. Shigella flexneri is the major cause of shigellosis, also known as bacillary dysentery, of which there are estimated to be 2 million cases per year worldwide, resulting in 650,000 deaths ( Allison and Verma, 2000). Although antibiotic therapy is considered an effective treatment, the increasing prevalence of antibiotic resistance has made the development of an effective vaccine a top priority for a number of global health organizations ( Ranallo et al., 2012). However, a safe and effective vaccine against S. flexneri remains elusive despite the improvements in vaccine development ( Levine et al., 2007).