A Vero cell line persistently infected with African swine fever virus was established by infecting the cells in the presence of 10 mM NH4CI (Vero-P cell line). The virus derived from the Vero-P cultures infected Vero cells, and virus titers were comparable to those obtained in Vero cells acutely infected with African swine fever virus. The structural proteins of the virus from Vero-P cells were similar to those of the virus produced in Iytic infections. Virus production was low when the Vero-P

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... ells were growing logarithmically and increased considerably in confluent cultures when lysis appeared in a fraction of the cell population.