The Brucella abortus double-mutant (ΔznuA ΔnorD Brucella abortus-lacZ [znBAZ]) was assessed for its protective efficacy after vaccination with a single nasal dose. Superior protection was achieved in znBAZ-vaccinated mice against pulmonary, wild-type B. abortus 2308 challenge when compared with conventional livestock Brucella abortus vaccines, the smooth S19 (smooth B. abortus strain 19 vaccine) and rough RB51 (rough mutant vaccine strain of B. abortus) strains. Nasal znBAZ vaccination reduced splenic and lung colonization by wild-type brucellae by >3-4 logs. In contrast, S19 reduced lung colonization by only 32-fold, and RB51 failed to reduce colonization. One profound attribute of znBAZ vaccination was the >3-fold increase in pulmonary CD8+ T cells when compared with other vaccinated groups. S19 vaccination increased only CD4+ T cells. All vaccines induced IFN-γ and TNF-α production by CD4+ T cells, but only znBAZ vaccination enhanced the recruitment of polyfunctional CD8+ T cells, by >100-fold. IL-17 by both CD4+ and CD8+ T cells was also induced by subsequent znBAZ vaccination. These results demonstrate that, in addition to achieving protective immunity by CD4+ T cells, CD8+ T cells, specifically resident memory T cells, also confer protection against brucellosis. The protection obtained by znBAZ vaccination was attributed to IFN-γ-producing CD8+ T cells, because depletion of CD8+ T cells throughout vaccination and challenge phases abrogated protection. The stimulation of only CD4+ T cells by RB51- and S19-vaccinated mice proved insufficient in protecting against pulmonary B. abortus 2308 challenge. Thus, nasal znBAZ vaccination offers an alternative means to elicit protection against brucellosis.

Salmonella Typhimurium is a causative agent of nontyphoidal salmonellosis, for which there is a lack of a clinically approved vaccine in humans. As an intracellular pathogen, Salmonella impacts many cellular pathways. However, the intercellular communication mechanism facilitated by host-derived small extracellular vesicles (EVs), such as exosomes, is an overlooked aspect of the host responses to this infection. We used a comprehensive proteome-based network analysis of exosomes derived from Salmonella -infected macrophages to identify host molecules that are trafficked via these EVs. This analysis predicted that the host-derived small EVs generated during macrophage infection stimulate macrophages and promote activation of T helper 1 (Th1) cells. We identified that exosomes generated during infection contain Salmonella proteins, including unique antigens previously shown to stimulate protective immune responses against Salmonella in murine studies. Furthermore, we showed that host EVs formed upon infection stimulate a mucosal immune response against Salmonella infection when delivered intranasally to BALB/c mice, a route of antigen administration known to initiate mucosal immunity. Specifically, the administration of these vesicles to animals stimulated the production of anti- Salmonella IgG antibodies, such as anti-OmpA antibodies. Exosomes also stimulated antigen-specific cell-mediated immunity. In particular, splenic mononuclear cells isolated from mice administered with exosomes derived from Salmonella -infected antigen-presenting cells increased CD4+ T cells secreting Th1-type cytokines in response to Salmonella antigens. These results demonstrate that small EVs, formed during infection, contribute to Th1 cell bias in the anti- Salmonella responses. Collectively, this study helps to unravel the role of host-derived small EVs as vehicles transmitting antigens to induce Th1-type immunity against Gram-negative bacteria. Understanding the EV-mediated defense mechanisms will allow the development of future approaches to combat bacterial infections.

Understanding the migration of lymphocytes to nonintestinal mucosal sites is fundamental to developing mucosal vaccination strategies. Studies have shown that nasal and oral immunization with cholera toxin (CT) stimulates, in addition to α4β7 + , the induction of αE (CD103)β7 + B cells. To determine the extent to which αE-associated β7 contributes to antigen (Ag)-specific immunoglobulin (Ig)A responses in the upper respiratory tract, nasal CT vaccination was performed in wild-type (wt) and β7 −/− mice. At 16 days postprimary immunization, upper respiratory tract IgA responses were greater in β7 −/− mice than in wt mice. IgA induction by distal β7 −/− Peyer’s patches, mesenteric lymph nodes and small intestinal lamina propria was minimal, in contrast to elevated gut IgA responses in wt mice. By 42 days postprimary immunization, β7 −/− gut IgA responses were restored, and upper respiratory tract Ag-specific IgA responses were equivalent to those of wt mice. Examination of homing receptor expression and cell-sorting experiments revealed that β7 −/− mice have increased usage of β1 and αE integrins by upper respiratory tract B cells, suggesting that alternative integrins can facilitate lymphocyte migration to the upper respiratory tract, especially in the absence of β7.

