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

Abstract

Francisella tularensis is 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. tularensis SchuS4 strain. Two different vaccine formulations and immunization schedules were used. The immunized mice were challenged with lethal (10xLD100) doses of F. tularensis LVS 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. tularensis antigens. 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. tularensis proteins 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.

Evaluation of Francisella tularensis ΔpdpC as a candidate live attenuated vaccine against respiratory challenge by a virulent SCHU P9 strain of Francisella tularensis in a C57BL/6J mouse model

“…In addition, under some conditions culture of live vaccine strains can result in emergence of poorly immunogenic variants . Other variant strains with low pathogenicity have recently been developed as vaccines against tularemia .…”

Intranasal delivery of a protein subunit vaccine using a Tobacco Mosaic Virus platform protects against pneumonic plague

“…We hypothesize that direct uptake of the viral particle, albeit a recombinantly expressed plant pathogen, enhances the response to the associated subunit protein by simulate antiviral signaling. This hypothesis is supported by studies demonstrating enhanced protection from respiratory challenge with both F. tularensis and Influenza A [22–24]. L. plantarum is a commensal organism, and may not induce the same level of activation as TMV, though further study is needed to confirm this.…”

“…TMV is a plant virus that cannot infect animals cells, but has been shown to interact with and stimulate mammalian dendritic cells [21]. TMV-conjugate vaccines have demonstrated protection against challenge with Francisella tularensis [22], and Influenza H1N1 [23] and H5N1 [24]. Here we demonstrate that TMV-conjugated to LcrV and F1 conferred protection against lethal pneumonic challenge with Y. pestis.…”

In Preparation for Outdoor Pharming: Griffithsin Can Be Expressed in Nicotiana excelsiana and Retains Activity After Storage as Silage

“…However, GRFT and TMV coat protein were both stable through the process, but they both have pIs below 5.5. Interestingly, TMV has been explored as an antigen carrier in many subunit vaccines and may be another target for silage storage (Mallajosyula et al, 2014;Banik et al, 2015;McCormick et al, 2018). In the future we will evaluate the infectivity of TMV and the stability of the virion to better understand if it would be suitable for antigen presentation.…”