Evaluation of P. falciparum antigen Pf332 as a target for parasite neutralizing immune responses
This project is based on the P. falciparum antigen Pf332, which we identified in 1989 together with Mattei et al. at the Pasteur Institute in Paris. Subsequent data on Pf332, obtained mainly by our groups by laboratory experiments and epidemiological investigations, indicate that the antigen stands out as an attractive target for vaccine development. However, the previous research on Pf332 has involved mainly a 157 amino acids long fragment (EB200) of the antigen; the complete 5506 a.a. sequence became recently available from the sequencing of the P. falciparum genome. Due to the high degree of cross-reactivity of antibodies to EB200 with other P. falciparum antigens, it is difficult to deduce which antigen is the true target for them. This project will expand the studies on Pf332 to select new sequences in both the C- and N-terminal parts of the antigen, in order to evaluate it as a target for parasite neutralizing immune responses and its suitability as a vaccine component. The main objectives of the project are: - To define possible polymorphisms in Pf332; - To produce non-cross reactive antibodies to different parts of Pf332 and assessment of their parasite neutralizing activity; - To define epitopes in Pf332 which are targets for parasite neutralizing antibodies; - To analyze antibody responses to Pf332 in naturally primed individuals; - To analyze Pf332 synthesis, transport and location; - To design, construct and test the immunogenicity of nucleic acid-vaccines based on Pf332-epitopes.
Reference:
Adersson C, Vasconcelos N-M, Sievertzon M, Haddad D, Liljeqvist S, Berglund P, Liljeström P, Ahlborg N, Ståhl S and Berzins B: Comparative Immunization Study Using RNA and DNA constructs Encoding a Part of the Plasmodium falciparum Antigen Pf332. 2001. Scand J Immunol 54, 117-124.
Effects of immune pressure on parasite diversity
The overall aim of this project is to define mechanisms for P. falciparum parasites to evade neutralizing immune responses. The results generated in the project should provide new information of importance for a rational design of strategies for vaccine development. The project includes, on one hand, longitudinal studies with field isolates of parasites and immunoglobulins (Ig) from the same donors and, on the other hand, studies with established P. falciparum laboratory strains and antibodies to various vaccine candidate antigens. The specific objectives of the project are: -To analyse parasite neutralization in vitro of field isolates of P. falciparum in relation to parasite population dynamics and antigen expression; -To analyse the impact of the use of impregnated curtains on parasite neutralizing immune responses and on the complexity of infecting parasite populations; -To produce parasite neutralizing human monoclonal antibodies to conserved epitopes of different vaccine candidate antigens; -To analyse the effects of immune pressure exerted in vitro by antibodies on the growth and antigen expression of laboratory strains of P. falciparum.
Reference:
Bolad A and Berzins B: Antigenic diversity of Plasmodium falciparum and antibody-mediated parasite neutralization. 2000. Scand J Immunol 52, 233-239.
