Vaccination with a ΔnorD ΔznuA Brucella abortus mutant confers potent protection against virulent challenge

Abstract

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.

Targeting resident memory T cell immunity culminates in pulmonary and systemic protection against Brucella infection

“…Hence, protection conferred by znBAZ is not solely attributed to being a smooth vaccine, but is associated more with its altered pathogenicity as a result of the absence of znuA and norD genes. Despite its difference from RB51, the znBAZ clearance rate is similar to that of RB51, while S19 is retained longer and not cleared as effectively from the host [19]. The protection conferred by S19 is equivalent to RB51, and also found to be CD4 + , not CD8 + T cell-dependent, and S19 was not able to confer complete protection as does znBAZ (manuscript in preparation).…”

“…To counter mucosal exposures to Brucella, we queried whether mucosal vaccination with znBAZ would prove efficacious against pulmonary challenge with virulent B. abortus. When administered by the intraperitoneal route, two doses of znBAZ were found to be required for optimal protection [19]. In light of this, groups of BALB/c mice were orally primed on day 0 and nasally boosted on day 28 with znBAZ, RB51, or sPBS.…”

“…The importance of the T cell subsets varies by the route of immunization and the vaccine components [11][12][13][14][15][16][17][18]. Recent reports showed that mucosal exposure to this pathogen stimulates IFN-γ-producing CD8 + T cells for protection against brucellosis, not by their cytotoxic function [19][20][21][22][23].…”

Development of new generation of vaccines for Brucella abortus

“…Deletion of B. abortus 2308 norD and high affinity zinc uptake system (znuA) genes cause sufficient attenuation of the strain in mouse and human cell studies. Moreover, in contrast to classic RB51 vaccinated groups, this live recombinant strain efficiently increased T cells and pro-inflammatory cytokines [77]. Based on these observations, further evaluation of this candidate vaccine in cattle is need for highlighted potency and safety.…”

Alternative strategies for vaccination to brucellosis

“…Immunity to Brucella requires the stimulation of IFN-γ for protection as evidenced by disease exacerbation and impotency of vaccines in IFN-γ -/- mice [49-51]. The source of IFN- γ can be CD4 + [51-59], CD8 + T cells [50, 58-60], or both [61]. Both T cell subset responses have been studied after Brucella infections in various immunization and challenge paradigms, but their role in Brucella infections remains controversial.…”