Intranasal immunization protects against Acinetobacter baumannii-associated pneumonia in mice

Multidrug-resistant Acinetobacter baumannii has become an important causative agent of healthcare associated infections. Hospital- and community-acquired pneumonia is the most common clinical manifestation of A. baumannii infection worldwide and is often associated with high mortality. Most experimental vaccine studies to date have evaluated vaccines against systemic A. baumannii infections following systemic immunization. We recently demonstrated that a mouse model of respiratory A. baumannii infection using the strain LAC-4 results in disease progression that is similar to that observed in humans. Here we used this model in conjunction with an inactivated whole cell vaccine to evaluate the feasibility of developing protective mucosal vaccines against respiratory A. baumannii infection and to investigate the potential mechanism of protection of such vaccines. Our results showed that intranasal immunization with formalin-killed whole cells of the LAC-4 strain elicited mucosal and systemic antigen-specific immune responses, and protected mice against lethal intranasal or intraperitoneal challenges. Compared to naïve mice, immunized mice had significantly fewer bacteria in their lungs, and the pathogen was barely detectable in blood and spleens at 24 h post challenge, indicating the ability of immunized mice to control extrapulmonary dissemination of the pathogen. Mechanistic studies using gene-deficient mice, neutropenic mice, or passive immunization showed that B cells and neutrophils, but not FcRγ, played crucial roles in the protection against respiratory A. baumannii challenge of intranasally immunized mice whereas passive transfer of hyperimmune sera only prolonged the survival time of challenged mice by 48 h. These results provide immunological insights for the rational design of novel mucosal vaccines to protect against respiratory A. baumannii infection and demonstrate the feasibility to develop such vaccines.     

Pathogenesis of Brucella ovis in pregnant mice and protection induced by the candidate vaccine strain B. Ovis ΔabcBA

Ovine brucellosis caused by Brucella ovis is a major cause of reproductive failure in sheep. This study aimed to evaluate transplacental infection and pathogenicity of B. ovis wild type strain ATCC 25,840 (WT B. ovis) and the candidate vaccine strain B. ovis ΔabcBA in pregnant mice. A total of 40 BALB/c mice were equally divided into 4 groups: (i) non immunized and uninfected control mice (3/10 mice became pregnant); (ii) non immunized and challenged with WT B. ovis (5/10 pregnant); (iii) inoculated only with B. ovis ΔabcBA (6/10 pregnant); (iv) immunized with B. ovis ΔabcBA and challenged with WT B. ovis (5/10 pregnant). Female mice bred, and five days after visualization of the vaginal plug, they were inoculated intraperitoneally (ip) with 100 µL of sterile PBS, 100 µL of 1 × 10⁶ CFU of B. ovis ΔabcBA, or 100 µL of 1 × 10⁶ CFU of B. ovis WT, according to each group. At the 17th day of gestation, samples of spleen, liver, uterus, placenta, fetus and mammary gland were obtained for bacteriology, histopathology and immunohistochemistry. Non immunized mice challenged with B. ovis WT developed necrotizing placentitis as well as microgranulomas in the liver and spleen. These findings support the notion that B. ovis infection in pregnant mice induces lesions that are similar to those caused by B. abortus in the same animal model. B. ovis ΔabcBA was not recovered from any of the sampled organs, and it did not cause any gross or microscopic lesions, indicating that it is a safe and attenuated strain in this experimental model. In addition, B. ovis ΔabcBA was induced protective immunity as demonstrated by decreased numbers of B. ovis WT in the liver, uterus and fetuses of immunized mice after the challenge with B. ovis WT.     

