IL-10 and Its Related Superfamily Members IL-19 and IL-24 Provide Parallel/Redundant Immune-Modulation in Loa loa Infection

Abstract

Background: Interleukin-10 (IL-10) has been implicated as the major cytokine responsible for the modulation of parasite-specific responses in filarial infections; however, the role of other IL-10 superfamily members in filarial infection is less well studied.

Methods: Peripheral blood mononuclear cells from loiasis patients were stimulated with or without filarial antigen. Cytokine production was quantified using a Luminex platform and T-cell expression patterns were assessed by flow cytometry.

Results: All patients produced significant levels of IL-10, IL-13, IL-5, IL-4, and IL-9 in response to filarial antigen, indicating a common infection-driven response. When comparing microfilaria (mf)-positive and mf-negative patients, there were no significant differences in spontaneous cytokine nor in parasite-driven IL-10, IL-22, or IL-28a production. In marked contrast, mf-positive individuals had significantly increased filarial antigen-driven IL-24 and IL-19 compared to mf-negative subjects. mf-positive patients also demonstrated significantly higher frequencies of T cells producing IL-19 in comparison to mf-negative patients. T-cell expression of IL-19 and IL-24 was positively regulated by IL-10 and IL-1β. IL-24 production was also regulated by IL-37.

Conclusion: These data provide an important link between IL-10 and its related family members IL-19 and IL-24 in the modulation of the immune response in human filarial infections.

Clinical trials registration: NCT00001230.

Keywords: IL-10 superfamily members; T-cell responses; cytokine regulation; loiasis; microfilariae.

Published by Oxford University Press for the Infectious Diseases Society of America 2020.

Figures

Figure 1.

Cytokine levels in loiasis patients in response to antigen stimulation. Freshly isolated PBMCs from 31 loiasis patients were cultured for 2 days at 37°C, 5% CO2 in media alone or in the presence of (A) BmA or (B) TT. Supernatants were analyzed by different Luminex panels and we assessed Th2, Th9, and regulatory cytokines such as IL-4, IL-5, IL-13, IL-9, and IL-10. NS, P > .05. Abbreviations: BmA, Brugia malayi adult antigen; IL, interleukin; NS, nonsignificant; PBMC, peripheral blood mononuclear cell; Th, T helper cell; TT, tetanus toxoid.

Figure 2.

Spontaneous and parasite-driven IL-10 superfamily member cytokine production. Freshly isolated PBMCs from 31 loiasis patients (mf negative = 22, mf positive = 9) were cultured for 2 days at 37°C, 5% CO2 in media alone or in the presence of BmA. Supernatants were collected and analyzed by Luminex. A, Spontaneous production of IL-10 superfamily member cytokines was quantified. B, The fold changes of IL-19, IL-24, IL-22, and IL-28a were calculated to compare filarial antigen stimulated conditions to baseline. NS, P > .05. Abbreviations: BmA, Brugia malayi adult antigen; IL, interleukin; Loa mf −, Loa loa microfilaria negative; Loa mf+, Loa loa microfilaria positive; NS, nonsignificant; PBMC, peripheral blood mononuclear cell.

Figure 3.

Net frequencies of T cells expressing IL-19 and IL-24 in response to parasite antigen. PBMCs from loiasis patients (mf negative = 17, mf positive = 9) were cultured in media alone or in the presence of filarial parasite antigen. The cells were then assessed by flow cytometry to determine the frequencies of parasite-specific (A) CD4+IL-19+, (B) CD8+IL-19+, (C) CD4+IL-24+, and (D) CD8+IL-24+ cells. The samples were gated on singlet/lymphocytes/live/CD3+ cells. NS, P > .05. Abbreviations: IL, interleukin; Loa mf −, Loa loa microfilaria negative; Loa mf+, Loa loa microfilaria positive; NS, nonsignificant; PBMC, peripheral blood mononuclear cell.

Figure 4.

A–D, Cytokine correlations in loiasis patients. Freshly isolated PBMCs from 31 loiasis patients were cultured for 2 days at 37°C, 5% CO2 in the presence of filarial antigen. Supernatants were assessed by different Luminex panels. Spearman correlations were calculated for the different sets of cytokines. Abbreviations: IL, interleukin; PBMC, peripheral blood mononuclear cell.

Figure 5.

Frequencies of T cells producing IL-19 and IL-24 upon the addition of recombinant cytokine. PBMCs from loiasis patients were cultured in media alone or in the presence of 40 ng/mL of recombinant antigen (rIL-10, rIL-1β, or rIL-37) for 24 hours. The cells were then assessed by flow cytometry to determine the frequencies of (A) CD4+IL-19+ and CD8+IL-19+ (n = 8 for each subset), as well as (B) CD4+IL-24+ and CD8+IL-24+ (n = 13 for each). The samples were gated on singlet/lymphocytes/live/CD3+ cells. NS, P > .05. Abbreviations: IL, interleukin; NS, nonsignificant; PBMC, peripheral blood mononuclear cell.

Figure 6.

IL-24 production upon neutralization of certain cytokines. PBMCs from loiasis patients were cultured in the presence of isotype antibody or neutralizing antibody (anti-IL-10, anti-IL-1β, or anti-IL-37) for 15 hours. The cells were then stimulated with parasite antigen. The cells were assessed by flow cytometry to determine the frequencies of (A) CD4+IL-24+ (n = 10) and (B) CD8+IL-24+ (n = 10). The samples were gated on singlet/lymphocytes/live/CD3+ cells. NS, P > .05. C, Supernatants were collected from patient PBMC cultures and concentrations of IL-24 were assessed by ELISA (n = 7). Abbreviations: ELISA, enzyme-linked immunosorbent assay; IL, interleukin; NS, nonsignificant; PBMC, peripheral blood mononuclear cell.