Abstract: 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.