Preclinical identification of vaccine induced protective correlates in human leukocyte antigen expressing transgenic mice infected with Coccidioides posadasii

There is an emerging interest to develop human vaccines against medically-important fungal pathogens and a need for a preclinical animal model to assess vaccine efficacies and protective correlates. HLA-DR4 (DRB110401 allele) transgenic mice express a human major histocompatibility complex class II (MHC II) receptor in such a way that CD4⁺ T-cell response is solely restricted by this human molecule. In this study HLA-DR4 transgenic mice were immunized with a live-attenuated vaccine (ΔT) and challenged by the intranasal route with 50–70 Coccidioides posadasii spores, a potentially lethal dose. The same vaccination regimen offers 100% survival for C57BL/6 mice. Conversely, ΔT-vaccinated HLA-DR4 mice displayed 3 distinct manifestations of Coccidioides infection including 40% fatal acute (FAD), 30% disseminated (DD) and 30% pulmonary disease (PD). The latter 2 groups of mice had reduced loss of body weight and survived to at least 50 days postchallenge (dpc). These results suggest that ΔT vaccinated HLA-DR4 mice activated heterogeneous immunity against pulmonary Coccidioides infection. Vaccinated HLA-DR4 mice displayed early expansion of Th1 and Th17 cells and recruitment of inflammatory innate cells into Coccidioides-infected lungs during the first 9 dpc. While contraction rates of Th cells and the inflammatory response during 14–35 dpc significantly differed among the 3 groups of vaccinated HLA-DR4 mice. The FAD group displayed a sharply reduced Th1 and Th17 response, while overwhelmingly recruiting neutrophils into lungs during 9–14 days. The FAD group approached moribund by 14 dpc. In contrast, vaccinated HLA-DR4 survivors gradually contracted Th cells and inflammatory response with the greatest rate in the PD group. While vaccinated HLA-DR4 mice are susceptible to Coccidioides infection, they are useful for evaluation of vaccine efficacy and identification of immunological correlates against this mycosis.     

Novel csuC-DNA nanovaccine based on chitosan candidate vaccine against infection with Acinetobacter baumannii

Background Generating vaccines is a promising and effective method for stopping the spread of Acinetobacter baumannii (A. baumannii) infections that are becoming more and more drug-resistant (MDR). Developing a DNA vaccine and testing its efficacy and protective effects in BALB/c mice were the goals of this research.Methods We examined the genomes of 35 different strains of A. baumannii using the Vaxign online program, and we selected outer membrane and secreted proteins as potential vaccine candidates. Next, the proteins' immunogenicity, antigenic features, physical and chemical characteristics, and B and MHCI/II cell epitope concentrations were assessed. The DNA vaccine was synthesized. Then, to generate CS-DNA nanoparticles, the DNA vaccine was e encapsulated by chitosan (CS) nanoparticles (NPs). BALB/c mice were used to assess the vaccine's immunogenicity and immunoprotective effectiveness.Results CS-DNA NPs were nontoxic, positively charged (4.39 mV), and small (mean size of 285–350 nm) with ostensibly spherical shapes. It was possible to establish a continuously slow release profile and a high entrapment efficiency (78.12 %). CS-DNA vaccinated BALB/c mice elicited greater levels of csuC-specific IgG in plasma and IFN-γ in splenocyte lysate compared with non-encapsulated DNA vaccine. In addition, BALB/c mice immunized with CS-DNA nanovaccine showed decreased lung damage and bacterial loads in the lung and blood, as well as significant immunity (87.5 %) versus acute fatal intratracheal A. baumannii challenge.Conclusion In conclusion, acute fatal intratracheal A. baumannii exposure was prevented by CS-DNA NPs that induced specific IgG antibodies, Th1 cellular immunity, and other protective mechanisms. Our findings show that this nanovaccine is a promising contender for stopping the spread of A. baumannii infection.     

