Plasma cytokine levels during acute HIV-1 infection predict HIV disease progression

Abstract

Background: Both T-cell activation during early HIV-1 infection and soluble markers of immune activation during chronic infection are predictive of HIV disease progression. Although the acute phase of HIV infection is associated with increased pro-inflammatory cytokine production, the relationship between cytokine concentrations and HIV pathogenesis is unknown.

Objectives: To identify cytokine biomarkers measurable in plasma during acute HIV-1 infection that predict HIV disease progression.

Design: Study including 40 South African women who became infected with HIV-1 and were followed longitudinally from the time of infection.

Methods: The concentrations of 30 cytokines in plasma from women with acute HIV-1 infection were measured and associations between cytokine levels and both viral load set point 12 months postinfection and time taken for CD4 cell counts to fall below 350 cells/microl were determined using multivariate and Cox proportional hazards regression.

Results: We found that the concentrations of five plasma cytokines, IL-12p40, IL-12p70, IFN-gamma, IL-7 and IL-15 in women with acute infection predicted 66% of the variation in viral load set point 12 months postinfection. IL-12p40, IL-12p70 and IFN-gamma were significantly associated with lower viral load, whereas IL-7 and IL-15 were associated with higher viral load. Plasma concentrations of IL-12p40 and granulocyte-macrophage colony-stimulating factor during acute infection were associated with maintenance of CD4 cell counts above 350 cells/microl, whereas IL-1alpha, eotaxin and IL-7 were associated with more rapid CD4 loss.

Conclusion: A small panel of plasma cytokines during acute HIV-1 infection was predictive of long-term HIV disease prognosis in this group of South African women.

Figure 1

Comparison of plasma cytokine concentrations in women (n=14) before infection (median 25.5 weeks pre-infection) and during acute HIV-1 infection (median 6 weeks post-infection). A) Absolute IL-1α, IL-1β, IL-6, TNF-α, IL-8, fractalkine, IP-10, IL-10, IL-7 and IL-2 concentrations were elevated in women with acute HIV-1 infection relative to concentrations pre-infection. Wilcoxon Signed Ranks test was used for matched comparisons. P-values <0.05 were considered significant and highlighted. *Did not remain significant following false discovery rate adjustment for multiple comparisons. ** Remained significant following adjustment for multiple comparisons. B) Fold upregulation in plasma cytokine concentrations following infection. P-values <0.005 remained significant following adjustment for multiple comparisons (red bars). Blue bars (P<0.05) indicate cytokines that were significantly upregulated before adjustment for multiple comparisons. IQR: Interquartile range.

Figure 1

Comparison of plasma cytokine concentrations in women (n=14) before infection (median 25.5 weeks pre-infection) and during acute HIV-1 infection (median 6 weeks post-infection). A) Absolute IL-1α, IL-1β, IL-6, TNF-α, IL-8, fractalkine, IP-10, IL-10, IL-7 and IL-2 concentrations were elevated in women with acute HIV-1 infection relative to concentrations pre-infection. Wilcoxon Signed Ranks test was used for matched comparisons. P-values <0.05 were considered significant and highlighted. *Did not remain significant following false discovery rate adjustment for multiple comparisons. ** Remained significant following adjustment for multiple comparisons. B) Fold upregulation in plasma cytokine concentrations following infection. P-values <0.005 remained significant following adjustment for multiple comparisons (red bars). Blue bars (P<0.05) indicate cytokines that were significantly upregulated before adjustment for multiple comparisons. IQR: Interquartile range.

Figure 2

Plasma inflammatory cytokine concentrations are associated with concurrent plasma viral loads in women with acute HIV-1 infection. Only cytokines that correlated significantly with viral load before adjustment for multiple comparisons are represented (p-values and Spearman rho values below heat map). Women are ranked according to acute infection viral load. Relative acute infection plasma cytokine concentrations of study participants are shown as a heat map, with each row representing the cytokine concentrations in an individual woman and falling alongside her viral load. For each particular cytokine, the concentrations found in this group of women were ranked and assigned an appropriate colour ranging from white (lowest concentration) to red (highest concentration). Repeated values were assigned the same rank and hence colour. IP-10, TNF-α, IL-1α, IL-1β, IFN-γ and IL-10 correlated with viral load. PID: Patient Identity Number. # IP-10 and TNF-α remained significantly correlated with viral load following adjustment for multiple comparisons. * Not done

Figure 3

Acute infection IL-12p40, IL-12p70, IFN-γ, IL-7 and IL-15 concentrations are predictive of viral load set-point. A) Each cytokine was significantly associated with viral load set-point (p-values <0.005). The model fitted the data significantly (p>F<0.0001), and together the 5 cytokines predicted 65.77% (Adjusted R² = 0.6577) of the variation in set-point. B) Set-point viral loads (VL) as predicted by the model correlate with observed set-point viral loads.

Figure 4

Acute infection IL-12p40, GM-CSF, IL-1α, Eotaxin and IL-7 concentrations were associated with the time taken for the study participant CD4 counts to fall below 350 cells/μl. A) Each cytokine was significantly associated with survival time (p values <0.05) and the model fitted the data well (p>χ²<0.0001). B) Kaplan Meier survival estimates of women grouped according to risk score. Risk scores were calculated for each participant using the β coefficients of each cytokine included in the Cox proportional-hazards model, and women were divided into low (0-15), medium (15-20) and high (20-25) risk groups based on risk scores. Women in the high risk group experienced rapid CD4 loss, while women in the low risk group maintained CD4 counts above 350 cells/μl for the duration of follow-up. Each dash indicates a time point at which an individual woman left the study (censored event).