Mature stages of Plasmodium falciparum insert variant antigens (VSA) into the surface of
infected erythrocytes, and antibodies against such antigen provide variant-specific
protection against malaria. Because mature P. falciparum trophozoites normally sequester
away from the peripheral circulation, parasites for anti-VSA antibody studies are obtained
from patients as ring trophozoites, cryopreserved, and cultured to maturity when required.
However, this process is associated with problems of poor recovery from cryopreservation …