A novel <i>Galleria mellonella</i> experimental model for zoonotic pathogen <i>Brucella</i>

Brucellosis is a major threat to public health and animal husbandry. Several <i>in vivo</i> vertebrate models, such as mice, guinea pigs, and nonhuman primates, have been used to study <i>Brucella</i> pathogenesis, bacteria-host interactions, and vaccine efficacy. However, these models have limitations whereas the invertebrate <i>Galleria mellonella</i> model is a cost-effective and ethical alternative. The aim of the present study was to examine the invertebrate <i>G. mellonella</i> as an in vivo infection model for <i>Brucella</i>. Infection assays were employed to validate the fitness of the larval model for <i>Brucella</i> infection and virulence evaluation. The protective efficacy of immune sera was evaluated by pre-incubated with a lethal dose of bacteria before infection. The consistency between the mouse model and the larval model was confirmed by assessing the protective efficacy of two <i>Brucella</i> vaccine strains. The results show that <i>G. mellonella</i> could be infected by <i>Brucella</i> strains, in a dose- and temperature-dependent way. Moreover, this larval model can effectively evaluate the virulence of <i>Brucella</i> strains in a manner consistent with that of mammalian infection models. Importantly, this model can assess the protective efficacy of vaccine immune sera within a day. Further investigation implied that haemolymph played a crucial role in the protective efficacy of immune sera. In conclusion, <i>G. mellonella</i> could serve as a quick, efficient, and reliable model for evaluating the virulence of <i>Brucella</i> strains and efficacy of immune sera in an ethical manner.