Modelling paraneoplastic CNS disease: T-cells specific for the onconeuronal antigen PNMA1 mediate autoimmune encephalomyelitis in the rat

Abstract

Antibodies directed against onconeuronal antigens provide a specific diagnostic marker for paraneoplastic neurological syndromes (PNS) and suggest that these autoantigens are targeted during disease pathogenesis. However, so far attempts to generate autoimmune models of PNS have been unsuccessful. Here we show that the adoptive transfer of T-cells specific for the autologous onconeuronal antigen Pnma1 cause encephalomyelitis in the Dark Agouti (DA) rat. The sequence of rat Ma1 (rPnma1) was determined by RT-PCR using primers for human PNMA1, followed by 5' and 3' genome walking. Rat Pnma1 is 93.8% identical to human PNMA1 at the amino acid level. Rat Pnma1 was cloned into the expression vector pQE60, and recombinant protein purified by metal chelate chromatography. Female DA rats were immunized with recombinant rPnma1 and rPnma1-specific CD4+ T-helper 1 (Th1) T-cell lines generated from the draining lymph nodes 10 days post-immunization. Freshly activated T-cell blasts were transferred into naive female DA rats, which were killed up to 9 days later. Proliferation assays demonstrated that the CD4+ Th1 T-cells were highly specific for rPnma1. After T-cell transfer the recipients developed a perivascular inflammatory response involving CNS regions affected in human disease. Anti-Pnma1 antibodies were induced by protein immunization, but this was associated with minimal CNS pathology. The induction of an inflammatory response in the CNS following the adoptive transfer of rat Pnma1-specific T-cells demonstrates for the first time that a paraneoplastic autoantigen can initiate a pathogenic effector T-cell response. This animal model strongly supports the hypothesis that the pathogenesis of paraneoplastic CNS neurological syndromes in man involves an autoimmune T-cell component.

CD4+ and CD8+ T cells are both needed to induce paraneoplastic neurological disease in a mouse model

“…However, no clinical phenotype was observed. 22 In our model, antigen-specific CD4C T cells alone were unable to induce CNS inflammation or to control the underlying tumor. In contrast, CD8C T cells could partially control the tumor but were not sufficient to elicit T-cell infiltration into the CNS.…”

“…So far, attempts to model PND by immunization with protein or DNA. 20,21 or adoptive transfer of antigen-specific T cells failed to reproduce signs or pathological features of PND 22,23 In this study, we developed an original mouse model in which most CNS neurons express the same model antigen as an implanted tumor. In these mice, T cells specific for this antigen are activated in the periphery by the tumor antigen and further migrate into the CNS causing inflammation and tissue damage.…”

Autoimmune Epilepsies

“…Most likely, these antigenspecific activated T-cells cross the blood-brain barrier (BBB) and attack the neurons that express these antigens in a major histocompatibility complex class I restricted manner. Such mechanisms have been shown in various animal models [52][53][54][55].…”

Intravenous immunoglobulin therapy in paraneoplastic neurological syndromes

“…There is growing evidence, that the pathogenesis in PND of group B is primarily cellular [24,37]. The mode of action of IVIG may also affect the cellular immune system [10]: 1. modulation of pathogenic autoantibodies 2. inhibition of complement activation and interception of membranolytic attack complex formation 3. modulation of Fc receptors on macrophages 4. downregulation of pathogenic cytokines and adhesion molecules 5. suppression of T cell functions 6. interference with antigen recognition…”