An investigation into the mode of action of the HIV protease inhibitor lopinavir against human papillomaviruses (HPV)


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Gavin Batman, Lynne Hampson, Anthony Oliver, Henry Kitchener, Ian Hampson

University of Manchester, Manchester, UK

Abstract

Background

High-risk types of the human papillomavirus (HPV) are a major cause of human cancer. Many viruses, including HPV, inappropriately activate the proteasome to degrade cellular proteins that are detrimental to viral replication. Previous studies have shown that HIV protease inhibitors such as lopinavir can inhibit this ability. Interestingly lopinavir has proved effective against the SARS virus and we have previously shown that it may also have the potential to treat HPV infections.

Method

Proteins from lopinavir treated and control HPV16+ve SiHa cervical carcinoma cells were extracted and labelled with Cy3 and Cy5 fluors. These were then used to immuno-probe a Panorama Xpress 725 antibody microarray (Sigma) in order to investigate the effects of lopinavir on cellular protein expression.

Results

Of the 725 proteins covered by the antibody microarray, 3 had decreased expression and 48 had increased expression following lopinavir treatment. Predictably apoptosis related proteins such as survivin, p53 and annexin V were up-regulated but most significant was the observation that RNase L was also elevated by treatment with lopinavir.

Conclusion

RNase L is an interferon-inducible antiviral protein that is known to cleave viral RNA in infected cells. Our data is the first to indicate that the antiviral activity of lopinavir may be due, in part, to activation of RNA’ase L. We are currently confirming and validating this effect by immunoblotting and siRNA mediated silencing of RNAase L. This should establish this novel mode of action for lopinavir in relation to HPV and potentially to other viruses.

Background

High-risk types of the human papillomavirus (HPV) are a major cause of human cancer. Many viruses, including HPV, inappropriately activate the proteasome to degrade cellular proteins that are detrimental to viral replication. Previous studies have shown that HIV protease inhibitors such as lopinavir can inhibit this ability. Interestingly lopinavir has proved effective against the SARS virus and we have previously shown that it may also have the potential to treat HPV infections.

Method

Proteins from lopinavir treated and control HPV16+ve SiHa cervical carcinoma cells were extracted and labelled with Cy3 and Cy5 fluors. These were then used to immuno-probe a Panorama Xpress 725 antibody microarray (Sigma) in order to investigate the effects of lopinavir on cellular protein expression.

Results

Of the 725 proteins covered by the antibody microarray, 3 had decreased expression and 48 had increased expression following lopinavir treatment. Predictably apoptosis related proteins such as survivin, p53 and annexin V were up-regulated but most significant was the observation that RNase L was also elevated by treatment with lopinavir.

Conclusion

RNase L is an interferon-inducible antiviral protein that is known to cleave viral RNA in infected cells. Our data is the first to indicate that the antiviral activity of lopinavir may be due, in part, to activation of RNA’ase L. We are currently confirming and validating this effect by immunoblotting and siRNA mediated silencing of RNAase L. This should establish this novel mode of action for lopinavir in relation to HPV and potentially to other viruses.