Understanding the migration of lymphocytes to nonintestinal mucosal sites is fundamental to developing mucosal vaccination strategies. Studies have shown that nasal and oral immunization with cholera toxin (CT) stimulates, in addition to alpha 4 beta 7(+), the induction of alpha E (CD103)beta 7(+)B cells. To determine the extent to which alpha E-associated beta 7 contributes to antigen (Ag)-specific immunoglobulin (Ig)A responses in the upper respiratory tract, nasal CT vaccination was performed in wild-type (wt) and beta 7(-/-)mice. At 16 days postprimary immunization, upper respiratory tract IgA responses were greater in beta 7(-/-)mice than in wt mice. IgA induction by distal beta 7(-/-)Peyer's patches, mesenteric lymph nodes and small intestinal lamina propria was minimal, in contrast to elevated gut IgA responses in wt mice. By 42 days postprimary immunization, beta 7(-/-)gut IgA responses were restored, and upper respiratory tract Ag-specific IgA responses were equivalent to those of wt mice. Examination of homing receptor expression and cell-sorting experiments revealed that beta 7(-/-)mice have increased usage of beta 1 and alpha E integrins by upper respiratory tract B cells, suggesting that alternative integrins can facilitate lymphocyte migration to the upper respiratory tract, especially in the absence of beta 7.

Brucellosis remains the most common zoonotic disease globally. Currently no vaccines for humans exist, and conventional brucellosis vaccines for livestock fail to confer complete protection; hence, an improved vaccine is needed. Although Brucella infections primarily occur following a mucosal exposure, vaccines are administered parenterally. Few studies have considered mucosal vaccinations, or even targeting of tissue-resident memory T (TRM) cells. TRM cells protect against viral infections, but less is known of their role in bacterial infections, and even less for brucellosis. Oral prime, nasal boost with a newly developed Brucella abortus double mutant (znBAZ) confers nearly complete protection against pulmonary challenge with wild-type (wt) B. abortus 2308, and its protective efficacy is >2800-fold better than the RB51 vaccine. Vaccination with znBAZ potently stimulated CD8+ T cells, whereas mucosal vaccination with RB51 induced mostly CD4+ T cells. Subsequent analysis revealed these pulmonary CD44+ CD69+ CD8+ T cells to be either CD103+ or CD103- TRM cells, and these sequestered to the lung parenchyma as CXCR3lo and to the airways as CXCR3hi. Both CD8+ TRM subsets contained single-positive IFN-γ and TNF-α, as well as, polyfunctional cells. IL-17-producing CD8+ TRM cells were also induced by znBAZ vaccination, but in vivo IL-17 neutralization had no impact upon protection. In vivo depletion of CD4+ T cells had no impact upon protection in znBAZ-vaccinated mice. In contrast, CD4+ T cell depletion reduced RB51's protective efficacy in spleens and lungs by two- and three-logs, respectively. Although anti-CD8 mAb-treated znBAZ-vaccinated mice showed a significantly reduced pulmonary efficacy, this treatment failed to completely deplete the lung CD8+ T cells, leaving the CD103+ and CD103- CD8+ TRM cell ratios intact. Only znBAZ-vaccinated CD8-/- mice were fully sensitive to pulmonary challenge with virulent wt B. abortus 2308 since CD8+ TRM cells could not be induced. Collectively, these data demonstrate the key role of mucosal vaccination for the generation of CD8+ TRM cells in protecting against pulmonary challenge with virulent B. abortus.

