INDUCTION OF ANTIMALARIAL TRANSMISSION-BLOCKING IMMUNITY WITH A RECOMBINANT OOKINETE SURFACE-ANTIGEN OF PLASMODIUM-BERGHEI PRODUCED IN SILKWORM LARVAE USING THE BACULOVIRUS EXPRESSION VECTOR SYSTEM
H. Matsuoka et al., INDUCTION OF ANTIMALARIAL TRANSMISSION-BLOCKING IMMUNITY WITH A RECOMBINANT OOKINETE SURFACE-ANTIGEN OF PLASMODIUM-BERGHEI PRODUCED IN SILKWORM LARVAE USING THE BACULOVIRUS EXPRESSION VECTOR SYSTEM, Vaccine, 14(2), 1996, pp. 120-126
We have studied Pbs21, a major ookinete surface protein of Plasmodium
berghei, for the development of a model transmission blocking immunoge
n. lit the mouse recombinant Pbs21 expressed in the Escherichia coli e
xpression system (EcrPbs21) is not as effective in inducing transmissi
on blocking antibodies as native Pbs21 (nPbs21), possibly because of d
ifferences in post-translational processing between EcrPbs21 and nPbs2
1. In an attempt to improve the efficacy of the recombinant molecule,
we describe here the use of a baculovirus expression vector system in
the silkworm Bombyx mori. Following an injection of recombinant baculo
virus containing Pbs21 cDNA, B. mori larvae produced recombinant Pbs21
(BmrPbs21) with a molecular weight indistinguishable from nPbs21. Fif
ty micrograms of BmrPbs21 could be purified from the hemolymph of each
infected larva using affinity chromatography. Immunization of Balb/c
mice with BmrPbs21 induced high anti-BmrPbs21 and anti-ookinete antibo
dies but low anti-EcrPbs21 antibody. In contrast, EcrPbs21 induced hig
h anti-EcrPbs21 antibody but low anti-BmrPbs21 and anti-ookinete antib
odies This suggests that most B-cell epitopes on nPbs21 are conformati
onal and that many of the linear epitopes in EcrPbs21 are not normally
exposed in nPbs21. Oocyst formation in Anopheles stephensi mosquitoes
, which fed on mice immunized with purified BmrPbs21 and infected with
P. berghei, was blocked by 85.5-97.1%. These results suggest that the
baculovirus-silkworm system produces useful quantities of recombinant
Pbs21 which in limited studies is structurally and immunogenically in
distinguishable from the native molecule.