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Some pathogens have developed mechanisms to evade the immune system, making it difficult or impossible to develop effective Evaccines against them. African sleeping sickness is caused by a protozoan called Trypanosoma brucei, carried by the tsetse fly. The trypanosome surface is dominated by one coat protein, the variable surface glycoprotein (VSG). The trypanosome genome encodes over 1000 different versions of VSG. All of the cells in an initial infection feature the same VSG coat on their surfaces, and this is readily recognized as foreign by the immune system. However, an individual trypanosome in the broader population will switch and randomly begin expressing a different variant of the VSG coat. All the descendants of that cell will have the new and different protein on their surface. As the population with the second VSG coat increases, an individual cell will then switch to a third VSG protein coat, and so on. Select the statements that describe how Trypanosoma brucei can survive the immune response of its host. ◻ Trypanosomes use VSG to bind and attack host immune cells. ◻ Newly expressed VSG variants may bind antibodies and T-cell receptors with greater affinity. ◻ Immune proteins raised against the original trypanosome population do not recognize new VSG variants. ◻ Continuous switching allows some trypanosome cells to evade each successive immune response. 49 99 The human immunodeficiency virus (HIV) has an error-prone system for replicating its genome, effectively introducing mutations at an unusually high rate. Many of the mutations affect the viral protein coat.

Some pathogens have developed mechanisms to evade the immune system, making it difficult or impossible to develop effective Evaccines against them.
African sleeping sickness is caused by a protozoan called Trypanosoma brucei, carried by the tsetse fly. The trypanosome surface is dominated by one coat protein, the variable surface glycoprotein (VSG). The trypanosome genome encodes over 1000 different versions of VSG. All of the cells in an initial infection feature the same VSG coat on their surfaces, and this is readily recognized as foreign by the immune system.
However, an individual trypanosome in the broader population will switch and randomly begin expressing a different variant of the VSG coat. All the descendants of that cell will have the new and different protein on their surface. As the population with the second VSG coat increases, an individual cell will then switch to a third VSG protein coat, and so on.
Select the statements that describe how Trypanosoma brucei can survive the immune response of its host.
◻ Trypanosomes use VSG to bind and attack host immune cells.
◻ Newly expressed VSG variants may bind antibodies and T-cell receptors with greater affinity.
◻ Immune proteins raised against the original trypanosome population do not recognize new VSG variants.
◻ Continuous switching allows some trypanosome cells to evade each successive immune response.
49
99
The human immunodeficiency virus (HIV) has an error-prone system for replicating its genome, effectively introducing mutations at an unusually high rate. Many of the mutations affect the viral protein coat.

Added by Francisco W.

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