Findings from human immune system study could lead Haiti closer to malaria eradication

A comparison of immune system responses among Haitian malaria patients revealed unique traits among those with the highest risk of transmitting the disease to others. Identifying such patients could lead to a sharp decline in malaria transmission in the country, according to a University of Florida researcher.

‘‘Asymptomatic patients are responsible for the bulk of malaria transmission in Haiti, said Anthony Cannella, M.D., M.Sc. an assistant professor in the Department of Medicine’s Division of Infectious Diseases and Global Medicine at the UF College of Medicine and a member of the Emerging Pathogens Institute. Finding these carriers could play a key role in eradicating malaria from Haiti by 2020, a goal established in 2015 by the Centers for Disease Control and Prevention.

“This research demonstrates a profound step forward in identifying asymptomatic from symptomatic patients based on immune responses to the local malaria parasite,” Cannella said. “My belief is that by identifying these asymptomatic individuals, it is feasible to treat and monitor them, thus reducing malaria transmission over time. These findings provide the scientific community insight into how malaria could be eliminated not only in Haiti, but also in other parts of the globe.”

The results were published in the April edition of PLOS ONE.

Cannella worked with Jason Lehmann, Ph.D., a former postdoctoral fellow in the department of medicine’s division of infectious diseases and global medicine, to analyze the immune system data. The study’s patients come from Sud-Est on Haiti’s southern peninsula, south of Port-au-Prince.

By analyzing the immune systems of malaria patients, Cannella found that asymptomatic patients displayed a unique set of immune responses that most likely is muting a robust inflammatory response to the malaria infection.

The researchers collected blood samples from patients who had been previously were diagnosed with malaria, then separated on whether or not they had symptoms, and measured the recall immune responses to the to the local malaria parasite. While both symptomatic and asymptomatic patients displayed similar antibody responses to malaria antigens, the researchers observed significant differences in both T cell immune responses and cytokine responses-biochemicals secreted during immune responses-to the local Plasmodium falciparum strain.

In symptomatic patients, the cytokines reduced the effectiveness of the immune system. In asymptomatic infections, however, a mix of inflammatory and stimulatory cytokines led to a more controlled response to the malaria infection. These patients also demonstrated a higher number of certain immune system cells — specifically, T regulatory cells, NKT-like cells and CD8^mid T cells. This information could be used to identify infected patients with malaria including asymptomatic patients for treatment and monitoring purposes.

Cannella hopes these findings will contribute to efforts to create practical tools that identify people with asymptomatic malaria infections. Currently, he is looking into ways of inhibiting the growth of the malaria parasite in humans.

“The key to unlocking how to eradicate malaria revolves around not only understanding the P. falciparum biology and the local mosquito vector, but also the human immune responses to the parasite,” Cannella said.