• Vaccine Name: Recombinant ABRA protein vaccine
• Target Pathogen: Plasmodium spp.
• Target Disease: Malaria
• Vaccine Ontology ID: VO_0000778
• Type: Subunit vaccine
• Host Species as Laboratory Animal Model: mouse
• Antigen: The acidic basic repeat antigen (ABRA) of Plasmodium falciparum is a vaccine candidate against erythrocytic stages of malaria (Kushwaha et al., 2001).
• ABRA gene engineering:
  • Type: Recombinant protein preparation
  • Description:
  • Detailed Gene Information: Click Here.
• Adjuvant:
  • Adjuvant name:
  • VO adjuvant ID: VO_0000139
  • Description: Complete Freund's adjuvant (CFA) was used as the first adjuvant. Boosters of the same amount of protein were given in incomplete Freund's adjuvant (IFA) (Kushwaha et al., 2001).
• Preparation: The four fragments of ABRA, including N-terminal [ABRA (N); aa 24–369], middle [ABRA (M); aa 370–507], N-terminal + middle [ABRA (P); aa 24–507] and the C-terminal [ABRA (C); aa 508–743], were expressed as fusions with either maltose binding protein (MBP) or 6X histidine tag at their amino terminii using pMALc-2 vector from NEB (New England Biolabs, Beverly, MA, USA) or pQE30 vector (Qiagen GmbH, Germany), respectively. These recombinant proteins were purified to near homogeneity by affinity chromatography of the soluble fraction, concentrated, and the purity of the protein judged by SDS-PAGE.

Mouse Response

• Host Strain: BALB/c
• Vaccination Protocol: Groups of BALB/c mice were immunized by i.p. injection with ABRA protein/MBP emulsified in complete Freund's adjuvant (CFA). Control mice received only PBS in the adjuvant. Boosters of the same amount of protein were given in incomplete Freund's adjuvant (IFA). Sera were collected from each group and treated as described earlier (Kushwaha et al., 2001).
• Persistence: Humoral and cell-mediated response was still robust up to 70 days post-immunization (Kushwaha et al., 2001).
• Immune Response: Results showed that ABRA (M), ABRA (C) and ABRA (P) were highly immunogenic in these animals; end point titres greater than 10^5 were observed in these constructs. Mice were immunized using standard methods. Relative concentrations of the antibodies elicited by them in mice at different intervals of immunization were measured at a dilution of 1 : 3000. ABRA (N) and ABRA (C) did not show a boostable antibody response; two secondary immunizations did not result in any increase in the antibody titre. Immunogenicity studies with these constructs in rabbits and mice indicated that the N-terminal region is the least immunogenic part of ABRA. T-cell proliferation experiments in mice immunized with these constructs revealed that the T-cell epitopes were localized in the middle portion of the protein (Kushwaha et al., 2001).
• Efficacy: The purified immunoglobulin G specific to middle and C-terminal fragments prevented parasite growth at levels approaching 80-90% (Kushwaha et al., 2001).
• Description: This antibody response was the focus of intense interest when it was found that mice could be rendered resistant to sporozoite challenge by passive immunisation with monoclonal antibodies against circumsporozoite protein (Kwiatkowski et al., 1997).