Adenoviral vector expressing murine β-defensin 2 enhances immunogenicity of an adenoviral vector based H5N1 influenza vaccine in aged mice

Promising role of defensins peptides as therapeutics to combat against viral infection

Antimicrobial peptides (AMPs) are ubiquitously present small peptides, which play a critical function in the innate immune system. The defensin class of AMPs represented an evolutionarily ancient family containing cationic cysteine residue and frequently expressed in epithelial or neutrophils cells. It plays myriad functions in host innate immune responses against various infection. Defensin has a broad spectrum of antimicrobial activities, including anti-bacteria, anti-viruses (AVPs), anti-fungi, anti-cancers, and also overcoming bacterial drug resistance. In this review, we compiled the progress on defensin, particularly incorporating the mechanism of action, their application as an antiviral agent, prospects in different areas, and limitations to be solved as an antiviral peptide. Defensins were explored, in particular, their capacity to stimulate innate and adaptive immunity by trigging as anti-coronavirus (COVID-19) peptides. The present review summarised its immunomodulatory and immunoenhancing properties and predominantly focused on its promising therapeutic adjuvant choices for combat against viral infection.

The Improvement of Immune Effect of Recombinant Human Beta-Defensin 2 on Hepatitis B Vaccine in Mice

Immunization with hepatitis B vaccine is an effective measure for prevention and control of hepatitis B Virus (HBV) infection. Although lots of efforts to improve the effect of hepatitis B vaccine have been made, the function of human beta defensin 2 (hBD2) on hepatitis B vaccine keeps unclear. In this article, we report that hBD2 not only promoted the activation and maturation of immature dendritic cells (iDCs) by increasing MHC II and CD86 expression, but it also significantly upregulated the mRNA level of IL-6 and IL-12B in mouse bone marrow-derived dendritic cells. The serum concentrations of IFN-γ in mice stimulated with 300 ng hBD2 increased from 25.21 to 42.04 pg/mL, with a time extension from 4 to 12 h post-injection. During the process of three times immunization (1, 14, 28 days) with 3 μg hepatitis B vaccine combined with or without 300 ng hBD2 with a 2 week interval in BALB/c mice, the antibody against HBsAg (HBsAb) concentration in serum at every time point of observation in the combined group was statistically higher than the hepatitis B vaccine group. The serum concentration of IgG2a subclass HBsAb on the 14th day post last injection in the combined group was significantly higher than the hepatitis B vaccine group. Further, the splenic cells from the mice treated with both hBD2 and hepatitis B vaccine possessed a greater ability to produce a surface antigen of hepatitis B virus (HBsAg) specific IFN-γ than those treated with hepatitis B vaccine alone. The percentages of CD3⁺/CD4⁺ T cells and CD3⁺/CD8⁺ T lymphocytes in spleens from the mice treated with 300 ng hBD2 were statistically higher than the phosphate buffered saline group. These data suggest that hBD2 improves iDC maturation and the immune efficiency of hepatitis B vaccine in BALB/c mice.

Adenoviral Vector-Based Vaccine Platforms for Developing the Next Generation of Influenza Vaccines

Ever since the discovery of vaccines, many deadly diseases have been contained worldwide, ultimately culminating in the eradication of smallpox and polio, which represented significant medical achievements in human health. However, this does not account for the threat influenza poses on public health. The currently licensed seasonal influenza vaccines primarily confer excellent strain-specific protection. In addition to the seasonal influenza viruses, the emergence and spread of avian influenza pandemic viruses such as H5N1, H7N9, H7N7, and H9N2 to humans have highlighted the urgent need to adopt a new global preparedness for an influenza pandemic. It is vital to explore new strategies for the development of effective vaccines for pandemic and seasonal influenza viruses. The new vaccine approaches should provide durable and broad protection with the capability of large-scale vaccine production within a short time. The adenoviral (Ad) vector-based vaccine platform offers a robust egg-independent production system for manufacturing large numbers of influenza vaccines inexpensively in a short timeframe. In this review, we discuss the progress in the development of Ad vector-based influenza vaccines and their potential in designing a universal influenza vaccine.

