Showing papers on "Anthrax vaccines published in 2018"

A Bacteriophage T4 Nanoparticle-Based Dual Vaccine against Anthrax and Plague

Abstract: Bacillus anthracis and Yersinia pestis, the causative agents of anthrax and plague, respectively, are two of the deadliest pathogenic bacteria that have been used as biological warfare agents. Although Biothrax is a licensed vaccine against anthrax, no Food and Drug Administration-approved vaccine exists for plague. Here, we report the development of a dual anthrax-plague nanoparticle vaccine employing bacteriophage (phage) T4 as a platform. Using an in vitro assembly system, the 120- by 86-nm heads (capsids) of phage T4 were arrayed with anthrax and plague antigens fused to the small outer capsid protein Soc (9 kDa). The antigens included the anthrax protective antigen (PA) (83 kDa) and the mutated (mut) capsular antigen F1 and the low-calcium-response V antigen of the type 3 secretion system from Y. pestis (F1mutV) (56 kDa). These viral nanoparticles elicited robust anthrax- and plague-specific immune responses and provided complete protection against inhalational anthrax and/or pneumonic plague in three animal challenge models, namely, mice, rats, and rabbits. Protection was demonstrated even when the animals were simultaneously challenged with lethal doses of both anthrax lethal toxin and Y. pestis CO92 bacteria. Unlike the traditional subunit vaccines, the phage T4 vaccine uses a highly stable nanoparticle scaffold, provides multivalency, requires no adjuvant, and elicits broad T-helper 1 and 2 immune responses that are essential for complete clearance of bacteria during infection. Therefore, phage T4 is a unique nanoparticle platform to formulate multivalent vaccines against high-risk pathogens for national preparedness against potential bioterror attacks and emerging infections. IMPORTANCE Following the deadly anthrax attacks of 2001, the Centers for Disease Control and Prevention (CDC) determined that Bacillus anthracis and Yersinia pestis that cause anthrax and plague, respectively, are two Tier 1 select agents that pose the greatest threat to the national security of the United States. Both cause rapid death, in 3 to 6 days, of exposed individuals. We engineered a virus nanoparticle vaccine using bacteriophage T4 by incorporating key antigens of both B. anthracis and Y. pestis into one formulation. Two doses of this vaccine provided complete protection against both inhalational anthrax and pneumonic plague in animal models. This dual anthrax-plague vaccine is a strong candidate for stockpiling against a potential bioterror attack involving either one or both of these biothreat agents. Further, our results establish the T4 nanoparticle as a novel platform to develop multivalent vaccines against pathogens of high public health significance.

Trimethyl Chitosan Nanoparticles Encapsulated Protective Antigen Protects the Mice Against Anthrax.

Abstract: Anthrax is an era old deadly disease against which there are only two currently available licensed vaccines named Anthrax Vaccine Adsorbed (AVA) and precipitated (AVP). Though they can provide a protective immunity, their multiple side-effects owing to their ill-defined composition and presence of toxic proteins (LF and EF) of Bacillus anthracis, the causative organism of anthrax, in the vaccine formulation makes their widespread use objectionable. Hence, an anthrax vaccine that contains well-defined and controlled components would be highly desirable. In this context, we have evaluated the potential of various vaccine formulations comprising of Protective Antigen (PA) encapsulated trimethyl-chitosan nanoparticles (TMC-PA) in conjunction with either CpG-C ODN 2395(CpG) or Poly I:C. Each formulation was administered via three different routes, viz., subcutaneous (SC), intramuscular (IM) and intraperitoneal (IP) in female BALB/c mice. Irrespective of the route of immunization, CpG or Poly I:C adjuvanted TMC-PA nanoparticles induced a significantly higher humoral response (total serum IgG and its isotypes viz., IgG1, IgG2a, and IgG2b), compared to their CpG or Poly I:C PA counterparts. This clearly demonstrates the synergistic behavior of CpG and Poly I:C with TMC nanoparticles. The adjuvant potential of TMC nanoparticles could be observed in all the three routes as the TMC-PA nanoparticles by themselves induced IgG titers (1-1.5 x105) significantly higher than both CpG PA and Poly I:C PA groups (2-8x104). The effect of formulations on T-helper (Th) cell development was assessed by quantifying the Th1-dependant (TNF-α, IFN-γ, and IL-2), Th2-dependant (IL-4, IL-6, and IL-10) and Th17-type (IL-17A) cytokines. Adjuvanation with CpG and Poly I:C, the TMC-PA nanoparticles triggered a Th1 skewed immune response, as suggested by an increase in the levels of total IgG2a along with IFN-γ cytokine production. Interestingly, the TMC-PA group showed a Th2 biased immune response. Upon challenge with the Bacillus anthracis Ames strain, CpG and Poly I:C adjuvanted TMC-PA nanoparticles immunized via the SC and IM routes showed the highest protective efficacy of ~83%. Altogether the results suggest that CpG or Poly I:C adjuvanted, PA-loaded TMC nanoparticles could be used as an effective, non-toxic, 2nd generation subunit-vaccine candidate against anthrax.

