Salmonella vaccine study in an attenuated strain using an animal infection model with Galleria mellonella moth larvae

BALLESTEROS, MF.; LOPEZ, FE; PESCARETTI, MM; DELGADO, MA

Salta

Congreso; 54ta Reunión Anual de la Sociedad Argentina de Investigación Bioquímica y Biología Molecular (SAIB).; 2019

SAIB

SALMONELLA VACCINE STUDY IN AN ATTENUATED STRAIN USING AN ANIMAL INFECTION MODEL WITH GALLERIA MELLONELLA MOTH LARVAEBallesteros MF, López FE, Pescaretti MM, Delgado MA.INSIBIO (CONICET-UNT) and Instituto de Química Biológica ?Dr. Bernabe Bloj?. E-mail: mflorenciaballesteros@gmail.comThe Salmonella RcsCDB system regulates the expression of numerous virulence genes. In previously studies, we demonstrated that the Salmonella rcsC11 mutant is attenuated in virulence, and produces the constitutive activation of the RcsB regulator, manly during infection in an animal model. The goal of the present study was analyzed the rcsC11 attenuation effect on Galleria mellonella (G. mellonella) larvae, which can be used as a new animal infection model. This possibility is due to the great benefits that its offer as a host model including profitability, high reproducibility, ethical approval, easy handling and maintenance. The G. mellonella infection model allows the study many stages of Salmonella infection at 37 °C, the real temperature of the human body since its innate immune response has remarkable similarities with the vertebrate. To this end, we followed the infection protocol used previously in mice to improved G. mellonella larvae infection assays. For this purpose, the test was organized in 3 infection groups containing 10 larvae per assay infected with: i- wild type 14028s Salmonella Typhimurium strain, ii-Salmonella clinical isolates obtained from patients suffering diarrhea iii- PBS infected as control, while the iv group were infected with rcsC11 attenuated mutant but using 20 larvae. The number of larvae was increased in the iv lot in order to carried out a second infection challenger with 14028s virulent strain. In these assays we evaluated the protective effect of rcsC11 mutant against the 14028s virulent strain and the clinical isolates. We here observed that rcsC11-infected larvae as well those of the control lot, were able to survive and no disease-symptoms were manifested, in contrary to the wild type strain-infected larvae. In addition, in this control lot we observed a 90% of death after the second day of infection. On other hands, the Salmonella clinical isolates displayed an increased virulence than the 14028s laboratory strain. Moreover, we show that the rcsC11-surviving larvae were immune to a second infection challenge with the 14028s virulent strain. It is important to mention that similar results were previously obtained using a mice animal infection model. We show here that G. mellonella larvae can be used as a new model for the study of Salmonella infection, comparable to the murine infection model, but with less ethical restriction and with the possibility to used high number of sample per test. In addition, in these trials the minimum infective dose to be used in this model was determined. Moreover, we demonstrated once again the ability of the rcsC11 mutant to attenuate virulence, generating immunity against virulent Salmonella strains.