$1.2 million NIH grant devoted to study leishmaniasis

source-image
Jul 01, 2002

Ames, Iowa-How can an infectious organism prevent the development of an effective cell-mediated immune response?

Leishmania amazonensis is a little protozoan that researchers postulate can trick the immune system. Researchers at Iowa State University want to know how the protozoan does it. The National Institutes of Health is just as interested. It will cough up $1.2 million over five years so Dr. Doug Jones can figure it out.

Jones, assistant professor of veterinary pathology at Iowa State University (ISU) tells DVM Newsmagazine, "It was discovered several years ago that there were different types of CD4 positive T cells. They call them TH-1, which promoted cell-mediated immunity, and TH-2 cells that promoted humoral immunity like antibodies. Leishmania was a wonderful experimental model to show the importance of these TH-1 cells in promoting a cell-mediated immune response in vivo," he says.

So why Leishmania amazonensis? Because it is inhibiting the immune response.

"Leismania amazonencis seems to inhibit the development of this TH-1 response. It does that without having the CD-4 positive T cells, TH-2 cells," he explains. "Somehow the parasite is inhibiting the development of this immune response, and we are trying to understand why that is and how it happens," Jones adds.

Cuteneous leishmaniasis is prevalent and emerging in tropical and subtropical regions of the world. Jones says the disease is burdensome to parts of the world, but is different than the visceral form that has been linked to last year's Foxhound outbreak. Nonetheless, the disease is transmitted by the sandfly. The cutaneous form can present as a skin ulcer to facial disfigurations, organ failure and immune malfunctions.

Cutaneous leishmaniasis is an infection of the skin that produces multiple ulcers or sores. The sores can lead to permanent scarring. This form of the disease is most common in South America and the Middle East. Very rarely, cutaneous leishmaniasis is reported in southern Texas.

The threat to dogs and people in the United States isn't that severe, but the benefit to successfully figuring out how this protozoan works on the immune system could be applicable to other pathogens.

Jones explains, "The principles of immune evasion that the parasites employ are probably not unique to leishmania. They will be applicable to other pathogens that are agents of chronic infectious diseases, such as mycobacteria."

In fact, Jones likens this form of cutaneous leishmaniasis amazonensis with Johne's disease in cattle.

Jones says there won't be any quick answers. "It's a beginning to a continued understanding. Once we start to understand the host side, we have to understand how the parasite is making the host respond in this particular way."

While Jones adds that this particular disease may not wreak havoc in canine populations, it is a very real concern for many parts of the world. But in today's mobile society, it's important for veterinarians to keep up with emerging and global disease threats.