Short Communication: HIV Blips While on Antiretroviral Therapy Can Indicate Consistently Detectable Viral Levels Due to Assay Underreporting

Abstract

Viral blips, where HIV RNA plasma viral load (pVL) intermittently increases above the lower limit of assay detection, are a cause for concern. We investigated a number of hypotheses for their cause. We assessed HIV RNA, and total and episomal HIV DNA from 16 individuals commencing antiretroviral therapy (ART) consisting of raltegravir and tenofovir/emtricitabine for 3 years, using two assays: a single-copy assay [SCA; lower limit of quantification (LLOQ), < 1 copy/ml] and the Amplicor assay (LLOQ of 50 copies/ml). Two individuals exhibited viral blips. From week 20 onward, the period where ART had achieved its final suppressive levels, pVL ranged from < 1 to 330 copies/ml, except for one individual at the final time. Both assays were 98% consistent (108/110) in assessing pVL < 50 copies/ml, but the Amplicor assay registered 56% of samples (19/34) as below the LLOQ that were in the 50 to 1000 copy/ml range as quantified by SCA. pVL changes between successive time points did not correlate with changes in cellular infection as measured through either total or episomal HIV DNA. Changes in pVL were correlated (negatively) with changes in total CD4+ T cell numbersPatients receiving stable, seemingly suppressive ART can have pVL near the 50 copy LLOQ at multiple time points. The high Amplicor assay error rate around this level implies that viral blips underrepresent pVL being more consistently above the LLOQ. Activation of latently infected cells is less likely to contribute to this phenomenon. S uppression of HIV plasma viral load (pVL) to as low levels as possible and for as long as possible is the primary goal of antiretroviral therapy (ART). Sudden rises of pVL in a patient after extended periods in the undetectable range ( < 50 copies/ml for many assays) can be a cause for concern for both physician and patient. A consistent increase in pVL is often a sign of ART failure, most likely due to noncompliance, low plasma drug levels, or the outgrowth of a drug-resistant viral quasispecies. The clinical implications of viral "blips," where seemingly random detectable pVL levels occur amongst undetectable ones, are less clear.A number of theories have been advanced to explain viral blips, but there are essentially two hypotheses: (1) differences in detection of pVL at or around the lower limits of assay quantification (LLOQ) occur through errors in the reproducibility of the assays and fluctuations of pVL around mean HIV RNA levels below the LLOQ 1-3 ; and (2) new rounds of viral replication arise through a variety of mechanisms resulting in rapid increases in pVL above the LLOQ from previously low levels. [4][5][6] An underlying assumption with the second hypothesis is that successful ART suppresses pVL much lower than 50 copies/ml and a blip represents a large change in pVL.We investigated these questions using data from 16 HIVinfected, therapy-naive patients [eight primary (PHI) and eight chronic (CHI)] commencing raltegravir and Truvada (tenofovir/emtricitabine) who were followed for 3 years (the PINT Study 7...

Factors associated with HIV viral load “blips” and the relationship between self-reported adherence and efavirenz blood levels on blip occurrence: a case–control study

“…Given the validity of SRA and drug levels, combined with the high adherence in this population, this study provides additional support that blips are unlikely to be associated with lack of adherence. Alternative hypotheses suggest that blips may be secondary to assay variability, decreased assay sensitivity at lower viral load or release from a latent reservoir [ 10 , 11 , 26 ]. In a study by Murray et al [ 10 ], HIV RNA and total and episomal HIV DNA were assessed using a single copy assay with a lower limit of quantification (LLOQ) of <1 copy/mL and the Amplicor assay with a LLOQ of 50 copies/mL.…”

“…Proposed explanations for the appearance of blips include transient increases in viral production due to fluctuations in adherence [ 6 ], concurrent illnesses or vaccinations [ 7 , 8 ], and artifact due to variability in the VL assay [ 9 – 11 ]. Another possibility, with considerable clinical implications, is that blips may represent ongoing low-level viral replication and may ultimately result in virologic failure and the development of drug resistance [ 10 , 12 – 15 ].…”

Neuropathogenesis of HIV-associated neurocognitive disorders

“…An overall plasma HIV blip (> 50 HIV RNA copies/ml) frequency of ~25% has been demonstrated in an observational cohort study (n=3550 virally suppressed patients) [18]. Several causes of blipping are proposed, including differences in VL assay sensitivity [19] and factors affecting HIV replication (ART adherence, immune activation, viral resistance, among others) [18,20*,21]. A role for blips in contributing to increased immune activation and accelerated disease progression has been suggested [20*] although this has been challenged [22].…”

Time above 1500 copies

“…These studies were not intended to characterize the transmission potential of patients, because the temporary increases in viral load may not reach a level that heightens that risk. Although studies have found isolated instances of HIV transmission occurring between serodiscordant heterosexual couples when viral load was less than 1000 copies/ml [6], for the overwhelming majority of couples, risk for transmission increased when viral load was above 1500 copies/ml [7–9]. …”