TABLE 1.

Characteristics of cells persistently infected by Hz-1 virus

Cell line	Spontaneous reactivationa at passage:		Titer of virusb at passage:		Viral DNA content in host cells		PAT1 expression	Viral interferencec
	30	200–230	30	200–230	%	Copies of viral genome/cell		Hz-1 virus	AcMNPV
TNP1	210 ± 90	0	8.2 × 104	0	5.3	1,686	+++	Strong	None
TNP2	32 ± 8	0	4.4 × 103	0	2.1	342	+	Strong	None
TNP3	21 ± 6	0	2.6 × 103	0	16.5	2,436	++	Strong	None
SFP2	21 ± 8	0	1.4 × 102	0	0.12	20	+	Strong	None
SFP4	81 ± 11	NDd	5.2 × 103	ND	0.66	145	++++	Strong	None

^aNumber of persistently infected cells undergoing spontaneous reactivation per 10⁵ cells. SFP4, a newly established persistently infected cell line, was assayed only at passage 30. Results are means and standard deviations. 

^bTiters of virus (PFU per milliliter per 48 h) released into the media. 

^cAfter challenge by Hz-1 virus or AcMNPV, the titer of the released virus was estimated as a reference for the occurrence of viral interference. 

^dND, not done.