Protection from lethal malaria in transgenic mice expressing sickle hemoglobin

Area of Science:

• Hematology
• Immunology
• Parasitology

Background:

• Previous studies demonstrated that high beta S globin expression in transgenic mice conferred protection against Plasmodium chabaudi and P. berghei.
• Sickle cell trait is known to offer protection against severe malaria, but the underlying mechanisms require further elucidation.

Purpose of the Study:

• To investigate the correlation between varying levels of beta S globin expression and protection against a virulent strain of Plasmodium yoelii (17XL).
• To explore the role of red blood cell reticulocytes and mature cells in malaria parasite resistance in the context of beta S globin expression.

Main Methods:

• Transgenic mice with low (39%), intermediate (57%), and high (75%) beta S globin expression levels were infected with P. yoelii (17XL).
• Survival rates and parasite distribution within reticulocytes and mature red blood cells were monitored in infected mice and controls.

Main Results:

• Protection against P. yoelii infection correlated positively with the level of beta S chain expression.
• Mice with intermediate and high beta S expression showed significant recovery (7/9 each), while control and low-expression groups succumbed to infection.
• Parasites were primarily found in reticulocytes during the recovery phase in mice with high and intermediate beta S expression, indicating mature cells are more resistant.

Conclusions:

• Beta S globin expression level is a critical determinant of protection against P. yoelii malaria.
• Mature red blood cells expressing beta S globin exhibit increased resistance to malaria parasite invasion and development.
• These findings provide mechanistic insights into the protective effects of sickle cell trait against Plasmodium falciparum malaria.