Neutralization of aggregated strains of enterovirus 71 and echovirus type 4 in RD and Vero or GMK-AH1 cells.

Strains of enterovirus 71 and echovirus type 4 containing aggregates which were poorly neutralized by antibody in cell lines of green monkey kidney origin such as Vero and GMK-AH1, were as easily neutralized as non-aggregated strains when grown in human RD cells, The explanation for this may be a lesser degree of aggregation of viral materials originating from RD cells and/or the use of lower doses of virus for neutralization tests in such cells. The latter was a consequence of a higher sensitivity of RD cells to minimal amounts of virus than that shown by Vero and GMK-AH1 cells. Thus, virus grown in RD, Vero or GMK-AH1 cells reached a titre 10 to 100 times higher in RD cells than in the other cell lines.