Serodiagnosis of recent hepatitis B infection by IgM class anti-HBc.

The time sequence, relative reactivity, and persistence of anti-HBc IgM were assessed in patients with HBsAg-positive viral hepatitis. A solid-phase immunoassay was developed using the IgM capture procedure with anti-mu-coated polystyrene beads. HBcAg was purified from serum Dane particles and used as a probe with 125I-labeled anti-HBc IgG. This immunoassay exhibited a pronounced prozoning phenomenon, and relative titers of sera differed widely depending upon the dilution of serum tested. When all sera were tested at 1:5,000 dilution, results were comparable in different patient groups. Anti-HBc IgM persisted at detectable levels for up to 2 years, and it was necessary to establish relative titers to discriminate current from remote infections. A cut-off assay value was established, and in 12 cases of acute hepatitis B virus (HBV) infection, antibody exceeded this value for about 6 months after onset of HBs antigenemia. A similar profile of anti-HBc IgM persistence was observed in seven patients who developed an HBsAg chronic carrier state. Long-term viral replication did not sustain elevated IgM class-specific antibody levels. The studies suggest that anti-HBc IgM analyses may be useful for differentiating recent and current HBV infections from remote infections, eliminating HBV as the agent for non-A, non-B hepatitis in asymptomatic HBsAg carriers, and detecting HBV as the etiologic agent during silent (HBsAg negative) infections.

Biologic properties of nontoxic derivatives of a lipopolysaccharide from Escherichia coli K235.

Lipopolysaccharide (LPS)2 from Escherichia coli K235 was treated with o-phthalic anhydride to obtain a high degree of esterification of available hydroxyl groups, leaving a free carboxyl for each hydroxyl esterified (SPLPS). Although there was no demonstrable loss of fatty acids, this conversion of LPS to a polyanionic molecule altered dramatically the spectrum of biologic properties, most of which are normally attributed to the lipid A (LA) moiety. Mitogenicity for mouse B cells was decreased several hundred-fold; reaction with antibodies to LPS was abolished; pyrogenicity and toxicity were decreased by factors of 10(5) and 10(4); the ability to induce the Shwartzman reaction in rabbits was decreased 500-fold, and the ability to stimulate production of interferon in mice was decreased by more than 2 x 10(3). However, despite the loss of these properties, SPLPS retained the ability to act as an immunologic adjuvant. The nature of the anionic group is important, e.g., sodium succinyl-LPS (SuLPS) is 10-fold more pyrogenic and toxic than sodium phthalyl-LPS (SPLPS). Data on another LPS derivative, from which ester-linked fatty acid residues were removed before phthalylation, suggest that the ester-linked fatty acid groups in the lipid A moeity of SPLPS may not be necessary for its immunologic adjuvant effect.