Abstract
Visceral leishmaniasis (VL) is one of the major global health concerns due to its association with morbidity and mortality. All available diagnostic tools have been, until now, unable to provide a very specific and cost-effective mode of detection for VL globally. Therefore, the design of robust, specific, and commercially translatable diagnostic tests is urgently required. Currently, we are attempting to identify and explore the diagnostic potential of a novel parasite antigen. Repressor of differentiation kinase 2 (RDK2), a serine/threonine kinase, has a versatile role in parasite life cycle progression. However, its role as a diagnostic candidate for VL has not been investigated. Herein, we cloned and over-expressed LdRDK2 and studied the recombinant RDK2 for the diagnosis of human VL using serum and urine samples. In silico analysis predicted that RDK2 is conserved among Leishmania species with the least conservation in humans. RDK2 developed immune-reactive bands with antibodies present in VL patients’ sera, and it demonstrated no cross-reactivity with sera from healthy controls and other diseases. Additionally, RDK2 antigen demonstrated a significant reactivity with IgG antibodies of VL patients’ sera, with 78% sensitivity and 86.67% specificity as compared to healthy controls and other diseases. Furthermore, we evaluated its utility for non-invasive diagnosis of VL using patients’ urine samples and found 93.8% sensitivity and 85.7% specificity. RDK2 was found to have better sensitivity and treatment response in patients’ urine compared to serum samples, indicating its role as a promising point of care (POC) antigen. In a nutshell, we explored the role of RDK2 as a potential diagnostic marker for VL in both invasive and non-invasive modes as well as its utility as a promising POC antigen for treatment response cases.
Highlights
Cases occur annually, of which 90% of cases arise from Brazil, Ethiopia, Eritrea, India, Iraq, Kenya, Nepal, Somalia, South Sudan, and Sudan
The homology and pan-species conservation of Repressor of differentiation kinase 2 (RDK2) have been analysed by comparing amino acid sequences of RDK2 obtained from L. infantum, L. mexicana, L. major, T. brucei, T. cruzi, and
According to the conservation peaks obtained from the multiple sequence alignment tool (MSA) tool, RDK2 is conserved throughout Leishmania and Trypanosomes with the least conservation in humans (Figure ??)
Summary
Visceral leishmaniasis (VL), or kala-azar, caused by Leishmania donovani, is one of the deadliest parasitic diseases in terms of outbreak and mortality. The disease has been endemic mainly in the Indian Subcontinent, Latin America, and East Africa [1]. According to the World Health Organization (WHO) 2019 report, 50,000 to 90,000 new VL cases occur annually, of which 90% of cases arise from Brazil, Ethiopia, Eritrea, India, Iraq, Kenya, Nepal, Somalia, South Sudan, and Sudan (https://www.who.int/news-room/factsheets/detail/leishmaniasis, accessed on 20 May 2021). The onset of VL causes symptoms such as irregular bouts of fever, weight loss, splenomegaly, hepatomegaly, and anaemia that can overlap with symptoms of other diseases such as malaria and dengue [2,3]
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