Modulation of pro- and anti-inflammatory cytokines in active and latent tuberculosis by coexistent Strongyloides stercoralis infection

Abstract

Helminth infections are known to induce modulation of both innate and adaptive immune responses in active and latent tuberculosis (TB). However, the role of helminth infections in modulating systemic cytokine responses in active and latent tuberculosis (LTB) is not known. To define the systemic cytokine levels in helminth-TB coinfection, we measured the circulating plasma levels of Type 1, Type 2, Type 17, other pro-inflammatory and regulatory cytokines in individuals with active TB (ATB) with or without coexistent Strongyloides stercoralis (Ss) infection by multiplex ELISA. Similarly, we also measured the same cytokine levels in individuals with LTB with or without concomitant Ss infection in a cross-sectional study. Our data reveal that individuals with ATB or LTB and coexistent Ss infection have significantly lower levels of Type 1 (IFNγ, TNFα and IL-2) and Type 17 (IL-17A and IL-17F) cytokines compared to those without Ss infection. In contrast, those with ATB and LTB with Ss infection have significantly higher levels of the regulatory cytokines (IL-10 and TGFβ), and those with LTB and Ss infection also have significantly higher levels of Type 2 cytokines (IL-4, IL-5 and IL-13) as well. Finally, those with LTB (but not ATB) exhibit significantly lower levels of other pro-inflammatory cytokines (IFNα, IFNβ, IL-6, IL-12 and GM-CSF). Our data therefore reveal a profound effect of Ss infection on the systemic cytokine responses in ATB and LTB and indicate that coincident helminth infections might influence pathogenesis of TB infection and disease.

Keywords: Cytokines; Helminths; Strongyloides; Tuberculosis.

Figure 1. Helminth infections are associated with diminished plasma levels of Type 1 and Type 17 cytokines in active and LTB

The plasma levels of Type 1 (IFNγ, TNFα, IL-2) and Type 17 (IL-17A, IL-17F, IL-22) cytokines - were measured by multiplex ELISA in active pulmonary TB individuals with (ATB+Ss, n=42) or without Ss coinfection (ATB, n=46) and in latent - TB infected individuals with (LTB+Ss, n=44) or without Ss coinfection (LTB, n=44). The results are shown as scatterplots with each circle representing a single individual and the bar representing the GM. P values were calculated using the Kruskal-Wallis test with Dunn’s multiple comparisons.

Figure 2. Helminth infections are associated with elevated plasma levels of Type 2 and regulatory cytokines in active and LTB

The plasma levels of Type 2 (IL-4, IL-5, IL-13) and regulatory (IL-10, TGFβ) cytokines were measured by multiplex ELISA in active pulmonary TB individuals with (ATB+Ss, n=42) or without Ss coinfection (ATB, n=46) and in latent-TB infected individuals with (LTB+Ss, n=44) or without Ss coinfection (LTB, n=44). The results are shown as scatterplots with each circle representing a single individual and the bar representing the GM. P values were calculated using the Kruskal-Wallis test with Dunn’s multiple comparisons.

Figure 3. Helminth infections are associated with diminished plasma levels of pro-inflammatory cytokines in LTB

The plasma levels of Type 1 IFNs (IFNα, IFNβ), IL-1 family (IL-1α, IL-1β) and other pro-inflammatory (IL-6, IL-12, GM-CSF) cytokines were measured by ELISA in active pulmonary TB individuals with (ATB+Ss, n=42) or without Ss coinfection (ATB, n=46) and in latent-TB infected individuals with (LTB+Ss, n=44) or without Ss coinfection (LTB, n=44). The results are shown as scatterplots with each circle representing a single individual and the bar representing the GM. P values were calculated using the Kruskal-Wallis test with Dunn’s multiple comparisons.

Figure 4. Heatmaps depicting the trends in the modulation of cytokines in Ss-TB coinfection and in LTB versus ATB

Heatmaps of log2 transformed plasma levels for LTB vs. LTB+Ss, ATB vs. ATB+Ss, and ATB vs. LTB were shown in panel A, B, C respectively, in which each row stands for a sample and each column stands for a cytokine. The annotation bar indicates if there is a significant difference (SD) between two groups or not for each cytokine. The p value of each cytokine was calculated by Student’s t-test and adjusted by Benjamini-Hochberg Procedure.