Dual anthrax-plague vaccines that can protect against two tier-1 bioterror pathogens, Bacillus anthracis and Yersinia pestis

Abstract: Bivalent immunogenic compositions against anthrax and plague are disclosed herein. One bivalent immunogenic composition comprises a triple fusion protein containing three antigens, F1 and V from Yersinia pestis and PA antigen from Bacillus anthracia fused in-frame and retaining structural and functional integrity of all three antigens. Another bivalent immunogenic composition comprises bacteriophage nanoparticles arrayed with these three antigens on the capsid surface of the bacteriophage nanoparticles. These bivalent immunogenic compositions are able to elicit robust immune response in a subject administered said the bivalent immunogenic compositions and provide protection to the subject against sequential or simultaneous challenge with both anthrax and plague pathogens.

Single vector platform vaccine protects against lethal respiratory challenge with Tier 1 select agents of anthrax, plague, and tularemia

Abstract: Bacillus anthracis, Yersinia pestis, and Francisella tularensis are the causative agents of Tier 1 Select Agents anthrax, plague, and tularemia, respectively. Currently, there are no licensed vaccines against plague and tularemia and the licensed anthrax vaccine is suboptimal. Here we report F. tularensis LVS ΔcapB (Live Vaccine Strain with a deletion in capB)- and attenuated multi-deletional Listeria monocytogenes (Lm)-vectored vaccines against all three aforementioned pathogens. We show that LVS ΔcapB- and Lm-vectored vaccines express recombinant B. anthracis, Y. pestis, and F. tularensis immunoprotective antigens in broth and in macrophage-like cells and are non-toxic in mice. Homologous priming-boosting with the LVS ΔcapB-vectored vaccines induces potent antigen-specific humoral and T-cell-mediated immune responses and potent protective immunity against lethal respiratory challenge with all three pathogens. Protection against anthrax was far superior to that obtained with the licensed AVA vaccine and protection against tularemia was comparable to or greater than that obtained with the toxic and unlicensed LVS vaccine. Heterologous priming-boosting with LVS ΔcapB- and Lm-vectored B. anthracis and Y. pestis vaccines also induced potent protective immunity against lethal respiratory challenge with B. anthracis and Y. pestis. The single vaccine platform, especially the LVS ΔcapB-vectored vaccine platform, can be extended readily to other pathogens.

Immunogenicity of anthrax recombinant peptides and killed spores in goats and protective efficacy of immune sera in A/J mouse model

Abstract: Anthrax is primarily recognized as an affliction of herbivores with incubation period ranging from three to five days post-infection. Currently, the Sterne live-spore vaccine is the only vaccine approved for control of the disease in susceptible animals. While largely effective, the Sterne vaccine has several problems including adverse reactions in sensitive species, ineffectiveness in active outbreaks and incompatibility with antibiotics. These can be surmounted with the advent of recombinant peptides (non-living) next generation vaccines. The candidate vaccine antigens comprised of recombinant protective antigen (PA), spore-specific antigen (bacillus collagen-like protein of anthracis, BclA) and formaldehyde inactivated spores (FIS). Presently, little information exists on the protectivity of these novel vaccine candidates in susceptible ruminants. Thus, this study sought to assess the immunogenicity of these vaccine candidates in goats and evaluate their protectivity using an in vivo mouse model. Goats receiving a combination of PA, BclA and FIS yielded the highest antibody and toxin neutralizing titres compared to recombinant peptides alone. This was also reflected in the passive immunization experiment whereby mice receiving immune sera from goats vaccinated with the antigen combination had higher survival post-challenge. In conclusion, the current data indicate promising potential for further development of non-living anthrax vaccines in ruminants.

