Development of a Multivalent Subunit Vaccine against Tularemia Using Tobacco Mosaic Virus (TMV) Based Delivery System

Francisella tularensisis a facultative intracellular pathogen, and is the causative agent of a fatal human disease known as tularemia. F. tularensis is classified as a Category A Biothreat agent by the CDC based on its use in bioweapon programs by several countries in the past and its potential to be used as an agent of bioterrorism. No licensed vaccine is currently available for prevention of tularemia. In this study, we used a novel approach for development of a multivalent subunit vaccine against tularemia by using an efficient tobacco mosaic virus (TMV) based delivery platform. The multivalent subunit vaccine was formulated to contain a combination of F. tularensis protective antigens: OmpA-like protein (OmpA), chaperone protein DnaK and lipoprotein Tul4 from the highly virulent F. tularensisSchuS4 strain. Two different vaccine formulations and immunization schedules were used. The immunized mice were challenged with lethal (10xLD100) doses of F. tularensisLVS on day 28 of the primary immunization and observed daily for morbidity and mortality. Results from this study demonstrate that TMV can be used as a carrier for effective delivery of multiple F. tularensisantigens. TMV-conjugate vaccine formulations are safe and multiple doses can be administered without causing any adverse reactions in immunized mice. Immunization with TMV-conjugated F. tularensisproteins induced a strong humoral immune response and protected mice against respiratory challenges with very high doses of F. tularensis LVS. This study provides a proof-of-concept that TMV can serve as a suitable platform for simultaneous delivery of multiple protective antigens of F. tularensis. Refinement of vaccine formulations coupled with TMV-targeting strategies developed in this study will provide a platform for development of an effective tularemia subunit vaccine as well as a vaccination approach that may broadly be applicable to many other bacterial pathogens

OmpA, DnaK and Tul4 Specific Antibody Responses in Mice Immunized with TMV-Multiconjugate Vaccines using Schedule I and II of Immunization.

<p><i>F</i>. <i>tularensis</i> SchuS4 recombinant proteins OmpA, DnaK and Tul4 specific IgG, antibody levels on day 28 in serum samples of C57BL/6 mice immunized with TMV-multiconjugate vaccine using Schedule II were determined by ELISA. The plates were coated with recombinant <i>F</i>. <i>tularensis</i> SchuS4 proteins. Serum samples obtained from naïve mice or those inoculated with TMV alone were used as controls. The data are represented as Mean ±S.D. of absorbance values measured at 450nm. The comparisons are shown with the data obtained from mice immunized with TMV-multiconjugate vaccine using schedule I (shown in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0130858#pone.0130858.g007" target="_blank">Fig 7</a>). Table shows comparison of antibody titers between groups of mice vaccinated with Schedule I and II vaccination regimens.</p

Vaccine Formulations.

<p>Two different vaccine formulations were used. In the first vaccine formulation all three recombinant proteins OmpA, DnaK and Tul4 were conjugated to a single TMV virion (TMV-monoconjugate vaccine). The second vaccine formulation contained each recombinant protein of <i>F</i>. <i>tularensis</i> conjugated individually to TMV and then mixed in equal concentrations to generate a TMV-multiconjugate vaccine.</p

Expression and Purification of Recombinant DnaK, OmpA and Tul4 Proteins of <i>F</i>. <i>tularensis</i> SchuS4.

<p>Purification of recombinant OmpA, DnaK and Tul4 proteins of <i>F</i>. <i>tularensis</i> SchuS4 proteins was confirmed by SDS-PAGE and western blot analysis using anti-His antibodies.</p

OmpA, DnaK and Tul4 Specific Antibody Responses in Mice Immunized with TMV-Monoconjugate and TMV-Multiconjugate Vaccines using Schedule I of Immunization.

