Avidity of antineurocytoskeletal antibodies in Alzheimer's disease patients

Mucosal antibody quantity but not avidity predicts likelihood of Salmonella infection in red-eared slider turtles (Trachemys scripta)

Natural antibodies (NAbs) are polyreactive, have low avidity, and are a product of B-1 cells. Evidence suggests that NAbs may play a key role in immune defense in turtles, as increased total mucosal antibodies are associated with a decreased number of extracellular intestinal parasites. However, it is unknown if this trend extends to other types of pathogens and if avidity of the NAb to the pathogen is a factor in protection. We examined the relationship between a common intracellular bacteria in turtles-Salmonella-and NAbs. Plasma and mucosal samples were taken from red-eared slider turtles. We measured levels and avidity of antibodies that bound to lipopolysaccharide (LPS), a component of Salmonella cell wall. We examined the relationship between these measures and the ability of plasma to kill Salmonella as well as infection status. Higher mucosal antibody levels were significantly associated with a decrease in likelihood of infection with Salmonella; however, plasma antibody levels were not. There was a trend for bactericidal ability of the plasma to be positively correlated with plasma antibody levels bound to LPS, but not mucosal antibody levels. Avidity was not significantly related to either killing capacity or likelihood of infection suggesting that only increased quantity and not better binding is responsible for the decreased likelihood of infection. These findings suggest that NAb regulation was sufficient to isolate the infection to the gastrointestinal tract of the turtles, allowing it to be cleared with the mucus layer. Our results add further evidence that turtles use a general, nonspecific NAb response to combat pathogens.

Lower Serum Antibodies Against Tau Protein and Heavy Neurofilament in Alzheimer's Disease

BACKGROUND

Unlike antibodies against amyloid-β, little is known about serum antibodies to neuron-specific cytoskeletal proteins in patients with Alzheimer's disease (AD).

OBJECTIVE

We aimed to study IgG autoantibodies against tau protein, light (NFL) and heavy subunits (NFH) of neurofilaments in serum of AD patients and elderly controls and to explore the evolution of antineurocytoskeletal antibody levels over time.

METHODS

Antibodies against three targets (tau, NFL, and NFH) were measured using ELISA in 100 serum samples from 51 cognitively normal elderly controls and 49 patients with AD. Our primary cross-sectional design was further extended to monitor fluctuations over 1-2 years in a subset of individuals.

RESULTS

The AD patients had lower levels of anti-tau antibodies (p = 0.03) and even lower anti-NFH antibodies (p = 0.005) than those in the control group at baseline. On the contrary, anti-NFL antibodies or total IgG concentrations in serum did not differ. All three antibodies remained stable in both groups except for a selective and significant anti-tau decline in AD patients (p = 0.03).

CONCLUSIONS

The different responses to these antigens suggest some antibody selectivity in AD. The significant decline was observed for only serum anti-tau antibodies in AD patients over time and it corresponds to lower anti-tau levels in these patients. Our findings indicate a special feature of disease-relevant antigens and humoral autoimmunity in AD.

Changes in concentrations of tau-reactive antibodies are dependent on sex in Alzheimer's disease patients

The presence of pre-existing natural antibodies against Alzheimer's disease (AD) pathological proteins might interfere with immune responses to therapeutic vaccination with these proteins. We aimed to compare levels of antibodies in CSF and serum: We observed higher reactivity of natural tau-reactive antibodies towards phosphorylated bovine tau protein than to human recombinant (non-phosphorylated) tau protein. Males with MCI-AD had higher amounts of these antibodies than corresponding controls. Concentrations of antibodies were lower in females with the MCI-AD than in control females. These findings may have implications for tau vaccination trials.

Naturally occurring antibodies against serum amyloid A reduce IL-6 release from peripheral blood mononuclear cells

Serum amyloid A (SAA) is a sensitive inflammatory marker rapidly increased in response to infection, injury or trauma during the acute phase. Resolution of the acute phase and SAA reduction are well documented, however the exact mechanism remains elusive. Two inducible SAA proteins, SAA1 and SAA2, with their variants could contribute to systemic inflammation. While unconjugated human variant SAA1α is already commercially available, the variants of SAA2 are not. Antibodies against SAA have been identified in apparently healthy blood donors (HBDs) in smaller, preliminary studies. So, our objective was to detect anti-SAA and anti-SAA1α autoantibodies in the sera of 300 HBDs using ELISA, characterize their specificity and avidity. Additionally, we aimed to determine the presence of anti-SAA and anti-SAA1α autoantibodies in intravenous immunoglobulin (IVIg) preparations and examine their effects on released IL-6 from SAA/SAA1α-treated peripheral blood mononuclear cells (PBMCs). Autoantibodies against SAA and SAA1α had a median (IQR) absorbance OD (A₄₅₀) of 0.655 (0.262–1.293) and 0.493 (0.284–0.713), respectively. Both anti-SAA and anti-SAA1α exhibited heterogeneous to high avidity and reached peak levels between 41–50 years, then diminished with age in the oldest group (51–67 years). Women consistently exhibited significantly higher levels than men. Good positive correlation was observed between anti-SAA and anti-SAA1α. Both anti-SAA and anti-SAA1α were detected in IVIg, their fractions subsequently isolated, and shown to decrease IL-6 protein levels released from SAA/SAA1α-treated PBMCs. In conclusion, naturally occurring antibodies against SAA and anti-SAA1α could play a physiological role in down-regulating their antigen and proinflammatory cytokines leading to the resolution of the acute phase and could be an important therapeutic option in patients with chronic inflammatory diseases.