(15) Assay Card

General Information
Summary Circulin A and B shown to possess antiviral cytoprotective activity.
Condition An invitro XTT-based anti-HIV assay was used to screen for the effects of circulins A and B on virus-induced cell killing in diverse HIV-infected cultures. Ten different strains of HIV and two different hostcell lines were employed. Confirmatory assays examined the effects of the compounds upon viral replicative indices, including p24 antigen, supernatant reverse transcriptase and syncytium-forming units.
Result For both compounds,the antiviral cytoprotective concentrations (EC50s) ranged from about 40 to 260 nM, depending upon the particular virus strain and host cell line used in the assay. The cytotoxicity index concentrations (IC50s) were quite constant at about 500 nM in all assays. The concentration-dependent increase in cytoprotection observed in the XTT assays was paralleled with decreases in supernatant levels of viral p24, reverse transcriptase and infectious virions. The mechanism of anti-HIV activity for circulins A and B has not yet been defined; however, in a reverse transcriptase (RT) assay they had no activity at concentrations as high as 660 nM.
AssayType Anti-HIV

Gustafson KR, Sowder RC, Henderson LE, Parsons IC, Kashman Y, Cardellina JH, McMahon JB, Buckheit RB, Pannell LK, Boyd MR (1994) Circulins A and B. Novel human immunodeficiency virus (HIV)-inhibitory macrocyclic peptides from the tropical tree Chassalia parvifolia. J Am Chem Soc 116:9338-8

Proteins Assayed circulin B
circulin A