The FomA Porin from Fusobacterium nucleatum Is a Toll-Like Receptor 2 Agonist with Immune Adjuvant Activity

Abstract

Many bacterial components selectively activate immune and nonhematopoietic target cells via Toll-like receptor (TLR) signaling; modulation of such host responses defines the immune adjuvant properties of these bacterial products. For example, the outer membrane protein porins from Neisseria, Salmonella, and Shigella are known TLR2 agonists with established systemic and mucosal immune adjuvanticity. Early work indicated that the FomA porin from Fusobacterium nucleatum has immune adjuvant activity in mice. Using a purified recombinant FomA, we have verified its immune stimulatory properties and have defined a role for TLR2 signaling in its in vitro and in vivo activity. FomA induces interleukin 8 (IL-8) secretion and NF-B-dependent luciferase activity in HEK cells expressing TLR2, IL-6 secretion, and cell surface upregulation of CD86 and major histocompatibility complex (MHC) II in primary B cells from wild-type mice, but it fails to activate cells from TLR2 knockout mice. Accordingly, the immune adjuvant activity of FomA is also TLR2 dependent. In a mouse model of immunization with ovalbumin (OVA), FomA induces enhanced production of OVA-specific IgM and IgG, including IgG1 and IgG2b antibodies, as well as enhanced secretion of IL-10 and IL-6, consistent with a Th2-type adjuvant effect. We also observe a moderate production of anti-FomA antibodies, suggesting that FomA is also immunogenic, a quality that is also TLR2 dependent. Therefore, modulation of host immune responses by FomA may be effective for targeting general host immunity not only to pathogens (as a novel TLR2 adjuvant) but also to F. nucleatum itself (as an antigen), expanding its use as a self-adjuvanted antigen in an immunization strategy against polymicrobial infections, including those by F. nucleatum.

BCG vaccine mediated reduction in the MHC-II expression of macrophages and dendritic cells is reversed by activation of Toll-like receptors 7 and 9

“…IRAK-4 occupies a pivotal position for ligands activating TLR-1/2, TLR-4, TLR-7 and TLR-9 (Fig.4a). NF-kB has also been found a key down-stream player during TLR-induced cytokine secretion and MHC-II synthesis [28-30]. MΦs treated with inhibitors for either IRAK1/4 or NF-kB, activated with ligands for TLR-9 TLR-2 and TLR4 followed by BCG infection showed a significant reduction in antigen presentation in vitro (Fig.4i).…”

Immuno-Modulatory Role of Porins: Host Immune Responses, Signaling Mechanisms and Vaccine Potential

“…Porins from many gram-negative bacteria such as Fusobacterium nucleatum , Haemophilus infl uenza e, Helicobater pylori , Neisseria , Salmonella and Shigella spp. induce pro-infl ammatory cytokines like TNFα, IL-6 and IL-1β secretion in a variety of cell lines and primary cells, such as monocytes and macrophages of human and mouse origin (Table 6.1 ) (Tufano et al 1994(Tufano et al , 1995Toussi et al 2012 ;Galdiero et al 2001aGaldiero et al , b , 2004Vitiello et al 2004Vitiello et al , 2011Liu et al 2010 ;Singleton et al 2005 ;Massari et al 2006 ;Al-Bader et al 2004 ;Moreno-Eutimio et al 2013, Galdiero et al 2005, 2006aRay et al 2003 ;Biswas et al 2007 ;Elena et al 2009 ;Pore et al 2012 ). Vibrio cholerae OmpU stimulates monocytes and macrophages to produce TNFα and IL-6 (Sakharwade et al 2013 ).…”

“…Other porins of C. trachomatis , Porin B and Porin D, when administered to mice in the form of V. cholerae ghosts, induced cross-reactive chlamydial specifi c genital mucosal T and B cell responses (Eko et al 2011 ). FomA of F. nulceatum , bacteria involved in periodontal disease, leads to IgG and IgM antibody production along with IL-6 and IL-10 secretion upon treatment in mice (Toussi et al 2012 ). Neiserria lactamica is a commensal found in infants that can cause pneumonia in children.…”

Vaccination with major outer membrane protein proteosomes elicits protection in mice against a Chlamydia respiratory challenge

“…Proteosomes are protein micelles, free of detergents that do not have toxic effects. Proteosomes from Neisseria , Salmonella, Fusobacterium and Plasmodium have been used as antigens and adjuvants to elicit protection in humans and animal models [18-22]. Here, to assess the feasibility of formulating a vaccine using Chlamydia proteosomes, we extracted the nMOMP trimer and prepared nMOMP-Ps.…”