TABLE 1.

HIV isolates used in the study

Virus	Major coreceptor(s) used	Source
Primary isolates
HIV-192US660	R5	NIHa
HIV-192HT599	X4	NIHa,b
HIV-260415K	R5	NIHa,c
HIV-220.04d	X4	Nuno Taveira
Lab-adapted strains
HIV-1NL4-3	X4	MRCe
HIV-2ROD10	R5, X4	MRCe

^aFrom the Multicenter AIDS Cohort Study, NIH AIDS Reagent Program, Division of AIDS, NIAID, NIH.

^bProvided by Neal Halsey.

^cProvided by Feng Gao and Beatrice Hahn.

^dPreviously represented as PTHCC20/2004 (26) and 19/2004 (27).

^eNIBSC, Centre for AIDS Reagents, Medical Research Council, United Kingdom.