FIG 4.

F proteins on spRSV harboring partially cleaved p27 show prefusion conformation with higher thermal stability. Changes in OD at 450 nm from indirect ELISA analysis of site II, site Ø, and p27 from spRSV/A/Bernett and spRSV/B/BA are shown. Individual spRSV aliquots were heated for 10 min at different temperatures (x axis) before ELISA (A and B). Differences in F protein content between spRSVs were adjusted by adopting site II as measure of total F protein. Changes in MAb binding to site Ø and p27 were determined at each temperature by the changes in site Ø/site II and p27/site II ratios relative to those at 25°C (C and D). Error bars are standard deviations (n = 3 replicates).