Maternal Vaccination. Immunization of Sows during Pregnancy against ETEC Infections

Abstract

The immunology of pregnancy is an evolving consequence of multiple reciprocal interactions between the maternal and the fetal-placental systems. The immune response must warrant the pregnancy outcome (including tolerance to paternal antigens), but at the same time, efficiently respond to pathogenic challenges. Enterotoxigenic Escherichia coli (ETEC) strains are a major cause of illness and death in neonatal and recently weaned pigs. This review aims to give an overview of the current rationale on the maternal vaccination strategies for the protection of the newborn pig against ETEC. Newborn piglets are immunodeficient and naturally dependent on the maternal immunity transferred by colostrum for protection—a maternal immunity that can be obtained by vaccinating the sow during pregnancy. Our current knowledge of the interactions between the pathogen strategies, virulence factors, and the host immune system is aiding the better design of vaccination strategies in this particular and challenging host status. Challenges include the need for better induction of immunity at the mucosal level with the appropriate use of adjuvants, able to induce the most appropriate and long-lasting protective immune response. These include nanoparticle-based adjuvants for oral immunization. Experiences can be extrapolated to other species, including humans.

Oral Immunogenicity in Mice and Sows of Enterotoxigenic Escherichia Coli Outer-Membrane Vesicles Incorporated into Zein-Based Nanoparticles

“…Results show that the immunization with OMVs containing nanoparticles elicited specific antibodies and, more importantly, the piglets whose mothers were vaccinated with this new vaccine presented high levels of antibodies. Several maternal vaccines are on the market [24]. These are mainly applied parenterally in the pregnant sow; passive protection thus decreases rapidly and, consequently, the newly weaned piglet becomes highly susceptible [8].Therefore, the results obtained with OMVs encapsulated in the here-described zein nanoparticles support further studies into the immunization of sows to follow the protective effect after experimental challenge of the offspring piglets.…”

“…Several maternal vaccines are on the market with this goal. These vaccines, which are mainly applied parenterally, contain different virulence factors such as fimbriae, LPS, outer membrane proteins (OMPs) and LT enterotoxins [24][25][26]. However, they tend to stimulate the systemic rather than the mucosal immune system required to provide protection against ETEC bacteria in the gut [17].…”

Swine Enteric Colibacillosis in Spain: Pathogenic Potential of mcr-1 ST10 and ST131 E. coli Isolates

“…Pig diarrhea caused by E. coli is a worldwide economically important disease for the swine industry. While ETEC neonatal diarrhea can be effectively controlled by vaccination of pregnant sows, passive protection is quickly lost after weaning ( Melkebeek et al, 2013 ; Matías et al, 2017 ). Currently, few vaccines are commercially available for PWD, and few provide protection against different E. coli pathotypes ( Nadeau et al, 2017 ; Won and John Hwa, 2017 ).…”

Pig vaccination strategies based on enterotoxigenic Escherichia coli toxins

“…For approaches on immunization strategies based on antiadhesin approach and problems related to ETEC-mediated PWD in piglets, you can refer to recently published reviews [16][17][18].…”