Primed Immune Responses to Gram-negative Peptidoglycans Confer Infection Resistance in Silkworms

Abstract

Background: Primed immune responses contribute to vertebrate host defense. Results: Silkworms acquire resistance to a pathogen by a preinjection of its heat-killed cells or its cell surface peptidoglycans. The amount of antimicrobial peptides is increased at the second round of infection. Conclusion: Invertebrates acquire infection resistance by peptidoglycan recognition and antimicrobial peptide increase. Significance: Molecular mechanisms of invertebrate primed immunity were revealed.

Divergent immune priming responses across flour beetle life stages and populations

“…Growing evidence suggests that a low dose of a pathogen may prime the immune response in insects, reducing the risk and severity of infection by the same pathogen later in life. Evidence for such priming‐induced immune protection has been reported in many insects including mealworm beetles (Daukšte, Kivleniece, Krama, Rantala, & Krams, ), bumble bees (Sadd & Schmid‐Hempel, ; Tidbury, Pedersen, & Boots, ), silkworms (Miyashita, Kizaki, Kawasaki, Sekimizu, & Kaito, ), fruit flies (Pham, Dionne, Shirasu‐Hiza, & Schneider, ), mosquitoes (Contreras‐Garduño, Rodríguez, Rodríguez, Alvarado‐Delgado, & Lanz‐Mendoza, ), and flour beetles (Roth, Sadd, Schmid‐Hempel, & Kurtz, ). Immune priming can also confer sustained protection via (i) ontogenic priming, where the benefit of priming can persist through metamorphosis (Moreno‐García, Vargas, Ramírez‐Bello, Hernández‐Martínez, & Lanz‐Mendoza, ; Thomas & Rudolf, ) and (ii) transgenerational immune priming, where the benefits are manifested in the next generation (Dubuffet et al., ; Moreau, Martinaud, Troussard, Zanchi, & Moret, ; Sadd & Schmid‐Hempel, ; Sadd & Schmid‐hempel, ; Zanchi, Troussard, Moreau, & Moret, ).…”

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

“…I have previously reported that a pre-injection of heat-killed cells of Gram-negative bacteria, or its cell wall moiety (peptidoglycans), confers infection resistance to otherwise lethal bacterial infection in silkworm (Miyashita et al, 2014; Miyashita et al, 2015). Although the peptidoglycan-inducible immune priming conferred a full resistance to pathogenic Gram-negative bacteria, its proposed molecular mechanism (i.e.…”

“…Although the peptidoglycan-inducible immune priming conferred a full resistance to pathogenic Gram-negative bacteria, its proposed molecular mechanism (i.e. antimicrobial peptide upregulation) takes long time to activate (Miyashita et al, 2014), which thus is not sufficient to suppress bacterial infection ongoing.…”

Understanding of bacterial virulence using the silkworm infection model

“…Insects, including silkworms, have innate immune systems conserved with mammals. In addition, silkworms have a primed immune system that has several characteristics that resemble acquired immune systems in vertebrates (24,25).…”