A comparison of immune system responses among Haitian patients with malaria reveals 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 researchers with the University of Florida College of Public Health and Health Professions and Haiti’s Laboratoire National de Sante Publique.
Asymptomatic patients are responsible for the bulk of malaria transmission in Haiti, said Dr. Anthony Cannella, an assistant professor at Florida’s College of Medicine’s division of infectious diseases and global 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.
The Florida research team also included Dr. Jason Lehmann, a former postdoctoral fellow in the division of infectious diseases and global medicine, and Dr. Valery Madsen Beau De Rochars, an assistant professor of health services research, management and policy in the College of Public Health and Health Professions. The results were published in the journal PLOS ONE.
“This research demonstrates a profound step forward in identifying asymptomatic from symptomatic patients based on immune responses to the local malaria parasite,” Dr. 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.”
By analyzing the immune systems of malaria patients, the team 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 diagnosed with malaria, then separated them based on whether or not they had symptoms, and measured the recall immune responses 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 CD8mid T cells. This information could be used to identify infected patients with malaria, including asymptomatic patients, for treatment and monitoring purposes.