Recombinant Hexon Protein as a New Bovine Adenovirus Type 3 Subunit Vaccine Candidate.

Introduction: Bovine adenovirus (BAdV) type 3 causes respiratory and gastroenteric diseases of varying severity in cattle, particularly newborn calves. Trials have been conducted of a vaccination against the diseases caused by BAdV using both modified live-virus and inactivated-virus preparations in cattle, but no commercial BAdV-3 vaccine has yet reached the market. Therefore, there is an urgent need to develop new, safe, and effective vaccines against BAdV-3. Material and Methods: Recombinant hexon protein (rhexon) of BAdV-3 was expressed in the E. coli system to evaluate immune response in mice and goats. Antibody responses and cytokine levels were analysed and the effects of administrations of different amounts of recombinant protein compared. Long-term antibody production was evaluated by indirect ELISA, and the total immunoglobulin G secreted by goats and mice immunised with the purified rhexon protein was determined. Results: The immunised mice had a stronger antibody response than the control group at eight weeks post vaccination. The immunised groups also showed significantly higher (P ˂ 0.05) expression of interferon-γ, interleukin 2 (in mice), and interleukin 21 (in goats) at four weeks. Furthermore, vaccination with rhexon was able to induce long-term antibody production for at least 16 weeks in mice and goats. Conclusion: The rhexon protein induced immune responses, especially long-term antibody production and T helper 1 cell cytokine production in mice and goats. The immunogenic properties of this protein make it a promising subunit vaccine antigen.

Oral DNA vaccine adjuvanted with cyclic peptide nanotubes induced a virus-specific antibody response in ducklings against goose parvovirus.

BACKGROUND: Cyclic peptide nanotubes (cPNTs) formed from the spontaneous beta-sheet stacking of peptide rings may serve as a safe and effective oral delivery vehicle/adjuvant for DNA vaccines. AIM: In this study, we sought to determine if a DNA vaccine expressing the VP2 protein of goose parvovirus, adjuvanted with cPNTs, may elicit virus-specific antibody response through oral vaccination. MATERIAL AND METHODS: Forty 20-day-old Muscovy ducks were randomly assigned to two groups of 20 ducks each and vaccinated. Ducks were orally vaccinated (Day 0) and boosted (Day 1 and Day 2) or were mock-vaccinated with saline as the negative control. For immunohistochemical staining, the primary antibody used comprised a rabbit anti-GPV antibody, and the secondary antibody was a goat anti-rabbit antibody. Goat-anti-mouse-IgG was used as a tertiary antibody. IgG and IgA antibody titers in serum were analyzed by the GPV virus-coated ELISA. For IgA antibody analysis, intestine lavage was harvested too. RESULTS: A DNA vaccine, coated with cPNTs, can induce a significant antibody response in ducklings. Immunohistochemical staining of tissues from vaccinated ducklings showed that VP2 proteins can be detected in the intestines and livers for up to six weeks, confirming the antigen expression by the DNA vaccine. Antibody analysis found that this vaccine formulation was very efficient at inducing IgA antibodies in the serum and the intestinal tract. CONCLUSION: A DNA vaccine adjuvanted with cPNTs can effectively express the antigen and can significantly induce an antibody response against goose parvovirus through oral vaccination.

A protein-based subunit vaccine with biological adjuvants provides effective protection against Pasteurella multocida in pigs.

Streptococcus suis (S. suis) and Pasteurella multocida (P. multocida) are pathogens that can cause zoonotic diseases. P. multocida toxin (PMT) is an important virulence factor that causes atrophic rhinitis in pigs. Suilysin (Sly) is an extracellular protein of S. suis and has been shown to be a potential adjuvant. Previous studies have indicated that subunit vaccines containing several fragments of PMT as antigens are safer than traditional inactivated or live-attenuated vaccines. However, protein-based vaccines need strong adjuvants to enhance their immunogenicity. In this study, recombinant PMT-NC (rPMT-NC) protein antigen was formulated with either recombinant Sly (rSly) or CpG oligodeoxynucleotides (CpG) as the adjuvant. The immune responses elicited by these vaccines and the protective efficacy after challenge with live P. multocida were evaluated in piglets. In the dose-dependent test, piglets immunized with the low dose (100 µg) of rSly had increased antigen-specific total IgG, interferon (IFN)-γ gene expression, and CD4+ and CD8+ T-cell populations. Compared to piglets in the commercial (Al-gel) adjuvant and the control groups (p < 0.05), piglets in the biological adjuvant groups showed significantly reduced turbinate atrophy, nasal distortion, and lung lesion scores after challenge with P. multocida serotype A. Vaccines containing rSly or CpG adjuvant enhanced humoral and cellular immune responses and protection against P. multocida. This combination of a protein-based antigen formulated with a biological adjuvant showed synergistic and protective effects against atrophic rhinitis and has potential to be developed as part of a bivalent vaccine.

Recombinant suilysin of Streptococcus suis enhances the protective efficacy of an engineered Pasteurella multocida toxin protein.

Suilysin (Sly) from Streptococcus suis has been shown to elicit strong immune responses and may act as a vaccine adjuvant. In the present study, we tested the adjuvant effect of Sly using an engineered Pasteurella multocida toxin, rPMT-NC, as the antigen. The antigen was also formulated with other conventional adjuvants (aluminum hydroxide, water-in-oil-in-water) for comparison. The efficacy of these vaccine formulations were evaluated in mice. The optimal dosage of purified rSly for enhancing immune responses in mice was first determined to be 40 µg/ml based on significantly (p < 0.05) increased serum antibody titers, expression of cytokines, including interleukin (IL)-4, IL-12, and interferon (IFN)-γ and the survival rate after challenge with P. multocida. Mice immunized with rPMT-NC + rSly had augmented antibody production and cellular immunity compare to those immunized with rPMT-NC plus other adjuvants. In addition, the survival rate of mice immunized with rPMT-NC + rSly was the highest (70% v.s. 30% of mice immunized with rPMT-NC alone) among all groups. In conclusion, rSly has the potential to be used as a biological adjuvant to enhance immune responses and protective efficacy of protein-based vaccines.

Cross-protection of recombinant Pasteurella multocida toxin proteins against atrophic rhinitis in mice.

Pasteurella multocida (P. multocida) infects the swine respiratory tract and mainly causes atrophic rhinitis (AR). Recently, many commercially inactivated and subunit vaccines have been used as preventive strategies. However, the best antigenic protein portion has not been selected, and the aluminum gel was used as the adjuvant, which may not induce full protection. P. multocida toxin (PMT) is the major virulence factor responsible for AR. PMT is a monomeric 146 kDa protein (approximately 1285 amino acids) encoded by the tox A gene. In this study, we expressed different fragments of recombinant PMT proteins, combined them with a water-in-oil-in-water adjuvant, and evaluated mice's immune response. The results indicated that the rPMT-C-immunized group showed significantly higher levels (p < 0.05) of IgG, IgG2a antibody and interferon-γ, IL-12 cytokine expression than other groups. Furthermore, vaccination with rPMT-C recombinant protein can provide homologous and heterologous protection against P. multocida challenge. In conclusion, our approach may be feasible for developing an effective subunit vaccine against atrophic rhinitis with a cost-down simple ingredient.