Trapping viruses in blood.

Trapping viruses in blood

An estimated 3 to 5 percent of U.S. recipients of blood transfusions will contract infections from contaminating viruses. Though blood is routinely screened to spot such viruses, a few still evade detection. To catch these, chemical engineers at the University of Michigan in Ann Arbor have developed an adsorbent-based virus-immobilizing filter for whole blood.

In tests with the herpes simplex virus, reports project leader Henry Wang, the experimental system reduced massive viral contamination in just one pass through the filter from 100,000 viruses per pint to around 100. But because the system is really aimed at finding and trapping just the trace quantities that elude blood-screening tests today, he and co-developer I-Fu Tsao believe it "can potentially remove all viral contaminants" from donated blood.

Viruses infect healthy cells by attaching to specific receptors on the cell surface. The Michigan researchers bind healthy cells carrying these receptors to sterile, 200-micron dextran beads. Then the bead-bound cells are packed into a 10-milliliter column. As blood passes through, viruses will leave the blood to bind with open receptors on the bound cells, Wang says. And his data suggest free viruses are not the only ones susceptible to such trapping.

"It is well known that the structure of the [normal] cell membrane undergoes certain modifications in the course of virus infection," he notes. These cells usually develop identifying marker antigens on their surface that match those on the surface of the virus infecting them. As long as this antigen is present, Wang says, an infected cell in the blood will be as fatally attracted to the filter as are free viruses.

Depending on which attractant cells are initially bound into the filter, Wang says, his system can be engineered to trap specific viruses or the whole range of those found contaminating blood. For example, upcoming tests will measure the filter's efficacy in immobilizing the AIDS virus using trapped T cells. Wang estimates that the cost for blood filtration using this device should be "much less than $10 per pint of blood."