Immunogenicity of a bovine herpesvirus 1 glycoprotein D DNA vaccine complexed with bovine neutrophil beta-defensin 3

Antimicrobial Mechanisms and Clinical Application Prospects of Antimicrobial Peptides

Antimicrobial peptides are a type of small-molecule peptide that widely exist in nature and are components of the innate immunity of almost all living things. They play an important role in resisting foreign invading microorganisms. Antimicrobial peptides have a wide range of antibacterial activities against bacteria, fungi, viruses and other microorganisms. They are active against traditional antibiotic-resistant strains and do not easily induce the development of drug resistance. Therefore, they have become a hot spot of medical research and are expected to become a new substitute for fighting microbial infection and represent a new method for treating drug-resistant bacteria. This review briefly introduces the source and structural characteristics of antimicrobial peptides and describes those that have been used against common clinical microorganisms (bacteria, fungi, viruses, and especially coronaviruses), focusing on their antimicrobial mechanism of action and clinical application prospects.

Intranasal delivery of plasmids expressing bovine herpesvirus 1 gB/gC/gD proteins by polyethyleneimine magnetic beads activates long-term immune responses in mice

Background

DNA vaccine is one of the research hotspots in veterinary vaccine development. Several advantages, such as cost-effectiveness, ease of design and production, good biocompatibility of plasmid DNA, attractive biosafety, and DNA stability, are found in DNA vaccines.

Methods

In this study, the plasmids expressing bovine herpesvirus 1 (BoHV-1) gB, gC, and gD proteins were mixed at the same mass ratio and adsorbed polyethyleneimine (PEI) magnetic beads with a diameter of 50 nm. Further, the plasmid and PEI magnetic bead polymers were packaged into double carboxyl polyethylene glycol (PEG) 600 to use as a DNA vaccine. The prepared DNA vaccine was employed to vaccinate mice via the intranasal route. The immune responses were evaluated in mice after vaccination.

Results

The expression of viral proteins could be largely detected in the lung and rarely in the spleen of mice subjected to a vaccination. The examination of biochemical indicators, anal temperature, and histology indicated that the DNA vaccine was safe in vivo. However, short-time toxicity was observed. The total antibody detected with ELISA in vaccinated mice showed a higher level than PBS, DNA, PEI + DNA, and PBS groups. The antibody level was significantly elevated at the 15th week and started to decrease since the 17th week. The neutralizing antibody titer was significantly higher in DNA vaccine than naked DNA vaccinated animals. The total IgA level was much greater in the DNA vaccine group compared to other component vaccinated groups. The examination of cellular cytokines and the percentage of CD4/CD8 indicated that the prepared DNA vaccine induced a strong cellular immunity.

Conclusion

The mixed application of plasmids expressing BoHV-1 gB/gC/gD proteins by nano-carrier through intranasal route could effectively activate long-term humoral, cellular, and mucosal immune responses at high levels in mice. These data indicate PEI magnetic beads combining with PEG600 are an efficient vector for plasmid DNA to deliver intranasally as a DNA vaccine candidate.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12985-021-01536-w.

Porcine β-defensin 2 inhibits proliferation of pseudorabies virus in vitro and in transgenic mice

Background

Porcine β-defensin 2 (PBD-2), produced by host cells, is an antimicrobial cysteine-rich cationic peptide with multi-functions. Previous studies have demonstrated that PBD-2 can kill various bacteria, regulate host immune responses and promote growth of piglets. However, the antiviral role of PBD-2 is rarely investigated. This study aimed to reveal the antiviral ability of PBD-2 against pseudorabies virus (PRV), the causative pathogen of Aujeszky’s disease, in PK-15 cells and in a PBD-2 expressing transgenic (TG) mouse model.

Methods

In this study, the cytotoxicity of PBD-2 on PK-15 cells was measured by CCK-8 assay. PK-15 cells were incubated with PRV pre-treated with different concentrations of PBD-2 and PRV titers in cell culture supernatants were determined by real-time quantitative PCR (RT-qPCR). TG mice and wild-type (WT) mice were intraperitoneally injected with PRV and the survival rate was recorded for 10 days. Meanwhile, tissue lesions in brain, spleen and liver of infected mice were observed and the viral loads of PRV in brain, liver and lung were analyzed by RT-qPCR.

Results

PBD-2 at a maximum concentration of 80 μg/mL displayed no significant cytotoxicity on PK-15 cells. A threshold concentration of PBD-2 at 40 μg/mL was required to inhibit PRV proliferation in PK-15 cells. The survival rate in PBD-2 TG mice was 50% higher than that of WT mice. In addition, TG mice showed alleviated tissue lesions in brain, spleen and liver compared with their WT littermates after PRV challenge, while viral loads of PRV in brain, liver and lung of TG mice were significantly lower than that of WT mice.

