Cell attachment and mouse virulence of echovirus 9 correlate with an RGD motif in the capsid protein VP1.

The recently analyzed sequences of the nonpathogenic prototype strain Hill and the mouse-virulent strain Barty of the human echovirus 9 differ particularly in an insertion coding for an RGD motif at the C-terminus of the capsid protein VP1 in the genome of strain Barty. To investigate molecular determinants of virulence, we generated a panel of recombinant viruses derived from cDNA clones of strains Hill and Barty. In this communication, we show that the mouse-pathogenic character of strain Barty correlates with a 310-aa segment including the RGD motif. By mutating the RGD to an RGE tripeptide, the infectivity of the resulting echovirus 9 clones for GMK cells is lost. Furthermore, we could show that synthetic peptides containing the RGD sequence influence binding of mouse-virulent echovirus 9 strains to GMK cells, whereas binding of apathogenic strains is not affected. These results suggest that the RGD motif is a significant factor affecting pathogenicity of echovirus 9 strains.

[Changes in the membrane fluidity of human neutrophilic granulocytes under the effect of a chemoattractant (FMLP) and of echo virus, type 9, A. Barty strain]. / Veränderungen der Membranfluidität menschlicher neutrophiler Granulozyten unter dem Einfluss eines Chemoattractant (FMLP) und von Echo-Virus, Typ 9, Stamm A. Barty.

Preincubation of human polymorphonuclear leucocytes (PMNs) with different concentrations of Echo virus, type 9, strain A. Barty results in viral dose- and time-dependent inhibition of chemotactic cellular response to chemoattractant (N-formylmethionylleucylphenylalanine = FMLP). In the present experiments, by means of biophysical methods using excimer forming lipids (pyrendecanoic acid) the influence of FMLP and Echo 9 virus on membrane fluidity of PMNs was investigated. It is shown that the increase of membrane fluidity elicited by FMLP is reduced by the virus in a dose dependent manner. These results indicate virus-induced disturbance of molecular architecture and failure of natural signal processing of PMN-membranes. This biophysical method, therefore, can be used as a functional histochemical method to demonstrate functional defects in membranes of living cells.

Inactivation of enteroviruses by ascorbic acid and sodium bisulfite.

Poliovirus type 1, coxsackievirus type A9, and echovirus type 7 were inactivated by sodium bisulfite and ascorbic acid. Inactivation rates depended upon concentration, temperature, and pH. RNA infectivity was lost during inactivation; the capsid was also altered by these inactivating agents, as determined by enzyme sensitivity assays and by tests of adsorption to cells. Structural modifications of the virus particles were not identical, suggesting that the mechanism of inactivation by ascorbic acid differs from that of sodium bisulfite.