Mucosal vaccination with a live attenuated B. melitensis double-mutant (BMDM) confers sterilizing protection against pulmonary challenge with wild-type (wt) BM 16M. Although T cell-dependent immunity is essential for protection, we queried the role of B cells in this response. We hypothesized that B cells enable BMDM to persist in the lungs for stimulation of robust adaptive responses. Using BALB/c B cell-deficient (μMT) mice, early and long-term immunity subsequent mucosal vaccination was examined. Groups of BALB/c and μMT mice were orally primed, nasally boosted, and 4 wks later, splenic and lung lymphocytes were antigen-pulsed to determine cytokine responses. μMT mice showed significantly reduced pulmonary proinflammatory responses by three-fold relative to BALB/c mice. Nasal challenge with wt BM 16M of BMDM-vaccinated mice resulted in impaired protective immunity in μMT mice evidenced by the significantly increased brucellae colonization of lungs and spleens. To determine the types of myeloid cells involved in brucellae recognition, μMT mice nasally vaccinated with a mCherry variant of BMDM showed a 23-fold reduction in lung mCherry expression relative to similarly vaccinated BALB/c mice at 5 days post-immunization. mCherry expression associated with various myeloid and B cells. Interestingly, although antigen-presenting cells (APCs) increased similarly in both groups of mice, mCherry expression in lung neutrophils and monocyte-derived macrophages in BALB/c mice was 23- and 4-fold enhanced, respectively, to μMT mice. We believe B cell retention of BMDM mutant enhances APC activity within the lungs facilitating the development of potent local T cell responses. Work supported by NIH R01 AI123244 and AI124244-03S1.

Human brucellosis remains a global health problem with no human vaccines existing. Most human infections occur mucosally with eventual systemic brucellae dissemination. Current interventions primarily focus on the systemic disease, rather than considering neutralizing the infection at its source. A number of studies show that the OPG mucosa is the principal site of brucellae uptake following oral or inhalational exposures. We have devised an OPG infection method using an attenuated Brucella mutant by allowing the mice to drink (ad bibitum) from a pipette tip. BALB/c mice were fed once daily for 3 days with 108 CFUs. Individual head and neck lymph nodes (HNLNs), and spleens were examined at 2 weeks post-infection for bacterial colonization and proinflamatory cytokine responses. Elevated colonization was observed in submandibular LNs (SmLNs) and deep cervical LNs (CLNs). Modest colonization was detected in the parotid LNs (PrLNs) and spleens. Splenic and individual HNLN lymphocytes were analyzed for IFN-g, TNF-a, granzyme B, and perforin production by flow cytometry. SmLN, CLN, and PrLN IFN-g-producing CD8+ T cells significantly exceeded IFN-g-producing CD4+ T cells by 2.5-, 2.5-, and 1.5-fold, respectively. Increased numbers of CD4+ and CD8+ T cells expressing TNF-a, granzyme B, and perforin were also observed. All activated lymphocytes were predominantly of effector-memory phenotype, CD44+CD62LlowCCR7low. These studies demonstrate that ad bibitum vaccination against brucellosis results in colonization and activation of the HNLNs, mimicking natural human infection, enabling future inquiry into the immune mechanisms responsible for protection to mucosal Brucella infections. Work supported by NIH AI-125546.

ABSTRACT Salmonella enterica serovar Typhimurium is a Gram-negative bacterium, which can invade and survive within macrophages. Pathogenic salmonellae induce the secretion of specific cytokines from these phagocytic cells and interfere with the host secretory pathways. In this study, we describe the extracellular proteome of human macrophages infected with S . Typhimurium, followed by analysis of canonical pathways of proteins isolated from the extracellular milieu. We demonstrate that some of the proteins secreted by macrophages upon S . Typhimurium infection are released via exosomes. Moreover, we show that infected macrophages produce CD63 + and CD9 + subpopulations of exosomes at 2 h postinfection. Exosomes derived from infected macrophages trigger the Toll-like receptor 4-dependent release of tumor necrosis factor alpha (TNF-α) from naive macrophages and dendritic cells, but they also stimulate secretion of such cytokines as RANTES, IL-1ra, MIP-2, CXCL1, MCP-1, sICAM-1, GM-CSF, and G-CSF. Proinflammatory effects of exosomes are partially attributed to lipopolysaccharide, which is encapsulated within exosomes. In summary, we show for the first time that proinflammatory exosomes are formed in the early phase of macrophage infection with S . Typhimurium and that they can be used to transfer cargo to naive cells, thereby leading to their stimulation.

Brucellosis remains burdensome for livestock and humans worldwide. Better vaccines for protection are needed to reduce disease incidence. Immunity to brucellosis and barriers to protection are discussed. The benefits and limitations of conventional and experimental brucellosis vaccines are outlined, and novel vaccination strategies needed to ultimately protect against brucellosis are introduced.

