Biological activity of synthetic heptaacyl lipid A representing a component of Salmonella minnesota R595 lipid A

A synthetic lipid A (preparation 516), containing seven acyl groups and representing one component of natural free lipid A of Salmonella minnesota R595, has been investigated for biological activity in a number of endotoxin test systems. It was found that the synthetic preparation was, in typical in vivo endotoxin tests (lethality, pyrogenicity, Shwartzman reactivity) as well as in its antigenicity and macrophage activation capacity, significantly less active than natural Salmonella lipid A. However, in other in vitro assay systems (B-cell mitogenicity, complement activation, Limulus amoebocyte lysate gelation) it expressed similar activity as Salmonella lipid A.