Neuroimmune Responses to Toxic Agents: Comparison of Organometal Electrophiles Using Detection of Antibodies to Neural Cytoskeleton and Myelin as Biomarkers

Neuroantibody biomarkers: links and challenges in environmental neurodegeneration and autoimmunity

The majority of neurodegenerative (ND) and autoimmune diseases (AID) remain idiopathic. The contribution of environmental chemicals to the development of these disorders has become of great interest in recent years. A convergence of mechanism between of ND and AID development has also emerged. In the case of ND, including neurotoxicity, the focus of this review, work over the last two decade in the realm of biomarker development, indicates that the immune response provides a venue whereby humoral immunity, in the form of autoantibodies to nervous system specific proteins, or neuroantibodies (NAb), may provide, once validated, a sensitive high throughput surrogate biomarker of effect with the potential of predicting outcome in absence of overt neurotoxicity/neurodegeneration. In addition, NAb may prove to be a contributor to the progression of the nervous system pathology, as well as biomarker of stage and therapeutic efficacy. There is a compelling need for biomarkers of effect in light of the introduction of new chemicals, such as nanoengineered material, where potential neurotoxicity remains to be defined. Furthermore, the convergence of mechanisms associated with ND and AID draws attention to the neglected arena of angiogenesis in defining the link between environment, ND, and AID.

Antibodies to neural proteins in organophosphorus-induced delayed neuropathy (OPIDN) and its amelioration

The development of OPIDN and the efficacy of experimental intervention using the calcium-channel blocker verapamil were used as a model to test the serial time-measurements of serum autoantibodies against neuronal cytoskeletal proteins [e.g., neurofilament triplet (NF)] and glial proteins [myelin-basic protein (MBP) and glial fibrillary-acidic protein (GFAP)] as biomarkers of neurotoxicity and its amelioration. Ten White Leghorn hens (>7 months, 1.2-1.8 kg) were administered phenyl-saligenin phosphate (PSP; 2.5 mg/kg; im), a dose reported to induce a 70% decrease in neurotoxic esterase (NTE) activity. Five of the hens were administered verapamil (7 mg/kg; im) for 4 days starting one day before PSP administration. Serum was isolated from blood collected by serial brachial venepuncture before PSP (day 0) administration and on days 3, 7 and 21 after PSP administration, each hen acting as its own control. Serum antibodies (IgG) to NF-L, NF-M, NF-H, MBP, and GFAP were assayed using an ELISA. There were no detectable levels of antibodies on days 0 and 3. IgG against all neural proteins were detected on days 7 and 21, with titer levels being significantly (p< or =0.05) higher in sera of hens receiving PSP only. Anti-NF-L titers were highest compared to those against NF-M, NF-H or MBP at 21 days. Titers of anti-NF-L and anti-MBP significantly (p< or =0.01) correlated with clinical scores at days 7 and 21. Detection of anti-NF and anti-MBP antibodies confirms the neuroaxonal degeneration accompanied by myelin loss reported in this model of OPIDN and the amelioration of neuropathy using verapamil. The detection of anti-GFAP antibodies suggests CNS involvement in OPIDN, since astrocytes are only found therein. This study demonstrates that detection of neuroantibodies can be used as biomarkers of neuropathy development and to monitor the amelioration resulting from therapeutic intervention. Together with biomarkers of exposure neuroantibodies can be used to monitor neuropathogenesis due to environmental or occupational exposures.