St John's wort protein found to suppress HIV in lab

"During the course of that study, we also looked to see whether these
plant extracts that we had isolated from the callus culture had any
anti-viral activity," said Khalili. "We soon discovered that the
plant extract inhibited HIV-1 gene expression and replication in
infected cells."

http://debunkbigpharma.blognation.us/blog/_archives/2005/10/25/1321798.html