Comparison of the nine polymorphic membrane proteins of Chlamydia trachomatis for their ability to induce protective immune responses in mice against a C. muridarum challenge

ObjectivesTo test vaccines, formulated with novel antigens, to protect mice against Chlamydia infections.MethodsTo determine the ability of polymorphic membrane proteins (Pmps) to induce cross-species protective immune responses, recombinant fragments from all nine C. trachomatis serovar E Pmps were used to vaccinate BALB/c mice utilizing CpG-1826 and Montanide ISA 720 as adjuvants. C. muridarum recombinant MOMP and PBS, formulated with the same adjuvants, were used as positive and negative controls, respectively. Mice were challenged intranasally with 10⁴ inclusion-forming units (IFU) of C. muridarum. Animals were weighed daily and at 10 days post-challenge, they were euthanized, their lungs harvested, weighed and the number of chlamydial IFU counted.ResultsFollowing vaccination the nine Pmps elicited immune responses. Based on body weight changes, or number of IFU recovered from lungs, mice vaccinated with Pmp C, G or H were the best protected. For example, over the 10-day period, the negative control group vaccinated with PBS lost significantly more body weight than mice immunized with PmpC or G (P < 0.05). C. muridarum MOMP vaccinated mice were better protected against body weight losses than any group immunized with Pmps. Also, the median number of IFU recovered from the lungs of mice vaccinated with PmpC (72 × 10⁶) or PmpH (61 × 10⁶) was significantly less than from mice immunized with PBS (620 × 10⁶; P < 0.05). As determined by the number of IFU, all Pmps elicited less protection than C. muridarum MOMP (0.078 × 10⁶ IFU; P < 0.05).ConclusionsThis is the first time PmpC has been shown to elicit cross-species protection against a respiratory challenge. Additional work with Pmps C, G and H is recommended to determine their ability to protect animal models against genital and ocular challenges.     

Oral administration of a recombinant attenuated Yersinia pseudotuberculosis strain elicits protective immunity against plague

A Yersinia pseudotuberculosis PB1+ (Yptb PB1+) mutant strain combined with chromosome insertion of the caf1R-caf1A-caf1M-caf1 operon and deletions of yopJ and yopK, χ10068 [pYV-ω2 (ΔyopJ315 ΔyopK108) ΔlacZ044::caf1R-caf1M-caf1A-caf1] was constructed. Results indicated that gene insertion and deletion did not affect the growth rate of χ10068 compared to wild-type Yptb cultured at 26 °C. In addition, the F1 antigen in χ10068 was synthesized and secreted on the surface of bacteria at 37 °C (mammalian body temperature), not at ambient culture temperature (26 °C). Immunization with χ10068 primed antibody responses and specific T-cell responses to F1 and YpL (Y. pestis whole cell lysate). Oral immunization with a single dose of χ10068 provided 70% protection against a subcutaneous (s.c.) challenge with ∼2.6 × 10⁵ LD₅₀ of Y. pestis KIM6+ (pCD1Ap) (KIM6+Ap) and 90% protection against an intranasal (i.n.) challenge with ∼500 LD₅₀ of KIM6+Ap in mice. Our results suggest that χ10068 can be used as an effective precursor to make a safe vaccine to prevent plague in humans and to eliminate plague circulation among humans and animals.     

Peritoneal B-1b and B-2 B-cells confer long-term protection from pneumococcal serotype 3 infection after vaccination with Prevnar-13 and are defective in sickle cell disease mice

Long-term immunity after inoculation with the pneumococcal conjugate vaccine (Prevnar-13) is impaired in sickle cell disease (SCD) mice. We sought to determine which B-cell subsets are defective in SCD mice after vaccination with Prevnar-13, yet confer long-term immunity in wild-type (WT) mice. We vaccinated WT and SCD mice three times at three week intervals with Prevnar-13. Fourteen weeks later, 5 1 10⁴ cells of isolated peritoneal B-1a, B-1b, and B-2 cells were harvested and intraperitoneally transferred to Rag −/− recipients. A week later recipients were intraperitoneally challenged with 10³ CFU of Streptococcus pneumoniae (serotype 3). Recipient mice that received either B-1b or B-2 B-cells from WT mice survived challenge, whereas mice that received B-1a cells died. Recipient mice that received B-1a, B-1b, or B-2 cells from SCD mice died after challenge. Both B-1b and B-2 cells appear to confer long-term immunity after Prevnar-13 vaccination, yet neither subset functions properly in SCD mice.     

