TABLE 1.

Specific infectivity of the vΔ2A-11 mutant particles

Time (hpi)	Genome copy number/RFUa		Relative particle specific infectivity (v18f/v2A-11)
	v18f	v2A-11
36	53	278	5.2
72	50	217	4.3

^aTo determine the genome copy number present in fraction 4 after fractionation of the infected cell extract on a sucrose gradient, virus particles were treated first with nuclease and then with proteinase K, and the resulting encapsidated RNAs were blotted and quantified after hybridization with a ³²P-labeled, negative-strand RNA probe, using a PhosphorImager. Comparison with a standard prepared from HAV RNA transcripts of known concentration allowed determination of the genome copy number present in the fraction. The number of infectious particles (RFU) present in the same fraction was determined by RIFA.