Fusion of C3d with hemagglutinin enhances protective immunity against swine influenza virus

A candidate DNA vaccine encoding a fusion protein of porcine complement C3d-P28 and ORF2 of porcine circovirus type 2 induces cross-protective immunity against PCV2b and PCV2d in pigs

Background

Porcine circovirus type 2 (PCV2) is an economically important viral pathogen for swine industry worldwide. However, current PCV2 vaccines provide incomplete protection against the PCV2d, which has recently emerged as the predominant pathogenic form of PCV2.

Methods

To develop a novel DNA vaccine with high efficacy against PCV2d virus, we fused the ORF2 of PCV2d to three copies of the minimum-binding domain of the complement C3 cascade terminal component, C3d-P28. Expression of ORF2 alone (pVO) or fused C3d-P28 (pVOC3) were verified by immunofluorescent assay. Vaccine efficacy was tested by measured the DNA copy and T and B cell immune response.

Results

Vaccination with pVOC3 reduced the levels of PCV2 genomic DNA after pigs were infected with either PCV2b or PCV2d genotypes, produced potent antibodies against PCV2, and stimulated PCV2-specific interferon-γ secreting cells.

Conclusion

Results suggested pVOC3 would be a safe and effective DNA vaccine to confer cross-protection against both PCV2b and PCV2d genotypes in pigs.

A bioinformatic approach to check the spatial epitope structure of an immunogenic protein coded by DNA vaccine plasmids

In this study, we used an approach to check the Hemagglutinin antigen-antibodies interactions after fusion of one or two gene segments to Hemagglutinin gene in some influenza DNA vaccines. We designed different DNA vaccine constructs containing Hemagglutinin 9 (H9) gene fused to four or eight 29 amino acids of C3d (4/8P29C3d) and/or 3, 4 domains of the Fc part of IgY (FcIgY) coding sequences. As there are receptors for P29C3d and FcIgY on the immune cells, fused H9 are targeted to these cells. Three dimensional (3D) structures of the DNA vaccine coded proteins were modeled and docked with two antibodies (1KEN, 1QFU) to evaluate the effect of the H9 gene fusion to the other gene segments (4, 8 P29C3d and FcIgY) on the interaction of two H9 spatial epitopes. Also, we docked DNA vaccine proteins containing Fc IgY to its receptor (CHIR AB1) and compare interaction affinity of Fc IgY alone with affinity of DNA vaccines containing Fc IgY. The average of 1KEN and 1QFU interface scores were 94.89 and 93.09% of H9 DNA vaccine-antibodies interface scores, respectively. These percentages showed a little change in the H9 immunogenic parts. Also, because of spatial freedom of H9 part in all DNA vaccine proteins, added parts may not interfere with antibody-antigen interactions. Once, H9+FcIgY and CHIR AB1 affinity decreased in comparison with affinity of Fc IgY alone and CHIR AB1, affinity of H9+8P29C3d+FcIgY and CHIR AB1 increased to 132%. So, this would be expectable that despite of loss of affinity in H9 and its antibodies in the H9+8P29C3d+FcIgY, dramatic increase of Fc IgY and CHIR AB1 affinity in this group, could repair the loss of H9 affinity and may lead to a better immunogenicity.

Towards a novel influenza vaccine: engineering of hemagglutinin on a platform of adenovirus dodecahedron

Background

The production process for the current influenza vaccine takes about 6 months and its antigenic composition must be modified annually. In the attempt towards developing influenza vaccine production that would be faster, safer and cheaper we engineered an influenza vaccine in which multiple copies of hemagglutinin (HA) would be delivered by a vector, adenovirus dodecahedron (Ad Dd). Dd is a virus-like particle, formed by assembly of twelve copies of pentameric penton base (Pb) proteins responsible for virus penetration. In order to attach HA to the vector, an adaptor containing WW domains was used. The WW domain is a linear peptide fragment identified as a partner of proline-proline-x-tyrosine (PPxY) motif present at the N-terminal extremity of the Pb protein, which is a building block of Dd. That tandem of three WW domains in fusion with the protein of interest enables interaction with Dd and efficient translocation to the cytoplasm of cells in culture.

Results

Since HA is an oligomeric protein with complicated processing, we prepared six different constructs of HA (A/swan/Poland/467/2006(H5N1)) in fusion with the WW adaptor. Herein we report baculovirus expression and functional analysis of six HA-WW variants. The best behaving variant was successfully delivered into human cells in vitro.

Conclusions

Engineering of a soluble complex of HA with Dd, a virus-like particle that serves as a vector, an adjuvant and as a multivalent presentation platform, is an important step toward a novel influenza vaccine.

