Biophysical studies on the action of guanidine hydrochloride and urea on influenza virus A/Singapore/57

Summary

Guanidine hydrochloride or urea selectively inactivated the haemagglutinin (HA) of influenza virus A/Singapore/57 (N2H2), with only slight reduction in neuraminidase (Nase) activity. The results of experiments with isotope-labelled virus, as well as the results of HA-antibody-blocking test suggested that the surface subunits were not released as monomers during the treatment. The inactivation of the HA was thus anin situ process. In this regard the action of guanidine or urea on influenza virus differs from that of other reagents such as detergents commonly used in disruption studies. Electron microscopic examination of treated particles showed that with low molar concentrations of guanidine (1.0 m or 1.5 m) the basic architecture of the virion was retained; higher concentrations (4.0 m or 7.0 m) produced striking swelling of the particles, with disorganized surface “spikes”. Ultracentrifugation studies showed that the residual Nase activity was virionassociated.