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In recent years, Plasmodium falciparum histidine-rich protein 2 gene deletion has been reported in India. Such isolates are prone to selective transmission and thus form a challenge to case management. As most of the rapid malaria diagnostic tests are based on the detection of HRP2 protein in the blood, we attempted to use Glutamate Dehydrogenase (GDH) as a biomarker for the diagnosis of P. falciparum. Recombinant PfGDH was successfully cloned, expressed and purified using the Ni-NTA approach. Polyclonal antibodies were raised against full-length rPfGDH and its peptides. Antibodies for rPfGDH showed a strong immune response against the recombinant protein. However, antibody showed no affinity towards the peptides, which suggests they failed as antigen. Antibodies for rPfGDH significantly detected the GDH in human blood specimens. This is the first report where P. falciparum GDH was detected in malaria cases from various parts of India. The raised polyclonal antibodies had shown an affinity for PfGDH in quantitative ELISA and are capable to be exploited for RDTs. This research needs further statistical validation on a large number and different sample types from candidates infected with P. falciparum and other species.

Five monoclonal antibodies (mAbs) that recognize human glutamate dehydrogenase (GDH) have been selected and designated as monoclonal antibodies hGDH60-6, hGDH60-8, hGDH63-10, hGDH63-11, and hGDH91-14. A total of five mAbs recognizing different epitopes of the enzyme were obtained, two of which inhibited human GDH activity. When total proteins of human homogenate separated by SDS- PAGE, were probed with mAbs, a single reactive protein band of 55 kDa, which co-migrated with purified recombinant human GDH was detected. When the purified GDH was incubated with each of the mAbs, its enzyme activity was inhibited by up to 58%. Epitope mapping analysis identified, two subgroups of mAbs recognizing different peptide fragments. Using the individual anti-GDH antibodies as probes, the cross reactivities of brain GDH obtained from human and other animal brain tissues were investigated. For the human and animal tissues tested, immunoreactive bands on Western blots appeared to have the same molecular mass of 55 kDa when hGHD60-6, hGHD60-8, or hGHD91-14 mAbs were used as probes. However, the anti-human GDH mAbs immunoreactive to bands on Western blots reacted differently on the immunoblots of the other animal brains tested, i.e., the two monoclonal antibodies hGDH63-10 and hGDH63-11 only produced positive results for human. These results suggest that human brain GDH is immunologically distinct from those of other mammalian brains. Thorough characterization of these anti-human GDH mAbs could provide potentially valuable tool as immunodiagnostic reagents for the detection, identification and characterization of the various neurological diseases related to the GDH enzyme.