Idiotypic-anti-idiotypic B cell interactions generated against a protective antigen of a morbillivirus in mice

Structural basis for the function of anti-idiotypic antibody in immune memory

We had earlier proposed a hypothesis to explain the mechanism of perpetuation of immunological memory based on the operation of idiotypic network in the complete absence of antigen. Experimental evidences were provided for memory maintenance through anti-idiotypic antibody (Ab(2)) carrying the internal image of the antigen. In the present work, we describe a structural basis for such memory perpetuation by molecular modeling and structural analysis studies. A three-dimensional model of Ab(2) was generated and the structure of the antigenic site on the hemagglutinin protein H of Rinderpest virus was modeled using the structural template of hemagglutinin protein of Measles virus. Our results show that a large portion of heavy chain containing the CDR regions of Ab(2) resembles the domain of the hemagglutinin housing the epitope regions. The similarity demonstrates that an internal image of the H antigen is formed in Ab(2), which provides a structural basis for functional mimicry demonstrated earlier. This work brings out the importance of the structural similarity between a domain of hemagglutinin protein to that of its corresponding Ab(2). It provides evidence that Ab(2) is indeed capable of functioning as surrogate antigen and provides support to earlier proposed relay hypothesis which has provided a mechanism for the maintenance of immunological memory.

A complementary La/SSB epitope anchored to Sequential Oligopeptide Carrier regulates the anti-La/SSB response in immunized animals

Complementary peptide epitopes, derived from complementary RNA sequences, have been used for suppressing the autoimmune response in experimental autoimmune diseases as myasthenia gravis, allergic neuritis and allergic encephalomyelitis. Aiming at contributing to the development of a tool that could regulate the autoantibody production against La/SSB, which is the main target of autoantibodies in Sjogren's syndrome (SS) and systemic lupus erythematosus (SLE), the complementary epitope, cpep349-364, of the minor T/major B cell epitope of La/SSB, pep349-364, was utilized for the induction of neutralizing anti-cpep349-364 antibodies in rabbit immunizations. Complementary peptides were coupled to an artificial carrier, developed in our laboratory, in order to enhance the complementary potency of cpep349-364 and its counterpart. This carrier, named Sequential Oligopeptide Carrier, SOC(n), formed by the repeating tripeptide Lys-Aib-Gly, adopts helical conformation, which allows the anchored peptide epitopes to preserve their initial reactivity such as molecular recognition, antigenicity/immunogenicity. Our study provides proof of evidence of specific interactions between idiotypic (Id)/anti-idiotypic (anti-Id) antibodies generated in immunized animals by the sense epitope (conjugate I) of La/SSB and its complementary counterpart (conjugate II). It was also demonstrated that the Id/anti-Id association is specifically disrupted by adding either the sense epitope (conjugate I) or its complementary counterpart (conjugate II). A mutual neutralization of Id/anti-Id antibodies was observed in vivo, which implies that generation of anti-Id antibodies by immunization with the complementary La/SSB epitope could scavenge the anti-La/SSB response.

A CD8+ T cell clone specific for antigen also recognizes peptidomimics present in anti-idiotypic antibody: implications for T cell memory

The relay hypothesis [R. Nayak, S. Mitra-Kaushik, M.S. Shaila, Perpetuation of immunological memory: a relay hypothesis, Immunology 102 (2001) 387-395] was earlier proposed to explain perpetuation of immunological memory without requiring long lived memory cells or persisting antigen. This hypothesis envisaged cycles of interaction and proliferation of complementary idiotypic B cells (Burnet cells) and anti-idiotypic B cells (Jerne cells) as the primary reason for perpetuation of immunological memory. The presence of peptidomimics of antigen in anti-idiotypic antibody and their presentation to antigen specific T cells was postulated to be primary reason for perpetuation of T cell memory. Using a viral hemagglutinin as a model, in this work, we demonstrate the presence of peptidomimics in the variable region of an anti-idiotypic antibody capable of functionally mimicking the antigen derived peptides. A CD8+ CTL clone was generated against the hemagglutinin protein which specifically responds to either peptidomimic synthesizing cells or peptidomimic pulsed antigen presenting cells. Thus, it appears reasonable that a population of activated antigen specific T cells is maintained in the body by presentation of peptidomimic through Jerne cells and other antigen presenting cells long after immunization.

Immunization of mice with DNA coding for the variable regions of anti-idiotypic antibody generates antigen-specific response

Understanding the mechanisms of generation and maintenance of immunological memory is crucial for rational vaccine design. A hypothesis known as relay hypothesis was earlier proposed which explains the maintenance of immunological memory through interaction of idiotypic and anti-idiotypic lymphocytes. In the present study, we have shown that immunization with rinderpest virus hemagglutinin protein specific anti-idiotypic antibody (Ab(2)v(beta)) DNAs coding for heavy and light chains generates antigen-specific antibody and T cell responses as well as Ab1 specific T cell response. We further show that boosting with the recombinant Ab(2)-vbeta proteins generates B and T cell memory response specific for antigen in anti-id DNA primed mice. This study provides experimental evidence for perpetuation of immunological memory through idiotypic network interactions.

Maintenance of antigen-specific immunological memory through variable regions of heavy and light chains of anti-idiotypic antibody

Immunological memory is characterized by a quick and enhanced immune response after re-exposure to the same antigen. To explain the mechanism involved in generation and maintenance of immunological memory, we had earlier proposed a hypothesis involving the relay of memory by idiotypic and anti-idiotypic B cells. The peptidomimic present in the hypervariable region of anti-idiotypic antibody was hypothesized to carry forward immunological memory. In the present work, we provide evidence supporting a role for the anti-idiotypic antibody in eliciting antigen-specific B-cell and T-cell responses. Employing the idiotypic monoclonal antibody (Ab(1)) specific for haemagglutinin (H) protein of rinderpest virus, Ab(2beta) was generated, which possesses an internal image of the H protein in the region between amino acids 527 and 556. We demonstrate that antigen-specific memory is perpetuated by immunization with Ab(2), as shown by maintenance of antigen-specific T-cell responses upon restimulation in vitro of Ab(2) immune splenocytes by antigen-presenting cells expressing H protein or pulsed with H-protein-derived peptides. We have also shown that boosting with antigen-specific anti-idiotypic B cells generates a memory response in antigen-primed mice. Evidence has been provided for the existence of an antigen-specific B-cell idiotypic network in the body that supports the perpetuation of immunological memory as proposed in the relay hypothesis.

Idiotype and anti-idiotype specific T cell responses on transplantation with hybridomas reactive to viral hemagglutinin and human tumor antigen

B cell hybridomas expressing class I and II MHC molecules and producing antibodies directed against hemagglutinin protein of Rinderpest virus and human Mucin-1 have been used as surrogate B cells to study T cell responses against the antigens. The observed CTL and lymphoproliferative response indicates that anti-idiotypic B cells termed Jerne cells stimulate both T helper and T cytotoxic cells by virtue of their ability to present recycled or regurgitated peptido-mimics of antigen to T helper cells through class II MHC and de novo synthesized peptido-mimics of antigens to CTLs. Thus, T cell memory response can be perpetuated by anti-idiotypic Jerne B cells and these findings lend support to the earlier proposed relay hypothesis for perpetuation of immunological memory (IM).