Evidence of persistent low-level viremia in long-term HAART-suppressed, HIV-infected individuals

Abstract

Background: HAART can effectively reduce plasma HIV RNA levels to below the level of detection in most HIV-infected patients. The degree to which residual low-level viremia persists during HAART remains unclear.

Methods: We identified 180 individuals (median duration of HIV infection 12 years) who had at least two consecutive plasma HIV-1 RNA levels below the level of detection (<50-75 copies/ml) while taking antiretroviral drugs; 36 of 180 had been virologically suppressed for more than 5 years. Longitudinal plasma samples that were taken from these individuals during periods of viral load suppression were selected and analyzed. The isothermal transcription-mediated amplification (TMA) (limit of detection <3.5 copies RNA/ml) assay was used to measure persistent viremia. A 'detuned' EIA assay was used to obtain quantitative HIV antibody levels.

Results: A total of 1606 TMA assays were performed on 438 specimens in 180 HAART-suppressed individuals (median 3 replicates per specimen). In the first year of viral suppression, plasma RNA levels declined significantly (P = 0.001), but after month 12 there was no evidence for a continued decline (P = 0.383). In the first year of viral suppression, HIV antibody levels also declined (P = 0.054), but after month 12 there was no evidence for a continued decline (P = 0.988).

Conclusion: Viremia continued to decline during the first 12 months after viremia became undetectable using conventional methods, and then remained stable. HIV antibody levels also decreased in the first year of viral suppression and then remained stable. Viremia and the HIV-associated host response appear to achieve a steady-state 'set-point' during long-term combination therapy.

Figure 1. In vitro spiking experiments showing relationship between HIV RNA level and TMA assay

Spiking experiments showing relationship between HIV RNA level and signal:cutoff (S/Co) ratio using the Transcription Mediated Amplification (TMA) assay. Each dot represents the mean of three replicates (randomly selected from 20 replicates) performed by 4 different laboratory technicians; the lines represent the mean S/Co for each viral load copy number (0, 1, 3, 10, 30, 100, and 300 copies/mL).

Figure 2

“Month 0 of viral suppression” refers to the first timepoint at which subjects had the first of at least 2 consecutive plasma HIV RNA levels below the level of conventional detection (<50-75 copies/mL) while taking antiretroviral drugs. A. Plasma HIV-1 RNA levels. Ultrasensitive plasma HIV RNA levels were measured using the Transcription Mediated Amplification assay in 180 HAART-suppressed subjects. Each dot represents the mean signal:cutoff (S/Co) of all replicates for each timepoint (median 3 replicates per specimen). The thick line indicates estimated change in plasma HIV RNA over time using mixed effect linear models. B. HIV-1 antibody levels. HIV antibody levels were measured using a “detuned” or less-sensitive EIA on 98/180 HAART-suppressed subjects. SOD=standardized optical density using the less-sensitive EIA. The thick line indicates estimated change in HIV antibody levels over time using mixed effect linear models.