Screening and characterization of specific anti-lipopolysaccharide antibodies in Belgian blood donors by enzyme-linked immunosorbent assays

The goal of this project was to find and collect high concentrations of endotoxin-specific antibodies for therapeutic IgG- or IgM-enriched preparations. Various enzyme-linked immunosorbent assays (ELISAs) were developed to perform longitudinal studies of the serological response to a large panel of smooth and rough purified lipopolysaccharide (LPS) extracts in a population of healthy blood donors. To accomplish this, 1612 human serum samples from volunteer blood donors collected by seven different blood banks in Belgium were screened and specific IgM and IgG activities were measured. Approximately 17% of the donors had anti-LPS concentrations higher than 40 mg L(-1). Of these, 10.9% had anti-smooth LPS antibodies, 3.7% had anti-rough LPS antibodies and 2.8% were found to be positive towards both types of LPS. The mean anti-LPS antibody concentration was 8 mg L(-1) for rough LPS and 14 mg L(-1) for smooth LPS. Age- and sex-related distributions of the activities indicated that the greatest prevalence of high anti-LPS concentration was in women aged 40-49 years and in men older than 60 years. Differential absorption experiments showed that the pooled serum of selected blood donors contained a mixture of specific and cross-reacting antibodies. We detected predominantly anti-LPS activities due to the IgG(1) and IgG(2) subclasses. The range of specificities to different LPS was increased by the pooling of selected sera. It was concluded that pools of naturally occurring specific anti-LPS immunoglobulin antibodies may be obtained in Belgium by screening blood donors using ELISAs that we have developed.