Question

What role does antibody play in Trypanosoma bruceiinfections? What role does VSG play in T. bruceiinfections?

Answer 1

Antibodies against a specific epitope of the parasite is synthesised by the body that is infected by the trypanosoma. These antibodies recognize these specific epitopes, opsonizing the protozoa and marking it for killing by macrophages, eosinophil, or cytotoxic T-cells.

VSG or variable surface glycoprotein, 60,000Dalton surface protein making up the protozoan's protein coat. A trypanosome can form many differnt forms of VSGs by antigenic variation. This property of the protozoan helps it to escape the host's immune system. How? Lets say the protozoan make type I VSG against which antibodies are made which eventually attack the parasite and kills it . As the protozoan titer decreases, it through antigenic shifts/switching form a different type of VSG lets say type II which is not recognized by the host's immune system and thus the protozoan thrives bypassing the immune system of the host.