Divergent Cytokine and Chemokine Responses at Early Acute Simian Immunodeficiency Virus Infection Correlated with Virus Replication and CD4 T Cell Loss in a Rhesus Macaque Model

Abstract

Cytokine and chemokine levels remain one of the significant predictive factors of HIV pathogenesis and disease outcome. Understanding the impact of cytokines and chemokines during early acute infection will help to recognize critical changes during HIV pathogenesis and might assist in establishing improved HIV treatment and prevention methods. Sixty-one cytokines and chemokines were evaluated in the plasma of an SIV-infected rhesus macaque model. A substantial change in 11 cytokines/growth factors and 9 chemokines were observed during acute infection. Almost all the cytokines/chemokines were below the baseline values for an initial couple of days of infection. We detected six important cytokines/chemokines, such as IL-18, IP-10, FLT3L, MCP-1, MCP-2, and MIP-3β, that can be used as biomarkers to predict the peripheral CD4+ T cell loss and increased viral replication during the acute SIV/HIV infection. Hence, regulating IL-18, IP-10, FLT3L, MCP-1, MCP-2, and MIP-3β expression might provide an antiviral response to combat acute SIV/HIV infection.

Keywords: SIV; acute infection; chemokines; cytokines; peripheral blood; rhesus macaque.

Figure 1

Animal schedule, plasma viral load (PVL), peripheral absolute CD4, lymphocytes, monocytes, neutrophils, and red blood cell (RBC) count are shown. (A) Schematic representation of the animal experiment using 10 SIV-infected and 4 control macaques. Note that the SIV-infected macaques were challenged at day 0 time point (green arrow). The red blood drop symbols indicate sample collection time points in days. (B) PVL with mean ± SE in macaques during the acute phase of SIV infection, as determined using RT-PCR (n = 10). (C) Absolute counts of peripheral CD4+ T cells at pre- and post-SIV infection. Each point of the scattered plot represents data from individual macaques. Asterisks indicate statistical differences between time points as calculated using Dunnett’s multiple comparison analysis (**, p ≤ 0.01; ***, p ≤ 0.001; ****, p ≤ 0.0001). Absolute counts of lymphocytes (D), monocytes (E), neutrophils (F), and RBCs (G) in peripheral blood of SIV infected (n = 10) and uninfected control (n = 4) macaques are shown. Data presented as mean ± SE of different cell populations for the entire 21 days study period. Mann–Whitney t-test analysis was used to determine statistically significant differences between SIV-infected and uninfected-control groups in all those cell populations for that specific time (*, p ≤ 0.05; **, p ≤ 0.01).

Figure 2

Plasma cytokine profile during early acute SIV infection. Scattered plot with mean ± SE for 11 different cytokine ((A), IL-9; (B), IL-15; (C), IL-17A/F; (D), IL-17F; (E), IL-18; (F), IL-1RA; (G), TNF-β; (H), YKL-40; (I), VEGF-α; (J), FLT3L; and (K), M-CSF) responses observed throughout the SIV infection time points are shown. Each point on the scattered plot denoted by different color represents the cytokine concentration for an individual macaque. Asterisks indicate statistical differences between day 0 and post-SIV infection time points as calculated using Dunnett’s multiple comparison analysis (*, p ≤ 0.05; **, p ≤ 0.01; ***, p ≤ 0.001; ****, p ≤ 0.0001).

Figure 3

Heat mapping of 20 essential cytokines/chemokines with continuous color shading over 21 days post-SIV infection (n = 10). Cytokines/chemokines are ordered from left to right on the X-axis and post-SIV infection time points are shown in days on the Y-axis. Most cytokine/chemokine levels remained low on days 2–3 post-SIV infection. The cytokine/chemokine level increased at day 5 and the majority remained high up to day 21 post-SIV infection.

Figure 4

Plasma chemokine profile during early acute SIV infection. Scattered plot with mean ± SE for nine different chemokine ((A), MCP-1; (B), MCP-2; (C), MCP-4; (D), MIP-1α; (E), MIP-3β; (F), MDC; (G), Eotaxin-1; (H), IP-10; and (I), SDF-1α) responses observed throughout the SIV infection time points are shown. Each point of the scattered plot denoted by different color represents the chemokine concentration for an individual macaque. Asterisks indicate statistical differences between day 0 and post-SIV infection time points as calculated using Dunnett’s multiple comparison analysis (*, p ≤ 0.05; **, p ≤ 0.01; ***, p ≤ 0.001; ****, p ≤ 0.0001).

Figure 5

Correlation of cytokine/chemokine with plasma viral load (PVL) and absolute peripheral CD4+ T cell count. Spearman’s rank correlation coefficient of determination between IL-18 and PVL (A), IP-10 and PVL (B), FLT3L and PVL (C), MCP-1 and PVL (D), and MIP-3β and PVL (E) is shown for all SIV-infected macaques. A significant positive correlation was detected with the expression of IL-18, IP-10, FLT3L, MCP-1, and MIP-3β with PVL during SIV infection. Spearman’s rank correlation analysis between IL-18 and CD4 count (F), IP-10 and CD4 count (G), FLT3L and CD4 (H), MCP-1 and CD4 (I), MCP-2 and CD4 count (J), and MIP-3β and CD4 count (K) showed a significant negative correlation with the increase in IL-18, IP-10, FLT3L, MCP-1, MCP-2, and MIP-3β and loss of peripheral CD4+ T cells (n = 10). The correlation and significant values are shown for each plot. Black open circles represent pre and post SIV infection time point from each SIV infected macaque. Red lines represent simple linear regression for each plot.