Antibody responses elicited in mice immunized with Bacillus subtilis vaccine strains expressing Stx2B subunit of enterohaemorragic Escherichia coli O157:H7

Abstract

No effective vaccine or immunotherapy is presently available for patients with the hemolytic uremic syndrome (HUS) induced by Shiga-like toxin (Stx) produced by enterohaemorragic Escherichia coli (EHEC) strains, such as those belonging to the O157:H7 serotype. In this work we evaluated the performance of Bacillus subtilis strains, a harmless spore former gram-positive bacterium species, as a vaccine vehicle for the expression of Stx2B subunit (Stx2B). A recombinant B. subtilis vaccine strain expressing Stx2B under the control of a stress inducible promoter was delivered to BALB/c mice via oral, nasal or subcutaneous routes using both vegetative cells and spores. Mice immunized with vegetative cells by the oral route developed low but specific anti-Stx2B serum IgG and fecal IgA responses while mice immunized with recombinant spores developed anti-Stx2B responses only after administration via the parenteral route. Nonetheless, serum anti-Stx2B antibodies raised in mice immunized with the recombinant B. subtilis strain did not inhibit the toxic effects of the native toxin, both under in vitro and in vivo conditions, suggesting that either the quantity or the quality of the induced immune response did not support an effective neutralization of Stx2 produced by EHEC strains.

Comparative Analysis of Bacillus subtilis Spores and Monophosphoryl Lipid A as Adjuvants of Protein-Based Mycobacterium tuberculosis-Based Vaccines: Partial Requirement for Interleukin-17A for Induction of Protective Immunity

“…Investigators using B. subtilis spores formulated with antigens from other pathogens have demonstrated the induction of significant antibody levels in inoculated mice (20)(21)(22). The role of antibody in protective immunity against tuberculosis remains controversial, and thus the ability of a vaccine adjuvant to induce antibodies may provide an extra dimension to its protective efficacy.…”

Salmonella enterica Serovar Typhimurium Vaccine Strains Expressing a Nontoxic Shiga-Like Toxin 2 Derivative Induce Partial Protective Immunity to the Toxin Expressed by Enterohemorrhagic Escherichia coli

“…MaxiSorp microtiter plates (Nalge Nunc) were coated with the purified recombinant Stx2 B subunit (1 g/ml) in PBS (pH 7.4) and were incubated overnight at 4°C, as previously described (17). The plates were blocked with PBS with 1% BSA for 1 h at 37°C, and aliquots of serum and fecal extracts, previously diluted in PBS with 0.05% Tween 20 (PBST), were added to the plates in a series of 2-fold dilutions, followed by incubation for a further 2 h at 37°C.…”

“…Both in vitro and ex vivo Stx2 neutralization activities of sera collected from mice immunized with the different S. Typhimurium vaccine strains were determined as described previously (5,12,17). The in vitro test was carried out with equal volumes of whole E. coli LDV15 extracts containing twice the dose of Stx2 that leads to 50% cytotoxicity (CD 50 ) in Vero cells, as described previously (5,12).…”

Desenvolvimento de uma nova estratégia vacinal com propriedades profiláticas contra a síndrome hemolítica urêmica (SHU) associada a linhagens de Escherichia coli enterohemorrágica (EHEC) produtoras da toxina "Shiga-like" (Stx2).

“…Tal comportamento imunológico é coerente com a evolução de um ambiente de supressão imunológica no trato gastrointestinal que, em condições saudáveis não permite a ativação de uma forte resposta inflamatória contra a flagelina, uma proteína altamente conservada entre várias espécies encontradas em enterobactérias (MIZEL et al, 2002;SANDERS et al, 2006;WINTER et al, 2009;YOSHIOKA et al, 2008). (BIELASZEWSKA et al, 1997;BYUN et al, 2001; GOMES, et al, 2009).…”