Figure 6.
(A) Determination of specificity of lymphocytes primed in vivo with polypeptide P1 (upper band of protective doublet band 16) by proliferative assay. Normal BALB/c mice were immunized with P1. Proliferative responses of P1-primed lymph node cells to culture stimulation with P1, P2 (lower band of protective doublet) recombinant pfHGXPRT, an unrelated band (A), and P. yoelii pRBC were examined ex vivo. Purified protein derivative (PPD) and Con A were used as positive controls. Based on N-terminal sequencing, both bands (P1 and P2) appear to be HGXPRT. The data are mean cpm ± SD of triplicate wells. The background cpm was 2,551 ± 396. (B) Parasitemia levels in BALB/c mice immunized with recombinant pfHGXPRT after challenge infection with P. yoelii 17XNL. Mice immunized with OVA and PBS are included as controls. The mice (five mice per group) were administered three successive vaccinations with antigen in Freund's adjuvants following a standard schedule described in Materials and Methods. All mice were challenged i.v. with 105 pRBC parasites 10 days after final booster vaccination. †, death.