Oral Infection in a Germ-Free Bombyx mori Model

Pathogens of the silkworm Bombyx mori reduce silk crop quality and quantity, causing significant economic losses to silkworm rearers and the silk industry globally. In order to combat microbial diseases at the agricultural level, it is informative to characterize the host immune responses activated during infection in environmentally controlled conditions. While conventional silkworm rearing is dependent on the seasonality of mulberry trees, in the field of scientific research, recent developments such as artificial diets have resulted in consistent and controlled rearing conditions throughout the year. In this chapter, we describe protocols to perform oral infection experiments in a simplified germ-free silkworm model, reared on artificial diet. Also, we provide simple assays to monitor the activation of the immune response after oral infection, including the evaluation of the pathogen passage from the gut into the hemolymph, the change in the number of hemocytes, the actual rate of melanization, and the antimicrobial activity kinetics of the hemolymph during infection. These standardized protocols will enable the reporting of comparable datasets for B. mori host-pathogen interaction among research groups.