Attempt to establish persistent infection in the HeLa-L cell line with the recombinant viruses rVBS/P80NS4m, rVBS/P80S, rVBS/P80ORFs2ab, rVBS/P80ORFs34, rVBS/P80ORFs234, and rVBS/GP5P98→L. Tissue culture supernatants from serial subcultures up to the 10th passage were harvested and titrated. Data representative of results from two separate experiments are shown.