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Clinical and Diagnostic Laboratory Immunology, November 2002, p. 1240-1247, Vol. 9, No. 6
1071-412X/02/$04.00+0     DOI: 10.1128/CDLI.9.6.1240-1247.2002
Copyright © 2002, American Society for Microbiology. All Rights Reserved.

Adjuvant Activity of Emulsan, a Secreted Lipopolysaccharide from Acinetobacter calcoaceticus

Bruce Panilaitis,^1* Atul Johri,² Walter Blank,^2, David Kaplan,² and Juliet Fuhrman¹

Department of Biology,¹ Department of Chemical and Biological Engineering, Biotechnology Center, Tufts University, Medford, Massachusetts 02155²

Received 7 January 2002/ Returned for modification 30 June 2002/ Accepted 9 August 2002

Several promising adjuvant candidates have been studied over the past 75 years; however, only alum is currently approved for human use. The complex acylated polysaccharide emulsan, secreted from Acinetobacter calcoaceticus, represents a new candidate. Unique features of this family of polymers are their amenability to structural tailoring and their emulsification behavior. We demonstrate that emulsan activates macrophages in a dose-dependent manner. This activation is dependent on the presence of the fatty acid side chains that decorate the polysaccharide backbone, and, furthermore, the level of activation can be affected by changes in the chemical characteristics of emulsan structural variants. One emulsan variant was examined in a classical hapten carrier immunization protocol and demonstrated significant adjuvant activity as determined by hapten-specific antibody titers. This immune response was characterized by a high immunoglobulin G2a titer, consistent with a Th1 response. The significant immunopotentiation demonstrated by this complex polymer establishes emulsan as an exciting new candidate adjuvant. Furthermore, by manipulating the chemical structure of this compound, we can explore the physical basis of pattern recognition receptors and macrophage activation.

Present address: Charles River Laboratories, Andover, Mass.