A study shows that stimulating the production of interleukin-17A (IL-17A), one of the cytokines released by cells of the immune system, can be an effective strategy for the treatment of visceral leishmaniasis, considered one of the six most important parasitic diseases affecting humans.
The principal investigator in this research is João Santana da Silva, Full Professor at the University of São Paulo’s Ribeirão Preto Medical School (FMRP-USP). According to the article, increased levels of IL-17A in an infected organism not only help to reduce parasite load but also protect organs against the lesions caused by an exacerbated inflammatory response, which is common in such cases.
“These findings pave the way to new therapeutic strategies,” Santana da Silva explained. “Drugs can be developed to stimulate production of IL-17A directly and also to neutralize the action of interleukin-27 [IL-27], another cytokine that is released by defense cells that inhibits synthesis of IL-17A.”
In the study, the group used parasites of the species Leishmania infantum, which are transmitted to humans by insect bites, and especially those of the sandfly Lutzomyia longipalpis.
“As soon as the parasite enters the organism, the host responds with a surge of cytokines,” Santana da Silva said. “Successful control of the infection depends on which substances are produced by the immune system. Some individuals are more resilient, others more susceptible. Even the former may develop lesions in their organs as a result of their inflammatory response.”
In susceptible individuals, the protozoan spreads to the liver, spleen, bone marrow and lymph nodes, causing these organs to swell and become inflamed and also leading to anemia, fever and immunosuppression. Without treatment, the disease is fatal in more than 90% of cases.
The new findings of the research group at FMRP-USP show that if IL-17A is produced in appropriate amounts in addition to IFNγ, the parasite can be eliminated without causing damage to the organism’s tissues. This is because IL-17A attracts neutrophils to the site of the infection. Neutrophils are defense cells capable of phagocytizing pathogens and diseased cells. When the parasite load decreases, so does the production of cytokines, such as IFNγ, that can damage tissue.
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