Test Vaccines Show Promise against Parasite of Cattle

An effective vaccine against a parasite-borne disease called neosporosis may be a few steps closer to development, thanks to Agricultural Research Service (ARS) scientists and cooperators.

Neosporosis, caused by the parasite Neospora caninum, affects cattle worldwide. Infected animals often abort their calves and develop other debilitating complications that can cost producers millions of dollars every year.

Animal scientist Wenbin Tuo and microbiologist Mark Jenkins work at the ARS Animal Parasitic Diseases Laboratory in Beltsville, Md. They collaborated with ARS Molecular Plant Pathology Laboratory molecular biologist Yan Zhao and National Institutes of Health researcher Daming Zhu to test a new neosporosis vaccine in a mouse model.

The team created the vaccine using the parasite’s own proteins. One of these proteins, called Neospora caninum cyclophilin (NcCyP), regulates the response of the host immune system that limits the survival of the parasite in the host after infection. The other protein--called NcSRS2-- helps the parasite attach to and invade host cells.

The researchers tested three different vaccine cocktails containing these proteins. One group of mice received a formulation of NcCyP. A second group received a formulation of NcSRS2. A third group was immunized with a mix of both proteins. After vaccination, the mice were inoculated with the parasite.

The researchers found mice that received the vaccine formulated with NcCyP alone exhibited the highest levels of protection against the disease. On average, only 13 percent of the mice in this group had detectable levels of N. caninum in brain tissue following infection. In contrast, more than 80 percent of the non-vaccinated mice were infected after challenge.

The scientists found that the serum antibody levels against the protein correlated well with the levels of protection. They also observed that the vaccine containing both NcCyP and NcSRS2 was no more effective than the vaccine that just contained NcCyP. However, more work is needed to evaluate the efficacy of these proteins in protecting cattle--the host animal--against the disease.

Results from this research were presented in earlier this month at the 53^rd annual conference of the American Association of Veterinary Parasitologists in New Orleans, La.

ARS is a scientific research agency of the U.S. Department of Agriculture.