Decoding poultry immune responses to Salmonella vaccines: Current advances and future directions for next-generation vaccine development

The global impact of chicken products contaminated with Salmonella threatens public health, requiring novel and more effective Salmonella vaccine formulations and interventions that can assist poultry farming in reducing the entrance of this pathogen into the food system. Even though recent research findings have provided valuable information regarding poultry Salmonella vaccine technologies, there is still a need to develop sufficiently immunogenic self-limiting vaccines that closely mimic the pathogen-host interaction without causing active infection, and to better understand the host-immune responses to their administration. In this review, we compiled the currently available information on poultry Salmonella vaccines and the immune responses they elicit with the goal of promoting the development of novel and more effective vaccine formulations for poultry. We gathered information on non-vaccine strategies to control Salmonella throughout the poultry production chain, the pathogenesis of Salmonella, the host immune mechanisms against the pathogen, commercially available Salmonella vaccines, and the immune responses these vaccines elicit. The information gathered in this review will lay the foundation for further development of novel Salmonella vaccine designs that are successful in activating both cell-mediated and humoral immunity, resulting in protective immunity and decreasing Salmonella loads in poultry. This review highlights the current impact of Salmonella infection in poultry and how Salmonella vaccines are a key strategy to manage this pathogen in the farm environment, thus preventing Salmonella contamination of poultry products and safeguarding the health of consumers. Further research is needed to advance vaccine adjuvant technology, delivery systems, and multivalent protection.