Oral Immunization with Recombinant Lactobacillus acidophilus Expressing espA-Tir-M Confers Protection against Enterohemorrhagic Escherichia coli O157:H7 Challenge in Mice

Abstract

Enterohemorrhagic Escherichia coli O157:H7 (EHEC O157:H7) causes hemorrhagic colitis and the formation of characteristic attaching and effacing (A/E) lesions in humans. Given the severe sequelae of EHEC O157:H7 infection, it is critical to develop effective vaccines for human use. However, for achieving this goal many hurdles need to be addressed, such as the type or subset of antigens, adjuvant, and the delivery route. We developed a candidate vaccine by inserting the bivalent antigen espA-Tir-M composed of espA and the Tir central domain into Lactobacillus acidophilus. The recombinant L. acidophilus (LA-ET) was safe in a cell model and excluded EHEC O157:H7 from LoVo cells at rates of nearly 94 and 60% in exclusion and competition assays, respectively. LA-ET inhibited the induction of A/E lesions by EHEC O157:H7 cells in vitro. Oral immunization with LA-ET induced higher levels of specific mucosal and systemic antibody responses in mice. Moreover, LA-ET enhanced interferon-γ and interleukin-4 and -10 production, which was associated with mixed helper T (Th1/Th2) cell responses, and protected against EHEC O157:H7 colonization and infection in mice at a rate of 80%. Histopathological analyses revealed that orally administered LA-ET reduced or inhibited A/E lesions and toxin-induced systemic injury. These findings demonstrate that LA-ET induces both humoral and cellular immune responses in mice and is therefore a promising vaccine against EHEC O157:H7 infection.

Development of an Antigen Delivery Platform Using Lactobacillus acidophilus Decorated With Heterologous Proteins: A Sheep in Wolf’s Clothing Story

“…The development of a safe oral vaccine could be of critical relevance for preventing HUS in children. Recently, two papers have proposed the adaptation of Lactobacillus for STEC vaccine development (Ferreira et al, 2011;Lin et al, 2017). In one of these reports, Lin et al (2017) engineered L. acidophilus to express a chimeric STEC antigen composed by EspA and Tir (named E-T) with a signal peptide for the secretion to the bacterial supernatant.…”

“…Recently, two papers have proposed the adaptation of Lactobacillus for STEC vaccine development (Ferreira et al, 2011;Lin et al, 2017). In one of these reports, Lin et al (2017) engineered L. acidophilus to express a chimeric STEC antigen composed by EspA and Tir (named E-T) with a signal peptide for the secretion to the bacterial supernatant. Interestingly, these authors have shown that E-T-vaccinated mice were protected against an experimental infection (10 10 E. coli O157), similar to what we have shown here.…”

New Progress Regarding the Use of Lactic Acid Bacteria as Live Delivery Vectors, Treatment of Diseases and Induction of Immune Responses in Different Host Species Focusing on Lactobacillus Species

“…The study by Lin et al showed that, recombinant Lactobacillus acidophilus (LA-ET) was safe in a cell model and excluded EHEC O157:H7 from LoVo cells at rates of nearly 94 in exclusion and 60% in competition assays. Lactobacillus acidophilus induced higher levels of specific mucosal and systemic antibody responses and improved interferon-γ and interleukin-4 and -10 productions, which was coupled with assorted helper T (Th1/Th2) cell responses, and protected against EHEC O157:H7 colonization and infection in mice [134].…”

“…Lactobacillus species are known to influence the immune response in a strain-dependent manner; therefore, they are good candidates for developing innovative oral vectors, comprising good options to reduce the strength of pathogens, meant for mucosal delivery approaches [124,130]. Lately, ever-increasing confirmation supported that Lactobacillus strains expression systems, through expression and delivery of antigens/adjuvant, are hopeful oral vaccine vectors, due to their: efficient delivery of immunogens to the mucosal inductive locations, exceptional safety, reduced antigen degradation and prevention of protein purification On the use of Lactobacillus species as mucosal delivery vectors for therapeutic proteins and DNA vaccines such as expression signals and host strains, for the heterologous expression of therapeutic proteins such as antigens, cytokines and enzymes [133,134]. Resulting recombinant Lactobacillus strains have been tested successfully for their prophylactic and therapeutic effects in different animal models: especially, anti-oxidative Lactobacillus casei, Lactobacillus plantaram and Lactobacillus reuteri strains were constructed and tested in different study models as delivery vehicles for presentation to the mucosa of compounds with pharmaceutical attention, mainly vaccines [35,124,130,135].…”

New Progress regarding the Use of Lactic Acid Bacteria as Live Delivery Vectors, Treatment of Diseases and Induction of Immune Responses in Different Host Species Focusing on <i>Lactobacillus</i> Species

“…et al showed that, recombinant Lactobacillus acidophilus (LA-ET) was safe in a cell model and excluded EHEC O157:H7 from LoVo cells at rates of nearly 94 in exclusion and 60% in competition assays. Lactobacillus acidophilus induced higher levels of specific mucosal and systemic antibody responses and improved interferon-γ and interleukin-4 and -10 productions,which was coupled with assorted helper T (Th1/Th2) cell responses, and protected against EHEC O157:H7 colonization and infection in mice[136].…”