الفهرس 
Introduction
Epidemiological criteriaOnly 14 pages are availabe for public view
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Abstract
Giardia lamblia a flagellated protozoan parasite is considered a neglected tropical disease by the World Health Organization (WHO). It is recognized as a key pathogen impairing health and development, and hindering socioeconomic improvement in developing countries.
The present study was designed to establish an experimental infection in rat model to assess the immune response to G. lamblia by analyzing cytokine transcription levels produced during the course of the infection and their effect on cyst output using a highly sensitive syber-green based qRT-PCR.
The experimental part of the study was carried out on 25 laboratory bred, parasite free albino rats infected by Cysts isolated from heavily infected fresh human stool. Samples from the duodenojejenal junction were taken from each scarified rat and prepared for the subsequent RNA extraction, reverse transcription and quantitation of gene expression level of the targeted cytokines using qRT-PCR.
The current study found that the cyst excretion was first detected on day 6 p.i. with a peak on day 14 p.i. The cyst shedding rapidly declined until day 19 p.i. (week 3 p.i.). About the gene expression level of the targeted cytokines results revealed that, in comparing these levels in infected group with that of the control, there was highly significant upregulation in the level IFN-γ over all days of the experiment. The gene expression level of TNF-α showed highly significant upregulation on days 7, 14 and downregulation at subsequent time points (which was highly significant on days 21, 28 p.i.). The gene expression level of IL4 showed highly significant upregulation on days 7, 14, 21 and downregulation at subsequent time points (which was highly significant only on day 35 p.i.). The gene expression level of IL10 showed upregulation on days 7 (which was highly significant), 14, 28 and downregulation at other time points (which was highly significant only on day 35 p.i.).
Comparing the gene expression level of the pro-inflammatory and anti-inflammatory cytokines in the infected rats, results revealed that there was highly significant increase in the level of IFN-γ than that of IL-4 and IL-10 over all days of the experiment. There was an increase in the level of TNF-α than that of IL-4 on days 14 p.i. (which was highly significant), 35 p.i. (not significant) and showed decrease less than that of IL-4 on other time points (highly significant on days 7, 21 and significant on day 28 p.i.). There was a highly significant increase in the level of TNF-α than that of IL-10 on days 7, 14 p.i. and its level showed decrease less than that of IL-10 on subsequent time points (which were not significant).
The correlation between G. lamblia cyst and the pro-inflammatory cytokines showed a highly significant strong positive correlation. Anti-inflammatory cytokines, IL10 gene expression level was moderately correlated with G. lamblia cyst count (highly significant difference) and IL4 gene expression level was weakly correlated with the same variable (which was not significant).
To sum it up, our results suggested that the high production of IFN-γ might contribute to the early control of the infection, probably in synergy with the production of TNF-α. It could be assumed that, the pattern of gene expression of the pro- inflammatory cytokines activated the immune response to overcome the infection. This was enhanced by the strong positive correlation between these cytokines and G. lamblia cyst output pattern. The gene expression pattern of the anti-inflammatory cytokines (IL-4, IL-10) was believed to balance the high production of pro-inflammatory cytokines to decrease pathology. Overall, the clearest differences in associations between cytokine levels and pathogen infection durations may relate to whether the pathogen induces an inflammatory or anti-inflammatory state.