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Influenza A viruses (IAVs) induce acute respiratory disease and cause severe epidemics and pandemics. Since IAVs exhibit antigenic variation and genome reassortment, the development of broad-spectrum influenza vaccines is crucial. The stem of the hemagglutinin (HA) is highly conserved across IAV strains and thus has been explored in broad-spectrum influenza vaccine studies. The present study aimed to identify viral epitopes capable of eliciting effective host immune responses, which can be explored for the development of broad-spectrum non-strain specific prophylactic options against IAV. In this study, a series of conserved linear sequences from the HA stem of IAV (H1N1) was recognized by sequence alignment and B/T-cell epitope prediction after being chemically coupled to the Keyhole Limpet Hemocyanin (KLH) protein. The predicted linear epitopes were identified by enzyme-linked immunosorbent assay (ELISA) after animal immunization and then fused with ferritin carriers. Three predicted linear epitopes with relatively strong immunogenicity, P3, P6 and P8 were fused with ferritin carriers P3F, P6F and P8F, respectively to further improve their immunogenicity. Antibody titre of the sera of mice immunized with the recombinant immunogens revealed the elicitation of specific antibody-binding activities by the identified sequences. While hemagglutinin-inhibition activities were not detected in the antisera, neutralizing antibodies against the H1 and H3 virus subtypes were detected by the microneutralization assay. The linear epitopes fused with ferritin identified in this study can lay the foundation for future advancements in development of broad-spectrum subunit vaccine against IAV (H1N1), and give rise to the potential future applicability of ferritin-based antigen delivery nanoplatforms. [ABSTRACT FROM AUTHOR]

Background: Canine distemper virus (CDV), which is highly infectious, has caused outbreaks of varying scales in domestic and wild animals worldwide, so the development of a high-efficiency vaccine has broad application prospects. Currently, the commercial vaccine of CDV is an attenuated vaccine, which has the disadvantages of a complex preparation process, high cost and safety risk. It is necessary to develop a safe and effective CDV vaccine that is easy to produce on a large scale. In this study, sequences of CDV haemagglutinin (HA) from the Yanaka strain were aligned, and three potential linear sequences, termed YaH3, YaH4, and YaH5, were collected. To increase the immunogenicity of the epitopes, ferritin was employed as a self-assembling nanoparticle element. The ferritin-coupled forms were termed YaH3F, YaH4F, and YaH5F, respectively. A full-length HA sequence coupled with ferritin was also constructed as a DNA vaccine to compare the immunogenicity of nanoparticles in prokaryotic expression. Result: The self-assembly morphology of the proteins from prokaryotic expression was verified by transmission electron microscopy. All the proteins self-assembled into nanoparticles. The expression of the DNA vaccine YaHF in HEK-293T cells was also confirmed in vitro. After subcutaneous injection of epitope nanoparticles or intramuscular injection of DNA YaHF, all vaccines induced strong serum titres, and long-term potency of antibodies in serum could be detected after 84 days. Strong anti-CDV neutralizing activities were observed in both the YaH4F group and YaHF group. According to antibody typing and cytokine detection, YaH4F can induce both Th1 and Th2 immune responses. The results of flow cytometry detection indicated that compared with the control group, all the immunogens elicited an increase in CD3. Simultaneously, the serum antibodies induced by YaH4F and YaHF could significantly enhance the ADCC effect compared with the control group, indicating that the antibodies in the serum effectively recognized the antigens on the cell surface and induced NK cells to kill infected cells directly. Conclusions: YaH4F self-assembling nanoparticle obtained by prokaryotic expression has no less of an immune effect than YaHF, and H4 has great potential to become a key target for the easy and rapid preparation of epitope vaccines. [ABSTRACT FROM AUTHOR]