(193a) Reduction of Virus Infectivity in the Presence of Protecting Osmolytes

Protecting osmolytes have the ability to reduce the infectivity by 4-logs of a model non-enveloped virus, porcine parvovirus (PPV) in cell culture.  Osmolytes are natural, organic compounds that stabilize intracellular proteins against environmental stresses, such as severe temperature or high osmotic pressure by changing the water content of cells.  Protecting osmolytes have the ability to fold proteins by structuring water around the protein surface, therefore stabilizing the protein.  We are currently working with PPV, a non-enveloped, icosahedral, single-strand DNA virus, to demonstrate the ability of osmolytes to attenuate non-nenveloped viruses.  We have discovered that both glycine and trimethylamine N-oxide (TMAO) reduce the initial 50% infectious dose of PPV from 8-logs to 4-logs.  This was quantified by the MTT assay, a cell viability assay that measured the cytopathic effects of PPV virus in susceptible pig kidney cells (PK-13 cells).  The reduction in infectivity decreased over time and approached 1 log reduction when the osmolyte was added 20 hours after initial virus infection.  We hypothesize that the osmolytes are disrupting the PPV infection cycle.  The PPV infection cycle starts with virus attachment to susceptible host cells, and then the virus penetrates the cells through the endosomal pathway to uncoat its genetic material.  The virus then uses the host cell’s replication machinery to produce viral DNA.  After replication, the virus assembles a protein coat, enveloping the nucleic acids, and then breaks open the cell to release progeny PPV particles.  It is possible that the osmolytes inhibit virus infectivity by disruption of either the virus interaction with receptors, the endosomal trafficking of virus through the cell or the transport of virus to the nucleus.  It appears that protecting osmolytes stabilize intracellular proteins in the initial stages of the PPV infection cycle.  We propose that the presence of protecting osmolytes can reduce virus infectivity of other non-enveloped viruses, such as the rhinovirus, which is known to cause the common cold in humans.