Multiple efficacy studies of an adenovirus-vectored foot-and-mouth disease virus serotype A24 subunit vaccine in cattle using homologous challenge

The safety and efficacy of an experimental, replication-deficient, human adenovirus-vectored foot-and-mouth disease virus (FMDV) serotype A24 Cruzeiro capsid-based subunit vaccine (AdtA24) was examined in eight independent cattle studies. AdtA24 non-adjuvanted vaccine was administered intramuscularly to a total of 150 steers in doses ranging from approximately 1.0 × 10⁸ to 2.1 × 10¹¹ particle units per animal. No detectable local or systemic reactions were observed after vaccination. At 7 days post-vaccination (dpv), vaccinated and control animals were challenged with FMDV serotype A24 Cruzeiro via the intradermal lingual route. Vaccine efficacy was measured by FMDV A24 serum neutralizing titers and by protection from clinical disease and viremia after challenge. The results of eight studies demonstrated a strong correlation between AdtA24 vaccine dose and protection from clinical disease (R² = 0.97) and viremia (R² = 0.98). There was also a strong correlation between FMDV A24 neutralization titers on day of challenge and protection from clinical disease (R² = 0.99). Vaccination with AdtA24 enabled differentiation of infected from vaccinated animals (DIVA) as demonstrated by the absence of antibodies to the FMDV nonstructural proteins in vaccinates prior to challenge. Lack of AdtA24 vaccine shedding after vaccination was indicated by the absence of neutralizing antibody titers to both the adenovector and FMDV A24 Cruzeiro in control animals after co-mingling with vaccinated cattle for three to four weeks. In summary, a non-adjuvanted AdtA24 experimental vaccine was shown to be safe, immunogenic, consistently protected cattle at 7 dpv against direct, homologous FMDV challenge, and enabled differentiation of infected from vaccinated cattle prior to challenge.     

Expression of H5 hemagglutinin vaccine antigen in common duckweed (Lemna minor) protects against H5N1 high pathogenicity avian influenza virus challenge in immunized chickens

A synthetic hemagglutinin (HA) gene from the highly pathogenic avian influenza (HPAI) virus A/chicken/Indonesia/7/2003 (H5N1) (Indo/03) was expressed in aquatic plant Lemna minor (rLemna-HA). In Experiment 1, efficacy of rLemna-HA was tested on birds immunized with 0.2 μg or 2.3 μg HA and challenged with 10⁶ mean chicken embryo infectious doses (EID₅₀) of homologous virus strain. Both dosages of rLemna-HA conferred clinical protection and dramatically reduced viral shedding. Almost all the birds immunized with either dosage of rLemna-HA elicited HA antibody titers against Indo/03 antigen, suggesting an association between levels of anti-Indo/03 antibodies and protection. In Experiment 2, efficacy of rLemna-HA was tested on birds immunized with 0.9 μg or 2.2 μg HA and challenged with 10⁶ EID₅₀ of heterologous H5N1 virus strains A/chicken/Vietnam/NCVD-421/2010 (VN/10) or A/chicken/West Java/PWT-WIJ/2006 (PWT/06). Birds challenged with VN/10 exhibited 100% survival regardless of immunization dosage, while birds challenged with PWT/06 had 50% and 30% mortality at 0.9 μg HA and 2.2 μg HA, respectively. For each challenge virus, viral shedding titers from 2.2 μg HA vaccinated birds were significantly lower than those from 0.9 μg HA vaccinated birds, and titers from both immunized groups were in turn significantly lower than those from sham vaccinated birds. Even if immunized birds elicited HA titers against the vaccine antigen Indo/03, only the groups challenged with VN/10 developed humoral immunity against the challenge antigen. None (rLemna-HA 0.9 μg HA) and 40% (rLemna-HA 2.2 μg HA) of the immunized birds challenged with PWT/06 elicited pre-challenge antibody titers, respectively. In conclusion, Lemna-expressed HA demonstrated complete protective immunity against homologous challenge and suboptimal protection against heterologous challenge, the latter being similar to results from inactivated whole virus vaccines. Transgenic duckweed-derived HA could be a good alternative for producing high quality antigen for an injectable vaccine against H5N1 HPAI viruses.     

