F. tularensis is a gram-negative Category A intracellular mucosal pathogen. Cellular immunity is critical for protection against this organism, while antibodies (Abs) delay the progression of infection. Targeting antigen (Ag) to Fc receptors (FcR) on Ag presenting cells (APC) can enhance humoral and cellular immunity. We hypothesize targeting infectious disease Ag, such as inactivated F. tularensis (iFt), to FcR at mucosal sites will enhance protection against mucosal challenge.
In Aim 1, we will investigate the ability of preformed mAb-iFt complexes and mAb plus iFt mixtures, to enhance binding, internalization, and presentation of iFt by APC to Ag-specific T cells, key events in initiating a protective immune response. We will: 1) Examine the impact of mAb:iFt ratio on mAb-iFt-binding, internalization, and Ag presentation by mouse APC;2) Determine, using mouse APC, if mAb plus iFt mixtures can be used in place of preformed mAb-iFt;3) Determine if the above FcR-targeting strategies also enhance IFt-binding, internalization, and presentation by human APC.
In Aim 2, we will determine in mice, the ability of mAb-iFt complexes and/or mAb plus iFt mixtures administered i.n., i.d., i.m., or s.c. to enhance protection against i.n. or i.d challenge with live F. tularensis, and identify the humoral and/or cellular components critical to the observed protection. We will: 1) Verify optimal FcR-mediated binding, internalization, and presentation observed in Aim 1, correlates with optimal protection generated by FcR-targeted immunogens administered i.n.;2) Determine the role of CD8 and CD4 T cells, B cells, FcR, Ab, and IFN-gamma in FcR-dependent protection, using mice lacking these immune components;3) Determine if FcR-targeted iFt preferentially localizes to lymphoid tissues, versus non-targeted iFt;4) Determine if protection against i.n. and i.d. challenge can be generated following peripheral (i.d., i.m., or s.c.) immunization;5) Determine if inclusion of CTB (i.n.) and Alum (i.d., i.m., or s.c.) further enhances protection generated by FcR- targeted immunogens.
In Aim 3, we will validate the flexibility and the multi-pathogen potential of this vaccine platform. Specifically, we will generate an FcR-targeted subunit vaccine (Fc-PspA) against S. pneumoniae, an extracellular mucosal pathogen of significant public health concern. PspA is a surface component of S. pneumoniae, which generates Ab-dependent protection in the presence of adjuvant. We will investigate the ability of mono- and multivalent Fc-PspA conjugates containing variable amounts of PspA, and administered via mucosal and peripheral routes, to protect against i.n. challenge with S. pneumoniae. The significance of the above studies is substantial: 1) New and safer vaccine platforms, which generate both humoral and cellular immunity are needed;2) The latter is particularly evident in the case of mucosal vaccines;3) There is an urgent need for an effective mucosal vaccine against F. tularensis, and a more efficacious vaccine against S. pneumoniae;4) Knowledge regarding the role of FcR in mucosal immunity, and the generation of protection against mucosal pathogens, is lacking. The proposed studies will fill significant gaps in all the above areas.

Public Health Relevance

The significance of the proposed studies to public health is multi-fold. There is a need for new and safer vaccine platforms, in particular as it applies to mucosal immunity. In addition, an effective mucosal vaccine against F. tularensis (a Category A biothreat agent), and a more efficacious vaccine against S. pneumoniae (a pathogen of significant public health concern), are also needed. We provide strong evidence the proposed studies will satisfy these needs, and fill significant gaps in our knowledge regarding the role and use of Fc receptors in mucosal and peripheral immunity against intracellular and extracellular pathogens.

National Institute of Health (NIH)
National Institute of Allergy and Infectious Diseases (NIAID)
Research Project (R01)
Project #
Application #
Study Section
Vaccines Against Microbial Diseases (VMD)
Program Officer
Zou, Lanling
Project Start
Project End
Budget Start
Budget End
Support Year
Fiscal Year
Total Cost
Indirect Cost
Albany Medical College
Schools of Medicine
United States
Zip Code
Franz, Brian J; Li, Ying; Bitsaktsis, Constantine et al. (2015) Downmodulation of vaccine-induced immunity and protection against the intracellular bacterium Francisella tularensis by the inhibitory receptor Fc?RIIB. J Immunol Res 2015:840842
Babadjanova, Zulfia; Wiedinger, Kari; Gosselin, Edmund J et al. (2015) Targeting of a Fixed Bacterial Immunogen to Fc Receptors Reverses the Anti-Inflammatory Properties of the Gram-Negative Bacterium, Francisella tularensis, during the Early Stages of Infection. PLoS One 10:e0129981
Bitsaktsis, Constantine; Babadjanova, Zulfia; Gosselin, Edmund J (2015) In vivo mechanisms involved in enhanced protection utilizing an Fc receptor-targeted mucosal vaccine platform in a bacterial vaccine and challenge model. Infect Immun 83:77-89
Pham, Giang H; Iglesias, Bibiana V; Gosselin, Edmund J (2014) Fc receptor-targeting of immunogen as a strategy for enhanced antigen loading, vaccination, and protection using intranasally administered antigen-pulsed dendritic cells. Vaccine 32:5212-20
Iglesias, Bibiana V; Bitsaktsis, Constantine; Pham, Giang et al. (2013) Multiple mechanisms mediate enhanced immunity generated by mAb-inactivated F. tularensis immunogen. Immunol Cell Biol 91:139-48
Bitsaktsis, Constantine; Iglesias, Bibiana V; Li, Ying et al. (2012) Mucosal immunization with an unadjuvanted vaccine that targets Streptococcus pneumoniae PspA to human Fc? receptor type I protects against pneumococcal infection through complement- and lactoferrin-mediated bactericidal activity. Infect Immun 80:1166-80
Periasamy, Sivakumar; Singh, Anju; Sahay, Bikash et al. (2011) Development of tolerogenic dendritic cells and regulatory T cells favors exponential bacterial growth and survival during early respiratory tularemia. J Leukoc Biol 90:493-507
Zarrella, Tiffany M; Singh, Anju; Bitsaktsis, Constantine et al. (2011) Host-adaptation of Francisella tularensis alters the bacterium's surface-carbohydrates to hinder effectors of innate and adaptive immunity. PLoS One 6:e22335
Gosselin, Edmund J; Bitsaktsis, Constantine; Li, Ying et al. (2009) Fc receptor-targeted mucosal vaccination as a novel strategy for the generation of enhanced immunity against mucosal and non-mucosal pathogens. Arch Immunol Ther Exp (Warsz) 57:311-23