Human brucellosis is a global health problem, and no human vaccines exist. Although Brucella infections primarily occur via the oropharynx and the upper respiratory tract mucosa, mucosal aspects of Brucella’s pathogenesis are often ignored. Mucosal vaccination with our live attenuated mutant was found to confer exceptional protection against Brucella challenge. While mice have been instrumental to study immunity to Brucella, they may be less suitable to evaluate mucosal infections. Domestic pigs’ close resemblance to human immune system and anatomical features of the oropharyngeal (OPG) mucosa enables studying mucosal brucellosis in a natural host. To assess our mutant’s immunogenicity, 8 wk-old pigs were vaccinated by directly applying 109 CFUs onto the tonsils and sublingual mucosa plus a buccal injection with 108 CFUs on days 0, 2, and 4, and study was terminated on day 60. Isolated peripheral blood mononuclear cells (PBMCs) on days 0, 15, 23, 35, and 60 as well as terminal head and neck lymphoid tissue lymphocytes were evaluated for IFN-g responses by flow cytometry. The greatest IFN-g came from CD8+ and CD4+ CD8+ T cells, as well as NK cells. Changes in peripheral blood T cells over the course of the response showed a significant reduction in the percentage of total CD4+ T cells, and a significant increase in the percentage of total CD8+ and CD4+ CD8+ T cells. Among the lymphoid tissues examined, with the exception of the tonsils where the IFN-g was mostly derived from CD8+ T cells, IFN-g came from CD4+CD8+ T cells, particularly in the mandibular lymph nodes. Thus, our Brucella mutant is immunogenic in swine and capable of eliciting elevated IFN-g responses following OPG vaccination. Work supported by R03 AI128123 & USDA-NIFA2013-01165.

Brucellosis remains a significant zoonotic threat worldwide. Humans and animals acquire infection via their oropharynx and upper respiratory tract following oral or aerosol exposure. After mucosal infection, brucellosis develops into a systemic disease. Mucosal vaccination could offer a viable alternative to conventional injection practices to deter disease. Using a nasal vaccination approach, the ΔznuA B. melitensis was found to confer potent protection against pulmonary Brucella challenge, and reduce colonization of spleens and lungs by more than 2500-fold, with >50% of vaccinated mice showing no detectable brucellae. Furthermore, 10-fold more brucellae-specific, interferon-γ (IFN-γ)-producing CD8(+) T cells than CD4(+) T cells were induced in the spleen and respiratory lymph nodes. Evaluation of pulmonary and splenic CD8(+) T cells from mice vaccinated with ΔznuA B. melitensis revealed that these expressed an activated effector memory (CD44(hi)CD62L(lo)CCR7(lo)) T cells producing elevated levels of IFN-γ, tumor necrosis factor-α, perforin and granzyme B. To assess the relative importance of these increased numbers of CD8(+) T cells, CD8(-/-) mice were challenged with virulent B. melitensis, and they showed markedly increased bacterial loads in organs in contrast to similarly challenged CD4(-/-) mice. Only ΔznuA B. melitensis- and Rev-1-vaccinated CD4(-/-) and wild-type mice, not CD8(-/-) mice, were completely protected against Brucella challenge. Determination of cytokines responsible for conferring protection showed the relative importance of IFN-γ, but not interleukin-17 (IL-17). Unlike wild-type (wt) mice, IL-17 was greatly induced in IFN-γ(-/-) mice, but IL-17 could not substitute for IFN-γ's protection, although an increase in brucellae dissemination was observed upon in vivo IL-17 neutralization. These results show that nasal ΔznuA B. melitensis vaccination represents an attractive means to stimulate systemic and mucosal immune protection via CD8(+) T-cell engagement.

