title: Influence of endosome-destabilizing peptides on efficacy of anti-HIV immunotoxins.
abstract: The effects on immunotoxin efficacy of fusogenic peptides derived from influenza virus hemagglutinin have been studied. These peptides have an amphipathic nature and change conformation from random at pH 7 to helical at pH 5. Fusogenic peptides are reported to destabilize endosomal membranes, resulting in the release of contents into the cytoplasm. The use of two related fusogenic peptides to enhance the efficacy of anti-HIV immunotoxins is described. The direct toxicity of the peptides was tested on HIV-infected H9/NL4-3 cells. Peptide HA24 was considerably more toxic than HA23. The peptides were mixed with two different immunotoxins. Immunotoxin action was enhanced by both peptides, with HA24 providing greater enhancement than HA23. Immunotoxins were then constructed by coupling HA23 or HA24 to the targeting antibody with disulfide-containing linkers. Peptide HA23 enhanced the activity of the immunotoxin 4-5-fold. Surprisingly, HA24 significantly inhibited immunotoxin activity. Coupling the peptides to the immunotoxin had no effect on antigen binding characteristics or the activity of the toxic moiety. Bafilomycin A1, an agent that inhibits vacuolar acidification, markedly potentiated the effects of all immunotoxins. These results demonstrate that amphipathic peptides can influence the efficacy of immunotoxins, but in sometimes unpredictable ways.
authors.affiliation: Laboratory of Microbial Structure and Function, Rocky Mountain Laboratories, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Hamilton, Montana 59840, USA.
authors.forename: V V
authors.initials: VV
authors.lastname: Tolstikov
authors.forename: R
authors.initials: R
authors.lastname: Cole
authors.forename: H
authors.initials: H
authors.lastname: Fang
authors.forename: S H
authors.initials: SH
authors.lastname: Pincus
mesh_terms: D000469:Alkaline Phosphatase / Q000378:metabolism; D000595:Amino Acid Sequence; D000818:Animals; D000900:Anti-Bacterial Agents / Q000494:pharmacology; D016860:CD4 Immunoadhesins / Q000378:metabolism / Q000627:therapeutic use; D002460:Cell Line; D011992:Endosomes / Q000378:metabolism*; D004791:Enzyme Inhibitors / Q000494:pharmacology; D004797:Enzyme-Linked Immunosorbent Assay; D006168:Guinea Pigs; D015699:HIV Envelope Protein gp120 / Q000276:immunology*; D015497:HIV-1; D006801:Humans; D000922:Immunotoxins / Q000627:therapeutic use*; D018942:Macrolides; D008958:Models, Molecular; D008969:Molecular Sequence Data; D010455:Peptides / Q000378:metabolism*; D006180:Proton-Translocating ATPases / Q000037:antagonists & inhibitors; D011817:Rabbits
chemical_list: D000900:Anti-Bacterial Agents; D016860:CD4 Immunoadhesins; D004791:Enzyme Inhibitors; D015699:HIV Envelope Protein gp120; D000922:Immunotoxins; D018942:Macrolides; D010455:Peptides; C040929:bafilomycin A1; D000469:Alkaline Phosphatase; D006180:Proton-Translocating ATPases