Riemerella anatipestifer (RA) infections can lead to high mortality in ducklings. Inactivated vaccines against RA are commercially available, but they fail to provide cross-protection against various serotypes. We have previously demonstrated that a subunit vaccine containing recombinant outer membrane protein A (rOmpA) antigen of serotype 2 formulated with CpG oligodeoxynucleotides (ODN) as the adjuvant was able to stimulate both humoral and cellular immunities. In the present study, thirty healthy 7-day-old Pekin ducks were randomly assigned to three equal treatment groups: rOmpA-vaccinated, rOmpA + CpG-vaccinated, and control. Vaccine was injected intramuscularly and a booster dose of the same vaccine was given two weeks after primary immunisation. The long-term antibody response and cross-serotype reaction of this vaccine were evaluated in ducks. Compared to ducks immunised with rOmpA alone, ducks immunised with rOmpA + CpG ODN had significantly (p < 0.05) increased serum antibody titre from two weeks until nine months after primary immunisation. In addition, expression of cytokines including interferon (IFN)-α, IFN-γ, interleukin (IL)-6, and IL-12 was significantly (p < 0.05) enhanced in PBMC of ducks immunised with rOmpA + CpG ODN two weeks after primary immunisation. Antibodies from ducks immunised with the rOmpA + CpG ODN vaccine could also detect RA serotypes 1 and 6 in Western blot analysis. Combination of rOmpA and CpG ODN could be a feasible strategy for developing a subunit RA vaccine with long term and broader-ranging protection.

Mycoplasma bovis is known as a causative agent of many disorders in cattle. In Europe, there is still a lack of commercial vaccines against M. bovis infection. Acute phase response (APR) is a non-specific host reaction to infection, most seen in changes in production of acute phase proteins. The aim of this study was to analyse APR in calves administered with an experimental M. bovis vaccine. Twelve healthy female calves were divided into two equal groups: experimental and control. The experimental vaccine containing the field M. bovis strain and two adjuvants such as saponin and lysozyme dimer was subcutaneously administered to the experimental group. Phosphate buffered saline was taken as the placebo and given to the control group by the same route as the vaccine. Blood samples were collected prior to the study (day 0), then daily up to day 7, and then each seven days until day 84 post vaccination. The concentrations of serum amyloid A (SAA), haptoglobin (Hp), interferon-γ (IFN-γ), and inteleukin-4 (IL-4) were determined using commercial ELISA kits. Following the vaccination, a significant increase in SAA, Hp, and IFN-γ concentrations was observed when compared to the unvaccinated calves, whereas the IL-4 concentration was not detectable. The experimental saponin-based M. bovis vaccine containing lysozyme dimer adjuvant visibly stimulated the APR in the calves, and some specific cytokines (Th1-dependent) directly involved in this response.

Introduction: Highly pathogenic Asian H5-subtype avian influenza viruses have been found in poultry and wild birds worldwide since they were first detected in southern China in 1996. Extensive control efforts have not eradicated them. Vaccination prevents such viruses infecting poultry and reduces the number lost to compulsory slaughter. The study showed the efficacy of inactivated H5 vaccine from the H5N8 virus against highly pathogenic H5N8 and H5N6 avian influenza viruses in chickens. Material and Methods: Reverse genetics constructed an H5 vaccine virus using the HA gene of the 2014 H5N8 avian influenza virus and the rest of the genes from A/PR/8/34 (H1N1). The vaccine viruses were grown in fertilised eggs, partially purified through a sucrose gradient, and inactivated with formalin. Chickens were immunised i.m. with 1 µg of oil-adjuvanted inactivated H5 antigens. Results: Single dose H5 vaccine recipients were completely protected from lethal infections by homologous H5N8 avian influenza virus and shed no virus from the respiratory or intestinal tracts but were not protected from lethal infections by heterologous H5N6. When chickens were immunised with two doses and challenged with homologous H5N8 or heterologous H5N6, all survived and shed no virus. Conclusion: Our results indicate that two-dose immunisations of chickens with H5 antigens with oil adjuvant are needed to provide broad protection against different highly pathogenic H5 avian influenza viruses.

