Monoclonal antibodies against lactate dehydrogenase of Plasmodium knowlesi

Lactate dehydrogenase (LDH) of malarial parasites has been demonstrated to be biochemically and immunochemically distinct from the equivalent host enzyme. The polyclonal antibodies raised against the purified plasmodial LDH showed specificity to Plasmodium spp. Six hybridoma cell lines secreting monoclonal antibodies specific to Plasmodium knowlesi LDH have been obtained. The two monoclonal antibodies (2A3B7 and 4A6A7) showed high reactivity with LDH from simian (P. knowlesi. P. cynomolgi), human (P. falciparum, P. vivax) and rodent (P. berghei, P. yoelii) malarial parasites and did not cross-react with red cell LDH as well as with isoenzymic forms of mammalian LDH (A4, B4 and C4). One monoclonal antibody (4A6A7) strongly inhibited the enzyme activity specifically of plasmodial LDH and did not have any effect on the activity of red cell LDH. The other monoclonal (2A3B7) did not show inhibitory effect on parasite LDH. These findings as well as competitive immunoassay studies suggest the presence of at least two parasite specific epitopes on plasmodial LDH.