A novel acute HIV infection staging system based on 4th generation immunoassay

Abstract

Background: Fourth generation (4thG) immunoassay (IA) is becoming the standard HIV screening method but was not available when the Fiebig acute HIV infection (AHI) staging system was proposed. Here we evaluated AHI staging based on a 4thG IA (4thG staging).

Findings: Screening for AHI was performed in real-time by pooled nucleic acid testing (NAT, n=48,828 samples) and sequential enzyme immunoassay (EIA, n=3,939 samples) identifying 63 subjects with non-reactive 2nd generation EIA (Fiebig stages I (n=25), II (n=7), III (n=29), IV (n=2)). The majority of samples tested (n=53) were subtype CRF_01AE (77%). NAT+ subjects were re-staged into three 4thG stages: stage 1 (n=20; 4th gen EIA-, 3rd gen EIA-), stage 2 (n=12; 4th gen EIA+, 3rd gen EIA-), stage 3 (n=31; 4th gen EIA+, 3rd gen EIA+, Western blot-/indeterminate). 4thG staging distinguishes groups of AHI subjects by time since presumed HIV exposure, pattern of CD8+ T, B and natural killer cell absolute numbers, and HIV RNA and DNA levels. This staging system further stratified Fiebig I subjects: 18 subjects in 4thG stage 1 had lower HIV RNA and DNA levels than 7 subjects in 4thG stage 2.

Conclusions: Using 4th generation IA as part of AHI staging distinguishes groups of patients by time since exposure to HIV, lymphocyte numbers and HIV viral burden. It identifies two groups of Fiebig stage I subjects who display different levels of HIV RNA and DNA, which may have implication for HIV cure. 4th generation IA should be incorporated into AHI staging systems.

Figure 1

Frequency of cell subsets in the peripheral blood at time of acute HIV infection using Fiebig and 4^th generation enzyme immunoassay staging systems for CD4+ T cells (A), CD8+ T cells (B), CD19+ B cells (C) and CD16+56+ natural killer cells (D). FI to IV are Fiebig acute HIV infection stages I to IV. 4thG 1 to 3 are 4thG acute HIV infection stages 1 to 3. The whiskers indicate median (inter-quartile range).

Figure 2

Reservoir size in the peripheral blood at time of acute HIV infection (A) and at 24 weeks of antiretroviral therapy (B) using Fiebig and 4th generation enzyme immunoassay staging systems. FI to IV are Fiebig acute HIV infection stages I to IV. 4thG 1 to 3 are 4thG acute HIV infection stages 1 to 3. The whiskers indicate median (inter-quartile range).