Towards the Application of Human Defensins as Antivirals

Defensins are antimicrobial peptides that participate in the innate immunity of hosts. Humans constitutively and/or inducibly express α- and β-defensins, which are known for their antiviral and antibacterial activities. This review describes the application of human defensins. We discuss the extant experimental results, limited though they are, to consider the potential applicability of human defensins as antiviral agents. Given their antiviral effects, we propose that basic research be conducted on human defensins that focuses on RNA viruses, such as human immunodeficiency virus (HIV), influenza A virus (IAV), respiratory syncytial virus (RSV), and dengue virus (DENV), which are considered serious human pathogens but have posed huge challenges for vaccine development for different reasons. Concerning the prophylactic and therapeutic applications of defensins, we then discuss the applicability of human defensins as antivirals that has been demonstrated in reports using animal models. Finally, we discuss the potential adjuvant-like activity of human defensins and propose an exploration of the ‘defensin vaccine’ concept to prime the body with a controlled supply of human defensins. In sum, we suggest a conceptual framework to achieve the practical application of human defensins to combat viral infections.

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.

A Single Intramuscular Dose of a Plant-Made Virus-Like Particle Vaccine Elicits a Balanced Humoral and Cellular Response and Protects Young and Aged Mice from Influenza H1N1 Virus Challenge despite a Modest/Absent Humoral Response

Virus-like-particle (VLP) influenza vaccines can be given intramuscularly (i.m.) or intranasally (i.n.) and may have advantages over split-virion formulations in the elderly. We tested a plant-made VLP vaccine candidate bearing the viral hemagglutinin (HA) delivered either i.m. or i.n. in young and aged mice. Young adult (5- to 8-week-old) and aged (16- to 20-month-old) female BALB/c mice received a single 3-μg dose based on the HA (A/California/07/2009 H1N1) content of a plant-made H1-VLP (i.m. or i.n.) split-virion vaccine (i.m.) or were left naive. After vaccination, humoral and splenocyte responses were assessed, and some mice were challenged. Both VLP and split vaccines given i.m. protected 100% of the young animals, but the VLP group lost the least weight and had stronger humoral and cellular responses. Compared to split-vaccine recipients, aged animals vaccinated i.m. with VLP were more likely to survive challenge (80% versus 60%). The lung viral load postchallenge was lowest in the VLP i.m. groups. Mice vaccinated with VLP i.n. had little detectable immune response, but survival was significantly increased. In both age groups, i.m. administration of the H1-VLP vaccine elicited more balanced humoral and cellular responses and provided better protection from homologous challenge than the split-virion vaccine.

Beta-defensin 2 enhances immunogenicity and protection of an adenovirus-based H5N1 influenza vaccine at an early time

Reports of human infections with highly pathogenic H5N1 avian influenza viruses in many countries in Asia and Africa with varying case fatality rates highlight the pandemic potential of these viruses. In order to contain a rapidly spreading influenza virus in a pandemic scenario, a vaccine which can induce rapid and robust immune responses, preferably in a single dose, is necessary. Murine beta-defensin 2 (Mbd2), a small molecular weight protein expressed by epithelial cells, has been shown to enhance antigen-specific immune responses by recruiting and activating professional antigen presenting cells to the site of vaccination. This study assessed the potential of Mbd2 to enhance the immunogenicity and protective efficacy of a human adenovirus (HAd)-based vaccine expressing the hemagglutinin (HA) and nucleoprotein (NP) [HAd-HA-NP] of an H5N1 influenza virus. A single inoculation of mice with both HAd-HA-NP and a HAd vector expressing Murine β-defensin 2 (HAd-Mbd2) resulted in significantly higher levels of both humoral and cell-mediated immune responses compared to the groups vaccinated only with HAd-HA-NP. These responses were evident even at day 7 post-immunization. Furthermore, the HAd-HA-NP+HAd-Mbd2-immunized group receiving the lowest vector dose (2 × 10(7)+1 × 10(7)) was completely protected against an rgH5N1 virus challenge on day 7 post-vaccination. These results highlight the potential of Mbd2 as a genetic adjuvant in inducing rapid and robust immune responses to a HAd-based vaccine.