Cellular responses and cytokine production in post-treatment hookworm patients from an endemic area in Brazil

Abstract

Human hookworm infections are distributed widely in tropical areas and have a significant impact on host morbidity and human health. In the present study, we investigated the cellular responsiveness and cytokine production in peripheral blood mononuclear cells (PBMC) from Necator americanus-infected schoolchildren who had recently received chemotherapy, and compared them with non-infected endemic controls. Hookworm patients and treated, egg-negative individuals showed a lower cellular reactivity against phytohaemagglutinin (PHA) and hookworm antigen when compared with egg-negative endemic controls. The baseline production of proinflammatory tumour necrosis factor-alpha (TNF-alpha) in PBMC from infected patients and treated, egg-negative individuals was elevated. On the other hand, PHA- or hookworm antigen-induced interleukin (IL)-12 and interferon (IFN)-gamma secretion was higher in endemic controls than in hookworm patients, who either continued egg-positive or were egg-negative after treatment. Also, PBMC from endemic controls secreted more IL-5 and IL-13 than the other patient groups. Opposite to that, the spontaneous as well as the antigen-driven IL-10 secretion was lower in endemic controls when compared with the other groups. In summary, patently hookworm-infected as well as egg-negative treated patients disclosed an elevated spontaneous cellular secretion of proinflammatory TNF-alpha, a prominent secretion of regulatory Th2-type IL-10 and an impaired production of IL-12, IFN-gamma, IL-5 and IL-13.

Fig. 1

PHA- and hookworm antigen-induced as well as baseline TNF-α production (PHA: 4 µg/ml; ANC: A. caninum adult worm antigen, 20 µg/ml) in PBMC cultures from hookworm patients (Nec; n = 9), hookworm egg-negative, cured patients (Cured; n = 14) and egg-negative endemic controls (EC; n = 7). Mean cytokine concentrations are indicated in pg/ml ± standard error of the mean. Baseline concentrations are separately indicated and are not subtracted from stimulated cells.

Fig. 2

Phytohaemagglutinin-induced (4 µg/ml; 48 h) and hookworm antigen-induced (ANC: A. caninum adult worm antigen, 20 µg/ml; 96 h) IL-10 production in PBMC cultures from hookworm patients (Nec; n = 9), hookworm egg-negative cured patients (Cured; n = 14) and egg-negative endemic controls (EC; n = 7). Mean cytokine concentrations are indicated in pg/ml ± standard error of the mean and significant differences between patient groups are indicated with an asterisk (*P ≤ 0·01, **P ≤ 0·05). Baseline concentrations are indicated separately and are not subtracted from stimulated cells.