Vaccine Immunogenicity versus Gastrointestinal Microbiome Status: Implications for Poultry Production

At the turn of the 21st century, the importance of maintaining a balanced microbiome was brought to the forefront of the microbiology, immunology, and physiology research fields. Exploring the complex interactions between vaccine administration, mucosal microbiome, oral tolerance, and enteric inflammation in health and disease is challenging since environmental factors (such as diet and sanitation) have major influences on gut microbiota composition. High enteric pathogen load has been shown to contribute to dampened cell-mediated and humoral immune responses to vaccines in human case studies, either through elevated enteric inflammation or increased tolerance to environmental microbes. Although antibiotic and probiotic interventions have been evaluated in human health as well as research animal models, effective measures to mediate vaccine hyporesponsiveness are still ill-defined. Research in this field is becoming increasingly important for managing flock health in commercial poultry production, especially as antibiotic-free production is more prevalent and vaccination programs remain extensive during the first weeks of a bird's life. By understanding the cellular interactions between commensal microbiota, vaccine antigens, and the host immune system (particularly in avian models), advancements in bacterial and viral vaccine immunogenicity could lead to improved flock health in meat-type and egg-type chickens in the future.