Dynamics of Th17-Associated Cytokine Responses During the Intestinal-Dwelling Protozoan Parasite Giardia duodenalis Infection in Mice and Human Subjects

Background

Giardia duodenalis is a major intestinal protozoan parasite responsible for over 200 million infections annually worldwide. The gut microbiota influences parasite colonization, disease outcome, and host immune responses. In this context, the present study aimed to evaluate Th17-associated cytokine levels during Giardia duodenalis infection.

Objectives

This study evaluated the influence of gut microbiota modulation during Giardia duodenalis infection by analyzing Th17-related cytokines (IL-17 A, IL-17 F, IL-22, IL-23, and IL-10) in antibiotic pre-treated, Lactobacillus pre-treated, and untreated Giardia-infected mice. Serum cytokine profiles were also assessed in Giardia-infected patients to examine their association with clinical severity.

Methods

Mice were divided into antibiotic pre-treated, probiotic (Lactobacillus) pre-treated, and untreated groups prior to Giardia infection. Animals were sacrificed on day 0 and on days 3, 7, and 14 post-infection. Th17 cytokines were quantified by ELISA, parasite burden was determined by RT-PCR, and intestinal pathology was assessed by hematoxylin and eosin staining. Additionally, 60 Giardia positive patients were clinically evaluated using the Vesikari scoring system and classified as mild and moderate to severe symptoms. Serum Th17 cytokines were measured by ELISA.

Results

Giardiasis increased both pro and anti-inflammatory cytokines in untreated mice and antibiotic pre-treatment exacerbated giardiasis, resulting in increased parasite load, heightened inflammatory cytokine responses, and severe intestinal mucosal damage. In contrast, probiotic pre-treatment induced an early and regulated cytokine response, reduced parasite burden, promoted mucosal healing, and facilitated faster recovery. Clinically, patients with moderate to severe disease exhibited elevated IL-17 A, IL-17 F, IL-23, and IL-10 levels, whereas higher IL-22 levels were associated with mild symptoms, suggesting a protective role.

Conclusions

Antibiotic-induced dysbiosis aggravates giardiasis, while probiotic modulation of gut microbiota enhances protective immunity and reduces disease severity, highlighting probiotics as potential preventive and therapeutic agents.