Microbiology MCAT Practice Question
A 28-year-old man from Cameroon presents to the clinic with his third episode of malaria over the past 18 months, despite previously receiving treatment with artemisinin combination therapy. Each infection was confirmed by blood smear showing P. falciparum parasitemia at different times. Serological studies show he has developed antibodies against multiple PfEMP1 variants over this time period. The parasites from his most recent infection are not recognized by antibodies generated during his previous infections. Which of the following best explains how P. falciparum achieves recurrent infections in this patient despite prior immune responses?
Answer choices
- ASequential expression of antigenically distinct PfEMP1 variants from the var gene family allows parasites to evade strain-specific antibodies generated from previous infectionsCorrect answer
- BPfEMP1 directly blocks MHC class I molecules on infected erythrocytes, preventing cytotoxic T lymphocyte recognition of all parasite antigens
- CVar gene recombination occurs in the human host during gametocyte formation, generating novel PfEMP1 variants not previously encountered by the immune system
- DPfEMP1 variants phosphorylate immunoglobulin G molecules, causing them to become functionally inert regardless of their antigenic specificity
- EAntigenic variation of PfEMP1 increases rosetting capacity, which physically shields parasites from both antibody and complement-mediated destruction
- FThe var gene family undergoes rapid mutation during erythrocytic schizogony, with mutation rates exceeding those of influenza hemagglutinin
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