Leishmania parasites are carried by sand flies. Credit: Pauline Zulueta, Cumming School of Medicine
Key points:
- Leishmania targets receptors on the surface of neutrophils to gain entry
- Once inside, the parasite stalls cell death to prevent an immune system response
- Understanding this strategy can aid in the development of effective vaccines
Researchers have discovered that an infectious parasite hijacks immune cells to hide from the body’s defenses. Overcoming this “Trojan horse” strategy will be crucial for effective vaccine development.
The University of Calgary team found that Leishmania, which causes the disease Leishmaniasis, targets a receptor on the surface of neutrophils to gain entry into the white blood cells. Once inside, the parasite is able to remain hidden while resisting the neutrophils’ own pathogen-killing molecules.
Key to Leishmania’s disguise is its ability to stall cell death within the neutrophil host to avoid alerting the rest of the immune system to the infection, the researchers found. Because the body’s defense system is unable to recognize the threat, the infection can persist without much interference.
The study, which was published in The Journal of Immunology, was conducted using mouse models and leveraged UCalgary’s specialized insectary. Incubators in the insectary are used to raise sandflies infected with Leishmania, with sandfly bites being the main mode of transmission to humans and other mammals.
Leishmaniasis is difficult to detect in its early stages, and previous attempts to develop a vaccine for the disease have proven unsuccessful. While scientists have realized that Leishmania likely manipulates the immune system in some way, the UCalgary study is the first to identify the parasite’s exact methods.
“The parasite’s behaviour interferes with our ability to vaccinate, because the immune system isn’t even aware that the parasite is there,” said principal investigator Nathan Peters, an associate professor at UCalgary’s Cumming School of Medicine.
The new findings explain the ineffectiveness of previous experimental vaccines and now bring scientists closer to developing a vaccine that can effectively circumvent Leishmania’s defense mechanisms, added first author Adam Ranson.