[Chronic infection of BHK-21 cells by the Machupo virus. The development of the system and properties of the virus produced by cells of this line].

A new model of chronic infection of BHK-21 cells with Machupo virus has been obtained. The chronically infected culture of BHK-21-M cells differed morphologically from the control culture by the presence of giant mono- and multinuclear forms with granular cytoplasm and by an increase in the number of small rounded cells. In the system of BHK-21-M cells, the persisting virus was produced permanently but the per cent of infected cells determined by indirect immunofluorescence and the infectious centre method was not high (12-17%). The main factor contributing to the development of Machupo virus persistence in this cell system appears to consist in the formation of defective interfering particles.