This study investigated if parenteral administration of a prototype adjuvanted vaccine against porcine circovirus type 2 (PCV2) could override maternally derived antibodies and induce acquired immunity in young piglets. Piglets with high levels of maternal PCV2 antibodies at 1 wk of age were randomly grouped into vaccinates and controls on the basis of body weight and inoculated with the vaccine or a control preparation twice, with an interval of 3 wk. Both groups were challenged 3 wk after the booster vaccination and euthanized 3 wk after challenge. The pigs were evaluated for clinical disease, histologic lesions in sections of gastric and left inguinal lymph nodes stained with hematoxylin and eosin, and the amount of PCV2 antigen in the lymph nodes by immunohistochemical study. The PCV2 antibody titers were monitored by competitive enzyme-linked immunosorbent assay throughout the experiment. The vaccinates showed significantly less decline (P < 0.05) in PCV2 antibody titers after the booster vaccination. Clinical disease did not develop in any of the piglets. The vaccinates and controls did not differ in either histologic lesions or amount of PCV2 antigen in the lymph nodes. This study demonstrated some evidence of priming of young piglets in the presence of maternal antibodies. Further studies are recommended to determine the optimum concentration of PCV2 antigen and a suitable adjuvant for the vaccine to achieve the full potential of the strategy of inducing acquired immunity in young piglets that have maternally derived antibodies.

During the spring of the first year of a vaccine study, 57 of 238 calves (24%), in which modified-live Pasteurella haemolytica vaccine (MLV) was injected twice, developed 1 or more abscesses. Abscesses were not observed after multiple visual examinations of 437 calves given killed P. haemolytica bacterin or placebo injections of similar adjuvants used in the vaccine and bacterin. Calves that developed abscesses after the second injection of MLV weighed significantly (P < 0.05) less (on the basis of body weight adjusted for weaning weight) at the second injection than did those that did not develop abscesses. Compared with calves given MLV that did not develop observable abscesses, calves developing abscesses after the second injection of MLV weighed 11.0 and 14.2 kg less, respectively, at 56 days and 112 days after injection, and they had 11.0 kg less gain at 56 days after injection. Abscess prevalence tended to be highest on certain days or at certain locations used for cattle processing, and the prevalence of abscesses increased in cattle processed later on a given day. Abscesses were not observed in 2 other groups of similarly treated calves vaccinated in the autumn or in the subsequent spring.

A study was conducted to determine the effect of mono-phosphoryl lipid A (MPL) and trehalose dimycolate (TDM) as adjuvants on the protective responses in BALB/c mice vaccinated with Brucella abortus salt-extractable protein (BCSP) or proteinase-K-treated B abortus lipopolysaccharide (PKLPS). Mice were vaccinated with different doses of BCSP or PKLPS given alone or in combination with MPL or TDM. Mice were challenge-exposed 4 weeks later with virulent B abortus strain 2308. Two weeks after challenge exposure, the number of B abortus colony-forming units (CFU) per spleen, spleen weights, and spleen cell interleukin 1 production were measured. Serum IgG and IgM concentrations specific for vaccinal immunogens were measured before and after challenge exposure with B abortus. Spleen weights and mean B abortus CFU per vaccine group were significantly lower in BCSP- and PKLPS-vaccinated mice, compared with those of nonvaccinated control mice. Monophosphoryl lipid A enhanced the suppression of splenic infection when given with the BCSP vaccine, but not when given with the PKLPS vaccine. Trehalose dimycolate had no effect on mean CFU when given with BCSP, but incorporation of TDM resulted in a significant increase in mean CFU when given with PKLPS. Spleen weights in BCSP- or PKLPS-vaccinated mice were not different when these vaccines were combined with MPL or TDM. Because of the wide variation in the results, we could not conclude that vaccination with BCSP or PKLPS alone, or in combination with MPL altered spleen cell interleukin-1 production in B abortus-infected mice. Increased host protection as defined by decreased CFU could not be related consistently to increased BCSP- or PKLPS-specific serum IgG or IgM antibodies introduced by any of the vaccines. These results do not eliminate a role for antibodies in the protection observed.

