Naturally occurring antibodies in human sera that react with the iron-regulated outer membrane proteins of Escherichia coli

Abstract

Sera from normal healthy human adults and infants, as well as sera from mice, rabbits, and guinea pigs, were examined by immunoblotting for naturally occurring antibodies reacting with outer membrane proteins of two Escherichia coli strains, 0111 and 018. Some individuals had antibodies reacting very strongly with the iron-regulated outer membrane proteins, including the ferric-enterochelin receptor protein (Mr, 81,000), as well as with ompA. However, sera from infants contained predominantly antibodies to ompA; antibodies recognizing the iron-regulated outer membrane proteins were either absent or barely detectable. In human serum the antibodies were mainly of the immunoglobulin G class. No serotype-specific antibodies to the lipopolysaccharide of E. coli 0111 or 018 were found in the sera tested.

Iron uptake mechanisms of pathogenic bacteria

“…Whatever their precise roles, however, it is clear that growth of many pathogenic species in vivo in the iron-limited conditions of an infected animal body induces the expression of a variety of envelope proteins, including receptors for ferric-siderophores and transferrin binding proteins. The iron-repressible outer membrane proteins of Gram-negative bacterial pathogens are often suggested as candidate immunogens for immunoprophylactic therapy [19,22,122,[276][277][278]. Polyclonal and monoclonal antibodies against the ferripyochelin-binding protein have been shown to block ferripyochelin uptake by Pseudomonas aeruginosa [279,280] and cause a ten-fold increase in the number of bacterial cells ingested by polymorphonuclear leukocytes [280].…”

Heat-stable serotyping antigens expressed by strains of Campylobacter jejuni are probably capsular and not long-chain lipopolysaccharide

“…Furthermore, SDS-PAGE and immunoblotting were used to demonstrate LPS-specific antibodies binding to LPS expressed by strains of E. coli and Salm. enteritidis (Chart and Griffiths 1985;Chart and Rowe 1991a).…”

Naturally Occurring Anti- Escherichia coli Protein Antibodies in the Sera of Healthy Humans Cause Analytical Interference in a Recombinant Nucleocapsid Protein-Based Enzyme-Linked Immunosorbent Assay for Serodiagnosis of Severe Acute Respiratory Syndrome

“…However, small portions of false positives have been reported (11,20,23), making this diagnostic tool less favorable for the early detection of possible resurfacing SARS infections. As the presence of anti-EP antibodies (Ab) in sera of healthy humans has been widely reported (5,9,14), herein we hypothesize that the interactions between the residual Escherichia coli proteins (REP) present in the coating antigen and the naturally occurring anti-E. coli protein (anti-EP) antibodies in healthy humans may serve as a potential interference (21).…”

“…The rNP 5 -based ELISA was first assessed by screening serum samples from 300 healthy individuals and 8 convalescent SARS patients. Briefly, wells were immobilized with 50 ng of rNP 5 and washed before a standard blocking procedure with blocking buffer (3% milk powder in phosphate-buffered saline with 0.05% Tween 20). Human serum samples (1:100 [vol/vol]) were then applied, and incubation was performed at 37°C for 25 min, followed by incubation of horseradish peroxidase (HRP)-mouse anti-human immunoglobulin G (IgG) (1:1,000 [vol/vol]; Zymed) for 25 min.…”

“…2B to E). Although the intensities of the corresponding bands of REP in purified rNP 5 were relatively weak ( Fig. 2E), these bands may accumulatively contribute to the overall optical density readings in the rNP 5 ELISA, leading to the false-positive signals.…”