Intranasal administration of a two-dose adjuvanted multi-antigen TMV-subunit conjugate vaccine fully protects mice against Francisella tularensis LVS challenge

Abstract

Tularemia is a fatal human disease caused by Francisella tularensis, a Gram-negative encapsulated coccobacillus bacterium. Due to its low infectious dose, ease of aerosolized transmission, and lethal effects, the CDC lists F. tularensis as a Category A pathogen, the highest level for a potential biothreat agent. Previous vaccine studies have been conducted with live attenuated, inactivated, and subunit vaccines, which have achieved partial or full protection from F. tularensis live vaccine strain (LVS) challenge, but no vaccine has been approved for human use. We demonstrate the improved efficacy of a multi-antigen subunit vaccine by using Tobacco Mosaic virus (TMV) as an antigen carrier for the F. tularensis SchuS4 proteins DnaK, OmpA, SucB and Tul4 (DOST). The magnitude and quality of immune responses were compared after mice were immunized by subcutaneous or intranasal routes of administration with a TMV-DOST mixture, with or without four different adjuvants. Immune responses varied in magnitude and isotype profile, by antigen, by route of administration, and by protection in an F. tularensis LVS challenge model of disease. Interestingly, our analysis demonstrates an overwhelming IgG2 response to SucB after intranasal dosing, as well as a robust cellular response, which may account for the improved two-dose survival imparted by the tetravalent vaccine, compared to a previous study that tested efficacy of TMV-DOT. Our study provides evidence that potent humoral, cellular and mucosal immunity can be achieved by optimal antigen combination, delivery, adjuvant and appropriate route of administration, to improve vaccine potency and provide protection from pathogen challenge.

An O-Antigen Glycoconjugate Vaccine Produced Using Protein Glycan Coupling Technology Is Protective in an Inhalational Rat Model of Tularemia

“…Whilst no single peptide antigen has been shown to be protective as a vaccine candidate for F. tularensis type A strains in mice, several recombinant F. tularensis proteins have been shown to invoke a cellular immune response [37–39]. Moreover, encapsulated recombinant peptide antigens [40], and recently a multiantigen Tobacco Mosaic virus-based vaccine [41], have been shown to protect against lethal LVS challenge to mice. An F. tularensis antigen expressed as part of a whole cell vaccine platform has also been shown to boost efficacy of a live attenuated vaccine [13].…”

Nanoparticle-Based Vaccines Against Respiratory Viruses

“…Studies have demonstrated that vaccination via the intranasal route provides a better protection when compared to subcutaneous immunization in the context of respiratory pathogens and mucosal immunity. Intranasal vaccination led to higher antigen-specific lymphocyte proliferation, cytokine production (interferon-γ, interleukins) and induction of antigenspecific IgA antibody (70)(71)(72)(73)(74). A promising formulation strategy is the intranasal spray, which delivers conveniently and safely the nanovaccines directly to the respiratory mucosa (75)(76)(77).…”

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.…”