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Background   Helicobacter pylori  is the first bacterium formally recognized as a carcinogen and is one of the most successful human pathogens, as over half of the world’s population is colonized by the bacterium.  H. pylori -induced gastroduodenal disease depends on the inflammatory response of the host and on the production of specific bacterial virulence factors. The study of  Helicobacter pylori  pathogenic action would greatly benefit by easy-to-use models of infection.    Results  In the present study, we examined the effectiveness of the larvae of the wax moth  Galleria mellonella  as a new model for  H. pylori  infection.  G. mellonella  larvae were inoculated with bacterial suspensions or broth culture filtrates from either different wild-type  H. pylori  strains or their mutants defective in specific virulence determinants, such as VacA, CagA, CagE, the whole pathogenicity island (PAI)  cag , urease, and gamma-glutamyl transpeptidase (GGT). We also tested purified VacA cytotoxin. Survival curves were plotted using the Kaplan-Meier method and LD 50  lethal doses were calculated. Viable bacteria in the hemocoel were counted at different time points post-infection, while apoptosis in larval hemocytes was evaluated by annexin V staining. We found that wild-type and mutant  H. pylori  strains were able to survive and replicate in  G. mellonella  larvae which underwent death rapidly after infection.  H. pylori  mutant strains defective in either VacA, or CagA, or CagE, or  cag  PAI, or urease, but not GGT-defective mutants, were less virulent than the respective parental strain. Broth culture filtrates from wild-type strains G27 and 60190 and their mutants replicated the effects observed using their respective bacterial suspension. Also, purified VacA cytotoxin was able to kill the larvae. The killing of larvae always correlated with the induction of apoptosis in hemocytes.    Conclusions   G. mellonella  larvae are susceptible to  H. pylori  infection and may represent an easy to use in vivo model to identify virulence factors and pathogenic mechanisms of  H. pylori . The experimental model described can be useful to screen a large number of clinical  H. pylori  strain and to correlate virulence of  H. pylori  strains with patients’ disease status.

Use of larvae of the wax moth Galleria mellonella as an in vivo model to study the virulence of Helicobacter pylori