Abstract
Visceral leishmaniasis (VL), caused by Leishmania donovani or Leishmania infantum, is prevalent in India and Brazil. Post-kala-azar dermal leishmaniasis (PKDL), a cutaneous form, can occur in patients who seem to have recovered from VL. The rK39 test, which detects circulating antibodies, shows high sensitivity and specificity for VL diagnosis in India, but its performance varies in other endemic regions, with a significant limitation being the inability to distinguish active disease from past infection. Herein, we investigated Aurora Kinase (LdAIRK), a conserved virulence factor across Leishmania species with a major role in cell division, for VL diagnosis. We analyzed serum samples from parasitologically confirmed symptomatic VL patients (n = 79), PKDL patients (n = 16), healthy controls, and other diseases (n = 53) from India, along with VL patients (n = 40) and healthy endemic controls (n = 19) from Brazil, using enzyme-linked immunosorbent assay with rLdAIRK. The sensitivity of rLdAIRK was 98.73% (95% CI: 93.17-99.94) for Indian patients and 97.5% (86.84-99.94) for Brazilian patients. It also demonstrated a sensitivity of 93.75% (71.67-99.68) for Indian PKDL sera. Specificity ranged from 94.33% to 94.74% for Indian samples and 84.21% for Brazilian samples. Notably, LdAIRK showed low reactivity (8.3%) with follow-up patient samples compared with rK39 rapid diagnostic tests, indicating its potential as a test-of-cure tool. These findings were supported by dipstick and lateral flow tests (LFTs), which are user-friendly and suitable for field settings. We recommend incorporating recombinant antigen Ldairk in serological assays for the diagnosis of VL.IMPORTANCEAn early detection and treatment of VL is essential in the control of this potentially fatal disease. Since signs and clinical symptoms of VL are non-specific, diagnosis is confirmed with serological tests. Rapid diagnostic tests (RDTs) against VL that detect antibodies are simple and field adaptable. rK39 antigen-based RDTs are in use, but their sensitivities vary in the different VL-endemic regions. Moreover, since the antibodies persist long after cure in healthy individuals, these RDTs cannot diagnose relapse of the disease. Here, we have identified a Ldairk as a new marker for the diagnosis of VL. We found that Indian VL and PKDL as well as Brazilian patient sera reacted to this protein consistently. Sensitivity was also maintained in the patient's urine samples. Low reactivity with antibodies after cure with Ldairk can help distinguish previously treated cases from active and relapsed ones.