Immunogenic response induced by wzm and wzt gene deletion mutants from Brucella abortus S19

Brucella melitensis Wzm/Wzt System: Changes in the Bacterial Envelope Lead to Improved Rev1Δwzm Vaccine Properties

The lipopolysaccharide (LPS) O-polysaccharide (O-PS) is the main virulence factor in Brucella. After synthesis in the cytoplasmic membrane, O-PS is exported to the periplasm by the Wzm/Wzt system, where it is assembled into a LPS. This translocation also engages a bactoprenol carrier required for further biosynthesis pathways, such as cell wall biogenesis. Targeting O-PS export by blockage holds great potential for vaccine development, but little is known about the biological implications of each Wzm/Wzt moiety. To improve this knowledge and to elucidate its potential application as a vaccine, we constructed and studied wzm/wzt single- and double-deletion mutants, using the attenuated strain Brucella melitensis Rev1 as the parental strain. This allowed us to describe the composition of Brucella peptidoglycan for the first time. We observed that these mutants lack external O-PS yet trigger changes in genetic transcription and in phenotypic properties associated with the outer membrane and cell wall. The three mutants are highly attenuated; unexpectedly, Rev1Δwzm also excels as an immunogenic and effective vaccine against B. melitensis and Brucella ovis in mice, revealing that low persistence is not at odds with efficacy. Rev1Δwzm is attenuated in BeWo trophoblasts, does not infect mouse placentas, and is safe in pregnant ewes. Overall, these attributes and the minimal serological interference induced in sheep make Rev1Δwzm a highly promising vaccine candidate.

Development of new generation of vaccines for Brucella abortus

Brucella abortus is a Gram-negative facultative and intracellular bacteria, it causes bovine brucellosis, a zoonotic disease that is responsible for considerable economic loss to owners of domesticated animals and can cause problems in otherwise healthy humans. There are a few available live attenuated vaccines for animal immunization against brucellosis; however, these have significant side effects and offer insufficient protective efficacy. Thus, the need for more research into the Molecular pathobiology and immunological properties of B. abortus that would lead to the development of better and safer vaccines. In this paper we have reviewed the main aspects of the pathology and the responsive immunological mechanisms, we have also covered current and new prospective vaccines against B. abortus.

Newcastle disease virus-like particles induce dendritic cell maturation and enhance viral-specific immune response

Circulating of genotype VII Newcastle disease virus (NDV) is a great threat to the poultry industry worldwide. Virus-like particles (VLPs) are increasingly being considered as potential viral vaccines due to their safety and efficacy. In this study, we analyzed in vitro the stimulatory effects of VLPs containing the matrix and hemagglutinin-neuraminidase of genotype VII NDV on dendritic cells (DCs) and evaluated their immunogenicity in mice. The results showed that immature bone marrow-derived dendritic cells (BMDCs) responded to stimulation with VLPs by up-regulating expressions of MHC II, CD40, CD80, and CD86 molecules and by increasing the cytokine secretions of TNF-α, IFN-γ, IL-6, and IL-12p70. Besides, VLPs enhanced the immunostimulatory capacity of DCs to stimulate autologous T cell proliferation. Furthermore, VLPs can induce efficient humoral and cellular immune responses, and recruit mature DCs to the spleen in C57BL/6 mice, as shown by an obvious increase in double-positive proliferation of splenic CD11c+CD86+ cells. These data indicate that NDV VLPs can be a valuable candidate for NDV vaccine development.

A safe and molecular-tagged Brucella canis ghosts confers protection against virulent challenge in mice

Canine brucellosis, caused by Brucella canis, is a persistent infectious reproductive disease in dogs. The absence of effective treatment to the intracellular pathogen and the irreversible consequence of infection makes the need of a specific vaccine urgent. Bacterial ghosts (BGs) are the empty envelopes of bacteria with no genome content inside, which emerge as a proper vaccine candidate due to its intact outer antigen. It is generally derived from a genetically engineered strain, through the expression of Bacteriophage phiX174 lysis E gene upon induction. In this study, we combined the homologous recombination (HR) and bacterial ghost technologies, generating a genetically stable B. canis ghost strain which bears no drug resistance gene. When the ghost strain grows to OD₆₀₀ of 0.6, 100% inactivation can be achieved under 42°C in 60h. The resultant BGs showed guaranteed safety and comparable immunogenicity to a live vaccine. The bacterial B0419 protein was depleted during HR process, which is subsequently proved to work as a molecular tag in distinguishing natural infection and BGs immunization through ELISA. Additionally, the BGs also conferred protection against B. canis RM6/66 and B. melitensis 16M. Therefore, the application of current BGs as a vaccine candidate and the corresponding serological diagnostic approach may provide better B. canis prevention strategy.