USA As Represented by Secretary of the Navy

Srisin Khusmith

Stephen L Hoffman

Yupin Charoenvit

William O Rogers, Iv

Richard Hedstrom

A protein antigen (SSP2) on the surface of Plasmodium sporozoites is disclosed as a candidate immunogen for vaccination against malaria. This use of this protein, which is distinct from the extensively characterized circumsporozoite (CS) protein, will also facilitate research into host immunological responses to malaria. This antigen is detected by a monoclonal antibody (NYS4) which is specific for a 140 kilodalton (kD) protein on the sporozoite cell surface. Immunoreactive genomic clones are described which express this surface antigen gene and the primary nucleic acid sequence and the deduced amino acid sequence derived from this DNA sequence are disclosed. Unique repetitive sequences of amino acids are described which further demonstrate the distinction between SSP2 and the CS protein. A synthetic peptide containing repeating epitopes of SSP2 derived protein antigen and which are substantially shorter in length than the intact antigen are disclosed. The peptide when administered to a host elicits antibodies which bind to the SSP2 protein on the sporozoite surface. A recombinant plasmid bearing SSP2 DNA sequences expresses SSP2 epitopes in mammalian cells and the introduction of these transfected cells into mice elicits antibody and cytotoxic T-cell lymphocytic responses which confer partial protection to the recipient animals against challenge infection. In combination, the SSP2 protein and the CS protein elicit immunological responses in the mammalian host which confer 100% protection against challenge infection.

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Rockville, MD, United States of America

Srisin Khusmith