Shigella Vaccine Development: The Model Matters

Bacillary dysentery or shigellosis is mediated by the pathogenic enterobacteria Shigella. Shigella are transmitted through the fecal-oral route, no animal reservoir has been described, and remain a major cause of moderate-severe diarrhea worldwide since no Shigella vaccine is yet commercialized. The design of a pan-Shigella vaccine has been made difficult by the large variety of Shigella species and serotypes and the continuous identification of new serotypes due to the genomic plasticity of Shigella. The assessment of Shigella vaccine candidates remains complicated by the lack of a suitable animal model of shigellosis. Until know, several model of shigellosis have been characterized in the rhesus macaque, the rabbit, the mouse or the guinea pig, although none of them is satisfactory to assess the whole Shigella virulence process from an oral inoculation to the colonic mucosa colonization and disruption. The potential and limits of the different animal model of shigellosis used so far to study Shigella virulence mechanisms and to evaluate vaccine candidates’ efficacy are described here. Since no optimal animal model of shigellosis has been characterized, further efforts should be made to develop a suitable one, as a pre-requisite for the development of a successful Shigella vaccine.