Longitudinal spinal cord sections as substratum for anti-neurofilament antibody detection

Axonal degeneration in the pathogenesis of multiple sclerosis

Axonal degeneration plays an important role in the accumulation of disability in patients with multiple sclerosis (MS). Pathological studies have demonstrated axonal damage, particularly in areas of acute inflammation and demyelination, and in chronic lesions. Axonal loss and its progression, which is associated with neurological disability, has also been demonstrated by magnetic resonance imaging (MRI) studies. The mechanisms of axonal loss are uncertain, but may involve axonal degeneration secondary to demyelination, or damage to the axonal cytoskeleton. Inflammatory mediators, including cytokines and proteolytic enzymes may contribute to axonal damage, as may nitric oxide. Axonal destruction may also be due to immune attack directed at axonal components. The realisation that axonal degeneration is a fundamental component of MS that may occur early in the disease course should alter the approach to management and open avenues to a more targeted immunotherapy aimed at reducing the progression of disability.

Antisera to an axolemma-enriched fraction inhibit neurite outgrowth and destroy axons in vitro

Antisera prepared to an axolemma-enriched fraction derived from rat brain inhibited neurite outgrowth and destroyed mature axons in spinal cord-dorsal root ganglia cultures. Similar antibody-mediated anti-axon effects may be important in some diseases of the human nervous system.

Antineurofilament antibody: an increased incidence in murine chronic measles encephalitis and the use of rat sciatic nerve sections as substratum

Virus-associated autoimmune phenomena were investigated in the HNT-C57BL/6 chronic measles encephalitic mouse system. The incidence of serum antineurofilament autoantibodies was studied by an indirect immunofluorescence procedure using a FITC-conjugated goat anti-mouse immunoglobulin. Transversely cut cryostat sections of rat sciatic nerve post-treated with 1% Triton X-100 was used as substratum and had the advantages of increased reliability and reproducibility of neurofilament (NF) antibody titrations compared to the previously described longitudinal spinal cord sections. An increased incidence of anti-NF autoantibody was observed in sera from acutely, subacutely, chronically and asymptomatically infected mice compared to uninfected or mock-infected mice suggesting an association between the appearance of anti-NF antibody and HNT measles virus infection of the CNS.

The 200- and 150-kDa neurofilament proteins react with IgG autoantibodies from chimpanzees with kuru or Creutzfeldt-Jakob disease; a 62-kDa neurofilament-associated protein reacts with sera from sheep with natural scrapie

Sera from 46 chimpanzees with spongiform encephalopathy (18 kuru, 28 Creutzfeldt-Jakob disease) and sera from 12 sheep with natural scrapie were tested for reactivity with immunoblots of neurofilament preparations obtained from mouse brain. The sera from the chimpanzees reacted mainly with the 200- and 150-kDa proteins of the neurofilament triplet and less frequently with the 70-kDa component of the triplet and with a 62-kDa neurofilament-associated protein. In contrast, the sera of sheep with natural scrapie reacted exclusively against the 62-kDa protein. The specificity of the reactions was established by comparison of sera reactivities with those of rabbit and mouse polyclonal antibodies and mouse monoclonal antibody to neurofilament proteins.

The 200- and 150-kDa neurofilament proteins react with IgG autoantibodies from patients with kuru, Creutzfeldt-Jakob disease, and other neurologic diseases

Sera from 65 patients with spongiform virus encephalopathies (29 with kuru, 36 with Creutzfeldt-Jakob disease), 79 with other neurologic diseases, and 65 control subjects were examined for reactivity in immunoblots of preparations of myelinated axons and neurofilaments from mouse brain. The sera reacted most frequently with the 200-kDa and 150-kDa neurofilament proteins and less frequently with the 70-kDa neurofilament protein and a 62-kDa neurofilament-associated protein. The sera reacted with the same proteins as those which reacted with rabbit and mouse polyclonal antibodies and mouse monoclonal antibody to neurofilament proteins. Serum reactions were also seen with Trixon X-100 extracts of chimpanzee brain and bovine spinal cord but not with Triton extracts of liver, kidney, and muscle.

