Lipopeptides containing 2-(palmitoylamino)-6,7-bis(palmitoyloxy) heptanoic acid: synthesis, stereospecific stimulation of B-lymphocytes and macrophages, and adjuvanticity in vivo and in vitro.
Lipopeptides, carrying the N-terminal lipoamino acid 2-(palmitoylamino)-6,7-bis(palmitoyloxy) heptanoic acid (Pam3Adh-OH, 1), were obtained by solid-phase synthesis and by synthesis in solution. 2-Amino-6,7-dihydroxyheptanoic acid (Adh) can be regarded as a methylene analogue of S-glycerylcysteine, the N-terminal amino acid of lipoprotein from the outer cell membrane of Escherichia coli (a methylene group substitutes for the sulfur atom). The lipopeptides Pam3Adh-Ser-Ser-Asn-Ala 2a-d, in which the four possible stereoisomers of Pam3Adh-OH (2S,6S)-1 (1a), (2S,6R)-1 (1b), (2R,6S)-1 (1c), and (2R,6R)-1 (1d) are linked to the naturally occurring sequence Ser-Ser-Asn-Ala of the N-terminus of lipoprotein, and also Pam3Adh-Ser-(Lys)4 [2S,6S)-3), with a peptide part rendering the molecule water soluble, were capable of stimulating murine splenocytes polyclonally in vitro, as determined in a proliferation assay and in a hemolytic plaque assay against trinitrophenylated sheep erythrocytes. The diastereomers (2S,6S)-2 and (2R,6S)-2 with S-configurated C-6 were more active than the diastereomers (2S,6R)-2 and (2R,6R)-2 with R-configurated C-6; a change of the configuration at C-2 had less effect on the stimulatory activity. (2S,6S)-2 and (2S,6S)-3 are potent immunoadjuvants. A significantly enhanced primary immune response against trinitrophenylated sheep erythrocytes was obtained in vitro at lipopeptide concentrations of about 5 micrograms/mL and an immunization dose of 10(7) sheep erythrocytes/mL. Balb/c mice, which were immunized with a mixture of ovalbumin and (2S,6S)-2 or (2S,6S)-3, respectively, had a substantially higher antiovalbumin titer 28 days after immunization than mice which had received ovalbumin, (2S,6S)-2 or (2S,6S)-3 alone. Finally, the novel lipopeptides constitute potent macrophage activators: (2S,6S)-3 was able to induce tumor cytotoxicity against the tumor cell line L929 in bone marrow derived macrophages.
Metzger
J
J
Institute of Organic Chemistry, University of Tübingen, FRG.
Jung
G
G
Bessler
W G
WG
Hoffmann
P
P
Strecker
M
M
Lieberknecht
A
A
Schmidt
U
U
D000276:Adjuvants, Immunologic / Q000138:chemical synthesis* / Q000494:pharmacology; D000818:Animals; D001402:B-Lymphocytes / Q000187:drug effects*; D002460:Cell Line; D055598:Chemical Phenomena; D002621:Chemistry; D006462:Hemolytic Plaque Technique; D008074:Lipoproteins / Q000138:chemical synthesis* / Q000494:pharmacology*; D008262:Macrophage Activation / Q000187:drug effects; D008264:Macrophages / Q000187:drug effects*; D051379:Mice; D008807:Mice, Inbred BALB C; D009374:Neoplasms, Experimental / Q000188:drug therapy; D010455:Peptides / Q000138:chemical synthesis* / Q000494:pharmacology; D013237:Stereoisomerism; D013329:Structure-Activity Relationship
D000276:Adjuvants, Immunologic; D008074:Lipoproteins; D010455:Peptides