Kinetics of virus-induced hemolysis measured for single erythrocytes.

Individual erythrocytes are visible in bright-field microscopy because their enclosed hemoglobin provides a high degree of contrast against a glass slide. Lysis of these cells is detected as the loss of contrast of individual cells caused by the leakage of cell contents. Using these optical properties of erythrocytes, we have developed a new technique to examine the time course of hemolysis induced by Sendai virus at neutral pH and by influenza virus at acidic pH. Viruses were allowed to aggregate erythrocytes at 4 degrees and the temperature was raised to allow hemolysis. Influenza-induced hemolysis at low pH, as determined by this method, occurred at a faster rate than that induced by Sendai at neutral pH. As the lysis of individual cells is detected by this method, we have discerned a cooperative "cluster" effect: Once an erythrocyte within an aggregate lyses, the likelihood of lysis of another erythrocyte in that aggregate is increased.