A bivalent protein r-PB, comprising PA and BclA immunodominant regions for comprehensive protection against Bacillus anthracis

Abstract: Anthrax infection is primarily initiated by B. anthracis endospores that on entry into the host germinate to vegetative cells and cause severe bacteremia and toxaemia employing an array of host colonisation factors and the lethal tripartite toxin. The protective efficacy of conventional protective antigen (PA) based anthrax vaccines is improved by co-administration with inactivated spores or its components. In the present study, using structural vaccinology rationale we synthesized a bivalent protein r-PB encompassing toxin (PAIV) and spore components (BclACTD) and characterized its protective efficacy against B. anthracis infection. Active immunization of mice with r-PB generated high titer circulating antibodies which facilitated the phagocytic uptake of spores, inhibited their germination to vegetative cells and completely neutralized anthrax toxins in vivo resulting in 100 % survival against anthrax toxin challenge. Proliferation of CD4+ T cell subsets with up-regulation of Th1 (IFN-γ, IL-2, and IL-12), Th2 (IL-5, IL-10) cytokines and balanced expression of IgG1:IgG2a antibody isotypes indicated the stimulation of both Th1 and Th2 subsets. The immunized mice exhibited 100 % survival upon challenge with B. anthracis spores or toxin indicating the ability of r-PB to provide comprehensive protection against anthrax. Our results thus demonstrate r-PB an efficient vaccine candidate against anthrax infection.

Toll-like receptor 4 signalling regulates antibody response to adenoviral vector-based vaccines by imprinting germinal centre quality.

Abstract: Adenoviral vectors (AdV) are considered promising candidates for vaccine applications. A prominent group of Toll-like receptors (TLRs) participate in the adenovirus-induced adaptive immune response, yet there is little information regarding the role of TLR4 in AdV-induced immune responses in recent literature. We investigated the function of TLR4 in both adaptive and innate immune responses to an AdV-based anthrax vaccine. By immunizing wild-type and TLR4 knockout (TLR4-KO) mice, we revealed the requirement of TLR4 in AdV-induced innate responses. We also showed that TLR4 functions are required for germinal centre responses in immunized mice, as expression of the apoptosis-related marker Fas was down-regulated on germinal centre B cells from TLR4-KO mice. Likewise, decreased expression of inducible costimulator on follicular T helper cells was observed in immunized TLR4-KO mice. Moreover, a potent protective antigen-specific humoral immune response was mimicked using an adjuvant system containing the TLR4 agonist monophosphoryl lipid A. Overall, our findings showed that very rapid antigen-specific antibody production is correlated with the TLR4-imprinted germinal centre response to AdV-based vaccine. These results provide additional evidence for the use of the AdV and a TLR agonist to induce humoral responses. Our findings offer new insights into rational vaccine design.

Immunological Efficacy and Safety of Synthesized CpG Oligodeoxynucleotides

Abstract: The technology for synthesis is described, and the adjuvant properties of CpG oligodeoxynucleotides (CpG-ODNs) are assessed. CpG-ODN sequences were generated according to the available sequences on an automatic synthesizer. The adjuvant activity was evaluated with CpG-ODNs in combination with a recombinant protective antigen and EA1, an S-layer protein of the anthrax agent. It was established that the use of the synthesized adjuvant CpG 2006, along with immunogenic antigens, leads to the development of long-term, high-level immunity in test animals. The synthetic CpG 2006 antigenic product was shown to have an advantage over alhydrogel in terms of adjuvant activity. Experiments on biomodels provided data confirming the absence of toxic and damaging effects of CpG-ODNs on cells and tissues of the macroorganism. Comparison of the cell-mediated immunity (content of CD4+ and CD8+) after immunization by the B. anthracis STI-1 strain or a recombinant anthrax vaccine prototype with CpG 2006 or alhydrogel as an adjuvant is evidence of the activation of the cellular component of the immune system in all of the compared groups.

Effect of Antigens Obtained from the Recombinant Strain Bacillus anthracis 55ΔTPA-1Spo – on Organs and Tissues of Immunized Animals

Abstract: The recombinant B. anthracis strain 55ΔTPA-1Spo– was used for the development and trial of a method for the simultaneous production of immunogenic anthrax antigens, a protective antigen, and the EA1 protein of the S layer, which are components of a prototype anthrax vaccine. The proposed method includes inoculum preparation, cultivation in liquid medium without antibiotics, sterilizing filtration, concentration, diafiltration, and chromatographic purification on various carriers. This method provides for a high yield of both target products. The purified antigens (alone or in combination with each other) were shown to have no toxic effect on organs and tissues of vaccinated laboratory animals in amounts that were several times higher than immunizing doses. The minor changes revealed by histological examination reflect the adaptation-compensatory reactions of the macroorganism and tend to normalize. The response of immune-competent organs corresponded to moderate development of immunogenesis. The addition of EA1 protein to the recombinant protective antigen resulted in an increase in the expression of the genes determining TLR of innate immunity. Immunization of laboratory animals with the combined preparation caused more pronounced immunobiological alterations in lymphoid organs than the use of only the protective antigen.