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

Mangrove Helps: Sonneratia alba-Synthesized Silver Nanoparticles Magnify Guppy Fish Predation Against Aedes aegypti Young Instars and Down-Regulate the Expression of Envelope (E) Gene in Dengue Virus (Serotype DEN-2)

The control of dengue vectors with effective tools is crucial. Here, we fabricated silver nanoparticles (AgNP) using a cheap method relying to a mangrove extract (Sonneratia alba) as a reducing and stabilizing agent. AgNP were charac- terized by UV–vis spectroscopy, Fourier transform infrared spectroscopy, scanning electron microscopy and X-ray diffraction. LC50 of S. alba extract against Aedes aegypti ranged from 192.03 ppm (larva I) to 353.36 ppm (pupa). LC50 of AgNP ranged from 3.15 (I) to 13.61 ppm (pupa). Sub-lethal doses of AgNP magnified predation rates of guppy fishes, Poecilia reticulata, against Ae. aegypti and Chi- ronomus kiiensis larvae. Mangrove-fabricated AgNP were evaluated for their antimicrobial potential against Bacillus subtilis, Klebsiella pneumoniae, and Sal- monella typhi, using the agar disc diffusion and minimum inhibitory concentration protocol. Notably, S. alba-synthesized AgNP tested at doses ranging from 5 to 15 lg/mL down-regulated the expression of the envelope (E) gene and protein in dengue virus (serotype DEN-2), while only little cytotoxicity rates (i.e.\15%) were detected on Vero cells when AgNP were tested at 10 lg/mL. Overall, this study pointed out the potential of S. alba-synthesized AgNP to develop eco-friendly nanoformulations effective against dengue virus and its mosquito vectors