High-affinity memory B cells induced by conjugate vaccines against weak tumor antigens are vulnerable to nonconjugated antigen

Abstract

Induction of antibody-mediated immunity against hematologic malignancies requires CD4 ؉ T-cell help, but weak tumor antigens generally fail to induce adequate T-cell responses, or to overcome tolerance. Conjugate vaccines can harness alternative help to activate responses, but memory B cells may then be exposed to leaking tumor-derived antigen without CD4 ؉ T-cell support. We showed previously using lymphoma-derived idiotypic antigen that exposure to "helpless" antigen silences the majority of memory IgG ؉ B cells. Transfer experiments now indicate that silencing is permanent. In marked contrast to IgG, most coexisting IgM ؉ memory B cells exposed to "helpless" antigen survive. Confirmation in a hapten (NP) model allowed measurement of affinity, revealing this, rather than isotype, as the determinant of survival. IntroductionTumor antigens are generally weakly immunogenic, and T-cell responses can be subject to tolerogenic pressure. 1 To avoid this, vaccines have been designed as conjugates of tumor antigens with immunogenic molecules, such as KLH. 2 Conjugation captures the large undamaged CD4 ϩ T-cell repertoire, providing T-cell help for the antitumor immune responses. 2,3 Idiotypic (Id) Ig-KLH vaccines aimed to suppress B-cell tumors via an anti-Id response are one example of the promise of this approach. [4][5][6] We have used a similar strategy to deliver Id fusion proteins via DNA vaccines. 7,8 The Id is composed of tumor-derived single chain Fv and is linked to the fragment C (FrC) of tetanus toxin. DNA vaccines encoding Id-FrC fusion proteins induce high levels of anti-Id antibody and protective immunity against B-cell lymphoma. 9 Continuous suppression of lymphoma cell growth probably requires maintenance of antibody levels. Although long-lived plasma cells can secrete antibody for extended periods, 10 memory B cells are also required. Survival factors for memory B cells are unclear, but antigen appears unnecessary. 11,12 For antibody responses induced by conjugate vaccines, the question of the effect of confronting memory B cells with free unconjugated "helpless" antigen, potentially derived from residual or emergent tumor, arises. In the case of Id antigen, or for carbohydrate antigens, this led to dramatic loss of memory B cells. 13 We found previously that the major fraction of the IgG component of the memory B-cell response induced by a DNA Id-FrC fusion vaccine was completely and specifically silenced by Id protein alone. 14 In contrast, Id protein coupled to FrC protein rescued and boosted the anti-Id IgG response, indicating the critical importance of CD4 ϩ T-cell help for maintenance of the memory B-cell response.We have now shown that silencing of the anti-Id IgG response by unconjugated antigen is permanent, but the surprising observation was that the IgM response appeared relatively unscathed. To assess the wider applicability of these findings and to investigate the effects of antigen on memory B cells at different maturational stages, we have used a model antigen, the well-defined hapten...

Systems Analysis Reveals High Genetic and Antigen-Driven Predetermination of Antibody Repertoires throughout B Cell Development

“…It is well established that C57BL/6 mice mount a stereotypical antibody response against NP, with defined germline V-gene usage and common CDR3 aa motifs (Imanishi and Mä ukelä , 1973;Jacob and Kelsoe, 1992;Jacob et al, 1991aJacob et al, , 1991bSavelyeva et al, 2011). In each PC repertoire of NP-HEL-immunized mice, candidate NP-specific clones (identified by stereotypical V-genes and CDR3 sequence motifs, Table S3) were found both among the high-and low-frequency clones (Table S3), which is in line with theoretical predictions (Reshetova et al, 2017).…”

Robo4 vaccines induce antibodies that retard tumor growth

“…This approach efficiently induces an anti-tumor effect without further adjuvant and should be transferable to combinations of human Robo4 with carriers used in human vaccines given during childhood vaccination such as diphtheria toxoid (44). Conjugate vaccines have been used against tumor neoantigens, although not in the presence of preexisting T-cell memory (45). How vaccination with a combination of autoantigen and foreign carrier impacts on the longevity of the antibody response, e.g.…”

AID-induced remodeling of immunoglobulin genes and B cell fate

“…Secreted antibodies were thus shown to inhibit or even terminate GC proliferation with an efficiency directly correlated with their affinity for antigen [90]. Interestingly in the absence of T cell help, soluble antigen might also inhibit GC development [91]. …”