Ly Research Laboratories, Indianapolis, IN, USA) were made in dimethyl sulfoxide and diluted in medium, i.e., DMEM with 2.5 FBS, before use. Stock solutions of 10 mg/ml 2-AP; 4 mg/ml levamisole; 10 mg/ml L-NAME and 1 mg/ml L-NMMA were directly made in medium; hemin: a stock solution of 3.25 mg/ml was prepared by addingPage 8 of(page number not for citation purposes)Virology Journal 2008, 5:http:/