Induction of a striking systemic cytokine cascade prior to peak viremia in acute human immunodeficiency virus type 1 infection, in contrast to more modest and delayed responses in acute hepatitis B and C virus infections

Abstract

Characterization of the immune responses induced in the initial stages of human immunodeficiency virus type 1 (HIV-1) infection is of critical importance for an understanding of early viral pathogenesis and prophylactic vaccine design. Here, we used sequential plasma samples collected during the eclipse and exponential viral expansion phases from subjects acquiring HIV-1 (or, for comparison, hepatitis B virus [HBV]or hepatitis C virus [HCV]) to determine the nature and kinetics of the earliest systemic elevations in cytokine and chemokine levels in each infection. Plasma viremia was quantitated over time, and levels of 30 cytokines and chemokines were measured using Luminex-based multiplex assays and enzyme-linked immunosorbent assays. The increase in plasma viremia in acute HIV-1 infection was found to be associated with elevations in plasma levels of multiple cytokines and chemokines, including rapid and transient elevations in alpha interferon (IFN-alpha) and interleukin-15 (IL-15) levels; a large increase in inducible protein 10 (IP-10) levels; rapid and more-sustained increases in tumor necrosis factor alpha and monocyte chemotactic protein 1 levels; more slowly initiated elevations in levels of additional proinflammatory factors including IL-6, IL-8, IL-18, and IFN-gamma; and a late-peaking increase in levels of the immunoregulatory cytokine IL-10. Notably, there was comparatively little perturbation in plasma cytokine levels during the same phase of HBV infection and a delayed response of more intermediate magnitude in acute HCV infection, indicating that the rapid activation of a striking systemic cytokine cascade is not a prerequisite for viral clearance (which occurs in a majority of HBV-infected individuals). The intense early cytokine storm in acute HIV-1 infection may have immunopathological consequences, promoting immune activation, viral replication, and CD4(+) T-cell loss.

FIG. 1.

Plasma viral titers in subjects acutely infected with HIV-1, HCV, and HBV. Longitudinal viral nucleic acid titers in plasma samples from donors acquiring HIV-1 infection (A), HBV infection (B), and HCV infection (C) are shown. The sample time courses are aligned relative to a T₀, which is defined as the time point when the plasma viral load (VL) first reached detectable levels (100 RNA copies/ml for HIV, 200 DNA copies/ml for HBV, and 600 RNA copies/ml for HCV). The smooth lines are spline estimates.

FIG. 2.

Kinetics of changes in plasma cytokine levels in three subjects acutely infected with HIV. Plasma levels of six cytokines (IL-15, IFN-α, TNF-α, IL-18, IFN-γ, and IL-10) in samples collected at sequential time points from three representative HIV-infected plasma donors (donors 12008, PRB951, and 9015) are shown (black circles and solid lines), together with the plasma HIV titers, expressed as log₁₀ viral RNA copies/ml (white circles and dotted lines), for each of these individuals. For each subject, time is plotted relative to T₀, the time point when plasma viremia first reached 100 RNA copies/ml. The vertical dashed line in each panel indicates T₀. The horizontal dashed lines indicate the subject-specific baseline levels of each analyte, and the horizontal black lines indicate the 95% upper prediction bound, above which post-T₀ responses were termed positive.

FIG. 3.

Timing of initial elevation in plasma levels of different cytokines and chemokines in groups of subjects acutely infected with HIV, HBV, or HCV. Kaplan-Meier estimation was used to represent the distribution of time (relative to T₀) of the initial elevation in levels of different analytes in groups of subjects infected with HIV (A and B), HBV (C and D), and HCV (E and F). Each panel shows a composite of the results for 24 different analytes plotted as the cumulative proportion of the study population who had exhibited an elevation in plasma analyte levels over time (days from T₀). In A, C, and E, results for six cytokines are highlighted in color [lime green, IL-15; emerald green, TNF-α; orange, IFN-α; pink, IL-5; purple, IL-12(p70); dark blue, IL-4] in a single panel, while results for other analytes are in gray. In B, D, and F, there are 24 small panels, each of which shows the results for a single analyte highlighted in color, while results for other analytes are in gray. The panels in B, D, and F are ordered (left to right across four rows) according to the timing of initial analyte elevation in the HIV-infected subject group, with the analyte most rapidly elevated in 50% of subjects shown first.

