteria, which may act as a front-line defense. This finding highlights the potency of gelatin as a tool for investigating the primed immune responses in insect species.