Exploring plasmodium falciparum var gene expression to assess host selection pressure on parasites during infancy

Kivisi, C. A. et al. (2019) Exploring plasmodium falciparum var gene expression to assess host selection pressure on parasites during infancy. Frontiers in Immunology, 10, 2328. (doi: 10.3389/fimmu.2019.02328) (PMID:31681266) (PMCID:PMC6798654)

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In sub-Saharan Africa, children below 5 years bear the greatest burden of severe malaria because they lack naturally acquired immunity that develops following repeated exposure to infections by Plasmodium falciparum. Antibodies to the surface of P. falciparum infected erythrocytes (IE) play an important role in this immunity. In children under the age of 6 months, relative protection from severe malaria is observed and this is thought to be partly due to trans-placental acquired protective maternal antibodies. However, the protective effect of maternal antibodies has not been fully established, especially the role of antibodies to variant surface antigens (VSA) expressed on IE. Here, we assessed the immune pressure on parasites infecting infants using markers associated with the acquisition of naturally acquired immunity to surface antigens. We hypothesized that, if maternal antibodies to VSA imposed a selection pressure on parasites, then the expression of a relatively conserved subset of var genes called group A var genes in infants should change with waning maternal antibodies. To test this, we compared their expression in parasites from children between 0 and 12 months and above 12 months of age. The transcript quantity and the proportional expression of group A var subgroup, including those containing domain cassette 13, were positively associated with age during the first year of life, which contrasts with above 12 months. This was accompanied by a decline in infected erythrocyte surface antibodies and an increase in parasitemia during this period. The observed increase in group A var gene expression with age in the first year of life, when the maternal antibodies are waning and before acquisition of naturally acquired antibodies with repeated exposure, is consistent with the idea that maternally acquired antibodies impose a selection pressure on parasites that infect infants and may play a role in protecting these infants against severe malaria.

Item Type:Articles
Additional Information:This work was supported by Wellcome Trust grants; 084535 to PB, 084538 to KM, 209289 to AA, and 080883 to CK.
Glasgow Author(s) Enlighten ID:Otto, Dr Thomas
Authors: Kivisi, C. A., Muthui, M., Hunt, M., Fegan, G., Otto, T. D., Githinji, G., Warimwe, G. M., Rance, R., Marsh, K., Bull, P. C., and Abdi, A. I.
College/School:College of Medical Veterinary and Life Sciences > Institute of Infection Immunity and Inflammation
Journal Name:Frontiers in Immunology
Publisher:Frontiers Media
ISSN (Online):1664-3224
Copyright Holders:Copyright © 2019 The Authors
First Published:First published in Frontiers in Immunology 10:2328
Publisher Policy:Reproduced under a Creative Commons License

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