Evaluation of carbopol as an adjuvant on the effectiveness of progressive atrophic rhinitis vaccine

Immunogenicity of a novel inactivated canine adenovirus type 2 variant vaccine for dogs

Purpose

The immunogenicity of vaccines containing the canine adenovirus (CAdV) type 2 (CAdV-2) variant has not yet been reported. We prepared a novel inactivated CAdV-2 variant vaccine using the CAV2232-41 strain, and evaluated its safety and immunogenicity in raccoon dogs.

Materials and Methods

The growth kinetics of CAV2232-41 were determined using Madin-Darby Canine Kidney (MDCK) cells. The nucleotide sequences of CAV2232 and CAV2232-41 were determined by next-generation sequencing. To generate the CAdV-2 variant vaccine, CAV2232-41 propagated in the MDCK cells was inactivated with 0.1% formaldehyde. Two vaccines were prepared by blending inactivated CAV2232-41 with Cabopol and Rehydragel adjuvants. Safety and immunogenicity of the CAV2232C and CAV2232R vaccines were evaluated in guinea pigs. Safety and immunogenicity of the CAV2232C vaccine were also evaluated in raccoon dogs. The virus neutralizing antibody (VNA) titer against CAV2232-41 was measured in sera collected from immunized guinea pigs and raccoon dogs.

Results

CAV2232-41 showed the highest viral titer on days 4-6 post-inoculation and had a deletion in the E3 gene, which was confirmed as a CAdV-2 variant. Guinea pigs inoculated with CAV2232C showed slightly higher VNA titers than those inoculated with CAV2232R 2 weeks after booster vaccination. Raccoon dogs immunized with the CAV2232C vaccine developed high mean VNA titers, while non-vaccinated raccoon dogs were antibody-negative.

Conclusion

The CAV2232C vaccine is safe and induces a protective VNA titer in raccoon dogs.

Molecular Epidemiology of Porcine Parvovirus Type 1 (PPV1) and the Reactivity of Vaccine-Induced Antisera Against Historical and Current PPV1 Strains

Porcine Parvovirus Type 1 (PPV1) contributes to important losses in the swine industry worldwide. During a PPV1 infection, embryos and fetuses are targeted, resulting in stillbirth, mummification, embryonic death, and infertility (SMEDI syndrome). Even though vaccination is common in gilts and sows, strains mainly belonging to the 27a-like group have been spreading in Europe since early 2000s, resulting in SMEDI problems and requiring in-depth studies into the molecular epidemiology and vaccination efficacy of commercial vaccines. Here, we show that PPV1 has evolved since 1855 [1737, 1933] at a rate of 4.71 × 10⁻⁵ nucleotide substitutions per site per year. Extensive sequencing allowed evaluating and reassessing the current PPV1 VP1-based classifications, providing evidence for the existence of four relevant phylogenetic groups. While most European strains belong to the PPV1a (G1) or PPV1b (G2 or 27a-like) group, most Asian and American G2 strains and some European strains were divided into virulent PPV1c (e.g. NADL-8) and attenuated PPV1d (e.g. NADL-2) groups. The increase in the swine population, vaccination degree, and health management (vaccination and biosafety) influenced the spread of PPV1. The reactivity of anti-PPV1 antibodies from sows vaccinated with Porcilis^© Parvo, Eryseng^© Parvo, or ReproCyc^© ParvoFLEX against different PPV1 field strains was the highest upon vaccination with ReproCyc^© ParvoFLEX, followed by Eryseng^© Parvo, and Porcilis^© Parvo. Our findings contribute to the evaluation of the immunogenicity of existing vaccines and support the development of new vaccine candidates. Finally, the potential roles of cluster-specific hallmark amino acids in elevated pathogenicity and viral entry are discussed.

Immune Protective Efficacy of China's Traditional Inactivated and Attenuated Vaccines against the Prevalent Strains of Pasteurella multocida in Mice

Capsular type A and D strains of Pasteurella multocida are the main epidemic serogroups in pigs in China. In this study, we preliminarily evaluated the immune protective efficacy of the two traditional vaccines, an inactivated C44-1 aluminum-hydroxide-gel-adjuvanted (Alh–C44-1) vaccine and a live EO630 vaccine, against currently circulating strains of P. multocida in a mouse model. Mice immunized twice with conventional vaccines generated higher antibody titers, and significantly higher levels of IgG were observed in the mice inoculated with the inactivated Alh–C44-1 vaccine on day 35 (p < 0.05) than those with the live EO630 vaccine. The mice immune protection test showed that the vaccination groups had a 57% or 71% protection effect against the serogroup B strain, but had no protective effect against epidemic strains. In conclusion, our study found that the widely used traditional P. multocida vaccines in China provide good protection against homologous strains, but could not provide cross-protection against heterologous strains in a mouse model.

