FIG. 4.

Noninfectious particles are released by an HN site II variant with enhanced receptor binding and F triggering.

(a) Equal amounts of each sample collected from HAE cells infected with wt and HN variants (H552Q, T193A, and N551D) and treated with neuraminidase or zanamivir or untreated (Fig. ​(Fig.2b2b and ​and3)3) were subjected to immunoprecipitation with anti-HN antibodies and were immunoblotted with polyclonal anti-HPIV3 antibodies. The major viral protein band, NP (molecular mass of 64 kDa), was used for quantitation.

(b) Densitometric quantitation of viral protein intensities for each variant and treatment shown above (a). The relative intensity of the NP band for each scenario is shown on the y axis. (c) Ratios of viral titer (infectious particles) to viral protein for each virus and treatment.