Leishmaniasis is a parasitic disease found throughout tropical and sub-tropical areas of the world that affects approximately 12 million people according to World Health Organization estimates. Extensive work in the mouse model for leishmaniasis showed that resistance to the parasite is mediated by white blood cells known as Th1 T cells. There are other white blood cells (Th2 cells) that cause disease progression. This same Th1/Th2 phenomenon is now known to occur in tuberculosis and AIDS. Therefore, leishmaniasis has become a widely studied model since it provides insights into many of the world’s most serious diseases. Unfortunately, little is known about the disease process in humans infected with leishmaniasis since animal models frequently do not mimic human disease.
Garreis’s research lab found that cultivating mouse spleen cells with Leishmaniasis parasites resulted in the activation and proliferation of the Th1 and Th2 cells that are activated in mice with the disease. This discovery reduced the number of mice used in their lab and due to the controlled nature of in vitro assay systems, they obtained information that would be impossible to obtain using mice infected with leishmaniasis. Garreis also discovered the same in vitro response to Leishmaniasis occurs using peripheral blood mononuclear cells (PBMC) from human donors. This method eliminates the limitations of past research on humans and on animal models. The studies can be fully controlled and since the same donors can be repeatedly tested, their studies do not suffer from genetic variation. Garreis found that some donors responded with a strong T1-like (protective) response while others had a weak response. Results also showed differences between the human and mouse response to Leishmaniasis. Garreis and her colleagues did not detecte Th2 cell development in PBMC from human donors as they did in mice.
Using PBMC from human donors, Garreis has replaced the mouse as the major research tool for Leishmaniasis and sped up the development of vaccines for human Leishmaniasis and other diseases such as AIDS and tuberculosis.