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Active and passive immunization against Plasmodium yoelii sporozoites
Y Charoenvit1, M Sedegah, L F Yuan
1Infectious Diseases Department, Naval Medical Research Institute, Bethesda, MD.
Bulletin of the World Health Organization
|January 1, 1990
Summary
Subunit vaccines targeting Plasmodium yoelii circumsporozoite protein (CS protein) showed immunogenicity but lacked protection. However, passive transfer of a specific monoclonal antibody (MAb) provided complete protection, highlighting antibody avidity as a key factor in malaria vaccine development.
Area of Science:
- Immunology
- Vaccinology
- Parasitology
Background:
- Subunit vaccines based on the Plasmodium yoelii circumsporozoite protein (CS protein) repeat regions were developed.
- These vaccines elicited an immune response but failed to provide consistent protection against sporozoite challenge.
Purpose of the Study:
- To investigate the protective capacity of antibodies against the P. yoelii CS protein.
- To elucidate the role of antibody avidity in protection against malaria sporozoite infection.
Main Methods:
- Design, production, and testing of three subunit vaccines.
- Establishment of a passive transfer model using a monoclonal antibody (MAb), NYS1.
- Assessment of antibody binding, avidity (thiocyanate elution assay), and protection against sporozoite challenge.
Main Results:
- Passive transfer of NYS1 MAb conferred 100% protection against a high-dose sporozoite challenge.
- The epitope recognized by NYS1 was within the (QGPGAP)2 peptide.
- Protective NYS1 MAb exhibited lower avidity for the target epitope compared to non-protective vaccine-induced antibodies.
Conclusions:
- Antibodies targeting the CS protein can provide significant protection against intense sporozoite infection.
- Antibody avidity, rather than concentration, appears critical for protective immunity against malaria.
- Understanding differences between protective MAbs and polyclonal antibodies is crucial for future malaria vaccine design.