Vaccine for enterotoxigenic Escherichia coli causing post-weaning diarrhea (PWD) in piglets

Abstract

Post-weaning diarrhea (PWD) in piglets is primarily caused by the enterotoxigenic Escherichia coli (ETEC) strains. ETEC expresses adhesins attached to the intestinal mucosa, specifically fimbriae such as F4, F5, F6, F7 and F18. F4 and F18 are particularly prevalent in strains that cause PWD. ETEC then releases enterotoxins that play a central role in the pathogenic process, such as heat-labile enterotoxin (LT), heat-stable enterotoxin (ST), and a small amount of enteroaggregative heat-stable toxin 1 (EAST1), which lead to dehydration, electrolyte imbalances, damage to the intestine, reduced nutrient absorption, growth rate, and resulting in death. Vaccination is the most effective preventive measure against PWD. Although there is an existing ETEC vaccine based on fimbrial immunization, enterotoxins are the primary cause of diarrhea in ETEC. Therefore, the development of new-generation vaccine that target both adhesins and enterotoxins has been carried out. In recent years, many studies have successfully generated fusion antigens of these two factors and tested for their ability to induce immune responses in mouse, rabbit, and pig models. Along with the development of targeted M cell strategies, this opens a promising new direction for the creation of both general and specific ETEC oral vaccines. In this paper, the development strategies for vaccines based on fimbrial adhesins and enterotoxins to protect piglets from PWD are summarized. These studies also serve as a basis for the development of ETEC vaccines in humans.