Healthy individuals have T-cell and antibody responses to the tumor antigen cyclin B1 that when elicited in mice protect from cancer.

We previously identified the aberrantly expressed cell cycle regulator cyclin B1 as a tumor antigen recognized by antibodies and T cells from patients with breast, lung, and head and neck cancers. Ordinarily expressed only transiently in the G2/M stage of the cell cycle in normal cells, cyclin B1 is constitutively expressed at high levels in the cytoplasm of these and many other tumor types, leading to its recognition by the cancer patient's immune system. We report here an unexpected observation that cyclin B1-specific antibody and memory CD4 and CD8 T cells are also found in many healthy individuals who have no history of cancer. Moreover, young as well as older healthy people have these responses suggesting that events other than cancer, which occur either early in life or throughout life, may lead to aberrant cyclin B1 expression and anti-cyclin B1 immunity. The role, if any, of immunity to this tumor-associated antigen is not known. We wanted to determine specifically whether immunity to cyclin B1 might be important in the immunosurveillance of cyclin B1+ tumors. We therefore tested in mice the effectiveness of vaccine-elicited anti-cyclin B1 immunity against a cyclin B1+ mouse tumor that was chosen based on our published observation that cyclin B1 overexpression is associated with the lack of p53 function. We found that cyclin B1 DNA prime-protein boost vaccine protected mice from a challenge with a tumor cell line that was established from a tumor arising in the p53(-/-) mouse that spontaneously overexpresses cyclin B1.

GM1 binding-deficient exotoxin is a potent noninflammatory broad spectrum intradermal immunoadjuvant.

Intradermal (i.d.) immunization is a promising route of vaccine administration. Suitable i.d. adjuvants are important to increase vaccine efficacy in poorly responding populations such as the elderly or for dose-sparing strategies in the face of vaccine shortages. Bacterial exotoxins, such as Escherichia coli heat-labile enterotoxin (LT), exert strong immunostimulatory effects through binding to monosialoganglioside (GM1) cell surface receptors; however, injection is hampered by local inflammation. We demonstrate that the injection of LT formulations deficient in GM1 binding by mutation (LT(G33D)) or in vitro ligand coupling does not cause localized edema and inflammation in mice, yet these formulations retain potent adjuvant activity by enhancing functional Ab and cellular immune responses to coadministered Ags. Complete protection against in vivo lethal tetanus toxin challenge and the induction of Ag-specific CTL responses capable of killing target cells in vivo indicated in vivo efficacy of the induced immune responses. LT(G33D) proved superior to standard alum adjuvant regarding the magnitude and breadth of the induced immune responses. Immunizations in complex ganglioside knockout mice revealed a GM1-independent pathway of LT adjuvanticity. Immunostimulation by i.d. LT(G33D) is explained by its ability to induce migration of activated APCs to the proximal draining lymph nodes. LT(G33D) is a promising candidate adjuvant for human trials of parenteral vaccines in general and for current i.d. vaccine development in particular.

In vivo induction of tolerance by an Ig peptide is not affected by the deletion of FcR or a mutated IgG Fc fragment.

To induce tolerance to a variety of epitopes, we have designed a gene therapy approach in which peptides or antigens are expressed in frame on a soluble IgG fusion protein scaffold and delivered via retroviral gene therapy in B cells in vivo. Initially, tolerance to the lambda repressor cI sequence p1-102 or its immunodominant epitopes (e.g. p12-26 or p73-88) was elicited in both T cells and B cells when lipopolysaccharide (LPS) blasts are transduced and injected into naive or even primed recipients. While a role of secreted Ig fusion protein in this process is not clear, we have previously demonstrated the importance of antigen presentation on MHC class II of B cell antigen-presenting cells (APC) for tolerance induction. To further examine the role of the Ig and especially of the Fc portion of the IgG in tolerogenesis, we transduced LPS blasts from FcR gamma II(-/-), Fc gamma RI(-/-), Fc gamma RIII(-/-), FcR(-/-) or naive mice with retroviral vectors expressing IgG1-102, Delta IgG1-102 (mutated construct on position 297 of the Fc portion) or IgG12-26. When these transduced LPS blasts from FcR knockout mice were injected into normal (or knockout) syngeneic recipient mice, they induced tolerance both to the immunodominant epitopes and the full-length protein in that the antibody responses to the immunodominant epitopes were reduced. In this paper, we show that this tolerance resides at both the T and B cell level. Moreover, mutation of residue 297, which affects IgG functions including FcR binding, did not alter the tolerogenicity of the construct. These results suggest that the Fc portion of the IgG molecules is not required for humoral nor for cellular tolerance induction using the IgG-antigen tolerogens.

Gene transfer of Ig-fusion proteins into B cells prevents and treats autoimmune diseases.

Based on the tolerogenic properties of IgG carriers and B cell Ag presentation, we developed a retrovirally mediated gene expression approach for treatment of autoimmune conditions. In this study, we show that the IgG-Ag retroviral constructs, expressing myelin basic protein (MBP) or glutamic acid decarboxylase in B cells, can be used for the treatment of murine models for multiple sclerosis and diabetes. Transduction of syngeneic B cells with MBP-IgG leads to the amelioration of ongoing experimental allergic encephalomyelitis induced by the transfer of primed cells from PLxSJL F(1) mice with ongoing disease and could be effective even after symptoms appeared. This effect is specific and does not involve bystander suppression because treatment with MBP-IgG does not affect disease induced after immunization with proteolipid protein immunodominant peptide plus MBP. Interestingly, if donor B cells are derived from gld mice (Fas ligand-negative), then tolerance is not induced with a model Ag although there was no evidence for Fas ligand-mediated deletion of target T cells. In spontaneous diabetes in nonobese diabetic mice, we were able to stop the ongoing autoimmune process by treatment at 7-10 wk with glutamic acid decarboxylase-IgG retrovirally transduced B cells, or attenuate it with B cells transduced with an insulin B chain (B9-23) epitope IgG fusion protein. Furthermore, IgG fusion protein gene therapy can also protect primed recipients from Ag-induced anaphylactic shock, and thus does not cause immune deviation. These results demonstrate proof of principle for future efforts to develop this approach in a clinical setting.