Brucellosis remains a significant zoonotic threat worldwide. Humans and animals acquire infection via their oropharynx and upper respiratory tract following oral or aerosol exposure. After mucosal infection, brucellosis develops into a systemic disease. Mucosal vaccination could offer a viable alternative to conventional injection practices to deter disease. Using a nasal vaccination approach, the ΔznuA B. melitensis was found to confer potent protection against pulmonary Brucella challenge, and reduce colonization of spleens and lungs by more than 2500-fold, with >50% of vaccinated mice showing no detectable brucellae. Furthermore, 10-fold more brucellae-specific, interferon-γ (IFN-γ)-producing CD8 + T cells than CD4 + T cells were induced in the spleen and respiratory lymph nodes. Evaluation of pulmonary and splenic CD8 + T cells from mice vaccinated with ΔznuA B. melitensis revealed that these expressed an activated effector memory (CD44 hi CD62L lo CCR7 lo ) T cells producing elevated levels of IFN-γ, tumor necrosis factor-α, perforin and granzyme B. To assess the relative importance of these increased numbers of CD8 + T cells, CD8 −/− mice were challenged with virulent B. melitensis , and they showed markedly increased bacterial loads in organs in contrast to similarly challenged CD4 −/− mice. Only ΔznuA B. melitensis - and Rev-1-vaccinated CD4 −/− and wild-type mice, not CD8 −/− mice, were completely protected against Brucella challenge. Determination of cytokines responsible for conferring protection showed the relative importance of IFN-γ, but not interleukin-17 (IL-17). Unlike wild-type (wt) mice, IL-17 was greatly induced in IFN-γ −/− mice, but IL-17 could not substitute for IFN-γ's protection, although an increase in brucellae dissemination was observed upon in vivo IL-17 neutralization. These results show that nasal ΔznuA B. melitensis vaccination represents an attractive means to stimulate systemic and mucosal immune protection via CD8 + T-cell engagement.

There remains a need for an improved livestock vaccine for brucellosis since conventional vaccines are only ∼70% efficacious, making some vaccinated animals susceptible to Brucella infections. To address this void, a vaccine capable of evoking protective immunity, while still being sufficiently attenuated to produce minimal disease, is sought. In this pursuit, the ΔnorD ΔznuA B. abortus-lacZ (termed as znBAZ) was developed to be devoid of functional norD and znuA B. abortus genes, and to contain the lacZ as a marker gene. The results show that znBAZ is highly attenuated in mouse and human macrophages, and completely cleared from mouse spleens within eight weeks post-vaccination. Producing less splenic inflammation, znBAZ is significantly more protective than the conventional RB51 vaccine by more than four orders of magnitude. Vaccination with znBAZ elicits elevated numbers of IFN-γ+, TNF-α+, and polyfunctional IFN-γ+ TNF-α+ CD4+ and CD8+ T cells in contrast to RB51-vaccinated mice, which show reduced numbers of proinflammatory cytokine-producing T cells. These results demonstrate that znBAZ is a highly efficacious vaccine candidate capable of eliciting diverse T cell subsets that confer protection against parenteral challenge with virulent, wild-type B. abortus.

Brucellosis is the most common zoonotic disease worldwide, usually transmitted from Brucella-infected livestock after consumption of contaminated foods or by aerosol exposure. Since no vaccines for humans are available, we developed a live, double-mutant Brucella abortus (BADM) strain, that after mucosal vaccination, confers complete protection, but abated in IFN-γ−/− mice. Pulmonary infection of naive mice with wild-type BA fails to recruit innate and adaptive lymphocytes to the lungs. Thus, we hypothesize that BADM’s protection is tied to innate cell stimulation. To test this hypothesis, 5 days after nasal BADM vaccination, mice showed increased lung IFN-γ-producing ILCs and EOMES+ NK cells by 3- and 6-fold, respectively; CD4+ and CD8+ T cells increased 3- and 5-fold, respectively. By 2 wks, CD8+ T cells were the dominant IFN-γ source, being 15-fold > naive lungs. After pulmonary challenge, BADM-vaccinated lungs showed fewer CD4+ T cells, but a net increase in CD8+ T cells unlike naive mice, showed no differences in their numbers of CD4+ and CD8+ T cells. To assess if NK cells impact CD8+ T cells, vaccinated mice treated with anti-asialo GM1 Ab to deplete their NK cells, resulted in increased splenic weights, but reduced lung neutrophil influx 5 days after vaccination relative to isotype-treated, vaccinated mice. By 14 days, NK cell depletion reduced by 4-fold (P<0.001) the IFN-γ-producing CD8+ T cells. Thus, NK cell recruitment enhances protection to pulmonary BA in BADM-vaccinated, but not naive mice, which fail to activate NK cells. Supported by NIH AI123244.

