RESUMO
Disruption of one or more components of the Tol-Pal system, involved in maintaining the integrity of the outer membrane of Gram-negative bacteria, has been proposed as a method to increase the yield obtained from natural production of outer membrane vesicles (OMV). We present a new OMV-based product, obtained from genetically modified Shigella flexneri 2a with a non-polar deletion in tolR and heat-inactivated (HT-ΔtolR). The S. flexneri ΔtolR strain lead to a higher release of vesicles, more than 8-times when compared to the yield obtained from chemically inactivated wild type strain. S. flexneri mutant strain appeared to be more sensitive to different chemical compounds, including antibiotics, bile salts or human complement and it was also less virulent in both in vitro and in vivo assays. The mutation produced some changes in the LPS O-chain and protein expression. S. flexneri ΔtolR was enriched in long and very long LPS O-chain and expressed a different pattern of surface proteins or lipoproteins. In vitro toxicity and activation properties were determined in Raw 267.4 macrophage cell line. HT-ΔtolR antigenic complex was non-cytotoxic and activation markers, such as MHC-II or CD40, were highly expressed during incubation with this product. Finally, preliminary studies on the antibody response elicited by HT-ΔtolR demonstrated a robust and diverse response in mice. Considering these promising results, HT-ΔtolR antigenic extract appears as a new potential vaccine candidate to face shigellosis.
Assuntos
Proteínas da Membrana Bacteriana Externa/genética , Vacinas contra Shigella/imunologia , Shigella flexneri/genética , Animais , Antibacterianos/farmacologia , Formação de Anticorpos , Antígenos de Bactérias/genética , Antígenos de Bactérias/imunologia , Proteínas da Membrana Bacteriana Externa/imunologia , Disenteria Bacilar/prevenção & controle , Feminino , Lipopolissacarídeos , Macrófagos/efeitos dos fármacos , Camundongos , Proteômica , Células RAW 264.7 , Vacinas contra Shigella/genética , Vesículas Transportadoras , Vacinas de Subunidades Antigênicas/genética , Vacinas de Subunidades Antigênicas/imunologiaRESUMO
The burden of dysentery due to shigellosis among children in the developing world is still a major concern. A safe and efficacious vaccine against this disease is a priority, since no licensed vaccine is available. This review provides an update of vaccine achievements focusing on subunit vaccine strategies and the forthcoming strategies surrounding this approach. In particular, this review explores several aspects of the pathogenesis of shigellosis and the elicited immune response as being the basis of vaccine requirements. The use of appropriate Shigella antigens, together with the right adjuvants, may offer safety, efficacy and more convenient delivery methods for massive worldwide vaccination campaigns.