Anti-tumor effect of the alphavirus-based virus-like particle vector expressing prostate-specific antigen in a HLA–DR transgenic mouse model of prostate cancer

The goal of this study was to determine if an alphavirus-based vaccine encoding human Prostate-Specific Antigen (PSA) could generate an effective anti-tumor immune response in a stringent mouse model of prostate cancer. DR2bxPSA F₁ male mice expressing human PSA and HLA-DRB1^*1501 transgenes were vaccinated with virus-like particle vector encoding PSA (VLPV–PSA) followed by the challenge with Transgenic Adenocarcinoma of Mouse Prostate cells engineered to express PSA (TRAMP–PSA). PSA-specific cellular and humoral immune responses were measured before and after tumor challenge. PSA and CD8 reactivity in the tumors was detected by immunohistochemistry. Tumor growth was compared in vaccinated and control groups. We found that VLPV–PSA could infect mouse dendritic cells in vitro and induce a robust PSA-specific immune response in vivo. A substantial proportion of splenic CD8 T cells (19.6 ± 7.4%) produced IFNγ in response to the immunodominant peptide PSA_65–73. In the blood of vaccinated mice, 18.4 ± 4.1% of CD8 T cells were PSA-specific as determined by the staining with H-2D^b/PSA_65–73 dextramers. VLPV–PSA vaccination also strongly stimulated production of IgG2a/b anti-PSA antibodies. Tumors in vaccinated mice showed low levels of PSA expression and significant CD8+ T cell infiltration. Tumor growth in VLPV–PSA vaccinated mice was significantly delayed at early time points (p = 0.002, Gehan–Breslow test). Our data suggest that TC-83-based VLPV–PSA vaccine can efficiently overcome immune tolerance to PSA, mediate rapid clearance of PSA-expressing tumor cells and delay tumor growth. The VLPV–PSA vaccine will undergo further testing for the immunotherapy of prostate cancer.     

Evaluation of a new trilocus sequence-based multiplex-PCR to detect major Acinetobacter baumannii clonal complexes circulating in Brazil

Dissemination of carbapenem-resistant Acinetobacter baumannii (CRAB) is mainly due to the spread of clonal lineages, particularly those included into the clonal complexes (CC) CC1, CC2, CC15, CC25, and CC79. We evaluated the usefulness of a recently modified PCR-based trilocus sequence-based typing (m3LST) in comparison with the standard multilocus sequence typing (MSLT) of 7 housekeeping genes as per the Institute Pasteur Scheme to assign the clonal complexes in CRAB. A collection of 78 CRAB isolated from 67 different Brazilian health institutions was submitted to both methodologies, and concordance rate was calculated. The collection studied included mainly isolates belonging to endemic Brazilian Clonal Complexes (CC1, CC15, CC25 and CC79, n = 72, 92.3%) but also singletons sequence types (ST) with low prevalence in the country (ST107, ST113, ST188, ST317, ST584, ST733, n = 6; 7.7%). The m3LST correctly assigned all the isolates into the main CC responsible for the CRAB dissemination in Brazil. All the singletons ST were not misidentified as prevalent lineages. The PCR-based m3LST is a powerful tool to investigate molecular epidemiology of A. baumannii representative of prevalent Brazilian clonal complexes 1, 15, 25 and 79.     

