Correlation between Melatonin and Colostral Regulatory T Cells in <i>Giardia lamblia</i> Infection

Giardiasis is a parasitic disease caused by <i>Giardia lamblia</i> (<i>G. lamblia</i>) that affects people worldwide. Still, few studies report on the immunoregulatory effects of the biomolecules of colostrum during interactions with <i>G. lamblia</i>. This study aimed to assess the concentrations of melatonin and cortisol hormones, the percentage of Treg cells, and the levels of cytokines IL-10 and TGF-β in colostrum from mothers who tested positive for the parasite. This cross-sectional study analyzed colostrum samples from 25 puerperal. The samples were tested using an ELISA to determine if they were seropositive for <i>G. lamblia</i> and the type of antibody present (IgM and IgG). Based on the results, the samples were divided into three groups: a control group (N = 10) with no reaction to either IgM or IgG, a group seropositive for IgG (IgG⁺/IgM⁻; N = 8), and a group seropositive for IgM (IgM⁺/IgG⁻; N = 7). The concentrations of melatonin and cortisol were measured using the ELISA method. Additionally, cytokines IL-10 and TGF-β and immunophenotyping were analyzed using flow cytometry. In the group that tested positive for IgM anti-<i>G. lamblia</i>, the concentration of melatonin was lower. However, in the colostrum from mothers who tested positive for IgG anti-<i>G. lamblia</i>, the level of this hormone had increased. The cortisol levels were similar between the groups, regardless of seropositivity. There was a higher percentage of Treg cells in the colostrum from mothers who tested positive for IgM anti-<i>G. lamblia</i>. TGF-β levels also increased in the colostrum of mothers who tested positive for IgM anti-<i>G. lamblia</i>. In the seronegative group for <i>G. lamblia</i>, there was a positive correlation between melatonin concentration and the percentage of Treg cells. These data suggest that the increase in regulatory cells and cytokines and the reduction in melatonin in colostrum from mothers with recent giardia infection may contribute to the evolution and manifestation of the disease.