Evaluation of synthetic peptides of WbSXP-1 for the diagnosis of human lymphatic filariasis

Parasitic nematodes infect nearly half of the world's human population, resulting in significant morbidity and mortality. Though filariasis is not fatal, it is the second leading cause of permanent and long-term disability worldwide. Filariasis has a spectrum of disease manifestation and infectivity found among the infected individuals and also goes unnoticed for years. Furthermore, there are ample reports emerging on the genetic variation among the parasites population. Hence, it is necessary to develop diagnostics for early detection of the disease. Synthetic peptides that mimic the immunogenic regions and a conserved region similar to that of recombinant antigen will be more useful in developing diagnostics, vaccines, or therapeutics. WbSXP-1 was earlier proven as a good diagnostic antigen; B-cell epitopic analysis showed 4 potent immunodominant regions spanning the whole antigen. These synthetic peptides (N, N1, N2, and N3) were produced and used as a diagnostic candidate to detect anti-SXP antibody and conversely to detect the infected individuals. The monomeric peptides showed good reactivity against microfilareamic (MF) sera. Among them, the peptides N, N1, and N2 were found to be more reactive. Furthermore, multiple chimeric peptides in linear combinations of 2 peptides were tested for its efficacy to detect anti-SXP antibody in infected MF sera. The peptides N:N1 and N1:N2 were synthesized and tested against human clinical sera. This chimeric peptides constructed based on WbSXP-1 were found to be reactive, specifically with MF sera by ELISA. These peptide-based diagnostic method can serve as a standard better tool without cross-reactivity in lymphatic filariasis elimination program.