RESUMO
Plague caused by the Gram-negative bacterium, Yersinia pestis, is still endemic in parts of the world today. Protection against pneumonic plague is essential to prevent the development and spread of epidemics. Despite this, there are currently no licensed plague vaccines in the western world. Here we describe the means of delivering biologically active plague vaccine antigens directly to mucosal sites of plague infection using highly stable microvesicles (outer membrane vesicles; OMVs) that are naturally produced by the abundant and harmless human commensal gut bacterium Bacteroides thetaiotaomicron (Bt). Bt was engineered to express major plague protective antigens in its OMVs, specifically Fraction 1 (F1) in the outer membrane and LcrV (V antigen) in the lumen, for targeted delivery to the gastrointestinal (GI) and respiratory tracts in a non-human primate (NHP) host. Our key findings were that Bt OMVs stably expresses F1 and V plague antigens, particularly the V antigen, in the correct, immunogenic form. When delivered intranasally V-OMVs elicited substantive and specific immune and antibody responses, both in the serum [immunoglobulin (Ig)G] and in the upper and lower respiratory tract (IgA); this included the generation of serum antibodies able to kill plague bacteria. Our results also showed that Bt OMV-based vaccines had many desirable characteristics, including: biosafety and an absence of any adverse effects, pathology or gross alteration of resident microbial communities (microbiotas); high stability and thermo-tolerance; needle-free delivery; intrinsic adjuvanticity; the ability to stimulate both humoral and cell-mediated immune responses; and targeting of primary sites of plague infection.
Assuntos
Antígenos de Bactérias/metabolismo , Membrana Externa Bacteriana/metabolismo , Bacteroides thetaiotaomicron/metabolismo , Vacina contra a Peste/imunologia , Peste/imunologia , Proteínas Citotóxicas Formadoras de Poros/metabolismo , Vesículas Transportadoras/imunologia , Yersinia pestis/fisiologia , Administração Intranasal , Animais , Anticorpos Antibacterianos/sangue , Antígenos de Bactérias/genética , Bacteroides thetaiotaomicron/genética , Bioengenharia , Morte Celular , Células Cultivadas , Microbioma Gastrointestinal/genética , Humanos , Imunidade Celular , Imunidade Humoral , Imunoglobulina A/metabolismo , Imunoglobulina G/sangue , Macaca , Peste/prevenção & controle , Vacina contra a Peste/metabolismo , Proteínas Citotóxicas Formadoras de Poros/genética , Vesículas Transportadoras/metabolismoRESUMO
There is an urgent and unmet need to develop effective vaccines to reduce the global burden of infectious disease in both animals and humans, and in particular for the majority of pathogens that infect via mucosal sites. Here we summarise the impediments to developing mucosal vaccines and review the new and emerging technologies aimed at overcoming the lack of effective vaccine delivery systems that is the major obstacle to developing new mucosal vaccines.