Comparative virulence of Caribbean, Brazilian and European isolates of Toxoplasma gondii

Hamilton, C. M. et al. (2019) Comparative virulence of Caribbean, Brazilian and European isolates of Toxoplasma gondii. Parasites and Vectors, 12, 104. (doi: 10.1186/s13071-019-3372-4) (PMID:30871587) (PMCID:PMC6416883)

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Background: Toxoplasma gondii is a zoonotic parasite of global importance. The outcome of infection in humans can depend on a number of factors including the infecting stage of the parasite, inoculating dose and virulence of the infecting strain. Molecular epidemiological studies have demonstrated an abundance of atypical strains of T. gondii in South America, many of which have been associated with more severe sequelae of infection. The aim of this study was to compare the virulence of T. gondii strains isolated in the Caribbean to a virulent Brazilian strain and an avirulent European strain. Methods: One hundred and twenty Swiss CD-1 mice were split into 8 groups of 15 mice and each group was inoculated with 200 tachyzoites of one of 8 isolates, comprising ToxoDB genotypes #1, #141, #265, #13, #3 and #6. Five mice per group were euthanized at day 8 post-inoculation (p.i.) and parasite burden was determined in heart, lungs and eyes using quantitative PCR. Lungs and brain were also examined by histopathology and immunohistochemistry. The remaining 10 mice per group were part of a survival experiment to assess virulence. DNA was extracted from tachyzoites of each of the 8 T. gondii isolates and genotyped at four ROP gene loci, including ROP5, ROP16, ROP17 and ROP18 to look for association with markers of virulence. Results: Infection with ToxoDB genotype #13 from the Caribbean resulted in 100% of mice being euthanized which was comparative to infection with the virulent Brazilian strain (ToxoDB genotype #6). Significantly higher parasite burdens were recorded in the lungs and eyes of mice infected with ToxoDB genotypes #13 and #6. Genotyping of ROP loci revealed that the virulent Caribbean isolates had a different ROP18/ROP5 allelic profile (3/1) to the virulent Brazilian isolate (1/3); however, the avirulent Caribbean isolate (ToxoDB genotype #1) had the same ROP18/ROP5 profile as the avirulent European isolate (ToxoDB #3) (both 2/2). Caribbean isolates of intermediate virulence (ToxoDB #141 and #265) all had the same ROP18/ROP5 allelic profile (2/2). Conclusions: Isolates from the Caribbean with ToxoDB genotype #13 were acutely virulent for mice and comparable to a known virulent Brazilian isolate. The ROP protein allelic profile of the virulent Caribbean and Brazilian isolates differed indicating that perhaps other factors are involved in predicting virulence. Understanding virulence is important for predicting disease outcome in humans and may also aid vaccine design as well as drug discovery.

Item Type:Articles
Additional Information:Funding for this study was provided by Ross University School of Veterinary Medicine, the Moredun Research Institute and the Scottish Government (Rural and Environment Science and Analytical Services Division). SO received a scholarship from the Coordination for the Improvement of Higher Education Personnel (CAPES), Brazil (PDSE, project no. 88881.131561/2016-01).
Glasgow Author(s) Enlighten ID:Black, Lauren and Chianini, Dr Francesca
Authors: Hamilton, C. M., Black, L., Oliveira, S., Burrells, A., Bartley, P. M., Melo, R. P. B., Chianini, F., Palarea-Albaladejo, J., Innes, E. A., Kelly, P. J., and Katzer, F.
College/School:College of Medical Veterinary and Life Sciences > School of Biodiversity, One Health & Veterinary Medicine
Journal Name:Parasites and Vectors
Publisher:BioMed Central
ISSN (Online):1756-3305
Copyright Holders:Copyright © 2019 The Authors
First Published:First published in Parasites and Vectors 12: 104
Publisher Policy:Reproduced under a Creative Commons License

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