Two major Neglected Tropical Diseases are Leishmaniasis and Chagas disease. They are parasites belonging to the Trypanosomatidae family and as such they have very similar tactics when it comes to avoiding the body’s immune response. Immune response comes about as a result of the host’s recognition of disease specific antigens. These two Neglected Tropical Diseases possess a complex series of ways to avoid detection and cause the persistence of disease. Chagas disease is among a group of parasites able to avoid immune detection by hiding within the body’s own cells. This is called an intracellular infection. Furthermore, Chagas is capable of infecting different hosts and progresses through several stages of its life cycle in various vertebrate and invertebrate hosts.
The two relevant life cycles are the trypomastigote stage and the amastigote stage. Chagas disease is present in the Trypomastigote stage within its primary vector, the kissing bug. This stage possesses a single flagellum and is non-dividing. Within human hosts, Trypanosoma Cruzi takes the amastigote form which is an intracellular, actively dividing stage with no obvious flagellum, as well as the trypomastigote form in the blood.
Molecular Basis for Infection
Metacyclogenesis, the process by which these parasites differentiate between their dividing and non-dividing stages, is vital for their success as parasites. Once inside a host’s gut, T. Cruzi parasites transform from an epimastigote stage into metacyclic trypomastigotes in order to reproduce. Early in host infection, neutrophils are recruited by the immune system to rush to the area of the bite. Neutrophils are phagocytic cells: one of the body’s most common white blood cells. Neutrophils attempt to attack the parasite through the release of reactive oxygen species which serve to dissolve foreign things, through the release of an enzyme called Neutrophil Elastase (NE) which destroys pathogens and host tissues alike, and the use of Neutrophil Extracellular Traps (NETs).