A Novel Gene Delivery Vector of Agonistic Anti-Radioprotective 105 Expressed on Cell Membranes Shows Adjuvant Effect for DNA Immunization Against Influenza.

Tatsuya Yamazaki,Isao Ichimonji,Masanori Inui,Mrityunjoy Biswas,Susumu Tomono,Kouyu Kosugi,Sachiko Akashi-Takamura,Akira Ainai,Fumiaki Nagaoka,Joe Chiba,Hidekazu Takagi,Hideki Hasegawa,Maria Nagashima

doi:10.3389/fimmu.2020.606518

Abstract

Radioprotective 105 (RP105) (also termed CD180) is an orphan and unconventional Toll-like receptor (TLR) that lacks an intracellular signaling domain. The agonistic anti-RP105 monoclonal antibody (mAb) can cross-link RP105 on B cells, resulting in the proliferation and activation of B cells. Anti-RP105 mAb also has a potent adjuvant effect, providing higher levels of antigen-specific antibodies compared to alum. However, adjuvanticity is required for the covalent link between anti-RP105 mAb and the antigen. This is a possible obstacle to immunization due to the link between anti-RP105 mAb and some antigens, especially multi-transmembrane proteins. We have previously succeeded in inducing rapid and potent recombinant mAbs in mice using antibody gene-based delivery. To simplify the covalent link between anti-RP105 mAb and antigens, we generated genetic constructs of recombinant anti-RP105 mAb (αRP105) bound to the transmembrane domain of the IgG-B cell receptor (TM) (αRP105-TM), which could enable the anti-RP105 mAb to link the antigen via the cell membrane. We confirmed the expression of αRP105-TM and the antigen hemagglutinin, which is a membrane protein of the influenza virus, on the same cell. We also found that αRP105-TM could activate splenic B cells, including both mature and immature cells, depending on the cell surface RP105 in vitro. To evaluate the adjuvanticity of αRP105-TM, we conducted DNA immunization in mice with the plasmids encoding αRP105-TM and hemagglutinin, followed by challenge with an infection of a lethal dose of an influenza virus. We then obtained partially but significantly hemagglutinin-specific antibodies and observed protective effects against a lethal dose of influenza virus infection. The current αRP105-TM might provide adjuvanticity for a vaccine via a simple preparation of the expression plasmids encoding αRP105-TM and of that encoding the target antigen.

Highlights

Passive immunization using monoclonal antibodies is an important prophylactic and therapeutic method for a variety of diseases such as infections, cancer, and autoimmune diseases [1]
We could not detect the band using anti-rat IgG both under reducing and non-reducing conditions (Figures 1B, C, lower panel, lane 4). These results suggested that aRP105 could express a full-length antibody containing two heavy chain (HC) and two light chain (LC), which was derived from mouse constant regions, but not from rat constant regions, of the parental anti-Radioprotective 105 (RP105) monoclonal antibody (mAb)
The current study indicated, for the first time, that recombinant agonistic mAbs expressed on the cell membrane by gene vector delivery provides adjuvant efficacy for DNA immunization against the influenza virus

Summary

Introduction

Passive immunization using monoclonal antibodies (mAbs) is an important prophylactic and therapeutic method for a variety of diseases such as infections, cancer, and autoimmune diseases [1]. Clark and colleagues found that anti-RP105 mAb induces a general and rapid increase in the levels of serum antibodies of all classes except IgG2b and IgA [9, 15]. They demonstrated that targeting antigens to RP105 could induce the production of specific antibodies independent of T cells by using CD40-deficient mice [4]. These results suggest that the anti-RP105 mAb can induce a unique antibody against an antigen, compared with a conventional vaccine, which generally targets mature naïve B cells depending on T cells [20,21,22]

Methods

Results

Conclusion