Murine CR1/2 Targeted Antigenized Single-Chain Antibody Fragments Induce Transient Low Affinity Antibodies and Negatively Influence an Ongoing Immune Response

Abstract

We have generated a single-chain antibody which recognizes murine CR1/2 and carries a genetically fused influenza hemagglutinin derived peptide. Theoretically such a construct is able to crosslink the B cell antigen receptor and CR1/2 on peptide specific B cells. The construct was able to reach its CR1/2 positive target cells, yet intraperitoneal delivery of the construct elicited an IgM response only slightly exceeding that induced by the free peptide. Providing T cell help by the injection of peptide specific lymphocytes did not alter the response in essence, that is anti-peptide IgG was not detectable even after booster immunizations. When used as a booster vaccine following injection of the peptide in adjuvant, the construct even inhibited the development of IgG1 and IgG3 anti-peptide antibodies. These data indicate that although targeting of antigen to CR1/2 on B cells can enhance transient proliferation or differentiation of antigen specific B cells it cannot induce strong, longlasting humoral immune responses. Furthermore, CR1/2 targeting constructs may negatively influence an ongoing immune reaction.

Modulation of immune response by combined targeting of complement receptors and low-affinity Fcγ receptors

“…For this purpose we used an scFv which was generated from the monoclonal antibody 7g6 [17]. This antibody has been shown to augment antigen uptake and presentation in vitro [18], but did not induce an effective immune response in vivo [19]. We hypothesized that the efficacy of scFv-mediated targeting of CR1/2 could be increased by using it in combination with other activating strategies, such as targeting Fc receptors for IgG (Fc␥R) or with microparticles.…”

A new mouse anti-mouse complement receptor type 2 and 1 (CR2/CR1) monoclonal antibody as a tool to study receptor involvement in chronic models of immune responses and disease

“…They have been used in many assays based on the short term blocking of CR2 and CR1 function (Heyman et al , 1990), as well as used as a carrier for antigen delivery to B cells (Prechl et al , 1999;Prechl et al , 2007;Whipple et al , 2007;Whipple et al , 2004;Baiu et al , 1999). Nevertheless, the use of these reagents for recurrent treatment of long term chronic autoimmune diseases is limited (Whipple et al , 2007) due to anti-rat IgG development .…”

Models of Antigen Receptor Activation in the Design of Vaccines

“…In contrast, a monovalent construct containing only one complement fragment or Fc part cannot be transferred onto the surface of FDCs. Consequently, such antigens fail to induce germinal center formation when bound to marginal zone B cells [112]. The CR2-targeted antigen binds to non-antigen-specific B cells, and might be presented by them to T cells.…”

“…A CD21-recognizing whole antibody chemically conjugated to ovalbumin enhanced the anti-ovalbumin IgG response in a CR2-dependent fashion [80]. In contrast, a monovalent construct based on the same antibody, but comprised of a single chain antibody fragment linked to an influenza-derived subunit antigen, elicited a transient IgM response, but failed to induce class switching [112]. This construct, when administered as a second stimulus after a primary immunization with the antigen along with adjuvant, impaired the ongoing immune response [112].…”

“…Monovalent coligation of BCR and CD21 results in antigen-specific tolerance, an approach which might become useful in the battle against Th2-type autoimmunity [112]. A CD21-recognizing whole antibody chemically conjugated to ovalbumin enhanced the anti-ovalbumin IgG response in a CR2-dependent fashion [80].…”