Researchers at the Johns Hopkins Malaria Research Institute (JHMRI) have identified, for the first time, the molecular components that enable the malaria-causing parasite Plasmodium to infect the salivary glands of the Anopheles mosquito-a critical and final stage for spreading malaria to humans.
According to the researchers, saglin, a mosquito salivary protein, is a receptor for the Plasmodium protein Thrombospondin-Related Anonymous Protein (TRAP). The two proteins bind together to allow invasion of the salivary gland by Plasmodium sporozoites, which can be transmitted to a human when bitten by an infected mosquito. The findings are published in the January 16 edition of PLoS Pathogens .
Through a series of experiments, JHMRI researchers found that saglin bound with the artificial peptide SM1. The team then developed an antibody to find a protein similar to SM1 that existed naturally in the parasite, which they identified as TRAP. To further prove the interaction between saglin and TRAP, the team conducted experiments to down-regulate, or switch off, saglin expression, which greatly diminished salivary gland invasion in the mosquito.
"This work is the culmination of a decade-long research project in which peptide libraries were used to understand the mechanisms that the parasite uses to develop in its obligatory mosquito host," explained Marcelo Jacobs-Lorena, PhD, an author of the study and professor with the Johns Hopkins Bloomberg School of Public Health's W. Harry Feinstone Department of Molecular Microbiology and Immunology.