Type I pili,CsuA/B and FimA induce a protective immune response against Acinetobacter baumannii

BackgroundAcinetobacter baumannii, a nosocomial pathogen, is considered as a common cause of hospital and community-acquired infections. Emerging multidrug-resistance in this pathogen followed by subsequent problems in treatment has been increasing to alarming levels that warrant investigation of new therapeutic approaches. One strategy to reduce antibiotic resistance is to use of vaccines. Although there is no vaccine currently in development for this pathogen, different attempts have been made to develop one.MethodsIn this study, we used two different recombinant pilus proteins (CsuA/B and FimA) either singly or in combination to evaluate protective efficacy against A. baumannii in lethal and sub-lethal murine sepsis models.FindingsActive immunization with recombinant proteins in combination elicited high levels of IgG antibody after the first immunization and provided 62% (five of eight mice; p < 0·001) protection against a lethal dose (1·2 × 10⁶ CFU) of A. baumannii along with efficient clearance of bacteria in internal organs viz. spleen, liver, and lungs at sub-lethal challenge. Immunization with CsuA/B alone conferred partial protection as demonstrated by low survival rate (three [37%] of eight mice; p < 0·05) after lethal challenge and reduction of bacteria in internal organs of the mice after 24 h post-sub-lethal infection. Immunization with FimA, in comparison to CsuA/B, showed better protection (four [50%] of eight mice; p < 0·01) and reduction in CFU after 14 h.InterpretationOur results showed that pilus proteins in combination as a single immunogen could potentially impart protection against A. baumannii.FundingShahed University.     

A novel live attenuated anthrax spore vaccine based on an acapsular Bacillus anthracis Sterne strain with mutations in the htrA,lef and cya genes

We recently reported the development of a novel, next-generation, live attenuated anthrax spore vaccine based on disruption of the htrA (High Temperature Requirement A) gene in the Bacillus anthracis Sterne veterinary vaccine strain. This vaccine exhibited a highly significant decrease in virulence in murine, guinea pig and rabbit animal models yet preserved the protective value of the parental Sterne strain. Here, we report the evaluation of additional mutations in the lef and cya genes, encoding for the toxin components lethal factor (LF) and edema factor (EF), to further attenuate the SterneΔhtrA strain and improve its compatibility for human use. Accordingly, we constructed seven B. anthracis Sterne-derived strains exhibiting different combinations of mutations in the htrA, cya and lef genes. The various strains were indistinguishable in growth in vitro and in their ability to synthesise the protective antigen (PA, necessary for the elicitation of protection). In the sensitive murine model, we observed a gradual increase (ΔhtrA < ΔhtrAΔcya < ΔhtrAΔlef < ΔhtrAΔlefΔcya) in attenuation – up to 10⁸-fold relative to the parental Sterne vaccine strain. Most importantly, all various SterneΔhtrA derivative strains did not differ in their ability to elicit protective immunity in guinea pigs. Immunisation of guinea pigs with a single dose (10⁹ spores) or double doses (>10⁷ spores) of the most attenuated triple mutant strain SterneΔhtrAlef^MUTΔcya induced a robust immune response, providing complete protection against a subsequent respiratory lethal challenge. Partial protection was observed in animals vaccinated with a double dose of as few as 10⁵ spores. Furthermore, protective immune status was maintained in all vaccinated guinea pigs and rabbits for at least 40 and 30 weeks, respectively.     

A single dose of genetically-attenuated malaria blood-stage parasites protects against two Plasmodium species infections

Genetically-growth-attenuated blood-stage parasites were generated in Plasmodium falciparum by targeted deletion of NT1 (Nucleoside Transporter-1) gene, and Pfnt1(-) parasites only grew after providing the culture with supra-physiological concentrations of purines. Genetically-attenuated P. yoelii nt1(-) parasites induced sterile-protection against homologous blood-stage infectious challenge after immunization with single subpatent doses, which remained subpatent even in immune-compromised mice. Here, we showed that immunizations with frozen-stocks of equally-mixed P. berghei and P. yoelii nt1(-) parasites in single subcutaneous doses, which did not lead to patent blood-stage infection, conferred sterile protection against intravenous infectious blood-stage challenge with wild-type parasites of P. berghei ANKA and P. yoelii 17X-NL strains. This data highlights the possibility that a single subcutaneous sub-patent dose of two species of genetically-growth-attenuated parasites, which can protect humans against two Plasmodium spp. infections, could be developed in cultures provided with supra-physiological concentrations of purines, and shipped to endemic areas as frozen-stock doses.     

