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Researchers at Temple University School of Medicine discovered that a novel protein, p27SJ, extracted from a callus culture of the St. John’s wort plant ( Hypericum perforatum ) suppresses HIV-1 expression and inhibits its replication.

Their findings, “ p27SJ, a novel protein in St. John’s wort, that suppresses expression of HIV-1 genome,” is published in the journal of Gene Therapy.

Kamel Khalili, at Temple University and the study’s lead author, said the researchers were originally examining plant extracts from St. John’s wort cultured in the laboratory to see if they had any effect on cell growth or the behavior of brain cells in vitro.

“ 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.”

Next, the team sought to isolate the protein from the plant extract responsible for the observed anti-viral activity. After identifying the protein, the group cloned the gene, which they realized was a novel protein and named p27SJ.

After cloning the gene, the researchers then were able to identify the molecular mechanism by which the protein is able to suppress HIV-1 gene expression and replication, according to Khalili.

It is the expression of the viral gene and the replication of the viral genome that leads to the development of AIDS in HIV-infected individuals.

“ Our studies indicate that p27SJ has the capacity to inhibit expression of the HIV-1 gene by interacting with both cellular proteins and viral proteins,” said Khalili. “ Since HIV-1 gene expression relies heavily on these factors, p27SJ can block viral replication by interfering with the proteins recruited by HIV-1 to increase viral gene expression.”

Khalili strongly emphasized that the researchers do not know if the p27SJ protein they discovered is present in the St. John’s wort preparations sold as a dietary supplement, and therefore, those tablets should not be considered as a treatment for patients infected with HIV-1.

Source: Temple University, 2005