Abstract
BackgroundRecent researches have been focusing on mucosal immune adjuvants, which play the key roles in mucosal immunization and have become the limitation for non-injected vaccine development. Escherichia coli heat-labile enterotoxin B subunit (LTB) was regarded as a promising mucosal adjuvant for its nontoxicity and potent activity. LTB preparation issues have always been recurring, in part owing to that the recombinant LTB expressed by E. coli does not act as its native form.ResultsWe constructed an engineered Lactococcus lactis strain using a food-grade expression system. The LTB secreted by the engineered strain was detected in the culture supernatant, constituting 10.3% of the supernatant proteins, and recognized by mouse anti-LTB antibodies. The engineered strain, co-administered orally to SPF BALB/c mice with a H. pylori vaccine candidate expressing Lpp20 antigen, could significantly enhance the Lpp20-induced mucosal SIgA antibody responses against H. pylori.ConclusionsThis is the first report that LTB was efficiently produced and delivered via using a food-grade lactococcal expression system, which offers a novel production and utilization mode of this crucial mucosal adjuvant. The engineered L. lactis strain secreting LTB has considerable potential for oral vaccine formulation owing to its outstanding safety, adjuvant activity and high-level production.
Highlights
Recent researches have been focusing on mucosal immune adjuvants, which play the key roles in mucosal immunization and have become the limitation for non-injected vaccine development
This is the first report that labile enterotoxin B subunit (LTB) was efficiently produced and delivered via using a food-grade lactococcal expression system
This study offers a novel production and utilization mode of this crucial mucosal adjuvant
Summary
Recent researches have been focusing on mucosal immune adjuvants, which play the key roles in mucosal immunization and have become the limitation for non-injected vaccine development. As antibiotic resistance has been continually increasing, researches currently focus on developing vaccines against the causative agents, such as Helicobacter pylori, Shigella and enterotoxigenic E. coli (ETEC), for which no commercial vaccines are available [1]. Parenteral immunizations can protect against causative agents. Sun et al BMC Biotechnology (2017) 17:25 parasitizing host tissues via stimulation of serum antibody and cellular immune responses, they can hardly elicit mucosal immunity against noninvasive pathogens [3, 6]. Mucosal vaccination can stimulate secretory antibody responses preventing infection by the pathogens from the mucosal surface [5]. Mucosal immunizations have the advantages of simple manipulation, less invasion, lowered risks of disease transmissions and ease of manufacture over parenteral inoculations
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