Abstract
BackgroundThe well-known fact that avian pathogenic Escherichia coli (APEC) is harder to prevent due to its numerous serogroups has promoted the development of biological immunostimulatory materials as new vaccine candidates in poultry farms. Bacterial outer membrane vesicles (OMVs), known as spherical nanovesicles enriched with various immunostimulants, are naturally secreted by Gram-negative bacteria, and have gained much attention for developing effective vaccine candidates. Recent report has demonstrated that OMVs of APEC O78 can induce protective immunity in chickens. Here, a novel multi-serogroup OMVs (MOMVs) vaccine was developed to achieve cross-protection against APEC infection in broiler chickens.ResultsIn this study, OMVs produced by three APEC strains were isolated, purified and prepared into MOMVs by mixing these three OMVs. By using SDS-PAGE and LC–MS/MS, 159 proteins were identified in MOMVs and the subcellular location and biological functions of 20 most abundant proteins were analyzed. The immunogenicity of MOMVs was evaluated, and the results showed that MOMVs could elicit innate immune responses, including internalization by chicken macrophage and production of immunomodulatory cytokines. Vaccination with MOMVs induced specific broad-spectrum antibodies as well as Th1 and Th17 immune responses. The animal experiment has confirmed that immunization with an appropriate dose of MOMVs could not cause any adverse effect and was able to reduce bacteria loads and pro-inflammatory cytokines production, thus providing effective cross-protection against lethal infections induced by multi-serogroup APEC strains in chickens. Further experiments indicated that, although vesicular proteins were able to induce stronger protective efficiency than lipopolysaccharide, both vesicular proteins and lipopolysaccharide are crucial in MOMVs-mediated protection.ConclusionsThe multi-serogroup nanovesicles produced by APEC strains will open up a new way for the development of next generation vaccines with low toxicity and broad protection in the treatment and control of APEC infection.
Highlights
The well-known fact that avian pathogenic Escherichia coli (APEC) is harder to prevent due to its numerous serogroups has promoted the development of biological immunostimulatory materials as new vaccine candidates in poultry farms
Purified multi-serogroup OMVs (MOMVs) were made with each purified outer membrane vesicles (OMVs) from three Avian pathogenic E. coli (APEC) strains and observed by scanning electron microscopy (Fig. 1d) and transmission electron microscopy (Fig. 1e)
The results show that the APEC strains abundantly produced the spherical vesicles with a morphology of bilayer membrane
Summary
The well-known fact that avian pathogenic Escherichia coli (APEC) is harder to prevent due to its numerous serogroups has promoted the development of biological immunostimulatory materials as new vaccine candidates in poultry farms. A novel multi-serogroup OMVs (MOMVs) vaccine was developed to achieve cross-protection against APEC infection in broiler chickens. Avian pathogenic E. coli (APEC) refers to E. coli strains that can cause extraintestinal diseases in chicken and other avian species [1]. Hu et al Microb Cell Fact (2020) 19:119 bacterial pathogen in the poultry industry worldwide, APEC can cause typical colibacillosis in broiler chickens, such as colisepticemia, granuloma, air sacculitis, pericarditis and cellulitis [2]. With the gradual prohibition of antimicrobial drugs in animal husbandry and the emergence of multidrug-resistant bacteria, it becomes difficult and costly to control APEC infection [7]. It is urgently needed to search alternative preventive strategies to ameliorate APEC infection
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