MEASUREMENT OF HUMAN-IMMUNODEFICIENCY-VIRUS TYPE-1 PLASMA VIRUS LOAD BASED ON REVERSE-TRANSCRIPTASE (RT) ACTIVITY - EVIDENCE OF VARIABILITIES IN LEVELS OF VIRION-ASSOCIATED RT

Virus load based on levels of functional reverse transcriptase (RT) wa s measured in plasma from 50 human immunodeficiency virus (HIV) type 1 -infected persons, in 87 samples from 10 HIV-1 seroconversion panels, and in 100 uninfected persons by use of Amp-RT, an ultrasensitive RT a ssay, Of the 50 clinical samples, 38 (76%) were Amp-RT positive, while all uninfected controls were negative. Pearson's correlation coeffici ent of RNA and RT levels was .73 for all samples, .86 for seroconversi on samples, and .49 for clinical samples. Calculated ratios of RT acti vity to virion RNA varied widely during both early and late stages of infection. Mean RT:RNA ratios in 8 seroconversion panels and in 12 (34 .3%) of 35 individual clinical samples were significantly lower than t he ratio for a reference virus. However, ratios were stable in individ ual seroconversions over time. These data demonstrate that RT activity can be used to quantitate plasma virus load and provide evidence of d ifferent levels of virion-associated RT among HIV-1-infected persons.