Malaria is a common parasitic infection that may be linked to various long-term effects, even after the infection has cleared. Lee and colleagues found a direct link between malaria infection and bone loss and problems in bone growth, and suggest vitamin D supplementation as a treatment option.
Malaria is a common, life-threatening infection caused by the Plasmodium parasite. Symptoms include anemia and respiratory issues. Each year, there are 200 million new malaria infections, and half a million people die. Although most infected people recover, many suffer long-term “hidden” malarial symptoms, which can result in growth retardation in children. This is likely due to the interactions between Plasmodium and bone marrow, which affect bone growth and turnover. However, this process is not well understood.
Michelle Lee and colleagues published a study in Science Immunology in which they used mouse models to investigate the interactions between Plasmodium and bone loss. The researchers used two species of Plasmodium to mimic acute and chronic malarial infections. Adult mice were infected with each of these species, and bone condition was assessed using micro-CT at peak infection (at 8 or 14 days after infection), the convalescent period (day 30), and the chronic phase of infection (day 90). Additionally, Lee and colleagues infected young mice and assessed their size and bone density at 3 weeks and 6 weeks of age.
Mice with chronic infections had reduced bone density relative to other mice, and this effect persisted after the parasite was cleared from their systems. Further, mice that were infected before adulthood displayed shorter limbs and lower bone density relative to controls. At the cellular level, Plasmodium decreased activation of both bone-forming and bone-resorbing cells during infection, but bone-resorbing cells were reactivated more quickly after the infection. This is likely due to blood cell rupturing and immune function. Further, byproducts made by the Plasmodium parasites accumulate in bone marrow and trigger long-term immune responses. Finally, Lee and colleagues treated some of the mice with a Vitamin D derivative, which reduced inflammation and led to improved bone growth even in the presence of Plasmodium infection.
These findings clarify how malaria may be influencing bone health and bone growth in individuals who were once infected and suggests a possible course of treatment, using vitamin D supplementation. Future research must focus on applying these findings to treatment in humans.
Written By: C. I. Villamil
Reference: Lee et al. 2017. Plasmodium products persist in the bone marrow and promote chronic bone loss. Science Immunology 2:eaam8093.