Sequencing of Babesia genomes facilitates study of host-parasite interactions

The genomes of three cattle parasites belonging to the genus Babesia have now been sequenced, making it easier to untangle host-parasite interactions in this system.

Cow. © INRA
Updated on 10/14/2016
Published on 07/09/2014

Babesia species are protozoans that parasitize the red blood cells of mammals. The three main species that infect cattle are B. bovis and B. bigemina, in tropical regions, and B. divergens, in temperate regions.  Only the latter species can be transmitted to humans, by the tick Ixodes ricinus. By sequencing and performing comparative analyses of the genomes of these three species, researchers have been able to make significant strides in understanding the molecular mechanisms that mediate the parasites’ interactions with their vertebrate hosts and their invertebrate vectors.
 
In addition to having yielded genomic data on seven strains of these three species, this research is examining the evolution of gene families in these taxa. Genes in the ves family code for antigens that are expressed by the parasites on the surface of infected host red blood cells. These antigens are an essential part of the measures used by the parasites to escape from the host’s immune response, by exploiting antigenic variation and/or cytoadhesion that allows the parasite to isolate itself in the host’s capillaries. The 385 copies of ves genes that have been identified in B. divergens belong to two subfamilies. These copies vary greatly in their sequences, and the notable absence of regions encoding for the protein domains involved in cytoadhesion could explain the differences in pathogenicity observed among these particular species.  

This research is the product of a collaboration among INRA’s Joint Research Unit for Biology, Epidemiology and Risk Analysis (BioEpAR), the University of Liverpool (Department of Functional and Comparative Genomics), and the University of Glasgow (Institute of Biodiversity, Animal Health and Comparative Medicine).

Reference:
Jackson, A. P., Otto, T. D., Darby, A., Ramaprasad, A., Xia, D., Echaide, I. E., Farber, M., Gahlot, S., Gamble, J., Gupta, D., Gupta, Y., Jackson, L., Malandrin, L., Malas, T. B., Moussa, E., Nair, M., Reid, A. J., Sanders, M., Sharma, J., Tracey, A., Quail, M. A., Weir, W., Wastling, J. M., Hall, N., Willadsen, P., Lingelbach, K., Shiels, B., Tait, A., Berriman, M., Allred, D. R., & Pain, A. (2014). The evolutionary dynamics of variant antigen genes in Babesia reveal a history of genomic innovation underlying host–parasite interaction. Nucleic Acids Research. DOI: 10.1093/nar/gku322