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.

Study of Interactions between Antigens and Polymeric Adjuvants in Vaccines by Frontal Analysis Continuous Capillary Electrophoresis

Vaccine adjuvants are used to enhance the immune response induced by antigens that have insufficient immunostimulatory capabilities. The present work aims at developing a frontal analysis continuous capillary electrophoresis (FACCE) methodology for the study of antigen-adjuvant interactions in vaccine products. After method optimization using three cationic model proteins, namely lysozyme, cytochrome c, and ribonuclease A, FACCE was successfully implemented to quantify the free antigen and thus to determine the interaction parameters (stoichiometry and binding constant) between an anionic polymeric adjuvant (polyacrylic acid, SPA09) and a cationic vaccine antigen in development for the treatment for Staphylococcus aureus. The influence of the ionic strength of the medium on the interactions was investigated. A strong dependence of the binding parameters with the ionic strength was observed. The concentration of the polymeric adjuvant was also found to significantly modify the ionic strength of the formulation, the extent of which could be estimated and corrected.

A potent novel vaccine adjuvant based on straight polyacrylate

A structure-activity study was conducted to identify the structural characteristics underlying the adjuvant activity of straight (i.e. non-crosslinked) polyacrylate polymers (PAAs) in order to select a new PAA adjuvant candidate for future clinical development. The study revealed that the adjuvant effect of PAA was mainly influenced by polymer size (Mw) and dose. Maximal effects were obtained with large PAAs above 350 kDa and doses above 100 μg in mice. Small PAAs below 10 kDa had virtually no adjuvant effect. HPSEC analysis revealed that PAA polydispersity index and ramification had less impact on adjuvanticity. Heat stability studies indicated that residual persulfate could be detrimental to PAA stability. Hence, this impurity was systematically eliminated by diafiltration along with small Mw PAAs and residual acrylic acid that could potentially affect product safety, potency and stability. The selected PAA, termed SPA09, displayed an adjuvant effect that was superior to that of a standard emulsion adjuvant when tested with CMV-gB in mice, even in the absence of binding to the antigen. The induced immune response was dominated by strong IFNγ, IgG2c and virus neutralizing titers. The activity of SPA09 was then confirmed on human cells via the innate immune module of the human MIMIC® system.

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Straight polyacrylate (350 kDa < Mw < 650 kDa; termed SPA09) is a strong adjuvant easy to formulate with vaccine antigens

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SPA09 induces Th-1 type immune responses in mice, dominated by strong IFN-γ, IgG2c and virus neutralizing titers

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SPA09 can activate human antigen presenting cells when tested via the innate immune module (PTE) of the human MIMIC® system

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SPA09 constitutes a straightforward new adjuvant candidate for future clinical development

Immunogenicity of a new, inactivated canine adenovirus type 2 vaccine for dogs

PURPOSE

We constructed a new canine adenovirus type 2 (CAV-2) vaccine candidate using the recently isolated Korean CAV-2 strain; we termed the vaccine APQA1701-40P and evaluated its safety and immunogenicity in dogs.

MATERIALS AND METHODS

To generate the anti-CAV-2 vaccine, APQA1701 was passaged 40 times in MDCK cells growing in medium containing 5 mM urea and the virus was inactivated using 0.05% (volume per volume) formaldehyde. Two vaccines were prepared by blending inactivated APQA1701-40P with two different adjuvants; both were intramuscularly injected (twice) into guinea pigs. The safety and immunogenicity of the Cabopol-adjuvanted vaccine were evaluated in seronegative dogs. The humoral responses elicited were measured using an indirect enzyme-linked immunosorbent assay (I-ELISA), and via a virus neutralization assay (VNA).

RESULTS

The new, inactivated CAV-2 vaccine strain, APQA1701-40P, lacked six amino acids of the E1b-19K protein. In guinea pigs, the Cabopol-adjuvanted vaccine afforded a slightly higher VNA titer and I-ELISA absorbance than an IMS gel-adjuvanted vaccine 4 weeks post-vaccination (p>0.05). Dogs inoculated with the former vaccine developed a significantly higher immune titer than non-vaccinated dogs.

CONCLUSION

The Cabopol-adjuvanted, inactivated CAV-2 vaccine was safe and induced a high VNA titer in dogs.

