Sowing antiviral seeds.

Sowing antiviral seeds

Viruses are a hardy bunch. They survive exposure to many potent chemicals unscathed, and most compounds that can kill them wipe out the host cell as well. In Vancouver, researchers at the University of British Columbia are working with a class of phototoxic plant compounds that, they say, show promising though preliminary signs of antiviral activity.

Phototoxic compounds can cause allergic reactions, and sometimes illness or death, when they are eaten or touched by an animal that is then exposed to the ultraviolet A radiation in sunlight. But at last month's annual meeting of the American Society for Photobiology in Los Angeles, Neil Towers reported that five such compounds, found in plants of the marigold and sunflower families, appear to be even more toxic to viruses than to animal cells.

Towers and James Hudson grew Sindbis virus and mouse-cytomegalovirus in mouse cells, then exposed the cultures to the phototoxins in varying concentrations. According to Hudson, "relatively low' concentrations of the compounds destroyed the viral membranes while leaving the membranes of the mouse cells undamaged. The compounds appear to act on unsaturated fatty acids in the viral membranes, Towers says. Though the viruses were still able to penetrate the host cells, they were "essentially killed,' since they were no longer able to replicate.

There are other phototoxins that appear to have antiviral activity, the researchers say, many of them derived from plants traditionally considered to have medicinal value. Some of these compounds disrupt the virus's genetic material and are more likely to have harmful side effects on the host cells.

The researchers have not yet tried the membrane-specific compounds in animals, but if in vitro results are borne out, Hudson says, there is the potential for a new class of drugs, potent against many viruses but without some of the serious side effects that occur with other antiviral drugs.