Refocusing of B‐cell responses following a single amino acid substitution in an antigen

Abstract

Intranasal immunization of BALB/c strain mice was carried out using baculovirus-derived human chorionic gonadotrophin (hCG) beta-chain, together with Escherichia coli heat-labile enterotoxin. Gonadotrophin-reactive immunoglobulin A (IgA) was induced in a remote mucosal site, the lung, in addition to a systemic IgG response. The extensive sequence homology with luteinizing hormone (LH) results in the production of LH cross-reactive antibodies when holo-hCG is used as an immunogen. In contrast to wild-type hCGbeta, a mutated hCGbeta-chain containing an arginine to glutamic acid substitution at position 68 did not induce the production of antibodies which cross-react with LH. Furthermore, the epitopes utilized in the B-cell response to the mutated hCGbeta shifted away from the immunodominant region of the parent wild-type molecule towards epitopes within the normally weakly immunogenic C terminus. This shift in epitope usage was also seen following intramuscular immunization of rabbits. Thus, a single amino acid change, which does not disrupt the overall structure of the molecule, refocuses the immune response away from a disadvantageous cross-reactive epitope region and towards a normally weakly immunogenic but antigen-unique area. Similar mutational strategies for epitope-refocusing may be applicable to other vaccine candidate molecules.

Hyperglycosylated Mutants of Human Immunodeficiency Virus (HIV) Type 1 Monomeric gp120 as Novel Antigens for HIV Vaccine Design

“…The concept of diverting B-cell immune responses away from undesired epitopes has been discussed previously (26). A recent study (21) showed that, by introducing a single amino acid mutation in the ␤-chain of human chorionic gonadotrophin, cross-reactive antibodies to luteinizing hormone, which are normally elicited upon immunization with wild-type human chorionic gonadotrophin ␤-chain, could be eliminated. The immune response was thus refocused to epitopes that are normally only weakly immunogenic.…”

“…They suggested that epitope-specific molecules could be elicited by selectively mutating "undesired" epitopes, while preserving the overall fold of the protein and, hence, the desired B-cell (or T-cell) epitope(s). In a recent report (21), the ␤-chain of human chorionic gonadotrophin was used as a model system to show that this strategy is indeed feasible. That study showed that a single amino acid substitution, which does not disrupt the overall conformation of the protein, is sufficient to shift the immune response away from an unwanted epitope and toward a weakly immunogenic determinant (21).…”

Immunogenicity of Membrane-bound HIV-1 gp41 Membrane-proximal External Region (MPER) Segments Is Dominated by Residue Accessibility and Modulated by Stereochemistry

“…The immunogenicity of an epitope is dependent upon its context in a protein. Mutations in one segment can redirect B cell responses toward otherwise weakly immunogenic regions (20). Furthermore, the functionality of antibodies induced by West Nile virus is also strongly influenced by the quaternary structure of viral antigens, suggesting that the nature of the epitope in the native protein is key for interaction with B cell receptors (BCRs) (21).…”

Using an agent-based model to analyze the dynamic communication network of the immune response

“…The volume of the lungs in an adult is estimated to be 843 ± 110 ml [21], the volume of the lymph nodes in the thorax is approximately 12 ml [22,23], and the spleen volume ranges from 180-250 ml [18]. The volume of blood in a human is approximately 5000 ml.…”