Brucella spp. are zoonotic, facultative intracellular pathogens, which cause animal and human disease. Animal disease results in abortion of fetuses; in humans, it manifests flu-like symptoms with an undulant fever, with osteoarthritis as a common complication of infection. Antibiotic regimens for human brucellosis patients may last several months and are not always completely effective. While there are no vaccines for humans, several licensed live Brucella vaccines are available for use in livestock. The performance of these animal vaccines is dependent upon the host species, dose, and route of immunization. Newly engineered live vaccines, lacking well-defined virulence factors, retain low residual virulence, are highly protective, and may someday replace currently used animal vaccines. These also have possible human applications. Moreover, due to their enhanced safety and efficacy in animal models, subunit vaccines for brucellosis show great promise for their application in livestock and humans. This review summarizes the progress of brucellosis vaccine development and presents an overview of candidate vaccines.

Sublingual (s.l.) vaccination is an efficient way to induce elevated levels of systemic and mucosal immune responses. To mediate mucosal uptake, ovalbumin (OVA) was genetically fused to adenovirus 2 fiber protein (OVA-Ad2F) to assess whether s.l. immunization was as effective as an alternative route of vaccination. Ad2F-delivered vaccines were efficiently taken up by dendritic cells and migrated mostly to submaxillary gland lymph nodes, which could readily stimulate OVA-specific CD4+ T cells. OVA-Ad2F + cholera toxin (CT)-immunized mice elicited significantly higher OVA-specific serum IgG, IgA and mucosal IgA antibodies among the tested immunization groups. These were supported by elevated OVA-specific IgG and IgA antibody-forming cells. A mixed Th-cell response was induced as evident by the enhanced IL-4, IL-10, IFN-γ and TNF-α-specific cytokine-forming cells. To assess whether this approach can stimulate neutralizing antibodies, immunizations were performed with the protein encumbering the β-trefoil domain of C-terminus heavy chain (Hcβtre) from botulinum neurotoxin A (BoNT/A) as well as when fused to Ad2F. Hcβtre-Ad2F + CT-dosed mice showed the greatest serum IgG, IgA and mucosal IgA titers among the immunization groups. Hcβtre-Ad2F alone also induced elevated antibody production in contrast to Hcβtre alone. Plasma from Hcβtre + CT- and Hcβtre-Ad2F + CT-immunized groups neutralized BoNT/A and protected mice from BoNT/A intoxication. Most importantly, Hcβtre-Ad2F + CT-immunized mice were protected from BoNT/A intoxication relative to Hcβtre + CT-immunized mice, which only showed ∼60% protection. This study shows that s.l. immunization with Ad2F-based vaccines is effective in conferring protective immunity.

ABSTRACT Zoonotic transmission of brucellosis often results from exposure to Brucella -infected livestock, feral animals, or wildlife or frequently via consumption of unpasteurized milk products or raw meat. Since natural infection of humans often occurs by the oral route, mucosal vaccination may offer a means to confer protection for both mucosal and systemic tissues. Significant efforts have focused on developing a live brucellosis vaccine, and deletion of the znuA gene involved in zinc transport has been found to attenuate Brucella abortus . A similar mutation has been adapted for Brucella melitensis and tested to determine whether oral administration of Δ znuA B. melitensis can confer protection against nasal B. melitensis challenge. A single oral vaccination with Δ znuA B. melitensis rapidly cleared from mice within 2 weeks and effectively protected mice upon nasal challenge with wild-type B. melitensis 16M. In 83% of the vaccinated mice, no detectable brucellae were found in their spleens, unlike with phosphate-buffered saline (PBS)-dosed mice, and vaccination also enhanced the clearance of brucellae from the lungs. Moreover, vaccinated gamma interferon-deficient (IFN-γ −/− ) mice also showed protection in both spleens and lungs, albeit protection that was not as effective as in immunocompetent mice. Although IFN-γ, interleukin 17 (IL-17), and IL-22 were stimulated by these live vaccines, only RB51-mediated protection was codependent upon IL-17 in BALB/c mice. These data suggest that oral immunization with the live, attenuated Δ znuA B. melitensis vaccine provides an attractive strategy to protect against inhalational infection with virulent B. melitensis .

