title: Nasal vaccination stimulates CD8(+) T cells for potent protection against mucosal Brucella melitensis challenge.
abstract: 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.
authors.affiliation: Department of Infectious Diseases and Pathology, University of Florida, Gainesville, FL, USA.
authors.forename: Beata
authors.initials: B
authors.lastname: Clapp
authors.affiliation: Department of Infectious Diseases and Pathology, University of Florida, Gainesville, FL, USA.
authors.forename: Xinghong
authors.initials: X
authors.lastname: Yang
authors.affiliation: Department of Microbiology and Immunology, Montana State University, Bozeman, MT, USA.
authors.forename: Theresa
authors.initials: T
authors.lastname: Thornburg
authors.affiliation: Department of Microbiology and Immunology, Montana State University, Bozeman, MT, USA.
authors.forename: Nancy
authors.initials: N
authors.lastname: Walters
authors.affiliation: Department of Infectious Diseases and Pathology, University of Florida, Gainesville, FL, USA.
authors.forename: David W
authors.initials: DW
authors.lastname: Pascual
mesh_terms: D000818:Animals; D001428:Bacterial Vaccines / Q000276:immunology; D017347:Brucella melitensis / Q000502:physiology*; D002006:Brucellosis / Q000276:immunology* / Q000382:microbiology / Q000517:prevention & control*; D015496:CD4-Positive T-Lymphocytes / Q000276:immunology; D018414:CD8-Positive T-Lymphocytes / Q000276:immunology*; D016207:Cytokines / Q000378:metabolism; D005260:Female; D007156:Immunologic Memory; D018836:Inflammation Mediators / Q000378:metabolism; D007371:Interferon-gamma; D008168:Lung / Q000276:immunology / Q000382:microbiology / Q000473:pathology; D008807:Mice, Inbred BALB C; D008810:Mice, Inbred C57BL; D009297:Nasal Mucosa / Q000276:immunology* / Q000382:microbiology* / Q000473:pathology; D013154:Spleen / Q000473:pathology; D014611:Vaccination
chemical_list: D001428:Bacterial Vaccines; D016207:Cytokines; D018836:Inflammation Mediators; D007371:Interferon-gamma