No evidence for production of intrathecal immunoglobulin G against Acinetobacter or Pseudomonas in multiple sclerosis

Use of albumin quotient and IgG index to differentiate blood- vs brain-derived proteins in the cerebrospinal fluid of cats with feline infectious peritonitis

Background: Inflammation of the central nervous system (CNS) is a frequent condition in cats but etiology often remains unsolved. Routine cerebrospinal fluid (CSF) analysis can be extended through the calculation of the albumin quotient (Q_alb), a marker of the integrity of the blood–brain barrier (BBB), and IgG index, an estimate of intrathecal IgG synthesis.

Objectives: The purpose of this study was to validate nephelometric methods for CSF protein analysis, and to use the Q_alb and IgG index to discriminate blood‐ and brain‐derived immunoglobulin fractions in cats with feline infectious peritonitis (FIP).

Methods: Cats presented to our clinic between 2001 and 2005 were included in the study based on clinical and laboratory data and histopathologic findings at necropsy. Cats were grouped as having nonneurologic disease (controls; n=37), brain tumors (n=8), FIP involving the CNS (n=12), and extraneural FIP (n=12). CSF‐total protein (TP) was measured and albumin and IgG concentrations were measured in paired CSF/serum samples; Q_alb and IgG index were calculated. Intraassay and interassay precision of the nephelometric assays were determined using pooled samples.

Results: Coefficients of variation for the nephelometric assays ranged from 2.7% to 7.2%. In control cats, CSF‐TP concentration ranged from 0.06 to 0.36 g/L, Q_alb ranged from 0.6 to 5.7 × 10⁻³, and IgG index ranged from 0.3 to 0.6. Q_alb and IgG index were significantly higher in cats with brain tumors and cats with CNS‐FIP compared with other groups. Compared with control cats, pleocytosis was evident in 8 of 12 (67%) cats and CSF‐TP was increased in 3 of 12 (25%) cats with CNS‐FIP.

Conclusion: Nephelometry is a reliable method for measurement of CSF protein, albumin, and IgG in cats. The Q_alb and IgG index did not identify a CSF protein pattern specific for BBB dysfunction or intrathecal IgG synthesis in cats with CNS‐FIP.

From rabies to transmissible spongiform encephalopathies: An immune-mediated microbial trigger involving molecular mimicry could be the answer

The concept of experimental allergic encephalomyelitis (EAE) being linked to both rabies post-vaccination encephalomyelitis and multiple sclerosis (MS) has raised the intriguing question whether animal studies carried out for the induction and transmission of transmissible spongiform encephalopathies (TSEs) using brain antigens including prions do have a similar immunopathogenetic mechanism. Although an essential link between autoimmunity and MS has been well established, its role in the pathogenesis of TSEs is generally lacking. However, auto-antibodies to myelin proteins and/or other neuronal antigens such as neurofilaments and prion proteins have been reported in animals with bovine spongiform encephalopathy (BSE) and scrapie as well as in patients with Creutzfeld-Jakob disease (CJD) and kuru. Acinetobacter has been suggested as a possible triggering microbial factor in the initiation of the autoimmune responses in these diseases because bacterial molecular sequences resemble brain antigens, especially in animals affected with BSE and patients with MS and CJD. These possibilities need to be evaluated further with longitudinal prospective studies carried out on larger numbers of animals or humans with such diseases. The transplantation of saline suspensions of brain homogenates will evoke immunological responses and therefore, the results in the study of MS and other neurological diseases have to be interpreted with caution.

Measurement of high affinity antibodies on antigen-immunoblots

We describe a semi-quantitative method for measuring the relative affinity of antigen-specific oligoclonal IgG bands separated by isoelectric focusing followed by blotting onto antigen-coated membrane and incubation with sodium thiocyanate. When the developed blot is digitised in greyscale, densitograms can be made and peak areas calculated using ImageJ freeware. By expressing peak area as a percentage of the total area under the curve we have shown that there is a statistically significant rise in percentage of peak area for a given band which persists with increasing molarities of sodium thiocyanate.