Field evaluation of the safety and compatibility of a combined vaccine against porcine parvovirus 1 and porcine reproductive and respiratory syndrome virus in breeding animals

BACKGROUND

Porcine reproductive and respiratory syndrome virus (PRRSV) and porcine parvovirus 1 (PPV1) are two common causes of reproductive failure. ReproCyc® ParvoFLEX is a novel subunit vaccine based on the protective viral protein (VP) 2 of PPV1 that has been recently licensed in the European (EU) market, whereas ReproCyc® PRRS EU is a porcine reproductive and respiratory syndrome (PRRS) modified live virus (MLV) vaccine authorized in 2015. The present work sought to evaluate the safety and compatibility of the combined administration of the abovementioned vaccines in target animals under the context of a field PRRSV (experiment A) and PPV1 (experiment B) infection. To achieve this objective, safety and lack of vaccines' antigen interference were established according to the absence of significant differences between the combined vaccinated animals (PPRSV+PPV1) and the single vaccinated animals against PRRSV or PPV1. In both experiments, gilts and sows were evaluated for local and systemic reactions after vaccination as well as for reproductive and productive performance. In addition, tissues from abortions, mummified fetuses and stillborn piglets were analyzed for the presence of PRRSV and PPV1. Lastly, serology and viremia were determined in experiment B.

RESULTS

No relevant differences in terms of safety, reproductive and productive performance between the single vaccinated and the combined vaccinated animals in either experiment were observed.

CONCLUSIONS

ReproCyc® PRRS EU mixed with ReproCyc® ParvoFLEX can be used as a safe method of protection against the detrimental effects of PRRSV and PPV1 infections in breeding female pigs in one single injection. The present results also open up opportunities to tackle reproductive problems as a whole by combining control programs against swine reproductive pathogens.

A novel subunit vaccine based on the viral protein 2 of porcine parvovirus: safety profile in bred pigs at different stages of the reproduction cycle and in offspring

Porcine parvovirus 1 (PPV1) viral protein (VP) 2 is the primary antigen responsible for inducing specific protective immunity, so it is a desirable target for development of recombinant subunit vaccines to prevent PPV1 disease. The objective of this study was to evaluate repeated doses of a novel VP2-based PPV1 subunit vaccine, namely ReproCyc® ParvoFLEX, for safety in bred pigs and in offspring under experimental settings. Therefore, the investigation of safety at all breeding stages was evaluated in four independent studies involving: pre-breeding gilts (study A), breeding-age gilts and boars (study B), early and late gestating sows and offspring (study C) and lactating sows and offspring (study D). In all four studies, animals were free from PPV1 based on serology and PCR prior to inclusion. All studies comprised one or two vaccinated groups that received the PPV1 subunit vaccine and a negative control group. Thus, safety was established due to the lack of significant differences between the vaccinated groups and the corresponding unvaccinated (negative control) groups. Gilts, sows and boars were evaluated for local and systemic reactions after vaccination as well as for reproductive performance. The survival rate and average daily weight gain (ADWG) from birth to weaning in offspring was evaluated in studies C and D. Additionally, serology was determined in studies A, C and D. The vaccine was shown to be safe with no relevant significant differences between vaccinated and unvaccinated groups in any experiment. Therefore, repeated doses of ReproCyc® ParvoFLEX were safe in target animals at different stages of the reproductive cycle and in offspring, placing this vaccine as a suitable candidate for mass vaccination programs in breeding herds.

Pasteurella multocida isolates associated with ovine pneumonia are toxigenic

The P. multocida toxin (PMT), a dermonecrotic protein encoded by the toxA gene, is the major virulence factor of capsular type D P. multocida strains causing progressive atrophic rhinitis (PAR) in pigs. A high frequency of P. multocida isolates harboring the toxA gene has been found among ovine pneumonic isolates, although the ability of these isolates to express PMT has never been examined. In this study we have investigated the ability of ovine toxA+ P. multocida isolates (n = 57) to express a functional toxin by detection of PMT toxin antigen using an ELISA test and its cytopathic effect in a Vero cell assay. PMT antigen was expressed in the great majority (54/57; 94.7%) of toxA+ isolates. Moreover, the 100% toxA+ ovine isolates analyzed produced a cytopathic effect in Vero cells within 24-48 h post-inoculation, identical to that described for porcine toxigenic P. multocida isolates. These results show for the first time that, in addition to isolates associated with PAR, isolates of P. multocida associated with pneumonia in sheep are also toxigenic. In addition, we found a total agreement (Kappa = 1; C.I. 0.75-1.25) between the detection of the toxA gene and the toxigenic capability of P. multocida isolates, indicating the PCR detection of toxA would be a suitable predictive marker of the toxigenic fitness of P. multocida.