Latex fetuin spheres as probes for influenza virus neuraminidase in productively and abortively infected cells.

Fetuin bound latex spheres do not adhere to the membranes of non-infected cells but adhere to those of cells productively infected by fowl plague virus (FPV Dobson strain). In contrast, asialo fetuin spheres do not attach to the membranes of productively infected cells. Moreover latex fetuin spheres incubated with extracts of productively infected cells and extensively washed are specifically enriched in neuraminidase activity without any trace of haemagglutinin. These observations suggest that viral neuraminidase in the membrane is the site of attachment of the sialic acid moieties of fetuin spheres. These neuraminidase sites are detectable when L cells are productively infected by a mammalian cell adapted mutant of the Dobson strain (FPV-B) but are not detectable on L cells abortively infected by wild type (FPV+). However, even in the abortive system, neuraminidase is synthesised de novo as shown by its labelling with 14C-glucosamine and by its isolation from labelled extracts of infected cells by latex fetuin spheres. These results show that misintegration of viral neuraminidase in the plasma membrane of L cells is a feature of abortive infection of these cells by the Dobson strain of FPV. However the relationship (if any) of this misintegration to abortive infection remains to be established.