Effect of monophosphoryl lipid A on host resistance to bacterial infection.

The ability of monophosphoryl lipid A (MPLA) to enhance nonspecific host resistance to bacterial infections was studied. Mice were treated with MPLA prior to intraperitoneal challenge with Escherichia coli or Staphylococcus epidermidis. Animals received additional MPLA for 2 days postinfection, and survival rates were determined. Ten micrograms of MPLA per mouse significantly improved the survival of animals infected with either bacterial species. Dose-response studies showed significant MPLA-induced protection at doses of 6 micrograms/kg against E. coli challenge and 60 micrograms/kg against S. epidermidis challenge.

Human leukocyte interferon: separation of biologically different species by modification of carbohydrate moieties.

Human leukocyte interferon was studied to determine if its antiviral (AV) and growth inhibitory (GI) activities could be separated by enzymatic or chemical cleavage of carbohydrate moieties and electrophoretic procedures. The relative proportion of the two activities (AV:GI ratio) was determined for each gel fraction. Untreated interferon and interferon deglycosylated by glycosidases or metaperiodate were subjected to polyacrylamide gel electrophoresis in sodium dodecyl sulfate. The AV:GI ratio was similar for all fractions, indicating that no dissociation of activities was achieved based on molecular weight differences. The three preparations were then examined by isoelectric focusing to attempt separation based on charge. The untreated sample was resolved into several peaks each with a constant AV:GI ratio of 3:1. Both deglycosylated interferons showed inconstant AV:GI ratios yielding GI fractions that were enriched or depleted in AV activity. These results indicate that under the conditions used the AV and GI activities could not be separated, although molecules can be obtained that differ significantly in their relative antiviral and growth inhibitory properties.