TABLE 1.

Direct analysis of phenotypic resistance of HIV-1 RT activity to 3TC in plasma from 15 HIV-1-infected persons by determination of levels of RT inhibition by 3TC-TP^a

Sample	Week	Treatment	RT activity (U/ml)		% Inhibition of RT	Mutations
			No 3TC-TP	With 3TC-TP (5 μM)		Codon 184	Other
1B	Preb	AZT-ddC	1.7 × 10−9	NDc	100	M184	none
1E	12	AZT-3TC	2.1 × 10−6	5.1 × 10−7	75.6	V/M184	L41, Y215
1F	18	AZT-3TC	1.3 × 10−7	3.3 × 10−8	75.9	V184	none
2B	Pre	AZT-ddC	2.2 × 10−6	6.3 × 10−9	99.7	M184	none
2F	12	AZT-3TC	1.5 × 10−6	4.7 × 10−7	68	V184	none
3B	Pre	AZT	1.8 × 10−6	1.7 × 10−8	99.4	M184	none
3F	12	AZT-3TC	1.6 × 10−8	1.2 × 10−9	92.3	M/V184	none
3G	21	AZT-3TC	5.1 × 10−9	1.0 × 10−8	0	V184	none
4A	Pre	AZT	1.6 × 10−7	1.2 × 10−10	99.9	M184	R70
4B	12	AZT-3TC	ND	ND		V184	R70
5A	Pre	AZT	1.2 × 10−8	ND	100	M184	Y215
5B	4	AZT-3TC	ND	ND		M/V184	Y215
5C	10	AZT-3TC	ND	ND		V184	Y215
6A	Basal	Basal	7.7 × 10−5	3.6 × 10−8	99.9	M184	none
6B	12	AZT-3TC	2.3 × 10−5	1.5 × 10−5	34.7	V184	none
7A	Basal	Basal	1.2 × 10−8	ND	100	M/I184	none
7C	28	AZT-3TC	ND	ND		V184	none
8A	Pre	AZT	4.4 × 10−5	5.7 × 10−8	99.9	M184	L41, Y215
8B	8	AZT-3TC	5.0 × 10−5	4.3 × 10−5	15	V184	L41, Y215
9A	Pre	d4Td	2.9 × 10−6	6.3 × 10−8	97.8	M184	L41, Y215
9F	12	AZT-3TC	2.1 × 10−6	1.1 × 10−6	47	V184	L41, Y215
10A	4	AZT-3TC	8.9 × 10−5	9.1 × 10−6	87.8	M184	none
10C	12	AZT-3TC	1.9 × 10−7	1.9 × 10−7	0	M/V184	none
10G	52	AZT-3TC	2.6 × 10−5	3.5 × 10−5	0	V184	L41, Y215
11A	12	AZT-3TC	1.9 × 10−7	1.3 × 10−7	29.1	V/M184	R70
11C	36	AZT-3TC	1.7 × 10−7	7.0 × 10−8	58.5	V184	R70
12A	Pre	AZT	2.5 × 10−5	9.2 × 10−7	96.3	M184	none
12E	28	AZT-3TC	1.7 × 10−6	5.1 × 10−7	70	V184	R70, Y215
13A	Pre	d4T	1.5 × 10−6	6.2 × 10−8	95.9	M184	N69, R70
13F	60	d4T-3TC-INDe	6.3 × 10−5	7.4 × 10−5	0	V184	L41, D/N69, R70
14A	1	AZT-3TC	2.5 × 10−7	1.3 × 10−8	94.7	M184	L41, D69, R70, Y215
14F	44	IND-3TC	2.9 × 10−9	5.1 × 10−9	0	V184	D69, R70, Y215
15A	Pre	AZT	8.9 × 10−5	4.0 × 10−6	95.5	M184	D69
15D	40	AZT-3TC-IND	1.6 × 10−10	2.4 × 10−10	0	V184	D69, Y215

^aPrevious treatments were as follows: patient 9 was on AZT before the first sample was obtained, patient 13 was on AZT-ddC before the first sample was obtained, and patient 14 was on ddI for a period of time between the times that the first and second samples were obtained. 

^bPre, pretherapy. 

^cND, not detected. 

^dD4T, stavudine. 

^eIND, indinavir.