Plasmid DNA Prime/Protein Boost Vaccination against Campylobacter jejuni in Broilers: Impact of Vaccine Candidates on Immune Responses and Gut Microbiota

Abstract

Campylobacter infections, traced to poultry products, are major bacterial foodborne zoonoses, and vaccination is a potential solution to reduce these infections. In a previous experimental trial using a plasmid DNA prime/recombinant protein boost vaccine regimen, two vaccine candidates (YP437 and YP9817) induced a partially protective immune response against Campylobacter in broilers, and an impact of the protein batch on vaccine efficacy was suspected. This new study was designed to evaluate different batches of the previously studied recombinant proteins (called YP437A, YP437P and YP9817P) and to enhance the immune responses and gut microbiota studies after a C. jejuni challenge. Throughout the 42-day trial in broilers, caecal Campylobacter load, specific antibodies in serum and bile, the relative expression of cytokines and β-defensins, and caecal microbiota were assessed. Despite there being no significant reduction in Campylobacter in the caecum of vaccinated groups, specific antibodies were detected in serum and bile, particularly for YP437A and YP9817P, whereas the production of cytokines and β-defensins was not significant. The immune responses differed according to the batch. A slight change in microbiota was demonstrated in response to vaccination against Campylobacter. The vaccine composition and/or regimen must be further optimised.

Evaluation of Two Recombinant Protein-Based Vaccine Regimens against Campylobacter jejuni: Impact on Protection, Humoral Immune Responses and Gut Microbiota in Broilers

“…As seen in the previous study using a DNA prime/protein boost vaccine regimen against Campylobacter [35], a slight change in the microbiota was observed after vaccination. The results of this study suggest that differences between the groups reflect an effect of the frequency of inoculation or adjuvant rather than vaccination with the YP437 protein.…”

“…Moreover, the role of antibodies in the reduction of Campylobacter is not clear. Indeed, elevated antibody levels (IgY or IgA) do not necessarily result in effective protection among broilers, as already observed previously after a challenge by Campylobacter only [47] or in the case of a Campylobacter challenge with the use of different proteins as a vaccine [31,34,35,48,49]. On the contrary, humoral immunity, more specifically the intestinal mucosal immune response, appears to be involved in the reduction of Campylobacter in chickens [12,21,50].…”

“…In the first in vivo study, a plasmid DNA prime/recombinant protein boost vaccine regimen [34] induced a mean reduction of about 3.6 log 10 of caecal Campylobacter load accompanied by a production of systemic antibodies against Campylobacter in broilers. However, this reduction in Campylobacter load was not observed in two further trials [34,35].…”