Persistence of immunoreactive neurofilament protein breakdown products in transected rat sciatic nerve

Alterations occurring in nerve proteins of transected nerves were studied in rat sciatic nerves using polyclonal and monoclonal antibodies to identify and monitor neurofilament (NF) epitopes among nerve proteins following their electrophoresis and transfer to nitrocellulose paper. Immunoblot methods identified NF epitopes in NF triplet proteins (Mr 200,000, 150,000, and 68,000) and in NF nontriplet proteins (all other immunobands below Mr 200,000 and above Mr 40,000). NF triplet and nontriplet proteins were Triton-insoluble in both untransected and transected nerves. Extensive loss of NF triplet and most nontriplet proteins occurred during the 24-48-h period following nerve transection and was attributed to proteolytic degradation. Loss of protease-labile NF proteins led to a markedly reduced level of NF immunoreactivity in 2-day transected nerve. NF proteins which survived the 2-day posttransectional period were considered to represent protease-stable NF fragments. These fragments persisted in transected nerve for periods of at least 35 days. Most protease-stable NF fragments which retained immunoreactivity had Mr of 57,000-65,000. Low concentrations of the same immunobands were present in untransected nerves.

Serum antibodies to neurofilament antigens in patients with neurological and other diseases and in healthy controls

A total of 529 sera from patients with a wide variety of neurological and non-neurological diseases, and 101 sera from healthy control subjects, were examined by indirect immunofluorescence for the presence of autoantibodies to neurofilament antigens. Antibodies were found in approximately 50% of sera from patients with spongiform encephalopathies, 15-30% of sera from patients with other neurological and non-neurological diseases, and 7% of sera from healthy controls. The antigenic stimulus to these autoantibodies in very diverse disease processes is unknown, but as presently assayed, they are not of sufficient specificity to be useful as an aid to clinical diagnosis.

Antineurofilament antibodies in postencephalitic and idiopathic Parkinson's disease

Autoantibodies to neurofilaments were found by the immunofluorescence technique in serum of patients with postencephalitic (von Economo's) and idiopathic Parkinson's disease in the same proportion as in age-matched neurological and non-neurological controls. In addition, similar neurofibrillary staining was detected in age groups of 29 years and younger, but rarely in the first year of life. Persons over 70, with or without disease, showed a prevalence of antibodies significantly higher than in persons under 70. Serum from 1 case of Alzheimer's disease out of 4 tested, was positive for neurofilament antibodies; serum from the only case of Creutzfeldt-Jakob disease tested was negative. A total of 298 serum specimens, each from a different person, was tested. The use of cryostat-frozen longitudinal sections of normal rat spinal cord as a substrate has been confirmed to be an effective, reproducible and simple procedure for the detection of antineurofilament antibodies in human sera by indirect immunofluorescence.

Heterogeneic autoantibody against neurofilament protein in the sera of animals with experimental kuru and Creutzfeldt-Jakob disease and natural scrapie infection

Heterogeneic autoantibodies against axonal neurofilament proteins of mature mouse neurons grown in vitro were detected by the indirect immunofluorescence technique in 12.7% (9 of 71) of the sera from nonhuman primates infected with kuru, in 14.5% (17 of 117) and 4% (1 of 25), respectively, of the sera from nonhuman primates and laboratory rodents infected with Creutzfeldt-Jakob disease, and in 35% (7 of 20) of the sera from sheep naturally infected with scrapie. Autoantibody titers ranged from 1:16 to 1:512 in Creutzfeldt-Jakob disease-infected animals, 1:32 to 1:512 in kuru-infected animals, and 1:64 to 1:1,024 in sheep with natural scrapie. The sera from 11 monkeys and 17 hamsters infected with scrapie and from 19 chimpanzees inoculated with brain tissues from humans with other neurological diseases did not contain autoantibodies. Of the 41 chimpanzees with Creutzfeldt-Jakob disease, 6 had autoantibodies against neurofilament proteins before experimental inoculation, whereas 6 others developed autoantibodies after inoculation, 4 developed autoantibodies during the asymptomatic phase, and 2 developed autoantibodies during the terminal clinical phase. Of the 48 chimpanzees with kuru, 2 had autoantibodies before inoculation, 6 developed autoantibodies after inoculation, 3 developed autoantibodies during the asymptomatic phase, and 3 developed autoantibodies during the terminal clinical phase. Among the normal nonhuman primate controls, 4.6% (9 of 195) had autoantibodies. In contrast, no autoantibodies were detected in 49 control rodents and 13 control sheep. The increased incidence of autoantibodies against neurofilament proteins in animals with kuru, Creutzfeldt-Jakob disease, and scrapie constitutes the first evidence of an immunological reaction in this group of atypical infections caused by unconventional viruses and suggests that neurofilaments may be involved in pathogenesis.