<p><i>F</i>. <i>tularensis</i> SchuS4 recombinant proteins OmpA, DnaK and Tul4 specific IgG antibody levels on day 28 in serum samples of C57BL/6 mice immunized with TMV-monoconjugate and TMV-multiconjugate vaccine using Schedule I were determined by ELISA. Serum samples obtained from naïve mice or those inoculated with TMV alone were used as controls. The data are represented as Mean ±S.D. of absorbance values measured at 450nm. Table shows comparison of antibody titers between groups of mice vaccinated with these vaccine formulations.</p

Leverage of Salvadora persica and Pulicaria undulata extracts in Escherichia coli-challenged broiler chickens

ABSTRACT: Escherichia coli (E. coli) is a significant challenge in the poultry industry due to their related use of antimicrobial compounds and the drastic losses in production and livability. This study investigated the preventive impacts of dietary supplementation of Salvadora persica (SP) and/or Pulicaria undulata (PU) extracts on growth traits, biochemical and immune parameters, and related gene expression of E. coli-infected broilers. A total of 120 one-day-old Cobb broilers were used. The chicks were allocated into eight equal groups (3 replicates/ group; 5 chicks per each replicate) as follows: G1; control negative, G2; SP-treated, G3; PU-treated, G4; SP/PU-treated, G5; E. coli infected, G6; E. coli infected and SP-treated, G7; E. coli infected and PU-treated, G8; E. coli infected and SP/PU-treated groups. Results revealed significant improvement in average body weight (ABW), average weight gain (AWG) and feed conversion ratio (FCR) in broilers fed diets supplemented with SP and/or PU compared to control and E. coli infected groups. Moreover, significant (P < 0.05) reduction in ALT, AST, creatinine, and uric acid was reported in other treated groups compared to the single E. coli-infected broilers. On the contrary, a significant increase (P < 0.05) in serum immunoglobulin and protein concentration was also reported in treated groups when compared to E. coli-infected untreated group. In addition, feeding broilers with SP and/or PU significantly improved (P < 0.05) the relative weight of immune-related organs and gene expression of TLR-15, with subsequent down-regulation of IL-1β and TNF-α mRNA transcripts. Supplementing broilers with dietary SP and/or PU could be promising in the prevention of E. coli infection via stimulating significant improvement of immune-related gene expression, immune-related organ weight, and down-regulation of inflammatory-related genes, with subsequent enhancement of the growth performance of broiler chickens

Conjugation of DnaK, OmpA and Tul4 Proteins of <i>F</i>. <i>tularensis</i> SchuS4 to TMV.

<p>Purified OmpA, DnaK and Tul4 proteins were combined with purified TMV and incubated with EDC and NHS for 0, 30 min, 1, or 2 hours as described in Methods section. Two μg of TMV or recombinant proteins DnaK, OmpA, Tul4 or 4 μg of the TMV-protein mixtures were resolved on an 8–16% SDS-PAGE gel to observe conjugation products indicated by changes in the molecular masses of the starting materials. <b>(A)</b> Conjugation of DnaK, OmpA and Tul4 to a single TMV virion to generate TMV-monoconjugate vaccine. The progress of conjugation process was observed over a period of time: Lane M = Precision Plus Dual Color standard (BioRad) Marker; Lane 1 = TMV-protein mix, 0 min; Lane 2 = TMV-protein mix, 30 min; Lane 3 = TMV-protein mix,1 hour; Lane 4 = TMV-protein mix, 2 hours. <b>(B, C, D)</b> Kinetics of DnaK, OmpA and Tul4 TMV-protein conjugations over a two hour incubation period to generate TMV-protein conjugates. The individual TMV-protein conjugates were then admixed to generate TMV-multiconjugate vaccine. Lane M = Precision Plus Dual Color standard (BioRad) Marker; Lane 1 = TMV; Lane 2 = Recombinant protein; Lane 3 = TMV-protein mix, 0 hour; Lane 4 = TMV-protein mix, 1 hour; Lane 5 = TMV-protein mix, 2 hours. In all cases, 2 hour time points were used for scale-up and vaccine preparation. Solid arrows indicate TMV-protein conjugate(s), dashed arrows indicate free TMV or free proteins.</p

Protective Efficacy of TMV-Conjugate Vaccine.

<p><b>(A)</b> C57BL/6 mice (N = 8 per group) immunized with TMV-monoconjugate vaccine; <b>(C)</b> with TMV-multiconjugate vaccine (schedule I) or <b>(E)</b> with TMV-multiconjugate vaccine (Schedule II) were challenged i.n. with 10xLD₁₀₀ of <i>F</i>. <i>tularensis</i> LVS on day 28 post-immunization. Mice vaccinated with TMV alone were used as controls. Challenged mice were observed for morbidity and mortality for a period of 21 days post-challenge. The survival results are expressed as Kaplan-Meier survival curves and statistical analysis was performed using Log-rank test. <b>(B, D and F)</b> Body weight of the challenged mice at the indicate time points. The data are represented as Mean ± S.D.</p