The Eosinophil Response to Gastrointestinal Teladorsagia circumcincta Nematode Infection
No Thumbnail Available
Date
2024-02
Authors
Journal Title
Journal ISSN
Volume Title
Publisher
La Trobe University
Abstract
The aim of this thesis is to investigate the role of eosinophils in host defense against gastrointestinal nematode infections in sheep and goats with a particular focus on Teladorsagia circumcincta (T. circumcincta). Larval stages of T. circumcincta develop on the gastric mucosa, compromising nutrient absorption from the gastrointestinal tract, so infected animals have impaired growth, weight loss, and, in some cases, may die. Eosinophils and IgA appear to regulate worm growth and fecundity; they have been associated with resistance mechanisms associated with larvae. Goats are more susceptible than sheep to gastrointestinal worms. We compared nucleotide sequences and predicted the protein sequences of key eosinophil proteins between goats and sheep. We observed that nitrosylated tyrosine plays a key role in sheep EPX but is absent in goat EPX, which is important for post-translational nitration of eosinophil secondary granule proteins, which may influence protective responses.
Merino lambs and ewes naturally infected with GIN were examined to determine eosinophil distribution in abomasal tissue. Eosinophils followed a zero-inflated Poisson distribution. Eosinophil counts in lambs and ewes were positively skewed. Mean tissue eosinophil counts were higher in ewes (0.11 ± 0.01) compared to lambs (0.09 ± 0.01), with P = 0.016. Eosinophil counts in the left and right abomasal positions of ewes were also skewed. Mean eosinophil counts were similar between the left (0.11 ± 0.01) and right (0.10 ± 0.01) sides. There was no significant difference between the mean eosinophil numbers in different locations. The mode of eosinophil counts within both abomasal positions was zero. The number and distribution of eosinophils and mast cells in abomasum tissue in infected lambs with high and low fecal egg counts were determined. Blood but not tissue eosinophils were negatively associated with fecal egg count (P = 0.008). Resistant animals with low egg counts had more eosinophils and mast cells in tissue than susceptible animals. These results advance our understanding of eosinophil responses to nematode infection and confirm that blood eosinophils are a useful marker of resistance to infection.
Merino lambs and ewes naturally infected with GIN were examined to determine eosinophil distribution in abomasal tissue. Eosinophils followed a zero-inflated Poisson distribution. Eosinophil counts in lambs and ewes were positively skewed. Mean tissue eosinophil counts were higher in ewes (0.11 ± 0.01) compared to lambs (0.09 ± 0.01), with P = 0.016. Eosinophil counts in the left and right abomasal positions of ewes were also skewed. Mean eosinophil counts were similar between the left (0.11 ± 0.01) and right (0.10 ± 0.01) sides. There was no significant difference between the mean eosinophil numbers in different locations. The mode of eosinophil counts within both abomasal positions was zero. The number and distribution of eosinophils and mast cells in abomasum tissue in infected lambs with high and low fecal egg counts were determined. Blood but not tissue eosinophils were negatively associated with fecal egg count (P = 0.008). Resistant animals with low egg counts had more eosinophils and mast cells in tissue than susceptible animals. These results advance our understanding of eosinophil responses to nematode infection and confirm that blood eosinophils are a useful marker of resistance to infection.
Description
This thesis comprises five chapters, encompassing original experimental research disseminated through one peer-reviewed journal article and one manuscript formatted according to the thesis submission guidelines. Chapter 1 provides a comprehensive literature review of the research area. The experimental chapters are presented in Chapters 2, 3, and 4, with Chapter 5 providing an overall discussion of the new findings from this work.
The research chapters follow a structured format, encompassing an introduction, methodology, results, and discussion sections specific to each study. Furthermore, these research chapters commence with a summary of the completed research, inclusive of manuscript publication details, the co-authors' contributions, and a statement from the co-author affirming the master candidate's authorship contribution. Chapter 5 provides an overarching discussion, integrating the primary themes derived from the three manuscripts and offering recommendations for future research.
The published experimental chapters adhere to the respective referencing, citation, and formatting styles prescribed by the corresponding journals. A consistent referencing and citation style, namely APA 6th, has been employed across Chapters 1, 2, 3, 4, and 5. The reference list, encompassing all cited sources, is provided at the end of this thesis.
Keywords
resistance, gastrointestinal