FIG. 3.

Quantitation of HN receptor binding for wild-type and variants. RBC with different degrees of receptor depletion were prepared by treatment with various amounts of bacterial neuraminidase (see abscissa) as described in Materials and Methods. Aliquots of these and control (undepleted) RBC preparations were used to quantify HAD on cell monolayers transfected with constructs expressing wild-type (WT, open circles), C28 (open squares), C28a (open triangles), P111S (open diamonds), or ZM1 (hash mark) HN. The extent of binding of each of the “depleted” RBC is expressed (ordinate) as a percentage of the control (i.e., of the amount of untreated, nondepleted RBC bound on cells expressing the corresponding HN). The points are means of results for triplicate monolayers, with bars denoting standard deviation.