Parasite Challenges Previous Knowledge by Infecting Non-Immune Cells

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COLUMBUS, Ohio – Scientists have made a surprising discovery about the organisms responsible for visceral leishmaniasis, a severe form of the parasitic disease that usually affects the skin. These organisms can infect non-immune cells, persisting in unusual places within the host.

In a study involving mice, the researchers discovered the Leishmania donovani parasites in blood-related stem cells within the bone marrow—the very cells capable of regenerating all blood cell types. This discovery might shed light on why certain individuals with visceral leishmaniasis often experience blood disorders, including anemia.

Abhay Satoskar, the study's senior author and a professor of pathology at The Ohio State University College of Medicine, explained that while treatments can manage the disease, they don't eliminate all the parasites. "Perhaps these uncommon cells are the cells responsible for harboring these parasites in low numbers. Some drugs may not reach these cells properly or may not be effective with those parasites, and maybe the parasites in these kinds of cells are different compared to parasites in immune cells because they can adapt," Satoskar commented. He emphasized the significance of targeting these hidden parasites to prevent disease transmission.

By investigating this unexpected location of the parasites, scientists hope to gain a deeper understanding of the disease and potentially discover more effective treatments. The findings were detailed in the recent issue of Cell Reports.

Although cutaneous leishmaniasis, affecting the skin, is more common, affecting up to 1.2 million people annually, visceral leishmaniasis, which targets internal organs, is more severe, affecting around 100,000 individuals per year. Scientists had long suspected that L. donovani could exist outside their usual immune cell hosts, but proving this has been challenging due to the low number of infected cells.

Using advanced sequencing techniques, Satoskar's team found evidence of the parasites in both spleen and bone marrow cells in the mice. While many infected cells were indeed immune cells, others were not—a fact that challenges established knowledge about the disease.

The researchers are optimistic about the potential for their findings to be tested in human tissues, especially in areas where leishmaniasis is common. With more research, they hope to uncover how these parasites survive and then develop therapies to target these pathways.