Brucella abortus remains a threat to the health and well-being of livestock in states bordering the Greater Yellowstone Area. During the past several years, cohabitation of infected wildlife with cattle has jeopardized the brucellosis-free status of Idaho, USA; Wyoming, USA; and Montana, USA. Current livestock B. abortus vaccines have not proven to be efficacious in bison (Bison bison) or elk (Cervus elaphus nelsoni). One problem with the lack of vaccine efficacy may stem from the failure to understand wildlife immune responses to vaccines. In an attempt to understand their immune responses, bison were vaccinated with eukaryotic DNA expression vectors encoding the Brucella periplasmic protein, bp26, and the chaperone protein, trigger factor (TF). These DNA vaccines have previously been shown to be protective against Brucella infection in mice. Bison were immunized intramuscularly at weeks 0, 2, and 4 with bp26 and TF DNA vaccines plus CpG adjuvant or empty vector (control) plus CpG. Blood samples were collected before vaccination and at 8, 10, and 12 wk after primary vaccination. The results showed that bison immunized with bp26 and TF DNA vaccines developed enhanced antibody, proliferative T cell, and interferon-gamma (IFN-γ) responses upon in vitro restimulation with purified recombinant bp26 or TF antigens, unlike bison immunized with empty vector. Flow cytometric analysis revealed that the percentages of CD4(+) and CD8(+) T lymphocytes from the DNA-vaccinated groups were significantly greater than they were for those bison given empty vector. These data suggest that DNA vaccination of bison may elicit strong cellular immune responses and serve as an alternative for vaccination of bison for brucellosis.

Brucella abortus remains a threat to the health and well-being of livestock in states bordering the Greater Yellowstone Area. During the past several years, cohabitation of infected wildlife with cattle has jeopardized the brucellosis-free status of Idaho, USA; Wyoming, USA; and Montana, USA. Current livestock B. abortus vaccines have not proven to be efficacious in bison (Bison bison) or elk (Cervus elaphus nelsoni). One problem with the lack of vaccine efficacy may stem from the failure to understand wildlife immune responses to vaccines. In an attempt to understand their immune responses, bison were vaccinated with eukaryotic DNA expression vectors encoding the Brucella periplasmic protein, bp26, and the chaperone protein, trigger factor (TF). These DNA vaccines have previously been shown to be protective against Brucella infection in mice. Bison were immunized intramuscularly at weeks 0, 2, and 4 with bp26 and TF DNA vaccines plus CpG adjuvant or empty vector (control) plus CpG. Blood samples were collected before vaccination and at 8, 10, and 12 wk after primary vaccination. The results showed that bison immunized with bp26 and TF DNA vaccines developed enhanced antibody, proliferative T and interferon-gamma (IFN-gamma) responses upon in vitro restimulation with purified recombinant bp26 or TF antigens, unlike bison immunized with empty vector. Flow cytometric analysis revealed that the percentages of CD4(+) and CD8(+) T lymphocytes from the DNA-vaccinated groups were significantly greater than they were for those bison given empty vector. These data suggest that DNA vaccination of bison may elicit strong cellular immune responses and serve as an alternative for vaccination of bison for brucellosis.

Background: Immunization with recombinant carboxyl-terminal domain of the heavy chain (Hc domain) of botulinum neurotoxin (BoNT) stimulates protective immunity against native BoNT challenge. Most studies developing a botulism vaccine have focused on the whole Hc; however, since the principal protective epitopes are located within beta-trefoil domain (Hc beta tre), we hypothesize that immunization with the Hc beta tre domain is sufficient to confer protective immunity. In addition, enhancing its uptake subsequent to nasal delivery prompted development of an alternative vaccine strategy, and we hypothesize that the addition of targeting moiety adenovirus 2 fiber protein (Ad2F) may enhance such uptake during vaccination.Results: The Hc beta tre serotype B immunogen was genetically fused to Ad2F (Hc beta tre/B-Ad2F), and its immunogenicity was tested in mice. In combination with the mucosal adjuvant, cholera toxin (CT), enhanced mucosal IgA and serum IgG Ab titers were induced by nasal Hc beta tre-Ad2F relative to Hc beta tre alone; however, similar Ab titers were obtained upon intramuscular immunization. These BoNT/B-specific Abs induced by nasal immunization were generally supported in large part by Th2 cells, as opposed to Hc beta tre-immunized mice that showed more mixed Th1 and Th2 cells. Using a mouse neutralization assay, sera from animals immunized with Hc beta tre and Hc beta tre-Ad2F protected mice against 2.0 LD50.Conclusion: These results demonstrate that Hc beta tre-based immunogens are highly immunogenic, especially when genetically fused to Ad2F, and Ad2F can be exploited as a vaccine delivery platform to the mucosa.