Immune tolerance mediated by recombinant proteolipid protein prevents experimental autoimmune encephalomyelitis

Proteolipid protein (PLP), a transmembrane protein expressed only in the central nervous system (CNS), is a candidate target autoantigen for autoimmune-mediated demyelination. We have evaluated the effect of a recombinant form of the PLP protein, delta PLP4, in a murine model of experimental autoimmune encephalomyelitis (EAE). PLP-specific T-cell responses were observed following immunization of SJL/J, PL/J and SWR mice with delta PLP4, demonstrating processing of the protein to several distinct antigenic epitopes. Clinical EAE associated with inflammation and demyelination in the CNS also developed after sensitization of mice with delta PLP4 in adjuvant. Conversely, tolerance to delta PLP4 in adult mice and prevention of PLP peptide 139-151-induced EAE was induced by intravenous injection of soluble delta PLP4. The prevention of disease onset was paralleled by a significant reduction in demyelination and CNS inflammatory cell infiltration and diminished PLP139-151-specific T-cell proliferative responses. These results are consistent with the establishment of peripheral T-cell tolerance and reinforce the notion that recombinant myelin antigens and intravenous tolerance induction may prove useful in the modulation of the human demyelinating disease, multiple sclerosis (MS).

Treatment of experimental encephalomyelitis with a novel chimeric fusion protein of myelin basic protein and proteolipid protein

It has been shown that peripheral T cell tolerance can be induced by systemic antigen administration. We have been interested in using this phenomenon to develop antigen-specific immunotherapies for T cell-mediated autoimmune diseases. In patients with the demyelinating disease multiple sclerosis (MS), multiple potentially autoantigenic epitopes have been identified on the two major proteins of the myelin sheath, myelin basic protein (MBP) and proteolipid protein (PLP). To generate a tolerogenic protein for the therapy of patients with MS, we have produced a protein fusion between the 21.5-kD isoform of MBP (MBP21.5) and a genetically engineered form of PLP (deltaPLP4). In this report, we describe the effects of treatment with this agent (MP4) on clinical disease in a murine model of demyelinating disease, experimental autoimmune encephalomyelitis (EAE). Treatment of SJL/J mice with MP4 after induction of EAE either by active immunization or by adoptive transfer of activated T cells completely prevented subsequent clinical paralysis. Importantly, the administration of MP4 completely suppressed the development of EAE initiated by the cotransfer of both MBP- and PLP-activated T cells. Prevention of clinical disease after the intravenous injection of MP4 was paralleled by the formation of long-lived functional peptide-MHC complexes in vivo, as well as by a significant reduction in both MBP- and PLP-specific T cell proliferative responses. Mice treated with MP4 were resistant to disease when rechallenged with an encephalitogenic PLP peptide emulsified in CFA, indicating that MP4 administration had a prolonged effect in vivo. Administration of MP4 was also found to markedly ameliorate the course of established clinical disease. Finally, MP4 therapy was equally efficacious in mice defective in Fas expression. These results support the conclusion that MP4 protein is highly effective in suppressing disease caused by multiple neuroantigen epitopes in experimentally induced demyelinating disease.

Porcine vascular cell adhesion molecule (VCAM) mediates endothelial cell adhesion to human T cells. Development of blocking antibodies specific for porcine VCAM

Vascular cell adhesion molecule (VCAM) is expressed on activated endothelial cells and binds to the alpha 4 beta 1 integrin receptor, very late antigen-4 (VLA-4), expressed on human lymphoid cells. Anti-VCAM mAbs have been shown to prolong allograft survival. To explore the role of porcine VCAM (pVCAM) in xenotransplantation, a recombinant secreted form of pVCAM (spVCAM) was expressed in 293-EBNA cells and purified by metal affinity chromatography. A human lymphoid cell line bound to spVCAM in a VLA-4-dependent manner. Using spVCAM as an immunogen, we developed three anti-pVCAM mAbs that reacted with cell surface pVCAM on porcine aortic endothelial cells (PAEC) but not to human VCAM on human umbilical vein endothelial cells. Pairwise interaction analysis indicated that these mAbs recognized distinct epitopes on pVCAM. Two anti-pVCAM mAbs, 2A2 and 3F4, inhibited the binding of Ramos cells to spVCAM, while the third, 5D11, did not. Similarly, mAbs 2A2 and 3F4 inhibited binding of Ramos cells or human peripheral blood T cells to activated PAEC. The extent of inhibition with mAbs 2A2 and 3F4 was comparable to the inhibition obtained with a blocking mAb to human VLA-4. These anti-pVCAM mAbs will provide a means to specifically block pVCAM in a xenograft setting and allow the determination of the role of pVCAM in a primary xenogeneic immune response.

The synaptic vesicle-associated protein amphiphysin is the 128-kD autoantigen of Stiff-Man syndrome with breast cancer

Stiff-Man syndrome (SMS) is a rare disease of the central nervous system (CNS) characterized by progressive rigidity of the body musculature with superimposed painful spasms. An autoimmune origin of the disease has been proposed. In a caseload of more than 100 SMS patients, 60% were found positive for autoantibodies directed against the GABA-synthesizing enzyme glutamic acid decarboxylase (GAD). Few patients, all women affected by breast cancer, were negative for GAD autoantibodies but positive for autoantibodies directed against a 128-kD synaptic protein. We report here that this antigen is amphiphysin. GAD and amphiphysin are nonintrinsic membrane proteins that are concentrated in nerve terminals, where a pool of both proteins is associated with the cytoplasmic surface of synaptic vesicles. GAD and amphiphysin are the only two known targets of CNS autoimmunity with this distribution. This finding suggests a possible link between autoimmunity directed against cytoplasmic proteins associated with synaptic vesicles and SMS.

Autoantibodies to a 128-kd synaptic protein in three women with the stiff-man syndrome and breast cancer

BACKGROUND

The stiff-man syndrome is a rare disease of the central nervous system characterized by progressive rigidity of the body musculature. Autoantibodies directed against glutamic acid decarboxylase are present in about 60 percent of patients with the syndrome. In this group, there is a striking association of the stiff-man syndrome with organ-specific autoimmune diseases, primarily insulin-dependent diabetes mellitus.

METHODS

We studied three women with the stiff-man syndrome and breast cancer, seeking autoantibodies directed against nervous system antigens in serum and cerebrospinal fluid by immunocytochemical techniques, Western blotting, and immunoprecipitation.

RESULTS

Autoantibodies directed against a 128-kd brain protein were found in two of the women with the stiff-man syndrome and breast cancer. These results led to a search for breast cancer in the third patient with the stiff-man syndrome, who also had autoantibodies. A small invasive ductal carcinoma was detected by ultrasonography and removed. Serum samples from all three patients were negative for autoantibodies directed against glutamic acid decarboxylase. Autoantibodies against the 128-kd antigen were not detected in control patients with the stiff-man syndrome without breast cancer or in patients with cancer who did not have the syndrome. Within the nervous system, the 128-kd autoantigen was localized in neurons and concentrated at synapses.

CONCLUSIONS

In a subgroup of patients with the stiff-man syndrome, the condition is likely to have an autoimmune paraneoplastic origin. The detection of autoantibodies against the 128-kd antigen in patients with this syndrome should be considered an indication to search for an occult breast cancer.