FIG. 3.

Timing of initial elevation in plasma levels of different cytokines and chemokines in groups of subjects acutely infected with HIV, HBV, or HCV. Kaplan-Meier estimation was used to represent the distribution of time (relative to T₀) of the initial elevation in levels of different analytes in groups of subjects infected with HIV (A and B), HBV (C and D), and HCV (E and F). Each panel shows a composite of the results for 24 different analytes plotted as the cumulative proportion of the study population who had exhibited an elevation in plasma analyte levels over time (days from T₀). In A, C, and E, results for six cytokines are highlighted in color [lime green, IL-15; emerald green, TNF-α; orange, IFN-α; pink, IL-5; purple, IL-12(p70); dark blue, IL-4] in a single panel, while results for other analytes are in gray. In B, D, and F, there are 24 small panels, each of which shows the results for a single analyte highlighted in color, while results for other analytes are in gray. The panels in B, D, and F are ordered (left to right across four rows) according to the timing of initial analyte elevation in the HIV-infected subject group, with the analyte most rapidly elevated in 50% of subjects shown first.

FIG. 3.

Timing of initial elevation in plasma levels of different cytokines and chemokines in groups of subjects acutely infected with HIV, HBV, or HCV. Kaplan-Meier estimation was used to represent the distribution of time (relative to T₀) of the initial elevation in levels of different analytes in groups of subjects infected with HIV (A and B), HBV (C and D), and HCV (E and F). Each panel shows a composite of the results for 24 different analytes plotted as the cumulative proportion of the study population who had exhibited an elevation in plasma analyte levels over time (days from T₀). In A, C, and E, results for six cytokines are highlighted in color [lime green, IL-15; emerald green, TNF-α; orange, IFN-α; pink, IL-5; purple, IL-12(p70); dark blue, IL-4] in a single panel, while results for other analytes are in gray. In B, D, and F, there are 24 small panels, each of which shows the results for a single analyte highlighted in color, while results for other analytes are in gray. The panels in B, D, and F are ordered (left to right across four rows) according to the timing of initial analyte elevation in the HIV-infected subject group, with the analyte most rapidly elevated in 50% of subjects shown first.

FIG. 4.

Mean change relative to baseline in plasma analyte levels over time in groups of subjects infected with HIV, HBV, and HCV. The mean changes relative to baseline in plasma levels of 24 different analytes over time (relative to T₀) in the entire group of subjects infected with HIV (A), HBV (B), or HCV (C) are shown. Each panel includes a composite of the results for all 24 analytes, with data for a single analyte (as indicated by the label above) highlighted in color and data for other analytes shown in gray. The mean plasma viral load in the entire group of subjects (viral nucleic acid copies [cp]/ml, plotted on a log scale) is also shown in each panel (black line). Panels are ordered alphabetically by analyte.

FIG. 4.

Mean change relative to baseline in plasma analyte levels over time in groups of subjects infected with HIV, HBV, and HCV. The mean changes relative to baseline in plasma levels of 24 different analytes over time (relative to T₀) in the entire group of subjects infected with HIV (A), HBV (B), or HCV (C) are shown. Each panel includes a composite of the results for all 24 analytes, with data for a single analyte (as indicated by the label above) highlighted in color and data for other analytes shown in gray. The mean plasma viral load in the entire group of subjects (viral nucleic acid copies [cp]/ml, plotted on a log scale) is also shown in each panel (black line). Panels are ordered alphabetically by analyte.

FIG. 5.

Scaled proportional group mean change relative to baseline over time in plasma levels of selected analytes in subjects acutely infected with HIV. The proportional change relative to baseline in plasma levels of selected analytes (see key) and the viral load over time in the entire group of HIV-infected subjects are shown. The peak heights for different analytes are scaled according to the percentage of HIV-infected subjects studied who exhibited an elevation in plasma levels of the analyte concerned. Time is plotted in days relative to T₀. cp, copies.