Lipoproteins from vertebrate host blood plasma are involved in Trypanosoma cruzi epimastigote agglutination and participate in interaction with the vector insect, Rhodnius prolixus.

This study explores the role of high-density lipoprotein (HDL) from vertebrate host blood in promoting the infection of the insect Rhodnius prolixus by the parasite Trypanosoma cruzi, which causes Chagas disease. The evidence suggests that HDL enhances the parasites’ ability to infect the insect, leading to a higher rate of transmission of the disease.

Background and Objective

• Chagas disease, which affects about 8 million people in Central and South America, is caused by a protozoan parasite, Trypanosoma cruzi.
• The parasite’s transmission is through the bite of blood-sucking triatomine insects, such as Rhodnius prolixus.
• While the stages of the parasite’s life cycle in both the insect vector and human host are understood, the factors influencing the parasite’s infection within the insect gut remain unclear.
• This research investigates the potential role of gut agglutinins in Rhodnius prolixus in the life cycle of the parasite.

Methodology

• The researchers examined gut extracts from Rhodnius prolixus that were fed on various diets involving different components of vertebrate blood.
• They conducted cross-adsorption experiments and utilized agglutination assays with fractionated extracts of vertebrate plasma.
• The team used fluorescence and confocal microscopy with singly or doubly labeled HDL to trace the interaction between the labeled HDL and the parasite.
• Experiments regarding the parasitization of Rhodnius prolixus by Trypanosoma cruzi were carried out with different vertebrate blood components.

Findings

• It was found that Rhodnius prolixus has two distinct types of agglutinins in its gut; one for Trypanosoma cruzi (termed the parasite agglutinin or PA) and the other for erythrocytes (referred to as the hemagglutinin or HA).
• These gut agglutinins are derived from the plasma and erythrocyte components of the blood meal the insect consumes.
• The identity of the PA was determined to be high-density lipoprotein (HDL) found in the plasma of the vertebrate blood meal.
• The HDL binds to the surface of the parasite and is internalized over time. This facilitates the infection of Rhodnius prolixus by enhancing the parasites’ capacity to adhere and multiply in the insect’s gut.

Conclusion

• The results highlight the significant role of HDL in increasing the infectivity of Trypanosoma cruzi in Rhodnius prolixus, in turn promoting the transmission of Chagas disease.
• This finding is critical to understanding the complex interactions within the insect vector that influence the prevalence of this disease.