TABLE 3.

Phenotypic and genotypic PMPA susceptibility of virus isolates obtained from SIV-infected infant macaques following short-term PMPA treatment

Animal no.	PMPA treatment perioda	Time point (day) of virus isolateb	Phenotype IC95 (μM)c	RT codon 65d
30020	Days 5–19	26	40	K
30022		26	40	K
30023		26	40	K
30024		19	40	K
30053	Days 5–65	79	45	K
30054		79	40	K
30055		79	40	K
30061		65	40	K
30074	Days 5–65	65	45	K
30077		NA	NA	NA

^aAnimals were started on short-term PMPA treatment (30 mg/kg subcutaneously once daily) 5 days after oral wild-type SIVmac251 inoculation for a total duration of 14 or 60 days. 

^bVirus was isolated from PBMC at the end of PMPA treatment or at the first available time point after PMPA withdrawal. NA, not available (no virus could be isolated from animal 30077 during PMPA treatment or at time of euthanasia at day 65). 

^cIn vitro susceptibility to PMPA is indicated by the 95% inhibitory concentration. SIVmac mutants with K65R mutation in RT and fivefold-reduced susceptibility to PMPA, which emerged in SIVmac251-infected infant macaques following prolonged PMPA treatment, are described elsewhere (47). The IC₉₅ of PMPA for wild-type SIVmac251 was 30 to 50 μM (with a K at RT codon 65) and the IC₉₅ of PMPA for mutant SIVmac was 150 to 250 μM (with an R at RT codon 65). 

^dAmino acid at codon 65 of RT. K, arginine; R, lysine.