Abstract
In order to develop a novel and effective immunoregulator to enhance both the immune response and antimicrobial function, a recombinant eukaryotic expression plasmid-pVAX1 co-expressing fusion cathelicidin antimicrobial peptides (CAMPs) and fusion porcine interleukin-4/6 gene (IL-4/6) was constructed and encapsulated in chitosan nanoparticles (CS-VAP4/6), prepared by the ionotropic gelation method. Four-week-old female Kunming mice were divided into three groups and intramuscularly injected, respectively, with CS-VAP, CS-VAP4/6, and CS-pVAX1. On 28 days post-inoculation, the mice were challenged by intraperitoneal injection with Staphylococcus aureus (ATCC 25923) and Escherichia coli (ATCC 25922); IgG, IgG1 and IgG2a, CD4+, and CD8+ T cells increased significantly in the VAP- and VAP4/6- treated mice, detected by ELISA and flow cytometry, correspondingly (p < 0.05). As analyzed by qPCR, expression levels of Toll-like receptor (TLR) 1, TLR4, TLR6, TLR9, IL-1, IL-2, IL-4, IL-6, IL-7, IL-12, IL-15, IL-23, Tumor Necrosis Factor (TNF)-α, and Interferon-gamma (IFN-γ) genes were also significantly up-regulated in comparison with those of the control mice (p < 0.05). Their immunological markers were elevated significantly to different degrees in CS-VAP4/6-treated mice compared with CS-VAP in different days post-inoculation (p < 0.05). After challenge with E. coli and Staphylococcus aureus, most of the VAP- and VAP4/6- treated mice survived, and no symptoms of bacterial infection were observed. In contrast, 80% of control mice died of infection. Among the treated groups, VAP4/6 had a stronger resistance against challenge with E. coli infection. These results demonstrated that the fusion gene of antimicrobial peptide and interleukin-4/6 has the promising potential as a safe and effective immunomodulator for the control of bacterial infections.
Highlights
Drug resistance of animal pathogens is a continuously growing problem, and immunosuppressive pathogens worsen mixed infections to animals, which is still a massive challenge for the prevention and control of animal infectious diseases
In order to decrease the occurrence of drug resistance, more effective roles of T helper cells in optimizing antibody immune response and effector CD4+ or CD8+ T
The recombinant gene (TPA-PR39-linker-Tritrpticin-linker-PAMP23-linker-Protegrin1-His-tag) of downstream tissue plasminogen activator (TPA) signal sequence and antimicrobial peptides fusion gene-cathelicidin antimicrobial peptides (CAMPs), which was connected by GSGDDDDK linker with each other, was amplified from pVR1020-CAMPs (VRP), which constructed in our lab previously
Summary
Drug resistance of animal pathogens is a continuously growing problem, and immunosuppressive pathogens worsen mixed infections to animals, which is still a massive challenge for the prevention and control of animal infectious diseases. Vaccines 2020, 8, 552 countries and regions around the world since 2018, and all varieties of growth-promoting antimicrobial additives will be prohibited by the end of 2020 in China. There is a pressing need for the replacement of antimicrobial additives to prevent complicated infection of animals, as well as to improve their innate and acquired immunity, to strengthen the animal mucosal immune defense responses and antibacterial ability. In order to decrease the occurrence of drug resistance, more effective roles of T helper cells in optimizing antibody immune response and effector CD4+ or CD8+ T cells in eliminating intracellular pathogens are greatly expected [1]. Relevant evaluations of the immune effect of cytokines as vaccine adjuvants have been conducted [3,4]
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