Conclusions

PBD-2 could inhibit PRV proliferation in PK-15 cells and protect mice from PRV infection, which confirmed the antiviral ability of PBD-2 both in vitro and in vivo. The application of PBD-2 in developing anti-viral drugs or disease-resistant animals can be further investigated.

Protective immunity following vaccination with a recombinant multiple-epitope protein of bovine herpesvirus type I in a rabbit model

Bovine herpesvirus type 1 (BoHV-1) causes considerable economic losses to the cow industry. Vaccination remains an effective strategy to control the diseases associated with BoHV-1. However, live vaccines present safety concerns, especially in pregnant cows; thus, nonreplicating vaccines have been developed to control the disease. The envelope glycoproteins of BoHV-1 induce a protective immune response. In this work, selected epitopes on glycoproteins gD, gC, and gB were constructed in triplicate with linker peptides. Vaccination of rabbits demonstrated that P2-gD/gC/gB with AAYAAY induced higher specific antibodies than that with GGGGS linker. P2-gD/gC/gB with AAYAAY linker was fused with bovine interleukin-6 (BoIL-6) or rabbit IL-6 (RaIL-6) and bacterially expressed. Rabbits were intramuscularly immunized with 100 μg of P2-gD/gC/gB-BoIL-6, P2-gD/gC/gB-RaIL-6, P2-gD/gC/gB, P2-gD/gC/gB plus BoIL-6, P2-(gD-a)3-BoIL-6, or P2-(gD-a)3 emulsified with ISA 206 adjuvant thrice at 3-week intervals. P2-gD/gC/gB-BoIL-6 generated a higher titer of BoHV-1-specific antibodies, neutralizing antibodies, interferon (IFN)-γ, and IL-4 compared with P2-gD/gC/gB plus BoIL-6, P2-gD/gC/gB-RaIL-6, or other formulation. P2-gD/gC/gB-BoIL-6 triggered similar levels of antibodies and significantly higher titer of IFN-γ and IL-4 compared with inactivated bovine viral diarrhea (BVD)-infectious bovine rhinotracheitis (IBR) vaccine. Rabbits vaccinated with P2-gD/gC/gB-BoIL-6 dramatically reduced viral shedding and tissue lesions in lungs and trachea after viral challenge and reactivation compared with those with P2-gD/gC/gB plus BoIL-6 or P2-gD/gC/gB-RaIL-6. P2-gD/gC/gB-BoIL-6 provided protective effects against viral shedding and tissue pathogenesis similar to those of the inactivated vaccine. The data confirmed the safety and immunogenicity of multiple-epitope recombinant protein and a potential vaccine candidate to control the disease, especially for pregnant cattle.

Mapping a highly conserved linear neutralizing epitope on gD glycoprotein of bovine herpesvirus type I using a monoclonal antibody

Bovine herpesvirus type 1 (BoHV-1), a member of the Alphaherpesvirinae, causes a variety of diseases, which result in significant economic losses worldwide. Envelope glycoprotein D (gD) of BoHV-1 plays an important role in viral entry into the permissive cells, and protective immune response. The fine mapping epitope on the gD will contribute to the understanding of viral pathogenesis and development of alternative vaccines against various diseases associated with BoHV-1. We previously reported the preparation of a monoclonal antibody (MAb) 2B6, which was raised by a truncated recombinant gD protein, demonstrating a neutralizing activity against BoHV-1 infection in Madin–Darby bovine kidney cells. This study described the identification of a linear B-cell epitope on gD using MAb 2B6. A series of partially overlapping gD proteins with glutathione S-transferase tag were generated to define the epitope recognized by MAb 2B6. The amino acid (aa) sequence ³²³GEPKPGPSPDADRPE³³⁷ was recognized by MAb 2B6 using Western blot with the variedly truncated recombinant proteins. Importantly, this epitope was highly conserved among the typical members of BoHV-1, indicating that the epitope may be utilized in diagnosis of diseases due to BoHV-1 infection. Furthermore, the minimal linear epitope sequence ³²³GEPKPGP³²⁹ on gD recognized by MAb 2B6 was confirmed using single-aa residue deletion mutation in carboxyl terminal. This finding not only contributes to our understanding of gD of BoHV-1 virion but also shows a potential for the development of vaccine candidates and diagnostic techniques.

Β-defensins - Underestimated peptides in influenza combat

Defensins are a family of host defense peptides present in vertebrates, invertebrates and plants. They display broad antimicrobial activity and immunomodulatory functions. Herein, the natural anti-influenzal role of β-defensins, as well as their potential usage as anti-influenza vaccine adjuvants and therapeutic agents, is reviewed. This article summarizes previously published information on β-defensin modes of action, expression changes after influenza infection and vaccination, biotechnological usage and possible boosting of their production by dietary supplementation.