Question

Why is antigenic variation important for the establishment of trypanosomiasis in its host? How is this mediated?

Answer 1

due to Antigenic variation, a protozoan modifies its surface proteins to evade a host immune response. Antigenic variation is connected to phase variation. the Immune evasion of the host is necessary for organisms that infect hosts which have a long life cycle or organism which infect a single host and are readily transmittable.

the microbes can produce re-infection due to Antigenic variation, as their antigens are no longer identified by the host's immune system. When an organism is exposed to a particular antigen an immune response is aroused and antibodies are produced to target that particular antigen.

The immune system will now remember that antigen and will direct defences at that antigen and these defences will become part of the acquired immune response.

If the same pathogen attempts to re-infect the same host the antibodies will work quickly to target the pathogen for damage. Nevertheless, if the pathogen can modify its surface antigens, it can evade the host's acquired immune system. This will enable the pathogen to re-infect the host while the immune system produces new antibodies to target the recently recognized antigen.

this was one of the major reason why antigenic variation is important for the establishment of trypanosomiasis in its host.

the protozoan parasite coats itself with a thick, uniform coat of glycoprotein recognized as the variant surface glycoprotein(VSG)  to defend itself from host defences. during the primary stages of invasion, the thick protein coat preserves the parasite from immune discovery. after some time the host ultimately identifies the variant surface glycoprotein(VSG) as a foreign antigen and starts an attack against the microbe. The Trypanosoma brucei parasite has evolved a mechanism to display a completely new coat of VSG antigen, rendering it once again invisible to the host’s immune system.