Two commercially available synthetic adjuvant systems, trehalose dimycolate (TDM) and TDM + monophosphoryl lipid A (MPL), were compared with Freund complete adjuvant (FCA) for the ability to stimulate antibody production in New Zealand White rabbits (Oryctolagus cuniculus). In addition, each animal was evaluated for adverse reactions. The antigen, rat liver microsomal epoxide hydrolase, was administered sc emulsified with FCA, TDM, or TDM + MPL. Serum antibody titers were stimulated with all 3 adjuvant-antigen combinations. The highest titer was produced by use of FCA; TDM + MPL produced an intermediate response, and TDM produced the lowest titer. All of the rabbits immunized with FCA developed sterile subcutaneous abscesses. Rabbits immunized with TDM or TDM + MPL developed no abscesses, and only slight reactions at the injection sites. The synthetic adjuvant system TDM + MPL is recommended for use in rabbits, considering its adequate stimulation of antibody production with minimal adverse reactions.

To obtain immunogenic conjugate antigens, adipic acid dihydrazide (ADH), as a bridge, and 1-ethyl-3-(3-dimethylaminopropyl) carbodiimidehydrochloride (EDAC), as a coupling agent, were used to conjugate the purified fusion protein, clumping factor A-fibronectin binding protein ClfA A-FnBPA, and type 5 capsular polysaccharide (CP5). The conjugates were mixed with an adjuvant, and mice were immunized 3 times and challenged with Staphylococcus aureus 1 week later. Antibody titers were determined by indirect enzyme-linked immunosorbent assay (ELISA). At 14 days after the first immunization, antibodies against the purified protein and conjugate were detected; after 28 days, antibody levels increased; and a week after the third immunization, antibody levels continued to increase. However, the conjugate antibody titers were higher than those of the purified protein during the study, and no IgG antibodies against purified CP5 were detected during the entire experiment. The protection rate increased to 90% in the conjugate group, indicating that the conjugate imparts a relatively higher protective efficacy than the purified protein and purified CP5.

The bursa of Fabricius (BF) is a central humoral immune organ unique to birds. Four bursal peptides (BP-I, BP-II, BP-III, and BP-IV) have been isolated and identified from the BF. In this study, the immunoadjuvant activities of BPs I to IV were examined in mice immunized with H9N2 avian influenza virus (AIV) vaccine. The results suggested that BP-I effectively enhanced cell-mediated immune responses, increased the secretion of Th1 (interferon gamma)- and Th2 (interleukin-4)-type cytokines, and induced an improved cytotoxic T-lymphocyte (CTL) response to the H9N2 virus. BP-II mainly elevated specific antibody production, especially neutralizing antibodies, and increased Th1- and Th2-type cytokine secretion. BP-III had no significant effect on antibody production or cell-mediated immune responses compared to those in the control group. A strong immune response at both the humoral and cellular levels was induced by BP-IV. Furthermore, a virus challenge experiment followed by H and E staining revealed that BP-I and BP-II promoted removal of the virus and conferred protection in mouse lungs. BP-IV significantly reduced viral titers and histopathological changes and contributed to protection against H9N2 AIV challenge in mouse lungs. This study further elucidated the immunoadjuvant activities of BPs I to IV, providing a novel insight into immunoadjuvants for use in vaccine design.

The objective of this study was to compare the protection against challenge with porcine circovirus 2 (PCV2) induced by an experimental vaccine based on open reading frame (ORF) 2 of PCV2 DNA plus an adjuvant (aluminum hydroxide, cobalt oxide, or liposome) and a commercial PCV2 subunit vaccine. A total of 35 colostrum-fed, cross-bred, conventional piglets were randomly divided into 7 groups. The commercial vaccine was more efficacious against PCV2 challenge than the 4 experimental vaccines according to immunologic, virologic, and pathological outcomes. The pigs inoculated with the experimental vaccine containing the liposome adjuvant had significantly higher levels (P < 0.05) of neutralizing antibodies and interferon-γ-secreting cells, and significantly lower levels (P < 0.05) of PCV2 viremia than the pigs inoculated with the other experimental vaccines. The pigs inoculated with the experimental vaccines containing either the liposome adjuvant or the cobalt oxide adjuvant had significantly lower lymphoid lesion scores (P < 0.05) than the pigs in the group inoculated with the PCV2 DNA vaccine dissolved in phosphate-buffered saline. Liposome proved to be a potent adjuvant that efficiently enhanced both humoral and cellular immune responses induced by the PCV2 DNA vaccine.