A single dose and long lasting vaccine against pandemic influenza through the controlled release of a heterospecies tandem M2 sequence embedded within detoxified bacterial outer membrane vesicles

The influenza A virus undergoes genetic drift and shift, leaving the general population susceptible to emerging pandemic strains, despite seasonal flu vaccination. Here we describe a single dose influenza vaccine derived from recombinant outer membrane vesicles (rOMVs) that display an antigen-mapped heterospecies tandem sequence of the M2 protein from the influenza A virus, released over 30 days from poly(lactic-co-glycolide) (PLGA) microparticles. Four weeks post vaccination, BALB/c mice developed high anti-M2e IgG titers that were equivalent to those generated at 8 weeks in a typical prime/boost vaccine regimen. Challenge of mice with a lethal dose of mouse adapted influenza virus PR8 (H1N1) 10 weeks post vaccination resulted in 100% survival for both rOMV single-dose microparticle and prime/boost vaccinated mice. Anti-M2e IgG1 and IgG2a antibody titers were weighted toward IgG1, but splenocytes isolated from rOMV single-dose microparticle vaccinated mice produced high levels of IFNγ relative to IL-4 in response to stimulation with M2e peptides, supporting a more Th1 biased immune response. The protective immune response was long lasting, eliciting sustained antibody titers and 100% survival of mice challenged with a lethal dose of PR8 six months post initial vaccination. Together, these data support the potential of controlled release rOMVs as an effective single dose, long lasting and rapidly effective vaccine to protect against influenza.     

An influenza viral vector Brucella abortus vaccine induces good cross-protection against Brucella melitensis infection in pregnant heifers

Brucella melitensis can be transmitted and cause disease in cattle herds as a result of inadequate management of mixed livestock farms. Ideally, vaccines against Brucella abortus for cattle should also provide cross-protection against B. melitensis. Previously we created a novel influenza viral vector B. abortus (Flu-BA) vaccine expressing the Brucella ribosomal proteins L7/L12 or Omp16. This study demonstrated Flu-BA vaccine with adjuvant Montanide Gel01 provided 100% protection against abortion in vaccinated pregnant heifers and good cross-protection of the heifers and their calves or fetuses (90–100%) after challenge with B. melitensis 16 M; the level of protection provided by Flu-BA was comparable to the commercial vaccine B. abortus S19. In terms of the index of infection and colonization of Brucella in tissues, both vaccines demonstrated significant (P = 0.02 to P < 0.0001) protection against B. melitensis 16 M infection compared to the negative control group (PBS + Montanide Gel01). Thus, we conclude the Flu-BA vaccine provides cross-protection against B. melitensis infection in pregnant heifers.     

Early protection in sheep against intratypic heterologous challenge with serotype O foot-and-mouth disease virus using high-potency,emergency vaccine

In 2009–2011, spread of a serotype O foot-and-mouth disease virus (FMDV) belonging to the South East Asia topotype led to the culling of over 3.5 million cattle and pigs in Japan and Korea. The O1 Manisa vaccine (belonging to the Middle East-South Asian topotype) was used at high potency in Korea to limit the expansion of the outbreak. However, no data are available on the spread of this virus or the efficacy of the O1 Manisa vaccine against this virus in sheep. In this study, the early protection afforded with a high potency (>6 PD₅₀) FMD O1 Manisa vaccine against challenge with the O/SKR/2010 virus was tested in sheep. Sheep (n = 8) were vaccinated 4 days prior to continuous direct-contact challenge with donor sheep. Donor sheep were infected with FMDV O/SKR/2010 by coronary band inoculation 24 h prior to contact with the vaccinated animals, or unvaccinated controls (n = 4). Three of the four control sheep became infected, two clinically. All eight O1 Manisa vaccinated sheep were protected from clinical disease. None had detectable antibodies to FMDV non-structural proteins (3ABC), no virus was isolated from nasal swabs, saliva or oro-pharyngeal fluid and none became carriers. Using this model of challenge, sheep were protected against infection as early as 4 days post vaccination.     

