the present invention includes novel peptides gqdegeeneg , seq . id no : 1 grnglgantdqddqlede , seq . id no : 2 dqffdanpnlfqllepvefded , seq . id no : 3 and lvflvqqpflfvlwdqnekfpvfmgvydp seq . id no : 3 . such peptides are useful for detecting antibodies against circulating malarial antigens . in one aspect , these peptides may be copolymerized or crosslinked to form immunogens presenting epitopes of the malarial plasmodium falciparum antigen pf70 . preferably at least two of the above peptides are so crosslinked . most preferably , all four peptides are copolymerized . the crosslinking agent preferred is glutaraldehyde although , of course , other crosslinking agents such as dialdehydes of various lengths , for example , or even possibly the carbodiimides may be used . compositions of matter comprising such peptides in crosslinked or copolymerized forms are an important part of the present invention , particularly when used as immunogens . rabbits have been immunized with a composition of the four crosslinked peptides at a dose of 2 . 5 mg . an analogous dose for larger animals should , of course , produce the same response to induce immunity to malaria . the present invention also , of course , includes a method of producing an antigen usable to generate antibodies reacting with malarial organisms , plasmodium falciparum and plasmodium vivax . the above copolymerizing methodology utilizing crosslinking agents with the peptides of choice is the method of production .