A note on the use of trypsinized human group O erythrocytes in arbovirus titrations.

Twenty-two different arbovirus antigens derived from five antigenic groups were examined for their ability to agglutinate normal and trypsinized human group O erythrocytes. Trypsinization rendered the cells susceptible to agglutination by 18 viruses,chiefly in the pH 5.85 to 6.2 range, yielding hemagglutinin titers comparable with those obtained with gander cells at their optimal pH.