A rabies vaccine adjuvanted with saponins from leaves of the soap tree (Quillaja brasiliensis) induces specific immune responses and protects against lethal challenge

Quillaja brasiliensis (Quillajaceae) is a saponin producing species native from southern Brazil and Uruguay. Its saponins are remarkably similar to those of Q. saponaria, which provides most of the saponins used as immunoadjuvants in vaccines. The immunostimulating capacities of aqueous extract (AE) and purified saponin fraction (QB-90) obtained from leaves of Q. brasiliensis were favorably comparable to those of a commercial saponin-based adjuvant preparation (Quil-A^®) in experimental vaccines against bovine herpesvirus type 1 and 5, poliovirus and bovine viral diarrhea virus in mice model. Herein, the immunogenicity and protection efficacy of rabies vaccines adjuvanted with Q. brasiliensis AE and its saponin fractions were compared with vaccines adjuvanted with either commercial Quil-A or Alum. Mice were vaccinated with one or two doses (on days 0 and 14) of one of the different vaccines and serum levels of total IgG, IgG1 and IgG2a were quantified over time. A challenge experiment with a lethal dose of rabies virus was carried out with the formulations. Viral RNA detection in the brain of mice was performed by qPCR, and RNA copy-numbers were quantified using a standard curve of in vitro transcribed RNA. All Q. brasiliensis saponin-adjuvanted vaccines significantly enhanced levels of specific IgG isotypes when compared with the no adjuvant group (P ≤ 0.05). Overall, one or two doses of saponin-based vaccine were efficient to protect against the lethal rabies exposure. Both AE and saponin fractions from Q. brasiliensis leaves proved potent immunological adjuvants in vaccines against a lethal challenge with a major livestock pathogen, hence confirming their value as competitive or complementary sustainable alternatives to saponins of Q. saponaria.     

Comparative evaluation of the protective efficacy of two formulations of a recombinant Chlamydia abortus subunit candidate vaccine in a mouse model

Chlamydia abortus (C. abortus) is the causative agent of ovine enzootic abortion (OEA) and poses a zoonotic risk to pregnant women. Current live attenuated 1B vaccines are efficacious but cause disease in vaccinated animals and inactivated vaccines are only marginally protective. We tested the ability of a new C. abortus subunit vaccine candidate based on the conserved and immunogenic polymorphic membrane protein D (Pmp18D) formulated in CpG1826 + FL (Fms-like tyrosine kinase 3 Ligand; Flt3L) or Vibrio cholerae ghosts (VCG) to induce innate and cross protective immunity against genital C. abortus infection. We found that delivery of rPmp18D with VCG was more effective than with CpG + FL in up-regulating the expression of molecules critically involved in T cell activation and differentiation, including MHC II, CD40, CD80, and CD86, activation of TLRs and NLRP3 inflammasome engagement, and secretion of IL-1β and TNF-α but not IL-10 and IL-4. rVCG-Pmp18D-immunized mice elicited more robust antigen-specific IFN-γ, IgA and IgG2c antibody responses compared to CpG + FL-delivered rPmp18D. Based on the number of mice with positive vaginal cultures, length of vaginal shedding, and number of inclusion forming units recovered following challenge with the heterologous C. abortus strain B577, vaccine delivery with VCG induced superior protective immunity than delivery with a combination of CpG1826 and FL, a nasal DC-targeting adjuvant. These results demonstrate that the ability of VCG to enhance protective immunity against genital C. abortus infection is superior to that of CpG + FL adjuvants.