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Parasite Sequencing In Kenya, Genomics Helps ID Possible Cattle Vaccine


South Africa just might have to cede its role as genomics leader in Africa. The International Livestock Research Institute in Nairobi, Kenya, has developed a sequencing and screening pipeline to combat parasites responsible for millions of dollars in loss of cattle each year.

In partnership with TIGR, ILRI sequenced Theileria parva, a parasite responsible for East Coast fever that infects and kills about one million cows each year, affecting 11 countries in Africa. That’s an overall economic loss of about $300 million annually, says Evans Taracha, an ILRI scientist leading the vaccine project.

Taracha, whose background is in immunology, tackled the problem by focusing on the relationship between host and parasite. After more than 10 years of research, the institute “has generated a huge body of information on how cattle respond to parva,” he says. He and his team were able to identify the parasitic component that stimulates a cow’s killer T cells. With that and parva’s genome sequence, the institute could then “[apply] bioinformatics tools to generate a list of possible parasite genes that could be coding for those components that switch on cow killer T cells,” Taracha explains. From the resulting list of roughly 55 genes, the institute’s high-throughput screening assays sorted out three genes closely identified with the bovine immune response which could potentially be turned into a vaccine.

As a safety measure, ILRI used another approach as well: teaming up with the Ludwig Institute for Cancer Research in Brussels, where the team also performed random screening of the cDNA library for T. parva. The result: five more vaccine candidate genes.

ILRI is now evaluating each of the eight possible vaccines. That step may take another year, but Taracha certainly hopes that relief is in sight from the parva parasite. The total cost, including all background research into parva for the past decade, comes to about $20 million, Taracha says. Getting to a vaccine could cost $5 million to $10 million more — but “that’s nothing compared to the annual losses” caused by East Coast fever, he notes.

If all goes well with this vaccine, it could pave the way for research into other parasites. Taracha is already thinking about Theileria annulata, a parva relative found across Africa and large chunks of Asia as well. Using genomic sequence and high-throughput screening to predict potential vaccine targets, Taracha says, “is a big, big breakthrough in terms of identifying the candidate.”

— Meredith Salisbury


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