Analysis of immunity induced by the affinity-purified 21-kilodalton zygote-ookinete surface antigen of Plasmodium berghei

Abstract

By using affinity-purified ookinete surface antigen from the rodent malaria parasite Plasmodium berghei, a transmission-blocking immunity was induced in mice. Groups of mice were immunized via different routes, with total quantities of antigen ranging from 0.5 to 40 ,ug (with or without Freund adjuvant). Vaccination by the intramuscular route with 20 ,ug of antigen in the absence of adjuvant and boosted once with the same amount of protein induced a total transmission blockade. Immunoblot analysis confirmed that immune sera invariably recognized Pbs2l antigen. The isotype and titer of the anti-Pbs2l immunoglobulin G (IgG) response was determined by enzyme-linked immunosorbent assay. The antibody isotype was predominantly IgGl. The concentration of specific anti-Pbs2l IgG reached a peak of 182.45 92.13 ,ug/ml by week 7 postimmunization and fell progressively to 38 ,g/ml at week 34 (at which time the transmission was still inhibited by 98%).

Studies on the immunogenicity of a recombinant ookinete surface antigen Pbs21 from Plasmodium berghei expressed in Escherichia coli

“…The immunity induced reduced transmission of the parasite from the gametocyte infected host to the mosquito vector, but less effectively than the native antigen. We recorded an average reduction in intensity of infection of 33% compared to the 63-100% blockade inducible by the native antigen (Tirawanchai et al 1991). This immunity did not modify the bloodstage infection in any of the parameters measured (parasitaemia, gametocytaemia or exflagellation), which is consistent with earlier studies.…”

“…1993). In contrast specific (polyclonal) anti-Pbs2 1 IgG concentration in mice immunized with the native antigen correlated closely with the blockade induced, such that sera containing levels of IgG calculated to be greater than 100 pg/ml were invariably found to block transmission completely (Tirawanchai et al 1991). Here we found that Ig levels higher than 100 pg/ml when induced by the recombinant molecule did not induce a total blockade.…”

“…The concentration of specific anti-rPbs21 was estimated by comparison to a standard curve, generated using purified mouse IgG (Sigma; 1600 ng/ml to 6.25 ng/ ml) as the first antibody with goat anti-mouse IgG Fab fraction (Sigma) coated microtitre plates as 'antigen' (Tirawanchai et al 1991).…”

“…These molecules are expressed on the surface of the macrogamete, zygote ookinete and oocyst stages (Sinden et al 1987, Ranawaka et al 1992, Simonetti et al 1993, Kumar & Carter 1984, Kaushal et al 1983, Lensen et al 1992. Using native Pbs21 antigen purified from Plasmodium berghei ookinetes, Tirawanchai et al (1991) induced a long lasting (33 week) total blockade of transmission in the immunized and infected mice. Genes encoding these families of antigens have been cloned e.g.…”

Molecular interactions betweenPlasmodiumand its insect vectors

“…Fertilization ensues within about 1 h. There is no evidence of chemotaxis between the male and female gametes. Factors derived from both the vector and the vertebrate host, the latter including antibodies (Tirawanchai et al ., 1991;Kaslow, 1993;Yoshida et al ., 1999), complement (Grotendorst et al ., 1986;Healer et al ., 1997;Margos et al ., 2001), cytokines (Motard et al ., 1993;Naotunne et al ., 1993), leukocytes (Rutlege et al ., 1969;Sinden and Smalley, 1976) and the biochemical composition of the bloodmeal (Billker et al ., 1997) all contribute to success or failure of these events.…”