Regulatory effects of IL-12 and IL-18 on Onchocerca volvulus- and Entamoeba histolytica-specific cellular reactivity and cytokine profiles

Acetylcholine Upregulates Entamoeba histolytica Virulence Factors, Enhancing Parasite Pathogenicity in Experimental Liver Amebiasis

Entamoeba histolytica is an invasive enteric protozoan, whose infections are associated to high morbidity and mortality rates. However, only less than 10% of infected patients develop invasive amebiasis. The ability of E. histolytica to adapt to the intestinal microenvironment could be determinant in triggering pathogenic behavior. Indeed, during chronic inflammation, the vagus nerve limits the immune response through the anti-inflammatory reflex, which includes acetylcholine (ACh) as one of the predominant neurotransmitters at the infection site. Consequently, the response of E. histolytica trophozoites to ACh could be implicated in the establishment of invasive disease. The aim of this study was to evaluate the effect of ACh on E. histolytica virulence. Methods include binding detection of ACh to plasma membrane, quantification of the relative expression of virulence factors by RT-PCR and western blot, evaluation of the effect of ACh in different cellular processes related to E. histolytica pathogenesis, and assessment of the capability of E. histolytica to migrate and form hepatic abscesses in hamsters. Results demonstrated that E. histolytica trophozoites bind ACh on their membrane and show a clear increase of the expression of virulence factors, that were upregulated upon stimulation with the neurotransmitter. ACh treatment increased the expression of L220, Gal/GalNAc lectin heavy subunit (170 kDa), amebapore C, cysteine proteinase 2 (ehcp-a2), and cysteine proteinase 5 (ehcp-a5). Moreover, erythrophagocytosis, cytotoxicity, and actin cytoskeleton remodeling were augmented after ACh treatment. Likewise, by assessing the formation of amebic liver abscess, we found that stimulated trophozoites to develop greater hamster hepatic lesions with multiple granulomas. In conclusion, ACh enhanced parasite pathogenicity by upregulating diverse virulence factors, thereby contributing to disease severity, and could be linked to the establishment of invasive amebiasis.

Modulatory effects of interferon-γ and interleukin-4 on cellular immune responses against Hypoderma lineatum antigens

This study investigates the in vitro modulatory effects of interferon-γ (IFN-γ) and interleukin-4 (IL-4) on both proliferative bovine T cell responses and IL-10 production induced by different antigens [crude larval extract and the purified fractions hypodermin A, B and C (HyA, HyB, HyC)] obtained from first instars of Hypoderma lineatum (Diptera: Oestridae), alone or in the presence of the mitogen concanavalin A. Incubation with the different parasitic antigens resulted in significant inhibition of T cell proliferation and IL-10 production, which, in general, did not revert after the addition of IFN-γ and IL-4. In the absence of antigens, IL-4 induced significant inhibition of mitogen-induced T cell responses. Exogenous IFN-γ exhibited an inhibitory effect on cell proliferation in the presence of the purified fractions HyB and HyC. These in vitro data suggest that far from neutralizing the effects of larval antigens, the addition of IFN-γ potentiates their anti-proliferative activity; by contrast, IL-4 had no consistent effects on proliferative responses to Hypoderma. IL-4 provoked an increment of IL-10 levels in supernatants of HyB-stimulated cells. In conclusion, exogenous IFN-γ and IL-4 were unable to counteract the suppressor effects of H. lineatum antigens.