Influenza Virus-like Particle Containing Two Different Subtypes of Hemagglutinin Confers Protection in Mice Against Lethal Challenge With A/PR8 (H1N1) and A/HK (H3N2) Viruses

BACKGROUND

Preventing the seasonal or pandemic outbreak of influenza can be powerful and cost-effective.

OBJECTIVES

In this study, we constructed a novel virus-like particle (VLP) platform that contains two hemagglutinin (HA) subtypes and evaluated immunogenicity of constructed VLP in mice.

MATERIALS AND METHODS

This recombinant candidate vaccine model resulted in the expression of two HAs of H1N1 and H3N2 subtypes co-localized within a VLP. Following infection of insect cells with recombinant baculovirus co-expressing H1, H3 and M1 proteins, VLPs with size of 80-120 nm were self-assembled, budding, and released into the insect culture medium. The resulting VLPs which contained two different subtypes of hemagglutinin were purified by ultracentrifugation. The immunogenicity of VLPs was evaluated in mice following immunization.

RESULTS

Our data showed that vaccination using VLPs elicited robust levels of serum IgG, and viral neutralizing antibodies against A/PR8 (H1N1) and A/HK (H3N2) viruses. Following challenge with lethal dose of A/PR8 (H1N1) and A/HK (H3N2, vaccinated mice were protected, displaying no sign of weight loss and mortality compared to non-vaccinated control mice.

CONCLUSIONS

VLPs can serve as a promising vaccination strategy to control influenza virus.

Preparation and immunological effectiveness of a swine influenza DNA vaccine encapsulated in chitosan nanoparticles

Preparation conditions of a DNA vaccine against swine influenza encapsulated in chitosan nanoparticles were determined. The nanoparticles were prepared according to a complex coacervation method using chitosan as a biodegradable matrix forming polymer. Under the preparation conditions, chitosan nanoparticles containing the DNA vaccine were produced with good morphology, high encapsulation rate and high stability. Transfection test indicated that the vaccine could be expressed as an antigen in cells, and maintained good bioactivity. In addition, better immune responses of mice immunized with the chitosan nanoparticles containing the DNA vaccine were induced and prolonged release of the plasmid DNA was achieved compared to the DNA vaccine alone. These results laid a foundation for further development of DNA vaccines in nanoparticles before ultimate industrial application.

Recombinant pseudorabies virus expressing P12A and 3C of FMDV can partially protect piglets against FMDV challenge

One of the crucial factors for evaluation of an effective genetically engineered vaccine is whether susceptible animals are protected from virus challenge after vaccination. In this study, a recombinant pseudorabies virus (PRV-P12A3C) that expressed capsid precursor polypeptide P12A and nonstructural protein 3C of foot-and-mouth disease virus (FMDV) was used as a vaccine. The expression of P12A3C and its immunogenicity and protective efficacy against FMDV challenge were measured. Humoral and cellular immune responses were evaluated after each immunization. Subsequently, each piglet was challenged with 1000 ID(50) (50% infection dose) FMDV serotype O, named OR/80, which is used to produce vaccine in China. PRV-P12A3C induced a high level of neutralizing antibody and FMDV-specific lymphocytes. Inactivated vaccine provided 100% protection, and the vector strain (TK(-)/gE(-)/gI(-)) showed no protection. PRV-P12A3C induced 60% protection, compared with piglets that were vaccinated with TK(-)/gE(-)/gI(-). The severity of clinical signs for the remaining two piglets was lighter and the appearance of vesicles was delayed.

Comparison of humoral and cellular immune responses to inactivated swine influenza virus vaccine in weaned pigs

Humoral and cellular immune responses to inactivated swine influenza virus (SIV) vaccine were evaluated and compared. Fifty 3-week-old weaned pigs were randomly divided into the non-vaccinated control group and vaccinated group containing 25 pigs each. Pigs were vaccinated intramuscularly twice with adjuvanted UV-inactivated A/SW/MN/02011/08 (MN/08) H1N2 SIV vaccine at 6 and 9 weeks of age. Whole blood samples for multi-parameter flow cytometry (MP-FCM) and serum samples for hemagglutination inhibition (HI) assay were collected at 23 and 28 days after the second vaccination, respectively. A standard HI assay and MP-FCM were performed against UV-inactivated homologous MN/08 and heterologous pandemic A/CA/04/2009 (CA/09) H1N1 viruses. While the HI assay detected humoral responses only to the MN/08 virus, the MP-FCM detected strong cellular responses against the MN/08 virus and significant heterologous responses to the CA/09 virus, especially in the CD4+CD8+ T cell subset. The cellular heterologous responses to UV-inactivated virus by MP-FCM suggested that the assay was sensitive and potentially detected a wider range of antigens than what was detected by the HI assay. Overall, the adjuvanted UV-inactivated A/SW/MN/02011/08 H1N2 SIV vaccine stimulated both humoral and cellular immune responses including the CD4-CD8+ T cell subset.