A triple-sugar regulated Salmonella vaccine protects against Clostridium perfringens-induced necrotic enteritis in broiler chickens

Abstract

Gram-positive Clostridium perfringens type G, the causative agent of necrotic enteritis ( NE ), has gained more attention in the poultry industry due to governmental restrictions on the use of growth-promoting antibiotics in poultry feed. Our previous work has proved that regulated delayed lysis Salmonella vaccines delivering a plasmid encoding an operon fusion of the nontoxic C-terminal adhesive part of alpha toxin and a GST-NetB toxin fusion were able to elicit significant protective immunity in broilers against C. perfringens challenge. We recently improved our S. Typhimurium antigen delivery vaccine strain by integrating a rhamnose-regulated O-antigen synthesis gene enabling a triple-sugar regulation system to control virulence, antigen-synthesis and lysis in vivo traits. The strain also includes a Δ sifA mutation that was previously shown to increase the immunogenicity of and level of protective immunity induced by Salmonella vectored influenza and Eimeria antigens. The new antigen-delivery vaccine vector system confers on the vaccine strain a safe profile and improved protection against C. perfringens challenge. The strain with the triple-sugar regulation system delivering a regulated lysis plasmid pG8R220 encoding the PlcC and GST-NetB antigens protected chickens at a similar level observed in antibiotic-treated chickens. Feed conversion and growth performance were also similar to antibiotic-treated chickens. These studies made use of a severe C. perfringens challenge with lesion formation and mortality enhanced by pre-exposure to Eimeria maxima oocysts. The vaccine achieved effectiveness through three different immunization routes, oral, spray and in drinking water. The vaccine has a potential for application in commercial hatcher and broiler-rearing conditions.

Protective immunity enhanced Salmonella vaccine vectors delivering Helicobacter pylori antigens reduce H. pylori stomach colonization in mice

“…In this study, we employed a recently much improved PIESV vector strain with superior attributes compared to previously used recombinant attenuated Salmonella vaccine vector strains used by others or by us. Based on the succeed of Salmonlla-C. perfringens vaccine development (29), this PIESV vector strain c12341 was thus used to deliver and synthesize nine recombinant protective antigens of H. pylori. Mice were immunized with each construct alone or a combination of them.…”

“…Escherichia coli and S. Typhimurium UK-1 derivative strains were routinely cultured in LB broth [19] or on LB agar at 37°C. S. Typhimurium UK-1 mutant strains were supplemented with 50 mg/ml of diaminopimelic acid (DAP), 0.05% arabinose, 0.1% mannose and 0.1% rhamnose when necessary for bacterial growth as described in previous work (29,(52)(53)(54). For animal experiments, S. Typhimurium c12341 was cultured in LB broth with necessary supplements.…”

“…The construction and properties of c12341 have been recently described (29). Three sugars, arabinose, mannose and rhamnose which are not present in animal tissues, were used to regulate the virulence trait.…”

“…In this study, we employed recently developed much improved PIESVs that specifically synthesize heterologous antigens to enhance the induction of immune responses and protection against viruses and bacteria (27)(28)(29). The specific PIESV strain used in this study (29) has just been licensed by APHIS as the first genetically modified bacterial vectored vaccine in commercial distribution. Such mucosal PIESV delivery induces strong mucosal, systemic and cellular immunities against the targeted pathogen (30)(31)(32)(33)(34)(35).…”

Recombinant Limosilactobacillus (Lactobacillus) delivering nanobodies against Clostridium perfringens NetB and alpha toxin confers potential protection from necrotic enteritis

“…A nontoxic variant of NetB called W262A is commonly used for immunization and has been shown to partially protect birds from NE (Fernandes Da Costa et al, 2016 ; Hunter et al, 2019 ; Jiang et al, 2015 ; Keyburn et al, 2008 ; S. Wang et al, 2021 ; Wilde et al, 2019 ). The role of α toxin in NE is not clear; however, immunization with α toxin antigen partially protects birds from NE (Abildgaard et al, 2009 ; Al‐Sheikhly & Truscott, 1977a , 1977b ; Cooper et al, 2009 ; Fernandes Da Costa et al, 2016 ; Hunter et al, 2019 ; Jiang et al, 2015 ; Keyburn et al, 2006 ; Kulkarni et al, 2007 , 2010 ; S. Wang et al, 2021 ; Wilde et al, 2019 ; Zekarias et al, 2008 ). A combination of NetB and α toxin provides improved protection against NE (Fernandes Da Costa et al, 2016 ).…”