Table 1.

Comparison of biologically selected AZT-resistant virus with molecularly cloned derivatives^*

Virus	D3	D6	D9	D12	D15	D18
SK29-KISE − AZT	+	+++	++++	c.d.	n.d.	n.d.
SFVAZTres − AZT	+	+++	++++	c.d.	n.d.	n.d.
BK03QR-ITTK − AZT	+	+++	++++	c.d.	n.d.	n.d.
BK04RG-ITTK − AZT	+	+++	++++	c.d.	n.d.	n.d.
SK29-KISE + AZT	(+)	(+)	(+)	−	−	−
SFVAZTres + AZT	+	+	+	++	+++	++++
BK03QR-ITTK + AZT	+	+	+	++	+++	++++
BK04RG-ITTK + AZT	+	+	+	++	+++	++++

^*10⁵ BHK/LTR(SFVmac)lacZ cells were infected at a multiplicity of infection (MOI) of 0.001 with the respective viruses either in the absence (− AZT) or presence (+ AZT) of 50 μM AZT. The cultures were stained for blue cells at the indicated days after infection and the replication of virus was monitored. (+), <1% infected cells; +, 1–10% infected cells; ++, 10–25% of cells were infected; +++, 25–50% infected cells; ++++, more than 50% of the cell culture was infected; c.d., cell culture was destroyed; n.d., not done. SK29-KISE is the wild-type molecular clone-derived virus, SFVAZTres is the biologically selected AZT-resistant virus, BK03QR-ITTK and BK04RG-ITTK are viruses derived from molecular clones containing the two gag and four pol or only the four pol gene mutations, respectively.