An investigation into Toxoplasma gondii infection and the expression of Arginase-1 and iNOS in human lung tissue
This study aimed to investigate the relationship between Toxoplasma gondii infection and the expression of the immune modulating proteins Arginase-1 and iNOS in human lung biopsy samples. Previously, a 100% toxoplasmosis infection rate was found in 72 lung biopsy samples acquired from patients. This compared with 10% in healthy controls. Little is known of immune mechanisms acting on T. gondii infected lung tissue. Research on rat and mouse models found an association between resistance to the parasite and the expression of iNOS, whereas Arginase-1 expression was associated with susceptibility. The objectives of this study were to investigate the spatial distribution of iNOS and Arginase-1 expression in relation to T. gondii infection. Fifty-one of the samples, used in the Bajnok et al (2019) study, were sectioned onto slides and stained separately for the presence of T. gondii, Arginase-1, and iNOS using immunohistochemical specific staining. Analysis was performed on section images taken from randomised and specified fields of view. All samples were confirmed positive for toxoplasmosis. iNOS expression was consistently high throughout, whereas Arginase-1 was expressed minimally. No correlation was found in overall spatial distribution of T. gondii and Arginase-1 or iNOS expression. However, once the data was categorised into infection intensity grades, moderate positive spatial correlation could be seen between T. gondii and iNOS. Colocalisation analysis, using grid coordinates overlayed on the matched images, found a significant positive association in regions with high Arginase-1 and high T. gondii staining. Also, a negative association between iNOS and T. gondii high intensity staining was approaching significance. No tissue specific preferential staining could be determined for T. gondii, Arginase-1 and iNOS. In conclusion, interactions between Toxoplasma gondii, Arginase-1, and iNOS in these lung samples appear to be much more complicated than has been found in mice and rat models
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